Chicken Coop Plans

How to Build a Backyard Chicken Coop

Making your own chicken coop will probably be the best decision that you have ever made for your home. Why, do you ask? Building your own chicken coop does three things for you. First, it saves you a lot of money. Having someone else build a coop for you can set you back a lot of cash that you shouldn't have to spend. Second, you can build it how YOU want it done. A coop that comes with your house will likely not meet the specific needs of your flock. Third, you will look on what you have built with pride, knowing that you have built something lasting and high quality. This ebook teaches you how to build your own chicken coop from scratch without having to have any previous construction experience or much money at all. Make the coop that your flock deserves! Read more here...

How to Build a Backyard Chicken Coop Summary


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15 Chicken Coop Plans By Easy Coops

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15 Chicken Coop Plans By Easy Coops Summary

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Variation in Food Quality

Individual plants differ in their nutritional quality for a number of reasons, including soil fertility. Ohmart et al. (1985) reported that Eucalyptus blakelyi subjected to different N fertilization levels significantly affected fecundity of Paropsis atomaria, a chrysomelid beetle. An increase in foliar N from 1.5 to 4.0 increased the number of eggs laid by 500 and the rate of egg production by 400 . Similarly, Blumberg et al. (1997) reported that arthropod abundances were higher in plots receiving inorganic N (granular ammonium nitrate, rye grass cover crop) than in plots receiving organic N (crimson clover, Trifolium incarna-tum, cover crop). However, the effects of plant fertilization experiments have been inconsistent, perhaps reflecting differences among plant species in their allocation of N to nutritive versus nonnutritive compounds or differences in plant or insect responses to other factors (Kyto et al. 1996, G. Waring and Cobb 1992).

Wing Loss and Life History Tradeoffs

Food abundance and quality cannot be divorced from wing morphology because it is costly to produce and maintain the wings and their muscular and cuticular support (Roff and Fairbairn, 1991) insect flight muscle is one of the most metabolically active tissues known (e.g., Weis-Fogh, 1967). Flight behavior is also energetically demanding, and can alter the composition of hemolyph for up to 24 hr afterward in P. americana (King et al., 1986). These metabolic expenses place a significant demand on an insect's overall energy budget, and compete with other physiologically demanding life history processes. The best documented of these is egg production. Any easing of the selective pressure to maintain wings allows a female to divert more resources to egg production, increasing her fitness more than if she remained volant (flight-oogen-esis syndrome) (Roff, 1986, 1990 Roff and Fairbairn,

Physiological state and host use patterns

We know surprisingly little about the daily time window for foraging and its influence (see Casas 2000, for a quantification in the field). In collaboration with J. Casas, P. D'Ettorre measured the egg load of the parasitoid Pteromalus sequester attacking a seed weevil (Apion ulicis) on Ulex europeaus in the field over the entire daily foraging over three days. As shown in Fig. 3.2, the egg load declined over the day for this species, but did not reach zero. Why not lay all of the eggs Is the female unable to assess her own ovarian state closely enough Does the entire machinery of hormonal control and egg production maintain a minimal supply of eggs (see also Chapter 7 by Bernstein and Jervis) Is it optimal to behave in a way that leads to some small leftover at the end of the day, given the stochastic nature of host availability and metabolic needs This is not some oddity of this biological

Relationship between breeding and moult

Birds nesting in the high arctic have a very short season in which to raise young. They often have more synchronised and shorter breeding and moulting periods than closely related forms further south, and show more overlap between the different activities. For example, Snow Buntings Plectrophenax nivalis breed, moult and accumulate migratory fat within a period of only 10-12 weeks from mid-June, during which time food is very plentiful. They have one of the shortest nestling periods recorded among passerine birds (about 10 days), and while still feeding their young, the adults start moulting, shedding their flight feathers in such quick succession that for some days they can hardly fly. The whole moult is completed in about 4-5 weeks (Ginn & Melville 1983, Cramp & Perrins 1994). At the same time, they begin to put on weight for migration, leaving the bleakest breeding areas before the end of August. Many other arctic birds can only breed within this short period, postponing...

