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Daily Rates Of Weight Gain

Care is needed in assessing the rates of weight gain in birds because weight varies with time of day, and often drops (or increases less rapidly) for some hours after capture, as the bird may react to handling (e.g. Schwilch & Jenni 2001). Nevertheless, the repeated trapping of migrants in the days before they set off on migration, or at stopover sites en route, has provided information on their individual rates of weight gain (e.g. Figure 5.1), from which average and maximum rates for different populations have been calculated (Alerstam & Lindstr m 1990, Lindstr m 2003). Expressed as the daily (24-hour) gain in mass relative to lean body mass, average rates of pre-migratory weight gain (mostly fat), as measured in 58 populations, ranged from less than 1 to more than 7 (maximum 13 ). Exceptionally high rates were recorded on particular days, but not sustained over a longer period. In captive passerines, weight gain was often greater on the second than on the first day of...

The Role Of Foraging Theory In Understanding Food Habits

Such, food or prey items are ranked by profitability and added to the diet as long as there is an increase in net energy intake. The optimal diet model provides several useful predictions. If handling times (the time needed to pursue, capture, and consume) are typically short, the consumer should be a generalist (use a wide range of foods or prey). On the other hand, if handling times are long, the consumer should specialize on the most profitable foods. Consider prey selection by wolves (Canis lupus) that are usually in close proximity to large ungulates, such as moose. The time and energy required to capture a moose may be considerable. As a result, wolves may specialize on the most profitable or vulnerable segments of the population (juveniles and older animals in poor condition). Optimal foraging theory also predicts that a consumer should have a broader diet in an unproductive environment or during lean periods than in a productive environment or periods of food abundance (Gray...

Carbon isotopes and browse grass ratios in the diet

An even more important aspect of dietary nutrition emerged from the study. Even though adult elephants spend only half their time browsing, the browse or C3 plants contributed over 70 of the organic carbon that went into the synthesis of collagen. Thus, the browse plants provided proportionally higher quantities of protein used in the growth of the animal. This is again con The elephants of this southern Indian population have access to a variety of vegetation types, from semievergreen and moist deciduous forest to dry deciduous and dry thorn forest. The home ranges of several adult bulls and family groups studied cover virtually this entire diversity of habitats. Although a certain degree of dietary variation among elephant clans and solitary bulls exists due to constraints imposed by their spacing patterns, individual preferences, and home ranges, the 55 -83 range in protein contribution from C3 plants to adult elephants brings out the importance of browse in the overall diet....

Plants and plant parts in the diet

Most modern-day elephant observers in Africa and in Asia have commented on the diversity of plants in the diets of the two species. A unique organ, the trunk, makes it possible for the elephant to delicately pluck the tiny There are several figures in the literature on the number of plant species consumed by elephant populations in various habitats. These can be looked at broadly in dry habitats, such as savannas and woodlands, or in moist habitats, such as rain forests. One of the earliest scientific studies of feeding in elephants was in the savanna habitat of Uganda. Examination of stomach contents, reported by Irven Buss in 1961, revealed 25 plant species in the diet of these elephants. Similar examination of culled elephants during 1971-1972 at Wan-kie (Hwange) in Zimbabwe by B. R. Williamson identified 61 browse species. Direct observations of elephant feeding have turned in even higher species numbers. Peter Guy, on foot, followed elephants at the Sengwa Reserve in Zimbabwe...

Investigating Food Habits of Terrestrial Vertebrates

Why study food habits Probably one of the most fundamental questions that ecologists attempt to answer is, What resources does a particular species require to exist Indeed, the first principle among wildlife ecologists is to have a thorough understanding of the food, cover, and water requirements of an animal before initiating any effort to alter the factors that may be limiting it. Information on food habits is therefore an important introduction to the natural history of any species. This has been a justification for many studies of food habits of vertebrates (Martin et al. 1961) and is still a valid reason to investigate the diet of any species when little information is available (Salas and Fuller 1996). Food habits have been investigated for a variety of other reasons. Such information is essential in understanding the potential competitive interactions among sympatric species (Jaksic et al. 1992 Wiens 1993) or in determining how the foraging patterns of individuals affect...

Acorns in the Diet

The literature is rich with documentation of turkey food habits. Food habit studies have been thoroughly summarized by Schemnitz (1956), Schorger (1966), Korschgen (1967), and Hurst (1992). The studies in these reviews are based on field observations and foods identified from crops, stomachs, gizzards, and droppings (Hurst 1992). Data are usually reported as frequency of occurrence (e.g., percent occurrence in droppings), percent composition (by volume or weight), or qualitative criteria. Based on percent of the diet, acorn use for the eastern subspecies is generally higher than that for other subspecies (Table 16.1). On average, percent acorn composition of the diet of eastern birds is highest in the winter (33.2 ), followed by spring (20.5 ) and fall (20.4 ). Average summer use of acorns represent only 1.2 of the eastern diet. Acorns represent the highest volume of food in the eastern turkey diet during the winter and spring (Hurst 1992). Studies indicate that acorn composition of...

List of Illustrations

5.2 Relationship between 13C signatures of the diet of equilibrated plasma in black bears and polar bears 5.3 Relationship between 15N signatures of the diet of equilibrated plasma in black bears and polar bears 5.5 Information content and sample resolution of common methods used to investigate vertebrate food habits

Attack and Exploitation Models

Listed above, one can find recent reviews ofthe published tests ofthese models in Sih and Christensen (2001 134 published studies of the diet model) and Nonacs (2001 26 studies of the patch model). The diet model analyzes the decision to attack or not to attack. The items attacked are types ofprey items, and the forager decides whether to spend the necessary time handling and eating an item or to pass it over to search for something else. The model identifies the rules for attack that maximize the long-term rate of energy gain. Specifically, the model predicts that foragers should ignore low-profitability prey types when more profitable items are sufficiently common, because using the time that would be spent handling low-profitability items to search for more profitable items gives a higher rate of energy gain. The diet model introduced the principle of lost opportunity to ecologists, who have since used the concept in many other settings (e.g., optimal escape Ydenberg and Dill...

Hbe Research On Agricultural Origins

There is a small HBE literature on agricultural origins. Keegan (1986, 92) made an early and prescient argument that foraging models could be extended to the study of horticultural production. He highlighted horticulture because it represents a mixed subsistence system, transitional between the economies of hunter-gatherers and agriculturalists. Using data from the Machiguenga of Peru, Keegan argued that the key variables of the diet breadth and patch-use models have direct analogs in food production, facilitating the use of these cost-benefit models Layton et al. stimulated two follow-up papers, both of them making more explicit use of foraging theory to critique or amend specific predictions from their article. Hawkes and O'-Connell (1992 cf. Layton and Foley 1992) used a sharper distinction between search, and pursuit, and handling times the central conceptual distinction of the diet breadth model to argue that high-ranking resources will not drop out of a forager's diet in...

Benefits and Services Provided by Field Margin Retention within Intensively Managed Grasslands

The majority of essential mineral elements are associated with one or more catalytic functions in the cell (McDonald et al., 2002) and among the conditions known to be caused by mineral and trace element deficiency are abortion, stillbirth, death of young, infertility, retention of the placenta, scour, increasing susceptibility to infections such as pneumonia, mastitis, stiff joints, muscular weakness and a general lack of thrive (McDonald et al, 2002 Rogers et al, 1989). Certain herb or wildflower species can be highly beneficial as they add to the nutritive value of the herbage. For example Plantago lanceolata (ribwort plantain) has long been recognised as one of the most mineral-rich herbs available. Stapledon (1936) recommended its use where there were insufficient levels of Calcium and Phosphorus in the diet. In addition, P. lanceolata and other deep rooting herbs such as Sanguisorba minor (salad burnet), Achillea millefolium (yarrow), which may be...

Metabolism and Digestion

Animals are heterotrophs, and as such are unable to synthesize their own organic compounds from inorganic molecules and so rely on other organisms for nutrients. Energy is obtained from nutrients such as carbohydrates, lipids, and sometimes proteins (amino acids are required for protein systhesis but also produce energy when oxidized). Essential vitamins, minerals, and fatty acids are also needed for proper cell functioning and must also be obtained via the diet. Single-celled animals and sponges ingest food particles by phagocytosis. These are chemically and enzymatically reduced within a food vacuole to a few constituent substances (e.g., monosaccharides, fatty acids, and amino acids) that are transported into the cytoplasm. Most multicellular animals have a digestive system specialized for extracellular digestion. Food particles enter the digestive system where a series of physical and chemical digestive processes break down food particles into constituent molecules that are...

Food componentEnergy kcalg

Animals with simple stomachs require 10 essential amino acids, these being the forms that cannot be synthesized by the animal and must be obtained in the diet arginine, histidine, isoleucine, leucine, threonine, lysine, methionine, phenylalanine, tryptophan, and valine. Non-essential amino acids, therefore, are ones which can be synthesized in the body. Ruminants, and other species that rely on fermentation through the use of microorganisms, synthesize many of the amino acids themselves and so have a shorter list of essential amino acids.

