. Biology of the Heteromyidae. Heteromyidae. 642 BROWN AND HARNEY. ^Xi' Fig. 9.—a typical mound of D. spectabilis in the Chihuahuan Desert near Portal, Arizona. This mound is approximately 2 m in diameter, m above ground with burrows and chambers extending > m below the soil surface. Mounds frequently contain stored seeds and many commensal organisms. As major features of the landscape, these persist for many years and are utilized by many successive generations of banner-tailed kangaroo rats (see text and Jones, this volume). mice (, Bartholomew and Caswell, 1951; Eisenberg
. Biology of the Heteromyidae. Heteromyidae. 642 BROWN AND HARNEY. ^Xi' Fig. 9.—a typical mound of D. spectabilis in the Chihuahuan Desert near Portal, Arizona. This mound is approximately 2 m in diameter, m above ground with burrows and chambers extending > m below the soil surface. Mounds frequently contain stored seeds and many commensal organisms. As major features of the landscape, these persist for many years and are utilized by many successive generations of banner-tailed kangaroo rats (see text and Jones, this volume). mice (, Bartholomew and Caswell, 1951; Eisenberg, 1975; Webster, 1962; Webster and Webster, 1971, 1975, 1980, 1984). Be- havioral adaptations (, moonlight avoidance: Kaufman and Kaufman, 1982; Kotler, 1984fl;Lockard, 1978; Lockard and Owings, 1974; Price et al., 1984) also sug- gest the importance of predator evasion. Much of the influence of predation on community organization is probably subtle and indirect. There is increasing evidence that actual and perceived risk of predation influences the foraging and behavior and microhabitat use of individual rodents ( Bowers, 1988; Kotler 1984a. 1984^; Thompson, 1982Z7; see also references on moonlight avoidance, above). There is ev- ery reason to expect that these responses to predation should also affect allocation of re- sources and interspecific competitive rela- tionships in the community. Unfortunately, effects of predation risk on community organization are difficult to assess. There are few good "natural exper- iments," in which the intensity of predation or the occurrence of particular kinds of predators varies between regions but other variables that might affect community structure remain relatively constant. Be- cause most kinds of predator have extensive geographic and habitat distributions, most desert rodent communities probably expe- rience similar predation pressure. When the predators differ, many other environmental factors also vary, making
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