The Low Dose Issue and InvertedU Dose Response Relationships for EDCs

These types of inverted-U dose-response curves have been reported for drugs, such as DES, which stimulated the growth of the fetal mouse prostate at a low oral dose fed to pregnant mice of 0.02 mgkg_1d_1, a maximum stimulatory response occurred at 0.2 mgkg_1d_1, and a complete inhibition of prostate development occurred at 200 mgkg_1d_1. There are also examples of inverted-U dose-response curves for environmental chemicals, such as the chemical used to make polycarbonate plastic, bisphenol A. For example, in rat pituitary tumor cells, bisphenol A significantly stimulated a rapid (within 30 s) influx of calcium followed by prolactin secretion at the lowest dose that was examined (0.23 ppt) the greatest response occurred at 230 ppt, while the magnitude of the response decreased at 2.3 ppb, forming an inverted-U dose-response curve. In another study, human prostate cancer (LnCAP) cell proliferation was stimulated by bisphenol A, with the amount of proliferation increasing between 2 3 ppt...

Stress and Selection on Multiple Traits

A difficulty in making predictions based on G is that genetic interactions among traits, just like the genetic variance of traits, can change dramatically depending on environmental conditions particularly when these are stressful. For instance, there is a well-known interaction between development time and egg production (faster developing genotypes often have lower levels of egg production), but this interaction can change sign when organisms are exposed to stressful conditions such that rapidly developing individuals have a higher reproductive output.

Ecology of the Hudson River Zooplankton Community

Abstract Zooplankton in the Hudson River estuary include both freshwater and estuarine species and range in body lengths from microns to millimeters. Measurements of abundance and biomass as well as community rate processes indicate that Zooplankton do not generally exert significant grazing pressure on phytoplankton. In addition, recycling of nutrients by Zooplankton is not significant to primary producers because concentrations of dissolved nutrients are quite high in the Hudson and controlled by other processes. Zooplankton do provide an important linkage in the food web as they are key prey items for many young-of-year fish as well as fish that are primarily planktivorous throughout life. Long-term observations indicate many Zooplankton populations undergo regular seasonal cycles in abundance, typically with increases during warm, low-flow periods of the year. The invasion of the zebra mussel into the Hudson had strong impacts on Zooplankton in the freshwater section of the...

Zooplankton and the Zebra Mussel Invasion

Loss of phytoplankton as food is an obvious possible mechanism that couldlead to a decline inzooplankton. The most direct test of this idea, however, using available field data, is contradictory. Long-term records of egg production for Bosmina indicate little change in eggs per individual or clutch size following the invasion (Pace et al., 1998). Reproductive parameters are sensitive indicators of food limitation in zooplankton populations. Thus, the mechanisms whereby zebra mussels influence cladocerans are uncertain. Nevertheless, years of high freshwater flow and abundant zebra mussels are associated with reduced abundances.

The prelaying exodus of petrels

A different kind of 'within-season' movement is undertaken by some pelagic seabirds. Once they have returned to breeding areas, re-occupied nest-sites and re-established pair bonds, many procellariiform species leave their breeding areas for periods of days or weeks to feed up for egg production and incubation. In the process, they may travel to foraging areas hundreds or thousands of kilometres from the nesting colonies. For example, Manx Shearwaters Puffinus puffinus from Skokholm Island off Wales fly southwest to the Bay of Biscay off Spain during this two-week period, a major foraging area some 700 km from the colony (Perrins & Brooke 1976), while White-chinned Petrels Procellaria aequinoctialis nesting on South Georgia fly 2000 km northwest to the Patagonian Shelf off central Argentina, which is also a major wintering area for the same birds (Phillips et al. 2006). We must assume that any body reserves brought to the colony by birds on first arrival have largely gone by the...

Other changes that may be associated with inherited parasites

Beyond clutch size, extreme population sex ratio bias associated with sex-ratio-distorting microorganisms may select for alteration in female life history. If sperm limits egg production, selection on female life history is expected to favour reduction in development time and adult body size in favour of speed of development.

