Behavioural adaptations of desert rodents (Heteromyidae)

Abstract

Abstract. Heteromyid rodents (kangaroo rats, Dipodomys spp.; kangaroo mice, Microdipodops spp.; pocket mice: Perognathus spp. and Chaetodipus spp.) make excellent models for answering questions about the evolution of diverse behaviour patterns. Most heteromyids, unlike other rodents, are nocturnal inhabitants of arid environments. As many as six species of these seed-eating mammals co-exist in habitats ranging from wind-blown sand and desert shrub to grassland and chaparral. A key question in the foraging literature is how desert granivores co-exist. Foraging choices are complex, and heteromyids optimize foraging based on interactions of multiple factors: size, distribution, energy, nutritional value and water content of seeds; soil density and texture; and their ability to cache and recover seeds. Another question of interest is how heteromyids avoid diverse predators in open habitats. Many heteromyids avoid visually hunting predators on moonlit nights by switching their activity from open microhabitats to shrub habitat. Kangaroo rats and mice escape by bipedal locomotion after detecting either low-frequency sounds made by predator movements, or snake odours. Two kangaroo rat species confront snakes by kicking sand and footdrumming. Comparative studies of heteromyids also can answer questions about the evolution of mammalian social organization, such as: how social are solitary rodents? Solitary heteromyids have a well-integrated social system promoted by the establishment of familiarity with close neighbours. Spatial overlap and delayed dispersal, which lead to temporary family groups and long-term occupancy of the same home ranges, facilitate neighbour recognition. Heteromyids of both sexes mate with familiar neighbours in both exclusive and multiple matings. A final question related to social behaviour is: how do mammals communicate in desert environments? Kangaroo rats communicate identity through scent deposited at sandbathing sites, and at least one species ( D. spectabilis), through individual footdrumming signatures. Both means of communication appear to be effective in sandy soils and open habitats. In conclusion, heteromyids can be used in future studies to examine a variety of behavioural patterns, ranging from individual foraging and predator defence to mating strategies and other social interactions.