NTFPs and Local Populations

In developing countries, the dependence of people on NTFPs may be higher than in developed countries. In developing countries, unemployment is often high and unemployed people generally do not receive good government subsidies thus the extraction and sale of NTFPs can be an important contribution to income generation. Traditional medicines are often the only or principal healing aid in many forest communities. Fruits that are rich in vitamins can be important in the diet of local people. Ornamental plants extracted from forests are used by local people for their aesthetic value. Animals that inhabit the forest are often important sources of protein for local populations. However, overhunting has seriously depleted game populations in some tropical forests.

Beyond Derived And Graphical Solutions

The basic foraging models described above are products of mathematical derivation, often represented graphically. A desire for more realistic variants is associated with new analytic methodologies, such as simulation and agent-based modeling. For instance, Winterhalder and students (Winterhalder et al. 1988) simulated the population ecology of a foraging population interacting with multiple resource species. In this dynamic model, the human population grows or contracts in density as a function of foraging efficiency. It harvests species identified by the diet breadth model, in amounts required to meet its food needs. And, to complete the dynamic circuit, the densities of the resource species themselves expand or contract according to their degree of exploitation and their logistic potential to recover from being harvested. The result is a more realistic application of the diet breadth model exploitation actually changes prey densities and thus encounter rates in a plausible manner,...

Smoothcoated or smooth otter Lutrogale perspicillata Fig 218

On such spraint sites the nature of the diet of smooth otters is evident there are fish scales everywhere. The food is dominated by fishes, and quite large ones at that, up to 45 cm long (mean size > 15 cm), but they also take crabs, frogs and the odd snake. For preference, smooth otters take the rather slow-moving fishes, or those living in large, dense shoals. Where they occur in the same areas as Eurasian and small-clawed otters, the smooth otter is the most piscivorous, taking the largest prey, often as socially organized foragers, more cooperative than any of the others.

Future Discounting Explanation for the Persistence of a Mixed Foraging Horticulture Strategy among the Mikea of

Ment in patches of wilderness that remain more-or-less untended until harvest time, seems a curious strategy. Payoffs tend to be low on average, for the cultigens compete with wild plants for soil and solar resources. Returns are also highly variable, for the crop is left vulnerable to pests, predators, and unpredictable climatic conditions. Extensive horticulturalists compensate for low and variable harvests by hunting and gathering wild foods, which constitute the bulk of the diet in some years. Given this heavy reliance on foraging, one may well ask why plant cultigens at all Conversely, why refrain from intensifying agricultural inputs to produce a more dependable and satisfying agricultural payoff

Energy Needs And Body Composition

Per unit weight, fat provides much more energy than any other storable biochemical fuel available. The use of 1 g of fat will yield around 9.2 kilocalories (or 38 kilojoules) of energy, compared with only about 1.3 kcal (5.3 kJ) from 1 g of protein or 1.0 kcal (4.0 kJ) from 1 g of carbohydrate (Table 5.1). Weight for weight, fat therefore contains 7-9 times more energy than alternative fuels, and thus provides the maximum energy storage for the minimum weight gain. Fat is an even more efficient fuel than high-octane vehicle fuel, and also has the advantage for birds that its oxidation yields an equal weight of water, thus contributing to another of the bird's needs during long-distance flights. Not only can fat be

Animal Specific Biological Factors

Lipid content is important as this is the organic phase into which the organic compounds dissolve. However, some compounds such as metals and fluorinated chemicals are associated to the animal's proteins in the muscle. The animal's feeding ecology is important as this determines the exposure to the contaminants from the diet, just like habitat use is important in an environment where the chemicals are not evenly distributed, but may depend on water masses, depth, sediment type, etc. Reproduction is important as an elimination pathway, especially for female mammals, due to maternal transfer of lipid-soluble contaminants from the mother to the offspring. Often this results in a buildup of contaminants in male mammals with age, as they do not have this pathway of elimination, whereas females reach a steady-state level sooner. Biotransformation ability is the ability of an animal to transform the accumulated chemical into another, preferentially a more-water-soluble compound that can be...

Increased feeding rates and feeding times

Hyperphagia (eating more than needed to maintain a stable body weight) is evident especially in captive passerine migrants, which at appropriate seasons suddenly begin to eat around 25-30 more per day than usual (range 10-50 ). This promotes mean weight gains of up to 10 per day (Figure 5.4). On a 20-30-g bird, with a fattening rate of 1.0-1.5 g per day, fattening may take 4-10 days. Higher rates of weight gain have been recorded at 20 per day in White-crowned Sparrows Zonotrichia leucophrys (King 1972) at 25-30 in Bobolinks Dolichonyx oryzivorus (Gifford & Odum 1965), and at 40 in Garden Warblers Sylvia borin (Bairlein 1990). In studies of captive shorebirds, which could feed for 23 of the 24 hours per day under artificial light, maximum daily energy intakes reached 300-500 above existence levels (Lindstrom & Kvist 1995, Kvist & Lindstrom 2003).

The response of plants to changing atmospheric concentrations of CO2

Moreover, there is a general tendency for CO2 enrichment to change the composition of plants, and in particular to reduce nitrogen concentration in above-ground plant tissues - around 14 on average under CO2 enhancement (Cotrufo et al., 1998). This in turn may have indirect effects on plant-animal interactions, because insect herbivores may then eat 20-80 more foliage to maintain their nitrogen intake and fail to gain weight as fast (Figure 3.15).

Examples Of Changes In Body Composition

Body changes during migration have been studied in particular detail in the Garden Warbler Sylvia borin (Bairlein 1991a, 1991b, 1998, Biebach 1998, Biebach & Bauchinger 2003). This trans-Saharan migrant can increase its body mass from 18 g in summer or winter to a maximum of about 37 g shortly before setting out over the desert in autumn or spring (Bairlein 2003). This doubling in body mass is due largely to fat deposition, but also to increase in protein and water content. In autumn in northwest Africa, preparation takes 10-14 days, with mean rates of weight gain of 0.7-1.0 g per day, and maximum rates of 1.5 g per day (10 of lean body mass), depending on the food available. By comparing Garden Warblers Sylvia borin caught in autumn in Turkey (just before a southward Mediterranean-Saharan flight) with others caught in spring in Sinai (just after a northward Saharan flight), Biebach (1998) concluded that about 70 of the loss in body mass during migration comprised fat, and the rest...

Implications For The Evolution Of Intensive Cultivation

Trade represents another source of immediate food value. Foragers and farmers may develop symbiotic relationships. Foragers assure immediate food needs so that farmers can invest intensively in higher-yielding agricultural pursuits Farmers provide the majority of calories in the diet. The classic example is the relationship between the foraging Mbuti and Efe and their farming neighbors in the Congolese rainforest (Turnbull 1965). Relationships of this sort may have occurred at the origins of settled agriculture in the Levant, where foragers and farmers co-existed (Bar-Yosef and Meadow 1995). The need to exchange immediate and delayed-return

Digestion and assimilation of plant material

The large amounts of fixed carbon in plant materials mean that they are potentially rich sources of energy. It is other components of the diet (e.g. nitrogen) that are more likely to be limiting. Yet most of that energy is only directly available to consumers if they have enzymes capable of mobilizing cellulose and lignins, whereas the overwhelming majority of species in both the plant and animal kingdoms lack these enzymes. Of all the many constraints that put limits on what living organisms can do, the failure of so many to have evolved cellulolytic enzymes is a particular evolutionary puzzle. It may be that gut-inhabiting, cellulolytic prokaryotes have so readily formed In herbivorous vertebrates the rate of energy gain from different dietary resources is determined by the structure of the gut - in particular, the balance between a well-stirred anterior chamber in which microbial fermentation occurs (AF), a connecting tube in which there is digestion but no fermentation (D), and a...

Oxidation of Fats and Amino Acids

Proteins are first hydrolyzed into their component amino acids, followed by deamina-tion, removal of the amino group. Finally, each of the 20 amino acids is converted to either pyruvate, acetyl-CoA, or one of the other intermediates in the Krebs cycle, for further oxidation. Free amino acids are not stored in the body. Excess proteins in the diet thus must be eliminated by the mechanism just described. Deamination releases ammonia to the blood, which can be toxic and must be rapidly removed. This can be accomplished by incorporation into new amino acids or by excretion either directly as ammonia (fish), uric acid (birds and reptiles), or urea (mammals).

Other categories of resource

Two resources are said to be perfectly substitutable when either can wholly replace the other. This will be true for seeds of wheat or barley in the diet of a farmyard chicken, or for zebra and gazelle in the diet of a lion. Note that we do not imply that the two resources are as good as each other. This feature (perfectly sub-stitutable but not necessarily as good as each other) is included in Figure 3.27b by the isoclines having slopes that do not cut both axes at the same distance from the origin. Thus, in Figure 3.27b, in the absence of resource 2, the organism needs relatively little of resource 1, but in the absence of resource 1 it needs a relatively large amount of resource 2.

Proximate and ultimate causes of breeding failure

It is important to recognize that observational studies lead to assessments about the relative importance of proximate factors influencing breeding success and the causes of failure. However, there may be other ultimate factors that affect breeding success indirectly. Knowledge of these ultimate factors may be useful not only in improving understanding of population processes, but also in identifying factors that may be susceptible to management for conservation purposes. An example is the finding that Cirl Bunting Emberiza cirlus nestlings in a threatened population frequently succumbed to predation and starvation (Evans et al. 1997). Analysis of the weight gain rates of nestlings showed that young in broods that were taken by predators or starved both had low growth rates and that broods that survived grew considerably faster. This suggested that habitat management to improve the food supply might reduce both causes of nestling loss.