Evolutionary Shifts of Native Herbivorous Insects to Introduced Noncrop Plants

The short-winged morphs essentially lacked flight muscles and were capable of egg production earlier than long-winged morphs. On the flamegold tree, however, about half of the long-winged morphs also lacked flight muscles and thus were flightless. These individuals were also able to produce eggs earlier than long-winged bugs that were able to fly. Thus, selection apparently favored the maintenance of more individuals capable of flight in balloon vine areas, where flight was advantageous to enable bugs to locate new seed-producing plants throughout the year. In areas of flamegold trees, selection favored early egg production during the short period of the year when seeds were available.

Nutrient acquisition and allocation by parasitoids varies with life history

Nutrient acquisition and allocation strategies of parasitoids are strongly linked to two components of life-history (i) egg production and (ii) mode of parasitism. For the former, Flanders (1950) divided parasitoids into pro-ovigenic species that emerge as adults with a fixed complement of mature eggs and synovigenic species that continue to mature eggs during the adult stage. Pro-ovigenic parasitoids allocate nutrient reserves during the adult stage to maintenance, while synovigenic parasitoids confront the decision of whether to allocate reserves to egg production, maintenance, or both (Jervis & Kidd 1986, Heimpel & Collier 1996, Rivero & Casas 1999, Papaj 2000). Jervis et al. (2001) noted that para-sitoids actually exhibit a continuum of ovigeny that can be indexed. Relatively few species are strictly pro-ovigenic (ovigeny index 1) and synovigeny ranges from species that emerge with most eggs mature to species that emerge with no mature eggs (ovigeny index 0). Askew and...

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 Strong synovigeny has previously been associated with weak capital reserves compared to weak synovigeny or pro-ovigeny (Jervis et al. 2001), yet the preceding data suggest this is...

Lifehistory Constraints

Microparasites destroy tissue during replication, and thus their virulence is directly related to replication. In macroparasites, virulence is directly related to the density of worms in the gut and, in high-density infections with high virulence, density-dependent effects reduce egg production per worm (Fleming, 1988), so there is no intrinsic benefit to increased virulence (Anderson and May, 1991). Indeed, virulence may be decoupled from transmission under certain conditions. For example, in Strongylus species, nematodes that infect orally before migrating through the body, virulence is not caused by the adults but by the migrating larvae damaging tissue before they return to the gut to reproduce. In these nematodes, there is no clear relation between transmission and virulence (Medica and Sukhdeo, 2001). However, in trichostrongyles, such as H. contortus, where adult worms cause damage as they feed on tissue and reproduce, there is a positive...

The effects of physiological state on immune function can mask mimic or mediate tradeoffs

Figure 11.5 A schematic outline of possible relationships between immune function and reproduction. (a) In this model insect there are three immune components 1, 2, and 3. Component 1 represents changes in local immunity within the female reproductive tract. Component 2 represents a factor like phenoloxidase (PO) that is used by both immune function and reproduction. Component 3 represents other immune functions. (b) The predicted effects on disease resistance due to changes in the concentrations of immune components 1-3 induced by matching and egg production as shown in panel (a). The changes in concentrations of 1, 2, and 3 result in changes in disease resistance. Note the mixed effect of reproduction on disease resistance. Cho et al, 1998 Kim et al, 2005), and it is thought to be transported through the haemolymph to the ovary (Kim et al, 2005). If the hypothesis of Kim et al. (2005) is correct, egg production will not reduce PO activity in the haemolymph unless its uptake by the...

Is resistance affected by nutrient dynamics

Increases mortality or has other measurable fitness consequences when resources are limited (Rolff & Siva-Jothy 2003, Schmidt-Hempel & Ebert 2003). The prevalence of induced versus constitutive responses in immunity following parasite infection is also thought to have evolved, in part, to avoid the energetic cost of permanent defense. Support for this latter idea derives primarily from genetic modification of immune traits or selection studies. For example, mutations that constitutively activate systemic acquired resistance in plants increase resistance to certain pathogens but at the cost of reduced size and seed production (Heidel et al. 2004). Persistent activation of the pathways regulating antimicrobial peptide production in D. melanogaster also reduces fecundity presumably due to resources invested in defense molecules being unavailable for egg production (Zerofsky et al. 2005). As mentioned above, D. melanogaster selected for resistance to parasitoid attack produce more...

