A Theory of Habitat Selection

Abstract

A graphical theory of habitat selection is built in steps. The theory treats two species in an environment with two usable patch types in a matrix of unusable space. The first step assumes habitat selection is density independent and free of search costs. The second assumes density independence, and the third assumes neither. The first two steps produce results already known from earlier theories. The third, however, requires a new analytical device, the isoleg, which is a line in a two-dimensional-state space of the two species' densities. An isoleg is a set of points in such a density space, such that on one side of the set, individuals of a species optimize their foraging by being strict habitat selectors, whereas on the other side, they do so by using at least a bit of a poorer patch. The population dynamics of the competitors is analyzed using their isolegs. The isolegs allow us to deduce that the zero isoclines of the species are warped into nonlinear forms capable of producing competitive coexistence. It is shown that at the equilibrium point of this coexistence, there may be no overt competition remaining. The difficulties this presents to the field investigator are mentioned, and a modified definition of interspecific competition is suggested.

Density-dependent habitat selection: Testing the theory with fitness data

“…Rosenzweig, 1987a). Increased intraspecific density is assumed to increase the exploitation of limited resources and force individuals to occupy an ever-expanding range of habitats (Sv/irdson, 1949;Morisita, 1950 (cited in Rosenzweig, in press); Fretwell and Lucas, 1970;Rosenzweig, 1974Rosenzweig, , 1981. Habitat selection theory has been used to predict foraging behavior (e.g.…”

“…Habitat use is influenced by morphological, physiological and behavioral adaptations which place an upper limit on habitat expansion, and is constrained by the density-dependent demands of similar consumers (Sv~irdson, 1949;Grant, 1975;Rosenzweig, 1979aRosenzweig, , 1979bRosenzweig, , 1981Rosenzweig, , 1986Pimm and Rosenzweig, 1981). Other factors such as predation (Kotler, 1984;Price, 1984), mate selection (Rosenzweig, 1979b), and biogeographical and historical constraints no doubt also influence habitat use, but it is the effects of intra-and interspecific densities that have captured the imagination of evolutionary and behavioral ecologists.…”

Suitability of Butterflies as Indicators of Ecosystem Condition: A Comparison of Butterfly Diversity across four habitats in Gir Wildlife Sanctuary

“…The rich floral diversity in tropical forests promotes herbivores, many of which are generalists (Price, 1997). According to Rosenzweig (1981), diversity is enhanced by presence of specialists that exhibit distinct habitat preferences. So, Dedakri range had vegetational complexity and multilayered canopy which provided different sets of microclimates within the range.…”

Evolution of habitat selection: stochastic acquisition of cognitive clues?

“…On the other hand, species-habitat relationships are usually viewed as relatively predictable phenomena resulting from a simple optimization process (Rosenzweig, 1981). Our model shows that the evolution of habitat preferences could be as stochastic as the evolution of other species-speci®c traits.…”

“…These interspeci®c di erences have traditionally been interpreted as either (1) only a by-product of the physiological, morphological or bionomical interspeci®c di erences (Leisler, 1977), or (2) a result of di erent evolutionary histories (i.e., of independent evolution in di erent areas and consequent specialization to di erent habitats), or (3) a result of the interspeci®c competition followed by subsequent specialization to optimal habitats (Rosenzweig, 1981). Explanations (1) and (2) have some limitations.…”