Definition of Home Range

We do know that members of some species, probably many species, have cognitive maps of where they live (Peters 1978) or concepts of where different resources and features are located within their home ranges and of how to travel between them. Such cognitive maps may be sensitive to where an animal finds itselfwithin its home range or to its nutritional state for example, resources that the animal perceives to be close at hand or resources far away that balance the diet may be more valuable than others. From extensive research on optimal foraging (Ellner and Real 1989 Pyke 1984 Pyke et al. 1977), we know that animals often rank resources in some manner. Consequently, we might envision an animal's cognitive map of its home range as an integration of contour maps, one (or more) for food resources, one for escape cover, one for travel routes, one for known home ranges of members of the other sex, and so forth.

Evaluation of Specific Resistance K2

The Kozeny-Carman relationship (Billings and Wilder 1970 Carman 1956) is often used to describe pressure drop across a dust deposit. Rudnick and First (1978) showed that the Happel (1958) cell model corrected for slip flow gives better K2 estimates than the Kozeny-Carman relationship for a dust cake with no interaction between the fabric and cake. All theoretical models for K2 are sensitive to dust deposit porosity and dust particle size distributions. Porosity cannot usually be estimated correctly and varies with filtration velocity, humidity, and other factors. Whenever possible, K2 should be measured rather than calculated from theory. Leith and Allen (1986) suggest that the dust collected on a membrane filter and K2 should be calculated from the increase in pressure drop (AP2 - AP1) with filter weight gain (M2 - M1) as follows

Effects of Acorns on Mice

Tree seeds, and acorns in particular, are an important part of the diet of Peromyscus, forming the bulk of the winter diet (Hamilton 1941, Batzli 1977). Increases in the abundance of Peromyscus have been associated with large acorn crops (Hansen and Batzli 1978), and declines have been associated with mast failures (Hansen and Batzli 1979). The mechanisms for population increase following good acorn crops include winter breeding, increased overwinter survival, and earlier onset of breeding in the spring (Hansen and Batzli 1978). Winter breeding is uncommon, but it has been observed in eastern populations during years of good acorn crops (Wolff 1986). Similar relationships have been reported in English oak woodlands for Apodemus sylvaticus, whose ecological role is similar to P. leucopus (Watts 1969, Flowerdew 1972). In most years, the abundance of Peromyscus in the spring is positively correlated with seed production during the previous autumn (Gashwiler 1979, Kaufman et al. 1995),...

Effects Of Travel Distance On Return Rates

Projecting return rates beyond the actual distance that separates Courthouse Rock and the terrace at the Skidmore site illustrates the mathematical logic of the CPF model. Figure 3.6 represents in graphic form the decline and convergence of return rates as round-trip distance from the central place increases (Figure 3.6). Simulation results also highlight an important caveat with regard to resource rankings namely that they may be somewhat misleading when based on return rates while foraging, as in the diet breadth and patch choice models, rather than the rate of delivery to a central place, as in the CPF model. When travel costs are set at zero, rankings sort out first by habitat, second by domestication status, and finally by species. That is, floodplain options must be exhausted before any hillside options rise to the top-ranked position within habitats, domesticated resources always outrank wild ones within ecological status categories, Iva always outranks Chenopodium. The...

Identifying And Interpreting Weasel Diets

The nutritional value of each prey is related to its body size. We can see which items are the most profitable for weasels to hunt and eat by calculating the diet in terms of the weights of the various types of prey eaten rather than their number. The imbalance between large and small items is then corrected, because, for example, seven birds' eggs at 3 g each count the same as two mice at 10 g or one meal of 20 g taken off a dead rabbit. In a sample from which ten birds' eggs, eight mice, and six meals of rabbit were identified, the total weight of prey eaten would be 30 + 18 + 120 230 g, of which eggs contributed 13 , mice 35 , and rabbits 52 . That looks quite different from the same data expressed as percentage frequency of occurrence, that is, eggs 42 , mice 33 , and rabbits 25 . Wherever possible, we have standardized the data by recalculating all the results as the number of each item counted as a percentage of all items. This is not, in fact, the best way to compare the diets...

Foods Of Common Weasels In Britain And Western Europe

Figure 5.2 Some representative examples of the food habits of local populations of long-tailed weasels. (a) Manitoba (n 200, Gamble & Riewe 1982) (b) Ontario (n 34, Simms 1979b) (c) Pennsylvania (n 112, Glover 1942b) (d) New York (Hamilton 1933) (e) Colorado (n 84, Quick 1951) (f) Iowa, (n 166, Polderboer et al. 1941). Prey designated as in Figure 5.1A. The first general study of the foods of common weasels (and stoats) in Britain was that of Day (1968) (Figure 5.3i). Day's work has been widely quoted, and for many years was the only British study to include animals of both species of weasels collected (mostly from gamekeepers) from all over the country. His identification key to the hairs of the small mammals of Britain (Day 1966) opened the door to many later studies. Recently, McDonald et al. (2000) (Figure 5.3j) made a second comparative study of the two species, also from carcasses collected from gamekeepers across Britain. In both studies, small rodents dominated the diet of...

Bc 1200800 Bc 17001200 Bc

Section we discuss long-term trends in plant and animal use. We document changes in diet breadth that occurred from 1200 BC through AD 1150. Detailed investigations of the kinds of plants included in the diet and, eventually, dropped from the diet, provide further evidence for the increasing importance of cultivation after AD 150, contrary to B. Huckell's (1995) claim that Early Agricultural period subsistence economies were produced by sedentary, maize-dependent intensive farmers. In the fourth section we discuss, as a triggering event, the introduction or in situ invention of high-quality pottery vessels, that initiated an increase in the

Foods Of Least Weasels In North America And Northern Eurasia

Every year the tundra is occupied by vast flocks of migratory birds that forage and nest on the ground. During summers of lemming crash years, these birds become unwilling providers of eggs and young for hungry least weasels. In the lemming crash year of 1969 at Barrow, the nests of sandpipers and Lapland long-spurs suffered heavily. In such straitened circumstances, least weasels also kill less favored alternative prey, such as shrews, and scavenge carrion of large animals they could not kill themselves or leftovers from kills made by large predators (Nasimovich 1949). Averaged over many years, as in the long collection from the Arkhangelsk region in the far north of European Russia, these various subsidiary resources give a false impression of variety in the diet of the northern least weasels (Figure 5.3b). By the following winter, the migratory birds have returned south, the seasonally active mammals have gone into hibernation, and subzero air temperatures freeze carrion solid and...

Data Used In This Study

The same plant assemblage also has high ubiquities among many wild plant taxa. Instead, our approach compares assemblages from different prehistoric intervals, using the concepts of behavioral ecology as guidelines for evaluating changes in the organization of subsistence. Our ultimate goal is to resolve debates about the degree of foraging versus farming. We assume that prehistoric subsistence practices differed to the extent that the diet breadths were different, and to the extent that the kinds of resources that were used were different with respect to their phenology in space and time.

Special Issues In Ecotoxicology

Nutrition of test organisms is one of the most important variables in the conduct of any biological experiment. Deficiencies of vitamins, minerals, and other nutrients in the diet of captive and freeranging fish and wildlife can result in skeletal deformities, cataracts, histological lesions, abnormal behavior, and many other abnormalities. Excessive amounts of vitamins and minerals have also resulted in abnormalities. The quality of commercial or experimentally prepared diets of captive animals as well as diets consumed by wild animals can influence the acute and chronic toxicity of test compounds. Chapter 44 (Hamilton and Hoffman) examines interactions between nutrition and potentially toxic trace elements and interactions among trace elements. Limited information from dietary studies with trace elements, especially selenium, reveals that diet can have a profound effect on toxicity observed in contaminated ecosystems, yet water-quality standards are rarely derived taking this factor...

Working Memory and the Prefrontal Cortex Working Memory

One area in which foraging theory has successfully addressed issues of cognitive mechanism is the influence of previous experience with prey on foraging decisions. Many researchers have examined this issue theoretically and empirically (Devenport and Devenport 1994 Hirvonen et al. 1999 Kacelnik and Todd 1992 Shettleworth and Plowright 1992 Stephens 1987). Hirvonen et al. (1999) formulated the problem as follows Ideally, foraging decisions are made with complete information about the foraging environment. In the classic diet model, the decision to include a particular prey type in the diet depends on encounter rates with more profitable prey types (see chaps. 1 and 5). Foragers are not omniscient, and their only source of information about encounter rates is their memory ofprevious encounters with prey. Encounter rates may be stable or they may fluctuate, and how much they fluctuate can vary with time and place. How, then, should previous experience with prey be weighted in order to...

Conventional Approaches and Their Limitations Direct Observation

Direct observations have been widely applied to document the forage or prey used by a variety of species. Individual animals or groups are observed through binoculars as they graze or feed on an animal carcass. Observations at bird nests also have provided information on foods brought to juveniles (Errington 1932 Marti 1987 Bielefedt et al. 1992). The basic approach is simple and relies on limited equipment. For researchers studying herbivores, bite counts or feeding minutes by plant species are recorded. These values can then be translated into relative occurrence in the diet by comparing total bites or minutes of foraging and the contribution of each species to the total observed. Biomass consumed can be approximated by estimating the average mass per bite for each species incorporated in the diet (Smith and Hubbard 1954). Additionally, direct observations are useful in identifying differences in foraging among sexes or age classes (Illius and Gordon 1987). Unfortunately, this...