The power of a complete nutrient budget

To address these challenges, we conclude that quantified energy and nutrient budgets for both parasitoids and hosts are the only way to make sense of the myriad of evolutionary scenarios that can arise. The key advantage to this approach is that it enables us to assess the relative benefits and costs of different nutrient acquisition and allocation strategies. Building complete budgets is not an easy task but it is doable, even in small parasitoids. This is illustrated by the comprehensive total energy budget recently developed for the idiobiont Eupelmus vulleti that we discussed earlier in this chapter (Casas et al. 2005, see above). For this analysis, the sugar, glycogen, protein, and lipid reserves of single females at birth and death were quantified, as was daily maintenance. Each host feeding and oviposition event, along with the nutrient amounts acquired and invested in eggs, was recorded. The time of death was also used to compare model predictions in the presence and absence...

Utilization of reserves

In M. grandii, glycogen levels at adult emergence are below the maximum levels recorded in older, sucrose-fed individuals, indicating that glycogen reserves can be supplemented exogenously (Olson et al. 2000). Both the wasp D. insulare and the fly P. tricuspis can also supplement their glycogen levels when fed on sugar-rich materials (Fadamiro & Chen 2005, Lee et al. 2006). Glycogen mainly fuels somatic functions in insects (see above) and, according to Chapman (1998), contributes relatively little to egg production in comparison to lipid and protein reserves, but its role as a source of glucose in fueling ovigenesis should not be dismissed (Section 7.11). While parasitoid wasps generally can presumably synthesize storage proteins de novo from dietary amino acids, only those species that host-feed have a rich enough diet to be able to supplement or replenish their protein reserves from dietary 'income' to a significant degree. Many non-host-feeders are more likely to rely entirely...

Stoats as Introduced Pests in New Zealand

Across north america and Eurasia, both stoats and least common weasels are native predators that may attack introduced game birds in New Zealand, they are introduced predators that often attack native birds, many of them endemic. This simple fact makes a world of difference between the attitudes to small mustelids in the northern and southern hemispheres (McDonald & Murphy 2000). Regardless of their sins in chicken coops and on game estates, stoats and common weasels in their native countries have an intrinsic value that they do not have in New Zealand.

Statedependence of parasitoid foraging behavior

A priori, we would also expect females with a lower egg load to opt for feeding rather than for oviposition, when they have mature eggs in reserve and are thus faced with choice between the two behaviors (Chan & Godfray 1993, Briggs et al. 1995, Heimpel & Collier 1996, Jervis et al. 1996, McGregor 1997, Jervis & Kidd 1999). This has been confirmed empirically for host feeding parasitoids, both in the laboratory (Heimpel & Rosenheim 1995) and in the field (Heimpel et al. 1998). Note that this expectation assumes that females with a low egg load are in fact egg-limited and that the decision to feed would favor egg production rather than oviposition. This might not be the case, however, since a parasitoid female with oviposition opportunities that match her egg load would not be egg-limited and could prefer to host-search. Also, in the synovigenic parasitoids modeled here (see below) the female's food lacks the nutrients necessary to fuel any amount of egg production, so if...

Future work 7111 Empirical studies

Another important factor to consider is the nitrogen contained in nectar and honey-dew. Nitrogen may occur in typically minuscule amounts, but it could nevertheless make a significant contribution to egg manufacture either when (i) carry-over of EPRs is constrained due to poor larval feeding (Mevi-Schutz & Erhardt 2005, Jervis & Boggs 2005) or (ii) EPRs have been depleted post-emergence. However, in the host-feeder E. vuilleti, protein intake via blood meals has no effect on fecundity (Giron et al. 2004). Thus, there may be non-host-feeding parasitoids in which dietary nutrients are involved, to a significant degree, in egg manufacture, and so the resource compartmentalization scheme we adopted would not apply. Instead, at the most basic level, there would need to be one compartment involved in fueling both somatic functions and egg manufacture, while the other would be entirely devoted to egg manufacture (this might comprise only lipids). There may even be parasitoid species to...

