Population Ecology of Desert Rodent Communities: Habitats and Environmental Complexity

Abstract

We investigated the relative densities of granivorous, nocturnal desert rodents in small plots within two arid regions of Arizona to study how sympatric species avoid competitive extinction. The most common rodents were kangaroo rats, Dipodomys spp., and pocket mice, Perognathus spp. We attempted correlating the density of each species with several environmental measurements, derived from the soil's i) depth; ii) texture or iii) resistance to sheer stress; or from the plant's i) species diversity; ii) growth forms or iii) foliage density. Successful variables were derived from plant growth form and foliage density. The soil's resistance to sheer stress also seemed important for a few species. In general, kangaroo rats were associated with sparseness of vegetation; pocket mice with denseness. One group of mice, which we term bush mice, seemed to require bushes and included two Perognathus spp., three Peromyscus spp., and probably a harvest mouse (Reithrodontomys fulvescens). Two other Perognathus spp. were taken in grassy habitats. Some suitable habitats tended to be complementary to others, suggesting that species associated with them are competitors. Comparisons of the density and distribution of D. merriami, present in both regions but under different biotic circumstances, reinforces the opinion that competition is responsible for the complementariness of habitats. In some cases the evidence suggests that competitive coexistence is accounted for by the fact that different specializations are needed to escape predation in different environments. We use variables which correlate with the relative density of various species to construct a model of habitat complexity. The rodent species diversities obtained in our plots can be approximately accounted for by this model. The model is based on the premises that the rodents collectively discriminate four qualities of soil surface, and three heights and two densities of vegetation. In general, specializations based on biotic variables appear most important.

The Role of Microhabitat in Structuring Desert Rodent Communities

“…• I 4- To summarize, each species maintained utilization patterns distinct from those of other simultaneously-active rodents, even though microhabitat specificity changed seasonally. These and previous data (Rosenzweig and Winakur 1969, Brown and Lieberman 1973, Rosenzweig 1973, Wondoll'eck 1975 confirm that heteromyid rodents partition structural space, and that habitat discrimination can be remarkably fine-tuned.…”

“…Despite the lack of obvious seed partitioning, there remains con siderable evidence that heteromyid assemblages are competitively struc tured in North American deserts (Rosenzweig and Winakur 1969, Brown and Lieberman 1973, Rosenzweig 1973, Brown 1975, Wondolleck 1975. Brown (1973Brown ( , 1975 noted regular spacing of body size among coexisting species and inferred that coexistence is allowed by subdivision of a body size related resource.…”

Small mammal species diversity in brazilian tropical primary and secondary forests of different sizes

“…Several studies have shown that species compositions and relative abundances of small mammal communities can be partially explained by habitat structure and heterogeneity (ROSENZWEIG & WINAKUR, 1969;M'CLOSKEY, 1976;DUESER & SHUGART, 1978;AUGUST, 1983AUGUST, , 1984LACHER et al, in press; LACHER & ALHO, in press). Bird community studies have also revealed these correlations (JOHNSON, 1975;JAMES & WAMER, 1982;LYNCH & WHIGHAM, 1984).…”

Heterogeneidade estrutural e diversidade de pequenos mamíferos em um fragmento de mata secundária de Minas Gerais, Brasil

“…Enquanto alguns autores (M AcARTHUR & M AcARTHUR 1% 1; ROSENZWEIG & WINAKUR 1969;M'CLOSKEY 1976;ALHO 1981;FONSECA 1989;STALLlNGS et al 1990a) encontraram uma forte correlação entre estes fatores, outros têm falhado em demonstrar alguma relação (BOND et al 1980) ou encontram fraca associação (AUGUST 1983). Isto sugere que diferentes sistemas devem comportar-se de forma distinta e evidencia a necessidade de uma teoria geral que responda por estas di ferenças.…”