Responses Of Voles To Weasels

Voles can recognize and distinguish the odors of different predators and take appropriate action. For example, bank voles have a variety of antipredator responses to common weasels and stoats, but fewer reactions to foxes or polecats (Jgdrzejwski et al. 1993). This difference must surely be because in some habitats bank voles contribute more than half the diet of common weasels and stoats (Pekkarinen & Heikkila 1997), but less than 10 of the diet of foxes and polecats (Jgdrzejwski et al. 1993). A vole is safe from a fox in a narrow tunnel, and in the enclosure experiments reported by Jgdrzejwski et al., voles fled into tubes simulating underground burrows when presented with the odor of a fox. But a weasel can follow a vole into a tunnel, so voles presented with the odor of a weasel avoided the tubes and reduced their overall activity for as long as a day or more (Jgdrzejwski et al. 1993 Bolbroe et al. 2000). These antipredator reactions certainly seem to be innate and of long...

Grazing by wild pigs and bears

Bamboos also form around 70 of the diet of some spectacled bear Tremarctos ornatus populations in Venezuela, though this is unusual. Bromeliad hearts (outer leaves are torn off and discarded) are usually the most important part of the diet, though other leaves, fruits and nuts are collected from the tree canopy by these agile climbers. They often make nests high in the trees and sleep in them. Spectacled bears are the most caring and affectionate of mothers, taking care of their young in dens and staying with them for 3 whole years. Both these bears eat carrion at times and the spectacled bear occasionally kills small calves, but clearly their most important influence is on the population size and reproduction of the plants they live on.

Diet of Eurasian otters in Shetland

Table 7.1 lists all species that I recorded as part of the Shetland otter diet (Kruuk and Moorhouse 1990). This includes only those observations where an animal was actually seen swimming before catching a prey, and not those cases when I came on an otter eating on the shore. This often happened with large prey such as lumpsuckers Cyclopterus lumpus (Fig. 7.4), a bright red fish that took a long time to consume, or dogfish Scyliorhinus canicula (a small shark) (see Figs 7.2 and 8.10). It was less often that we saw otters catch any of these big fish, and I had to be careful not to distort the diet record towards large fish as it was, they were an insignificant, though spectacular, part of the list of species caught. Apart from lumpsuckers and dogfish, we also found otters with large cod Gadus morhua, ling Molva molva, conger eels Conger conger, octopus and various others, although more rarely. Lumpsuckers were an interesting prey, because of the sexual discrimination by In terms of...

Microbes In And On Foodstuffs

Because of the intimate association of microbial consortia and the substrate they are decomposing, both are ingested by detritivores. It is the microbial material, rather than the substrate that may serve as the primary source of nutrients (Berrie, 1975 Plante et al., 1990 Anduaga and Halffter, 1993 Gray and Boucot, 1993 Scheu and Setala, 2002). Scanning electron micrographs show that millipedes, for example, strip bacteria from the surface of ingested leaf litter (Bignell, 1989), and similar to cockroaches, they can be found feeding on corpses in advanced stages of decay (Hoffman and Payne, 1969). Most foods known to be included in the diet of cockroaches in natural habitats are profusely covered with microbes. Bacteria and fungi are present on leaves before they are abscised, and their numbers increase rapidly as soon as the litter has been wetted on the ground (Archibold, 1995). The floor of a tropical rainforest is saturated with microbial decomposers, and as decay is...

Reticulate evolution and chocolate

Dillinger et al. (2000) have provided an overview of the medicinal uses of chocolate. From its original application by the New World Maya, Olmec and Aztec civilizations through the early twentieth century, there were a number of ailments commonly treated through the ingestion of the product from the beans of Theobroma cacao (i.e., cacao or chocolate). These medicinal applications included a mechanism to generate weight gain in emaciated patients nervous system stimulation for apathetic or exhausted individuals and the improvement of digestion, kidney, and bowel functions (Dillinger et al. 2000). Though these same benefits could be derived from some of the current-day cacao products as well, the current use of these products is as a confection rather than a medicine (Ariefdjohan and Savaiano 2005).

How Insects Overcome The Glucosinolatemyrosinase System

Despite their toxic potential, certain insect herbivore species use glucosinolate-containing plants as their major or sole hosts, and may even employ glucosinolates or their hydrolysis products in host location.1'2 These insects must have developed the ability to circumvent the toxic effects of glucosinolate hydrolysis products, but, until recently, little was known about mechanisms that enable herbivores to overcome the glucosinolate-myrosinase system. These mechanisms may depend on the proportion of glucosinolate-containing plant species in the diet. Certain generalist insect herbivores that feed on a variety of species including Brassicaceae may have the capacity to detoxify isothiocyanates to a certain extent. Conjugation with glutathione by glutathione-S-transferases has been suggested as one route of isothiocyanate metabolism29'4951 since glutathione-S-transferase activity is induced in some insects upon ingestion of isothiocyanates or glucosinolates. While the reaction of...

Experimental Manipulations

Figure 5.2 Relationship between 13C signatures of the diet of equilibrated plasma in black bears (Ursus americanus, ( ) and polar bears (U. maritimus, (A). Copyright 1996 Hilderbrand et al. Reprinted by permission of the Canadian Journal of Zoology. Figure 5.2 Relationship between 13C signatures of the diet of equilibrated plasma in black bears (Ursus americanus, ( ) and polar bears (U. maritimus, (A). Copyright 1996 Hilderbrand et al. Reprinted by permission of the Canadian Journal of Zoology. Figure 5.3 Relationship between 15N signatures of the diet of equilibrated plasma in black bears (Ursus americanus, ( ) and polar bears (U. maritimus, (A). Copyright 1996 Hilderbrand et al. Reprinted by permission of the Canadian Journal of Zoology. Figure 5.3 Relationship between 15N signatures of the diet of equilibrated plasma in black bears (Ursus americanus, ( ) and polar bears (U. maritimus, (A). Copyright 1996 Hilderbrand et al. Reprinted by permission of the Canadian Journal of Zoology.

Deferred Return To Breeding Areas

Most of the first-year shorebirds that stay in 'wintering areas' show no sign of pre-migratory fat deposition or spring moult into breeding plumage, but remain light in weight and in well-worn winter plumage until the next 'post-breeding' moult in late summer into new winter plumage. In other individuals, 'pre-breeding' moult and fattening are much delayed, sometimes into July, too late for the birds to breed that year (McNeil et al. 1994). Lack of both weight gain and 'pre-breeding' moult was apparent among juvenile Curlew Sandpipers Calidris ferruginea in South Africa, among Turnstones Armaria interpres in Scotland, and among Western

The New World diet of the river otter

In none of these studies was the size of fish taken by otters measured. Overall, however, the diet of the North American river otter, mutatis mutandis, can be described in the same terms as that of the Eurasian otter the vast majority is fish of virtually all species, with emphasis on the slow-moving and bottom-living ones. These animals also take crayfish and some other invertebrates, and a few other odds and ends such as amphibians and reptiles, birds, insects and small mammals.

The differences in defence against parasites across the four groups of social insects

And transmission (Section 2) are normally not compensated by opposite differences in individual or collective defence (this section). The annual social bees and wasps face higher risks of introducing infections in their colonies when returning from foraging trips because they are more likely to ingest contaminated food away from the colony and have less effective filtering devices to prevent per os infections. Their individual antibiotic defences seem less general and elaborate, and their allogrooming, hygienic behaviour and waste management practices are generally less well developed or less frequent. Although task partitioning probably occurs in all major groups of social insects, physical worker castes that would help in defence against disease are restricted to the perennial ants and termites. In fact, the only factor that is not unambiguously pointing towards a significant advantage in disease defence for the long-lived, perennial societies of ants and termites is intracolonial...

Improving Sample Resolution And Information Content

There may be ways to enhance the information obtained from conventional approaches to examining food habits. Fecal samples are still the most convenient, nonintrusive method to examine food habits of vertebrates. Methods are currently available and others are being developed that may increase the infor mation obtained from such samples. Steroid concentrations (especially estrogen) have been used to examine pregnancy rates among free-ranging mammals (Kirkpatrick et al. 1990). This technique could be modified to distinguish male- and female-derived fecal samples. Even greater sample resolution is possible by using emerging molecular techniques. As indicated earlier, fecal samples contain epithelial cells shed from the intestine walls of the animal depositing the sample. DNA extracted from these cells has been used to identify the species that deposited the sample. Recently, several investigators have used this approach to identify sex and individual genetic markers (Kohn and Wayne 1997...