The Optimum Sex Ratio is Context Specific

Within some species, individuals adjust their sex ratios in response to the quality of the environment in which they reproduce, producing more offspring of the gender likely to contribute most to their individual fitness. In this case, environmental conditions (local or potentially short-term) affect the optimum sex ratio and, consequently, the pattern of natural selection on it. Under these conditions, natural selection can operate on the sensitivity and responses of animals or plants to environmental cues until individuals produce either male- or female-biased offspring sex ratios (if either yields higher fitness than a 1 1 ratio). In this case, sex ratio adjustment appears to be the adaptive outcome of natural selection operating to optimize individual responses to changes in local environmental conditions. One example can be seen among the Seychelles endemic warblers (Acrocephalus sechellensis). These birds are territorial, but individual territories may differ greatly with...

Body Condition And Subsequent Performance

Among shorebirds nesting in the High Arctic, the extent to which body reserves are available for egg production may depend on climatic and other conditions in particular years, and may differ between protein and lipid. In one study, isotope analysis revealed that in several species egg protein was formed from terrestrial rather than marine foods, and hence was influenced by food eaten after arrival in breeding areas (Klaassen et al. 2001). On the other hand, in another study, eggs in the earlier clutches of Red Knots Calidris canutus and Ruddy Turnstones Arenaria interpres in the northeastern Canadian High Arctic were rich in 13C and 15N, which suggested that some residual marine nutrients were used in their production (Morrison & Hobson 2004).

Parasite Behaviours within the Host

In almost all cases, the host is treated as a black box, and parasite behaviours are usually defined and interpreted only within an ultimate context. However, the lack of proximate details illustrates the challenges to understanding the behaviour of parasites in their hosts. The major obstacles relate to the technical difficulty of observing parasites in situ. Almost all of our understanding of parasite proximate behaviours comes from observations made after the host has been opened and the parasites removed. These actions create dramatic changes in the parasites' environment, which render classical behavioural studies virtually impossible. Additionally, parasite responses may be state-dependent, and their proximate strategies will change with changing conditions in the host. For example, tapeworms alter their reproductive strategies in response to food deprivation in the host (Sukhdeo and Bansemir, 1996), and blood flukes reduce their blood feeding and egg production when in hosts...

Regulation of Zooplankton

Estuaries are areas with abundant and diverse food for consumers and in the Hudson some combination of bacteria, algae, detritus, and microzooplankton provide food for zooplankton. Does food limit the abundance of populations and overallbiomass of the community As noted above since the early 1990s, zebra mussels have caused a very large reduction of phytoplankton in the Hudson. The lack of a decline in freshwater copepods (Fig. 16.4) and the relatively constant egg ratios (eggs per female) in cladocerans indicate food limitation was not necessarily the reason for the changes in zooplankton that accompanied the zebra mussel invasion. There is evidence, however, of food limitation of egg production by copepods in the lower, saline portion of the estuary. Supplementing natural food levels with an edible algal species resulted in increased egg production by calanoid copepods relative to ambient conditions at most times (Lonsdale et al., 1996). Moreover, egg production rates were...

Ecology of reproduction and preimaginal development

Reproductive effort into discrete clutches and or breeding periods. Furthermore, the rate of egg production as well as the clutch size and time interval between clutches vary in dependence of the age of an individual flea (e.g. Vashchenok, 2001 see also Chapter 5). The reader should therefore bear in mind that these parameters represent components of fecundity rather than the entire lifetime fecundity (Poulin, 2007a). In practice, the lifetime reproductive success of a flea is rarely known (see Chapter 5 for several exceptions). In most cases, reproductive success has been evaluated by the number of eggs, larvae, pupae and or newly emerged imagoes produced by a female flea after timed contact with a host (Buxton, 1948 Alekseev, 1961 Vashchenok, 1993 Krasnov et al., 2002a, 2004a). Figure 11.4 (a) Mean ( S.E.) egg production per female and (b) egg survival ( ) in Xenopsylla conformis and Xenopsylla ramesis when feeding on Sundevall's jird Meriones crassus (white columns) and Wagner's...

