Another interesting implication of the notion that habitats vary in quality is that we would expect organisms to evolve physiological or behavioral processes which increase their chances of finding, recognizing, and using higher-quality habitats. In fact, mechanisms for habitat selection are nearly ubiquitous in the natural world. Even sessile organisms exhibit habitat selection, albeit at the smaller spatial scales. Examples of microhabitat selection by sessile organisms include plants growing toward the light, or cnidarian colonies growing in directions that enhance the flow ofnutrient-rich water past their foraging polyps. However, the champions of habitat selection are mobile animals. In fact, one of the major advantages of mobility in animals is that it allows them to select different microhabitats or habitats in which to conduct different activities, instead of attempting to maximize every component of fitness at a single location. Animals are able to forage in some microhabitats which contain food and safety from predators, rest in other microhabitats which feature favorable abiotic features (temperature, moisture, light, etc.) and biotic features (protection from predators and ectoparasites), advertise for potential mates in microhabitats in which communication signals can be perceived over long distances, etc. At larger spatial scales, individuals can select some types ofhabitat for long-term use during reproductive periods (breeding home ranges or territories), other types of habitat for long-term use when they are not reproductive (e.g., juvenile home ranges, wintering areas), and still other types of habitat to use when traveling over long distances (migration or dispersal).
Just as habitat can be defined at different spatial scales, habitat selection can occur at the level of microhabitats, individuals, or populations. In each situation, habitat selection refers to the behavioral processes by which individuals choose particular locations for conducting particular types of activities. At the smaller spatial scales, habitat selection refers to the processes by which animals choose microhabitats to use for foraging, offspring production (e.g., oviposition or nest-site selection), courtship or mating, sleeping, or other activities. At medium spatial scales, habitat selection refers to the choice of areas in which individuals will spend extended periods of time, for example, the choice by natal dispersers of a new patch of habitat in which to establish a home range or territory. Finally, at larger (population level) spatial scales, habitat selection refers to the processes by which different individuals in the same population select a place in which to live. At this spatial scale, interactions between individuals within the population often play a major role in habitat selection. For instance, in some species newcomers are attracted to areas which already contain conspecifics (conspecific attraction), so that even if different areas contain the same biotic and abiotic features, newcomers are more likely to settle in areas that already contain members of their own species.
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