The Impact of Host Quality on Fitness

Host quality influences three main components of parasitoid fitness survival to the adult stage, size and development time (Waage and Godfray, 1985 Godfray, 1994). Size and age are usually considered the most important measures of host quality, although other factors, such as the diet a host feeds upon, are also important. Studies with a diversity of parasitoids indicate that host size strongly influences offspring survival and adult size, and that parasitoid size is positively correlated with other measures of lifetime reproductive success, such as fecundity, mating success and longevity. The relationship between host and parasitoid size is most direct for idiobionts, such as egg or pupal parasitoids, whose hosts are closed resources that do not change in size after parasitism. For solitary species, offspring fitness will be determined primarily by host size alone, while, for gregarious species, offspring fitness will be affected by both host size and the total number of other...

Largescale food production and distribution

In 1900, 39 percent of the US population lived and worked on family farms of less than a few hundred acres. Food animals were raised in small herds or groups, and slaughtered locally. Due to the lack of refrigeration, meat, milk, and eggs were transported only a few miles from their origin, and then consumed locally and relatively quickly. Fresh produce was limited to what was in season. Overall, food production was done manually and was labor intensive. Mechanization increased productivity and promoted competition. Farms became larger in size, requiring more capital investment, and today less than 2 percent of the population lives and works on US farms (see Table 8.3). Food animals now are raised commercially in very large herds or flocks under conditions to maximize weight gain in short grow-out periods. Meat, milk, and eggs are shipped considerable distances and, due to refrigeration, are consumed later after harvest. Importation of produce and other crops has brought an end to...

Causes of Diet Specialization

Why does an individual forager use a given set of resources This is a problem often addressed with optimal foraging theory. Although optimal foraging theory has not always been successful in generating qualitative predictions of foraging behavior, it can serve as a rough tool to understand what makes an individual choose its resources. According to optimal foraging theory, an individual is expected to choose its diet from among available resources to maximize its expected fitness. This might be achieved by maximizing energy income per unit time, or by some balance between energy income and another goal such as risk avoidance. The diet of an individual then depends on a variety of factors such as the

Predaceous invertebrates

Predators often are undiscriminating in their diets, capturing whatever they encounter that is small enough to subdue. Aspects of the predator that bias it toward consuming more of some prey than others include sensory capabilities, foraging mode, and behavioral mechanism of prey capture. For prey, many aspects of body plan, life style, and behavior influence their vulnerability. These traits of predator and prey are not easily separated. From the many studies of the diet of predaceous invertebrates, usually based on gut analyses and behavioral observations, body size, prey availability, and prey vulnerability are of particular importance in determining what is eaten. Analysis of gut contents typically reveals a good correlation between what is eaten and what is available. In a small and relatively species-poor stream in southern England, the caddis Plectrocnemia conspersa and the alderfly Sialis fuliginosa during summer consumed prey roughly in proportion to their abundance (Hil-drew...

Industrial smog See smog

Insecta The largest class of arthropods (see Arthropoda) and the largest class in the animal kingdom. Most insects can fly. The body is characteristically divided into a head, thorax, and abdomen. The head bears a pair of antennae, compound eyes, and simple eyes (ocelli). The mouthparts are modified according to the diet. The thorax bears three pairs of five-jointed legs and, typically, two pairs of wings. The abdomen is usually limbless. Most insects are terrestrial and respiration is carried out by tracheae (branching tubes) with segmen-tally arranged spiracles (tiny holes opening to the outside). Usually the life cycle includes complete metamorphosis, with a larval and pupal stage, but in some species metamorphosis is incomplete - the larvae (nymphs) resemble the adult and there is no pupal stage. Many insects are beneficial, being pollinators of flowers and predators of pests others are harmful, being pests of crops, disease carriers, and destroyers of clothes, furniture, and...

Switching and Facilitation by Grazers Mechanisms Sustaining Biodiversity

The processes used by herbivores to choose what to eat are complex. Some situations conform to 'optimal' selection the composition of the diet reflects how the grazer may be able to maximize the input of energy for the minimal expenditure of energy used to acquire the food. In some cases, the consumption of different species is altered by the risks imposed in feeding. For example, venturing into open spaces to gain access to some species of plant that is not found in shade under trees may make the herbivore vulnerable to attacks by predatory birds.

The Emergence Of Obecity

The proliferation of anxiety about the obesity epidemic is in part mobilized by the experience in the United States. In the US, it is reported that 60 percent of the population is overweight, and 21 percent obese (Revill 2003). This has more than doubled in the last two decades, with obesity now rising by 5 percent per annum. This is not evenly spread through the population. There are serious health inequalities, with more than half of black women in low socio-economic groups being obese. One in five children is overweight. Obesity is estimated to account for 12 percent of health care costs, 100 billion and rising. The US has provided the emblematic marker for the rest of the western world to signify where other countries are heading and as a context to examine the causes of obesity, the problems it generates and possible solutions. In this chapter, however, we take a different turn and examine how the crisis of fat deposition has started to raise the visibility of the...

Selection from prey populations in Shetland

How does variation in fish availability affect the diet of Eurasian otters along sea coasts Which prey (species, size) do the animals select from what is available by season and site Within the range of fish available, as in Shetland, they specialize in bottom-living species they do not aim for open-water species such as mackerel, or saithe and pollack in summer. But does their specialization go further than that When taking bottom-living marine animals in shallow water, do otters specialize in any particular species, or do they take them opportunistically Specialization could consist of searching particular sites, or of decisions of whether to carry to the surface the prey items that they encountered on the sea bed.

Indirect Effects in Aquatic Systems

The previously made statements regarding the abiotic components (see above) can be emphasized with examples related to the importance of detritus. For instance, Carrer and Opitz found that in the Lagoon of Venice about half of the food of nectonic benthic feeders and nectonic necton feeders passed through detritus at least once, while there was no direct transfer of such food according to the diet matrix. Whipple provided an analysis of the extended path and flow structure for the well-documented oyster reef model. Few simple paths and large number of compound paths were counted. The study provided structural evidence for feedback control in ecosystems, and illustrated importance of nonliving compartments (in this case, detritus) for the ecosystem's functioning. Even for the model with a low cycling index (i.e., 11 ) multiple cyclic passage paths provided a considerable (22 ) flow contribution. Therefore, it was envisaged that for ecosystems with higher cycling indexes the patterns...

The predatorprey interaction

Whenever more than one type of prey is present, gut analyses generally find that prey that are abundant in the environment are also common in the diet (Allan 1981). However, the correspondence often is not 1 1, indicating some degree of preference. Prey choice can be strongly influenced by contrast, motion, and size, all of which serve to make certain prey more conspicuous. Many studies have established that predation intensity increases with prey size (Metz 1974, Allan 1978). Larger prey items are expected to be preferred because they offer a greater energy reward and simply because they are more readily detected. Feeding behavior often changes with experience and learning in vertebrate predators. Ringler (1979) found that brown trout preferred large prey (the mealworm Tenebrio molitor) over small (the brine shrimp Artemia salina) however, this preference developed gradually over 4-6 days and the least preferred prey never was completely excluded from the diet (Figure 9.6)....

Black Bears in the Oak Forest

The food habits of black bears have been examined throughout their range. Most data on food habits come from analysis of fecal droppings collected in the wild, but occasionally stomach contents from harvested or road-killed bears are available for studies. The comparison of forage data from different studies is difficult, because often different measures are used to describe relative importance. In addition, because a food's abundance may vary annually, short-term studies may not give a true picture of food habits. Despite these difficulties, it is apparent that acorns are an important fall food for black bears (Table 15.1). Acorns are not particularly important to bears in the northwestern United States, but they are an important part of the fall diets of black bears in the southwestern, northeastern, and in particular, the southeastern United States (Table 15.1). In each of these regions the proportion of acorns in the fall diet depends in large part on acorn production if acorns...

Impacts of Acorns and Oaks on Bear Populations

In general, animal home range size varies inversely with food production (Schoener 1983), and bears are no exception. For instance, bears in Virginia increased the size of their fall ranges twofold in areas of gypsy moth-induced acorn failure (Kasbohm et al. 1998). But, home range size also may depend on the complexity of the diet as was the finding in a study in Arkansas, where fall home ranges of bears feeding on acorns were smaller than summer ranges (27 vs. 97 km2) when bears fed on a variety of foods (Smith and Pelton 1994).

Parasitoid nutrient dynamics

With these life history correlations in mind, it is not surprising that most idiobionts are able to lay a few eggs after adult emergence, but further increases in longevity and egg production require host feeding and or access to non-host resources like nectar ( Jervis & Kidd 1986, Heimpel & Collier 1996, Rivero & Casas 1999). Using biochemical methods and dietary stable isotope signatures, more recent studies have also begun to unravel the contribution of larval and adult diets to parasitoid nutrient budgets. Nutrients that are acquired during the larval stage and used during the adult stage are referred to as capital reserves. Studies of the ectoparasitic idiobiont Eupelmus vuilleti indicate that adult females emerge with high capital reserves of lipid, sugars, and glycogen. Host and sugar feeding Given that koinobionts are unable to host feed, we would also suggest that many species have evolved compensatory strategies for enhancing the acquisition of nutrients during...