Why does acute stressinduced immunosuppression exist

Furthermore, it is unclear whether stress-induced immunosuppression saves energy over the short term. For example, some mechanisms of stress-induced immunosuppression in vertebrates (e.g. apoptosis of precursor lymphoid cells leading to reduced lymphopoiesis see Trottier et al., 2008) require an initial increase in energy expenditure (Dhabhar, 2002). The need to suppress entire physiological systems to decrease energy demand may be more important for longer-term changes in energy expenditure (e.g. egg production) than for short-term flight-or-fight demands. Over the short term (e.g. minutes) insects do not seem to be energy-limited, even during intense activities such as flight (Chapman, 1998, p.220).

Mechanical Stimulation and Imposed Monogamy

Second, the imposed monogamy scenario is predicated on the assumption that multiple copulations within the first reproductive cycle confer benefits on female N. cin-era. In many insects, females profit from multiple matings because they can increase fitness via increased egg production and fertility (Arnqvist and Nilsson, 2000). A male, on the other hand, benefits by rendering females sexually unreceptive after mating, thus increasing the probability that his sperm will fertilize the majority of the female's eggs (Cordero, 1995 Eberhard, 1996 Gillott,

Age or Stage Based Models

The simple production model described in the previous sections assumes that all individuals in the population are more or less equals (e.g., the mean egg production per individual does not change over time, or the mean weight of each individual landed in the fishery does not change over time). In reality, there are additional demographic affects associated with the population age- or size-structure that could influence the dynamics of a given population. For example, older, larger fish contribute more eggs, or provide better parental care, etc., than younger, smaller fish. Furthermore, nearly all fishing gears are size-selective (i.e., small fish are less likely to be captured on large fish hooks, or the fishery operates in an area where only large fish reside) and it may take several years (even decades) for individual fish to grow to sufficient size that they become vulnerable to the fishing gear. These delays in production (production as seen by the fishery) are not sufficiently...

External interactions

It is also widely appreciated that variation in a given environmental variable might also influence responses to another. The simultaneous effects of two or more variables on survival, development, and egg production have been the subject of many studies, especially where insect pest species are concerned (Andrewartha and Birch 1954 Messenger 1959). Perhaps the most famous of these kinds of studies are those that were undertaken by Park, where the effect of environmental variation in insect performance was not only examined for single Tribolium (Coleoptera, Tenebrionidae) species, but also for the outcome of interactions between T. confusum and T. castaneum (Park 1962). Other studies of responses to two or more simultaneously varying parameters include several on diapause induction and termination (Denlinger 2002), and on the effects of temperature and hypoxia on development (e.g. Frazier et al. 2001).

Female influence

Females may also affect paternity by varying egg-laying rate. There is some evidence from Manduca sexta that a gradual decline in spermatophore mass is linked to egg-laying, since spermatophores within normally mated females show a greater decline in mass than those from females that were either prevented from egg laying or that had mated with castrated males (and therefore received a spermatophore with no sperm) (Sasaki and Riddiford, 1984). Svard and McNeil (1994) found that in Pseudaletia unipuncta (where paternity is also either first or second male), female egg-laying pattern differed depending on whether the first or the second male gained most of the fertilizations. Females were divided into those where the first male fertilized all the eggs and those where the second male fertilized all the eggs, and the number of eggs laid in the 4 days between the first and second matings was compared. When the first male had priority, not only was he more successful in sperm competition,...

Ro Cq N 1 eapD211

From this simplest of models, we can conclude that the mutant parasitoid that maximizes the product Cq aq optimizes its invasion capacity. When adopted by the resident population, this strategy cannot be invaded by any other strategy and, hence, is an 'evolutionary stable strategy' (ESS) (Maynard Smith & Price 1973). For this example, this conclusion is not particularly enlightening. A parasitoid should maximize its searching efficiency and increase its conversion efficiency. There may be a trade-off between these two parameters (i.e. energy used for searching is no longer available for egg production) but, if not, the parasitoids are expected to be at the physiological limit that maximizes the traits simultaneously.