European hake Merluccius merluccius

Throughout life, hake feed almost entirely on pelagic prey. The young fish feed at first on copepods, later on larger planktonic crustacea such as euphausids, and also on small fish and small cephalopods. The diet of older fish consists almost entirely of fish and cephalopods. The hake is cannibalistic, and sometimes small hake comprise as much as 20 per cent of the food of the larger adults. In addition a large range of shoaling fish is taken. Bottom-feeding fish are seldom eaten and hake appear to feed mainly at night, making diurnal feeding migrations from the 6.0-7.5 mm in length with a ventral yolk-sac which is resorbed within about eight days. When active feeding commences, the larvae take chiefly flagellates and small diatoms. As the larvae grow, larger diatoms, molluscan larvae, early stages of copepods and the larvaceans Fritillaria and Oikopleura are taken, the larvaceans being a particularly important component of the diet of plaice larvae, often forming virtually the...

Geographical variation in movement patterns within species

The two responses to change in food supply (delayed and simultaneous) found among rodent-eaters are not completely distinct, and different species of owls and raptors may be better described as forming a gradient in response, from the most sedentary at one end to the most mobile at the other. Moreover, the same species may show regional variation in movement behaviour depending on food supply, and the extent to which alternative prey are available when favoured prey are scarce. Examples of regional variation among diurnal raptors include Common Kestrel Falco tinnunculus and Hen (Northern) Harrier Circus cyaneus, in which the proportion of rodents in the diet differs from region to region. The more varied the diet, the less the chance of all prey types being scarce at the same time, the more stable are their local breeding densities and the greater the site-fidelity shown by individuals. Examples among owls include the Tengmalm's Owl Aegolius funereus, which has been described as a...

Food abundance and availability

For ground-layer plants that are the food of grazing birds, counts of leaves or seedling cotyledons can be done in quadrats or along transects. It may be useful also to score plants for signs of damage from grazing birds to give a measure of utilization as well as availability. This is especially useful when the plant structures being eaten vary little in their number per plant, size, and shape so that the researcher can easily judge what is missing. For example, by carefully scoring damage to the paired cotyledons of seedlings being grazed by Skylarks Alauda arvensis, it was possible to estimate the species composition of the diet and the dry weight of cotyledon material of each species being eaten per day. The diet species composition results agreed closely with an independent assessment based

Factors Affecting Acorn

The dietary proportion of acorns is influenced by a combination of factors, including acorn availability, food preference, and habitat structure. Acorn availability is probably the most influential factor in determining use. Availability is primarily related to oak composition of the habitat, acorn production, snow depth, edibility, and acorn persistence. Regardless of age, there is little difference between the diets of male and female turkeys (Korschgen 1973, Beasom and Wilson 1992). Juveniles (July-September) have a diet similar to that of adults (Hurst 1992). Healy (1992a) observed that young birds ate acorns as soon as they were available in the fall, and by mid-September poults could even swallow large northern red oak (Q. rubra) and chestnut oak (Q. prinus) acorns. Acorns were part of the summer diet for poults (2-24 weeks old) in Florida (Barwick et al. 1973). Acorn availability inevitably depends in part on the species of oak and their abundance in the habitat. As would be...

The Link Between Reproductive Success and Food Supplies

One possible cue indicating conditions favoring good breeding success could be a reproductive hormone in the diet. If stoats or weasels eating live rodents in breeding condition could absorb rodent gonadotropins in viable form, their own reproductive processes could get an unusual boost that they cannot get from eating nonbreeding rodents or other meat. A similar theory was proposed for red foxes by Lindstrom (1988), but it has never been tested. According to Rodney Mead (personal communication), one of the most experienced researchers on mustelid reproductive physiology, this mechanism is impossible.

Stage one know your species

For many endangered species, we still know only cursory details of their life history and biology. Several early attempts to restore populations failed because not enough was known about their ecology to address, in an effective manner, the problems they were encountering. Thus the first stage is to know the life history, ecology, distribution, and numbers of the species concerned. A study of a small number of pairs will answer questions about the diet, habitat needs, and nest success. Studies of captive individuals have often been used to supplement studies in the wild, if necessary using related species to develop techniques and train staff.

Morphological mimicry

Examples of escape mimicry involving two or more species that are all hard to catch, though several candidates among tropical butterflies have been put forward 40 . However, an example in which an easy-to-catch mimic resembles a hard-to-catch model was given by Hespenheide 41 . He described an unusual and novel case of mimicry in which a group of Central American beetles, mostly weevils from the subfamily Zygopinae, mimic agile flies, notably robust-bodied species, such as tachinids, muscids, and tabanids. The weevils share common color patterns with the flies, which are unlike those of other beetles, none of which is considered distasteful. The weevils and flies share a behavioral characteristic that puts them in close association spatially most perch on the same relatively isolated and exposed tree boles at midelevation in the canopy. Hespenheide 41 estimated that flies accounted for between 65 to 70 of flying insects in the area, and yet work carried out on the diet of neotropical...

Acquisition of Nutrients

Carnivores often feed on prey with a similar nutrient and biochemical composition as their own, suggesting that the diet often is close to balanced. In contrast, herbivores and detritivores frequently encounter a nutritionally imbal-anced diet both in terms of elemental and biochemical composition. They, therefore, need to maximize the uptake of the limiting nutrient. This can be achieved either by selective feeding or by selective digestion and absorption of the limiting substance. Many animals are capable of selecting food particles of high quality. A prerequisite for this ability is that they must have a sensory system that enables them to assess the quality of the food particles as well as an ability to capture suitable particles. Such a system may be energetically costly to produce, maintain, and use. This appears to be a drawback, but this energetic cost can be counteracted by a higher growth efficiency when feeding on a high-quality diet compared to feeding on a low-quality...

Southern Pines as a Food Supply for Squirrels

Pine seeds are a seasonal staple in the diet of tassel-eared squirrels in the southern Rocky Mountains (Farentinos 1972) and also of fox squirrels in southeastern United States (Loeb and Lennartz 1989, Weigl et al. 1989, Wigley et al. 1989). Even in Kansas, where pines are not native, fox squirrels feed on seeds from young cones when they can find them, and do so as early as June (C. C. Smith personal observation). Pine seed kernels are high in protein and lipid content and energy concentration. Although pine seeds are an effective source of highly nutritious food, they are available to squirrels only until the seeds are shed from the cones. The seeds are small enough that an animal as large as a squirrel is unlikely to be able to compete with smaller mammals and birds to exploit individual seeds on the ground once they have been shed from the cones, and squirrels have not evolved cheek pouches that would allow them to carry and cache seeds after extracting them from cones. Squirrels...

POPs and the Food Chain

Feeding relationships are more complicated than the simple definition 'food chain' suggests. Some species feed on organisms in two or more trophic levels and change their food sources during their life history. Studies in this area, that include both an assessment of the trophic position and the body burden of the contaminants of interest, are scarce. An extensive work has been done in recent years in the Baltic Sea. Pollutant concentrations in aquatic animals are determined by the levels both in the surrounding water and in their food. Most persistent organic pollutants are found in greater abundance in aquatic animals than in the planktonic algae, but their concentration levels are strongly influenced by their chemical-physical characteristics. According to the study carried out in the Baltic Sea, two of the more toxic PCB congeners occur in higher concentrations in consumer organisms such as herring and cod than in phytoplankton. The same tendency has been demonstrated for the...

Individual Variability

The relationship between nutrition and toxicity is now known to be a major factor affecting toxic response. The effect occurs through altered absorption and renal function and by affecting toxin distribution in tissues. Fasting or low-protein diets may reduce cytochrome P450 activity. This can either increase toxicity (e.g., DDT) or decrease it (e.g., chloroform). Lipids in the diet delay absorption of lipophobic substances and enhance it for lipophilic substances. Essential fatty acids, such as linoleic acid, are important to the cytochrome P450s. Fatty tissues can store lipophilic toxins away from receptors. Thus, obesity actually protects against chronic toxicity of these compounds. However, high-fat diets enhance absorption and retention of lead and fluoride.

The nature of predator perception poor mimics appear perfect to their predators

More likely candidates are birds such as Phylloscopus, Sylvia and Hippolais warblers, and others such as stonechats (Saxicola torquata). All these feed on syrphids, but we know virtually nothing about their selectivity among syrphid species. What we would be looking for would be evidence that (i) birds had contact with noxious models (ii) they also took syrphids and (iii) the spectrum of syrphids upon which they fed was biased towards non-mimetic species. This sort of evidence is amazingly sparse in the literature. For example, Greig-Smith and Quicke (1983) noted that stonechats fed many warningly coloured ichneumonids and large numbers of syrphids to their nestlings, but we do not know what kinds of syrphids these were, and hence whether they might have been mimics. Similarly, we know that wheatears (Oenanthe oenanthe) feed bees and 'large Diptera' to their older nestlings (Cramp, vol. 5 779), but were these large Diptera bee mimics Then there are other birds such as Ficedula...

Evidence from ecological niches

Most species seem to occupy ecological niches in their wintering areas that are similar to those they use in their breeding areas. They occupy places with similar climate at the time they are there, habitats of similar structure, and take similar types of foods in similar ways. The actual plant species that comprise the habitat, or the plant or animal species that comprise the diet, may differ between breeding and wintering areas, but superficially they look much the same. However, some bird species make switches in climate types or habitats between seasons, such as inland marsh to open ocean, or forest to scrub, or they make switches in the types of foods eaten, such as insects to seeds. Extreme examples include the sandpipers that switch from tundra to seashore and from insects to worms and molluscs, or the skuas that switch from tundra to the open sea and from lemmings to fish. Hypotheses regarding the evolution of migration would generally predict 'niche-following' as primitive,...

Absorption and Excretion

Excretion of PCBs is generally poor, and highly dependent on the structure of individual PCB congeners. Plants can lose PCBs by volatilization to air (or dissolution to water) (due to a change in a parameter controlling equilibrium - e.g., PCBs may partition back to the air after an increase in temperature, or after a change to low PCB concentrations in air relative to the plant), by shedding of surface cuticular fragments and waxes, and by senescence of leaves. PCBs are generally not accessible to the sites of metabolism in plants. Animals do not excrete PCBs effectively in feces (except those unabsorbed from the diet) unless partitioning to feces across the gastrointestinal tract is favored (e.g., if the diet has very low PCB concentrations compared to those accumulated in the body). Excretion of metabolized PCBs is the dominant elimination route for animals, but there is very wide variation in the ability of organisms to metabolize PCBs, and wide variation in the efficiency of...

Forest resources and products

In some areas natural forests are simply plundered for their finest and tallest trees, often taking out a very small percentage of the trees present, but leaving an impoverished ecosystem that may never fully recover. Studies of the effects of such selective logging in Amazonia, Africa and South-East Asia, have compared animal populations in undisturbed primary forest with those in which only the valuable species have been removed. Despite differences in the flora and fauna across such vast distances, results of these studies are remarkably similar (Terborgh, 1992). Disruption of the forest canopy caused a decline in numbers of frugivorous (fruit-eating) birds and primates, particularly the larger ones. This probably results from the loss of important food resources. Numbers of leaf-eaters (foliovores) are often unaffected and may even increase when the regenerating vegetation provides more young leaves. On occasions when commercially valueless fig trees were poisoned an essential...

Life in a Fluctuating World Implications for Foraging Strategies

How does temporal variation in resource availability affect this switch point Assume that the preferred prey has a constant abundance, but the less preferred prey varies greatly and unpredictably in abundance. Such variation does not matter to inclusion of the better prey in the diet because its inclusion does not depend on its abundance. By contrast, temporal variation in the abundance of the preferred prey can influence the predator's decision regarding the poorer prey, and in particular, makes indiscriminate consumption more likely. Let R1(t) be a function of time that describes the dynamics of the preferred prey about an arithmetic mean abundance of R. Assume that predators can instantly and accurately assess resource abundance. Then, if R1(t) > R', the predator should specialize on resource 1 if R1(t) < R', it should generalize. Ifthe predator can assess average foraging returns only over some

Other Possible Factors In Population Declines

Recently, additional predation on migratory birds in the Mediterranean region was found unexpectedly to involve the Giant Noctule Bat Nyctalus lasiopterus (Popa-Lisseanu et al. 2007). This mammal has a wingspan of 46 cm, and was first suspected of eating nocturnal migrants from the appearance of feather pieces in its droppings. More recently, blood samples taken from live bats over the period March-October showed that the isotope signatures of 15N and 13C changed seasonally in precisely the manner predicted if the bats shifted from a diet of insects in summer to birds in autumn. In spring, when migrant numbers were lower, signatures indicated a mixed diet of insects and birds. This bat hunts by aerial pursuit, and the virtual absence of birds from the diet in summer suggests a seasonal specialisation on passing migrants. Interesting though these findings are, the bats themselves are rare and localised, and it is unlikely that they have any appreciable impact on the collective migrant...

Group Effects and Development

From both decreased weight gain per stadium and increased stadium length (Griffiths and Tauber, 1942b Willis et al., 1958 Wharton et al., 1968 Izutsu et al., 1970 Woodhead and Paulson, 1983). In P. americana, nymphs isolated at day 0 are one-half to one-third the size of grouped nymphs after 40 days (Wharton et al., 1968).The effect is cumulative, with no critical period. It occurs at any stage of development and is reversible at any stage (Wharton et al., 1967 Izutsu et al., 1970). Respiration of isolates may increase, and new proteins, expressed as electrophoretic bands, may appear in the hemolymph (Brossut, 1975 pers. comm. to CAN). The physiological consequences seem to be caused by a lack of physical contact (Pettit, 1940 Izutsu et al., 1970) and the presence of even one other individual can ameliorate the effects (Izutsu et al., 1970 Woodhead and Paulson, 1983). The means by which tactile stimuli orchestrate the physiological changes characteristic of the group effect in...

Growth of selected fishes

Results with Atlantic tomcod yielded somewhat different results. In contrast to the YOY winter flounder and tautog, two species that lost weight under piers, YOY Atlantic tomcod gained weight when caged in under-pier habitats, though weight gain under piers was not as rapid as weight gain at edges or in open water (Fig. 29.3). In fact, though growth under the pier was positive, it occurred at nearly half the rate as growth at pier edges or outside of the pier, a substantial discrepancy that could have important impacts on the overall recruitment success of juveniles to the adult population (Sogard, 1997 Beck et al., 2001).

Feeding behaviour and selfmedication

Differences in parasite virulence in relation to diet may be because the structural, physical or chemical properties of a particular food (e.g. host plant) alter parasite transmission because the diet influences the host's parasite resistance mechanisms, and hence susceptibility to the parasite or because of an interaction between these two factors. Determining the precise nature of the host-parasite-diet interaction is difficult, because these different chemical and physical components interact in ways that are often complex and non-addictive (Duffey and Stout, 1996). In the case of baculoviruses of insect herbivores like gypsy-moth larvae, it appears that leaf phenolics may present a chemical barrier to viral infection (e.g. Young et al., 1995). The precise mechanism by which this occurs remains to be established, but phenolic extracts from leaves that inhibit NPV activity cause the viral OBs to form large aggregations (though this does not appear to reduce their infectivity Keating...

Behavioural fever and chills

Many ectotherms, including insects, also exhibit a fever response to infection. However, this response is behavioural rather than physiological, as found by Kluger et al. (1975), working on the desert iguana (Dipsosaurus dorsalis). Since then, similar experiments have been conducted on a range of insects and their parasites. For example, the North American grasshopper Melanoplus sanguinipes, exhibits behavioural fever in response to infection by the lethal protozoan Nosema acridophagus. Grasshoppers kept at these fever temperatures survive longer and gain weight more rapidly than when kept at temperatures (6 C cooler) preferred by uninfected conspecifics (Boorstein and Ewald, 1987). However, fever is not shown in this same grasshopper species in response to infection by a closely related parasite, Nosema locustae (Hanley, 1989 cited in Ewald, 1994). Indeed, even when fever is elicited by a parasite, its effectiveness may depend critically on the susceptibility of the parasite to...

Scales Of Analysis And Data Resolution Requirements

Them apart from the wide range of alternative approaches to understanding change and transition in the archaeological record is their apparent small scale, fine resolution context of application, at the individual or small group level, rather than in terms of larger and longer-term societal level adaptive responses to external pressures. In their concise and straightforward characterization of optimal foraging theory, for example, Winterhalder and Goland (1997) contrast the diet breadth model with other proposed approaches to explaining domestication and agricultural origins in terms of scale and specificity. They describe most previous explanations as involving extensive variables such as population growth, climate change, and technological innovation, which are generalized and normative, and which operate on the system level extensive variables are those measures that summarize population wide, interspecific (community level) or long-term (multi-generational) aspects of things...

Effects of grazing on sward condition

Grazing differs fundamentally from cutting and burning in that it removes the vegetation piecemeal, and more selectively, at least at low to medium grazing intensities. Grazing also produces dung, and its associated invertebrates can be important in the diet of some birds, notably Red-billed Choughs Pyrrhocorax pyrrhocorax (Roberts 1982). Trampling by stock can create a continuity of bare

Context Of Rational Action

A more plausible objection to applying foraging theory to the commingled assemblages of archaeology has to do with the context of rational action. The diet breadth model, the foraging theory most commonly employed by archaeologists, is about the behavior of individuals in relation to the natural environment, yet for human foragers the social environment may well be more important. They live in groups of differing size and change their behavior accordingly. How much this matters depends on the nature of the social group, the interactions between its individuals, and the divergence in their interests. If foraging remains an individual affair, as frequently it does, the effect will be mainly one of competition larger groups may decrease resource abundance enough to reward individuals who expand diet breadth. Here groups change the behavior of individuals, but not the context of that behavior. Baumhoff 1982. E.A. Smith 1985). Of direct relevance here, Winterhalder and Goland (1993) (see...

Food supplies and fattening rates

When birds stayed at a site, their refuelling rates (as judged by weight gains) were often correlated with spatial and temporal variation in food supplies Figure 27.3 Relationship between food supply (aphid density) at a stopover site (left) tendency to stay and (right) rate of migratory weight gain in Sedge Warblers Acrocephalus schoenobaenus. From Bibby & Green (1981). In general, migrants seem to stay at a site for some days if they have a good chance of replenishing their depleted body reserves there, but move on if conditions are unfavourable for replenishment, presumably in search of more suitable habitat elsewhere (Rappole & Warner 1976, Biebach 1985, Kuenzi et al. 1991). This inference is supported by feeding experiments in wild birds (for Northern Wheatear Oenanthe oenanthe see Dierschke et al. 2003), and by laboratory experiments with Spotted Flycatchers Muscicapa striata and Garden Warblers Sylvia borin, in which migratory restlessness was greatly reduced during...