For many models there comes a point at which the mathematical analysis becomes either too messy to be useful or impossible to conduct. When this occurs we are faced with two choices. First, we can resort to numerical and simulation techniques using computers, provided that we are willing to specify values for all of the parameters. Second, we can seek approximations that allow us to proceed further with the mathematical analysis. Often, our interest in a model focuses on cases where some parameter values are either very small (e.g., mutation rates) or very large (e.g., egg production in some fish species). In this section, we describe how to use such restrictions on the magnitude of parameters to find approximate values for equilibria and to perform approximate stability analyses. This material is more advanced and should be read only once you are comfortable with finding equilibria (section 5.2) and determining their stability (section 5.3).

Adaptive value

Wynne-Edwards (1962) has suggested that swarming, patchy distribution and the vertical migrations of zooplanktonts may involve aspects of social behaviour related to control of population density. By congregating within thin layers and moving up and down, animals which would otherwise be widely distributed in a homogeneous environment can compete for food without much risk of too seriously depleting the food stocks of the whole volume of water through which they pass. In many species the quantity of egg production varies with the food supply and therefore the number of progeny is to some extent regulated by the availability of food for the adults. In this way competition for food provides a natural mechanism which may prevent the population reaching a size which would over-exploit the food resources. Also, concentration of populations within thin layers or patches facilitates display behaviour in sexual competition, whereby reproduction may be limited at supportable numbers.


When several live prey are in sight, a weasel will kill one after another, and even search around for more, until it is exhausted. This is not because it enjoys killing, but because the entire sequence of killing behavior is instinctive and is set off by the sight of moving prey, whether or not the weasel is hungry. A weasel in a chicken coop is psychologically unable to ignore the fluttering of the live ones and settle down to eat one that it has killed. For a weasel, this behavior is completely logical, and has evolved because it is in an individual weasel's best interests to behave that way. In the wild, weasels never find prey as abundant as they are in a chicken coop. Most weasels do not know where the next meal will come from, and must search hard to find it. Consequently, when presented with more than one meal, a weasel will catch as many as it can, while it can, and store the extras for later. People do exactly the same thing when they buy more food at the grocery store than...

The grazing rate

Measurements of filtering rates and food intake in various herbivorous zooplanktonts indicate that, in high concentrations of phytoplankton, large numbers of plant cells are rapidly ingested, sometimes apparently in excess of the animals' needs. Some of these cells pass through the gut virtually undigested, suggesting a wasteful destruction of plant cells which has been termed 'superfluous feeding'. However, although superfluous feeding can be demonstrated for a time in laboratory conditions when food is exceptionally abundant, the filtering rate later reduces. It seems unlikely that in natural conditions much food is egested unassimilated. Normally, high rates of intake result in increased growth and egg production.

Mate Choice

Models constructed to investigate mate choice can be complicated by the existence of multiple mating. In many species (e.g., the majority of insects), females permit or actively seek multiple mating with different males, even though several female fitness costs of excess mating are known (e.g., additional time and energy devoted to mating, increased predation risk, higher chance of injury, higher probability of disease or parasite transmission, male-originating chemicals reducing female longevity or female fecundity). Nonetheless, the ubiquity and magnitude of this trait suggest large positive effects on female fitness. For example, a fresh supply of sperm can maintain egg fertility, accessory substances can increase egg production rate, and the mating act itself can stimulate egg production.


Hermaphroditic conspecifics (although schistosomes have separate sexes) and pass eggs (often with the host's faeces) out of the host. If resources become limited in the host, due to competition with other parasites, growth and egg production can suffer, as can be seen in experimentally induced, high-intensity infections with echinostomes (Mohandas and Nadakal, 1978).

Number of fleas

However, there was no effect on quantity (but not quality) of flea offspring between fleas parasitizing immune-naive and previously flea-exposed A. cahirinus (B. R. Krasnov and L. Ghazaryan, unpublished data see Chapter 11). In experiments by Gouy de Bellocq et al. (2006a) with X. conformis and M. crassus, fleas consumed more blood when they fed on previously parasitized than on non-parasitized animals. Among fleas that fed on previously parasitized animals, blood consumption was positively correlated with the initial leukocyte concentration of the rodents and negatively correlated with difference in leukocyte concentration between the first and 16th days of flea infestation, while there was no correlation between blood consumption in fleas that fed on control animals and any other immunological variable of the hosts, including the level of immunocompetence measured via the PHA test. Furthermore, mean egg production and hatching success of fleas were not related to either initial...