Statural Growth in Elephants

Size difference between the sexes is generally considered to be the outcome of selection favoring a larger body in males of polygynous species (chapters 3 and 4). While male and female calves seem to be similar sized at birth in both Asian and African elephants, differences in growth rate between the sexes become obvious by age 2-5 years, although one study at Etosha found a divergence in growth curves between the sexes only after 10 years (Lindeque and van Jaarsveld 1993). At about 10 years, when the elephants may be at the threshold of puberty, the male is distinctly taller and heavier than the female. There are hints of a secondary growth spurt in male African (Laws et al. 1975) and Asian (Sukumar et al. 1988) elephants during the postpubertal years, but this is by no means established as it has not been seen in any other elephant population for which growth has been studied. Female elephants attain their maximum height by age 20-25 years, but continue to gain weight for another...

The Archaeological Record

Setting all the theoretical objections aside, it is quite reasonable to ask, as Smith does, whether archaeological remains can be quantified with sufficient precision to demonstrate that patterns are more consistent with foraging theory than some alternative. It is equally reasonable to ask, as he also does, whether enough can be known about prehistoric environments to generate the rankings and estimates of abundance needed to model diet breadth. I share Smith's concerns about the quality of the archaeological record, but if excavated faunal and floral assemblages will not sustain inferences as to the relative importance of various foods, more than foraging theory is at risk a substantial fraction of any archaeological interpretation rests on knowing these things. Fortunately, we do not need to establish consumption in accordance with the diet breadth model at every site, any more than I need to be able to radiocarbon date every Rose Spring projectile point I find. Indeed, taken...

Concluding Remarks

Rates of weight gain, departure weights, frequency and duration of stopovers, and overall migration speed (2) carry-over effects of migration performance on subsequent survival or breeding success (3) which in turn influence population trend (Figure 27.2). Many studies have been concerned with the first aspect, providing evidence from stopover sites of interference and depletion competition, and of effects of disturbance and predation on the fuelling rates of individuals (involving some age and sex effects). Relatively few studies have provided evidence of migration conditions influencing subsequent breeding and survival, and even fewer of effects on subsequent breeding numbers. The paucity of examples of migration effects on breeding numbers may reflect the difficulties of study rather than the rarity of the phenomenon. Moreover, on all aspects, the evidence is based primarily on correlations, giving no direct evidence for causal relationships, although the provision of extra food...

Wintering Yellowhammers and Skylarks and their Seed Food Resources

In Britain, grain is an important component of skylark diet over the winter (Donald, 2004 Robinson, 2004). However, weed seeds are also present but usually compose only a small proportion of the diet (Wilson et al., 1999 Donald, 2004). This pattern may reflect the decline in weed species in farmland habitats. Because small seeds are more abundant in New Zealand, the foraging efficiency of the skylark may be similar or greater than that of skylarks feeding on supplies of large seeds in their native range. To understand the relative importance of small and large seed resources for skylarks in New Zealand, detailed studies of the weed seed composition and distribution are required as well as studies of skylark foraging behaviour and diet composition. More detailed comparative studies of the diet, foraging patterns, and population dynamics of bird species that inhabit both native and introduced ranges are required to understand better the influence of temporal variation in winter food...

Migratory fattening and restlessness

During the course of a journey, birds alternate periods of migratory flight (when body reserves are expended) with periods of stopover (when reserves are replenished through feeding). In general, periods of flight and refuelling must be integrated in such a way that leanness leads to feeding and fatness to migration. At departure and stopover sites, migrants have often been caught and weighed, and whereas lean birds are often recaught on subsequent days, as they gain weight, heavy (fat) ones are seldom recaught (Bibby & Green 1981, Yong & Moore 1993). Such findings imply that the fat levels of a bird influence its tendency to resume migration (Chapter 27 see also Dolnik & Blyumental 1967, Berthold 1996, Sandberg et al. 2002).

Brief History of Optimal Foraging Theory

A more subtle difficulty may have delayed the integration of foraging and danger the two models that dominated early tests of foraging theory, the diet and patch models, do not readily suggest ways to integrate danger (see Lima 1988b Gilliam 1990 Houston and McNamara 1999 for later treatments). Several graphical models dealt with predation and other aspects of foraging (Rosenzweig 1974 Covich 1976) and one chapter juxtaposed diet choice and antipredator vigilance models, both important contributions made by Pulliam (1976). Although the pieces seem to have been available, integration did not happen quickly. Even the early experimental tests treated danger as a distraction rather than a matter of life and death (Milin-ski and Heller 1978 Sih 1980). These studies would have reached similar conclusions if they had considered competitors rather than predators.

Mechanism of Biomagnification

Dietary Exposure A number of mechanisms have been proposed to describe the biomagnification process as it applies to persistent, hydrophobic organic compounds. The first model published to describe biomagnification of the insecticide DDT described the lipid co-assimilation mechanism. In this model, both lipids and contaminants are efficiently assimilated from food however, a smaller fraction of lipids are retained as a result of metabolism of these nutrients to satisfy energetic requirements. Recalcitrant contaminants are retained in tissues and over time, in conjunction with the number of feeding events, magnify in concentration over that of ingested food. Under this mechanism, the maximum biomagnification potential in nondeterminant growing animals is inversely related to growth-conversion efficiency (i.e., rate of tissue growth relative to food consumption) when contaminant elimination from the animal approaches a value of 0. For determinant growers, biomagnification will continue...

Consumption of carrion

Nicrophorus Breeding Milne

Arctic foxes (Alopex lagopus) illustrate the arctic fox a how the diet of facultative carrion- spp.) are the live prey of foxes over much of their range and for much of the time (Elmhagen et al., 2000). However, lemming populations go through dramatic population cycles (see Chapter 14), forcing the foxes to switch to alternative foods such as migratory birds and their eggs (Samelius & Alisauskas, 2000). In winter, marine foods become available when foxes can move onto the sea ice and scavenge carcasses of seals killed by polar bears. Roth (2002) investigated the extent to which foxes switched to carrion feeding in winter by comparing the ratios of carbon isotopes (13C 12C) of suspected food (marine organisms have characteristically higher ratios than terrestrial organisms) and of fox hair (since carbon isotope signatures of predator tissue reflect the ratios of the prey consumed). Figure 11.16 shows that in three of the 4 years of the study the isotope signature of fox hair samples...

The optimal foraging approach to diet width

These assumptions will not always be justified. First, other aspects of an organism's behavior may influence fitness more than optimal foraging does. For example, there may be such a premium on the avoidance of predators that animals forage at a place and time where the risk from predators is lower, and in consequence gather their food less efficiently than is theoretically possible (see Section 9.5.4). Second, and just as important, for many consumers (particularly herbivores and omnivores) the efficient gathering of energy may be less critical than of some other dietary constituent (e.g. nitrogen), or it may be of prime importance for the forager to consume a mixed and balanced diet. In such cases, the value of existing optimal foraging theory is limited. However, in circumstances where the energy maximization premise can be expected to apply, optimal foraging theory offers a powerful insight into the significance of the foraging 'decisions' that predators make (for reviews see...

Resources and Products in Industrial Systems

These materials and products are the output ofwhat is often a multistage production process carried out within the industrial system. Just as the diet of a carnivore depends on the consumption of plants by herbivores, the end-product purchased by the consumer requires many indirect as well as direct inputs. Large volumes of

Degradation and Bioaccumulation of Phthalates

Dehp Degradation

With some exceptions, bioaccumulation factors of phthalates are below 5000. The low bioavailability of the high molecular weight phthalate esters, as a consequence of their low water solubility and strong adsorption to (dissolved) organic carbon, is the main reason why these compounds too do not bioaccumulate to a considerable extent. It should be noted that although theoretical studies show that as much as 60 of the exposure of high molecular weight phthalates in predators could be derived from the diet, only limited data on dietary bioaccumulation have been reported.

Consumer regulation of nutrient cycling

Almost from the beginning of life on earth, organisms have evolved which consume primary producers. Modeling consumer regulation of nutrient cycling raises two major problems. First consumers have a very different chemical composition than primary producers. Many plant tissues are carbon rich because they have lignified cell walls, but consumers, having cell membranes rather than thick cell walls, are less carbon and consequently more nutrient rich. This difference in chemistry imposes a strong limitation on the efficiency by which plant biomass can be converted to consumer biomass and is consequently a major factor determining the diet of consumers. We will take up the problem of modeling stoichiometry, or the ratios of nutrients and carbon in plants and consumers, in the next chapter.

Causes of death and mortality rates

Survivirship Curve Southern Sea Otter

Sylvia Sikes related several signs of ill health in elephants in East African grassland habitat to arteriosclerosis or progressive thickening and blockage of arteries. This condition was much more common in habitats in which elephants had a diet dominated by nutritionally poor grass than in the riverine habitats in which they also browsed. She differentiated two major types of sclerosis. Medial sclerosis (deposition of lime on the artery wall), as a consequence of abnormal calcium metabolism or excessive vitamin D, was attributed to increased exposure to sunlight as well as an incorrect calcium-phosphorus balance in the diet. Another condition, atheroma (excessive fat deposits on the inner artery wall), also seemed related to a poor diet. The clinical significance

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