Adaptive sex ratios

Many more examples of biased sex ratios have been found in birds (see Komdeur and Pen, 2002 Pike and Petrie, 2003). As yet there is no single theory that can explain this adaptive behaviour, in part because the reasons seem to vary both within and between species. Timing of egg production, parental quality, environmental conditions, and helpers at the nest may all influence sex ratios. Furthermore, the mechanisms for sex ratio manipulation remain unclear. Non-random segregation of sex chromosomes, selective resorbtion of yolk, selective ovulation, sex-specific fertilization, and sex-specific inhibition of zygote formation are just some of the mechanisms that have been proposed (Pike and Petrie, 2003, and references therein). So far, molecular data have helped to demonstrate the existence of sex ratio allocation in birds, but there is considerable work to be done before we understand the adaptive reasons and the mechanisms for producing an excess of males or females.


Derive an expression for the fraction, k, of all eggs produced that contain the A allele, (b) Assume that each plant produces sperm in proportion to its egg production. Thus, the frequency of sperm carrying allele A will also be k from part (a). Show that, if mating occurs at random among gametes, and if B denotes the total number of eggs produced, we have

Vector Reproduction

Vector reproductive behaviour includes mating and oviposition. There are few reports of either being affected by infection, and changes in the former are unlikely, because most vectors have mated before they become infected. Reports of changes in oviposition behaviour are rare, because oviposition is often used as a measure of egg production and few studies have assessed the effect of parasites on egg retention as well as oviposition. However, El Sawaf et al. (1994) report that Leishmania major and L. infantum cause a significant reduction in both egg retention and oviposition in the sandfly Phlebotomus papatasi. A. stephensi and A. gambiae are being used to investigate the mechanisms underlying parasite-induced fecundity reduction caused by P. yoelii nigeriensis. Infection results in a significant reduction in egg production and egg hatch rate during an initial gonotrophic cycle after feeding on an infected host and also during subsequent gonotrophic cycles, when oocysts are present...

Egg manufacture

Eggs contain a small amount of yolk, which is mainly comprised of lipids (Le Ralec 1995), and it appears that few hydropic egg-producers practise host feeding (Heimpel & Collier 1996). Parasitoids that consume only non-host foods include both hydropic and anhy-dropic egg producers.

Allocation patterns

3 Extrinsic mortality selects for a concentration of egg production early on in adult life in smaller-bodied females (Jervis et al. 2001, 2003). Jervis et al. (2003) posited death due to desiccation as a likely selective factor in the evolution of the negative correlation between the ovigeny index and body mass.

Model assumptions

In our pro-ovigenic model, w represents the current egg load, i.e. all of a female's EPRs have already been converted to mature eggs by the start of adult life. In the synovigenic model, the female's EPRs and eggs are pooled in the same variable w. This means that there is no delay in egg production (a unit of EPRs is instantaneously transformed into an egg at oviposition). We assume that this is not an important shortcoming given that the parasitoid will be able to lay only a single egg per time interval. The assumption of an instantaneous conversion of EPRs into eggs implies that the parasitoid has an egg available whenever an oviposition opportunity arises (and w > 0).


The census size of a population often provides a starting point for unravelling population dynamics, although obtaining accurate counts of marine populations can be logistically challenging. One commonly used method, known as virtual population analysis, is based on commercial catches, although estimates derived in this way may be inaccurate for a number of reasons, including flawed reporting. Another approach is known as the annual egg production method. This combines estimates of the number of planktonic fish eggs with various population parameters, such as average female fecundity and population sex ratio, to obtain a size estimate of the total breeding population. This technique requires accurate identification of fish eggs, which can be problematic because multiple species produce eggs of a similar size and appearance. A recent study used species-specific probes in quantitative PCR reactions to determine just what proportion of codlike eggs in the Irish Sea had actually been laid...

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