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Diets of Black-Tailed Jack Rabbits in Relation to Population Density and Vegetation

1984; University of Arizona; Volume: 37; Issue: 1 Linguagem: Inglês

10.2307/3898830

2162-2728

Randal D. Johnson, Jay E. Anderson,

Fire effects on ecosystems

Diets of black-tailed jack rabbits (Lepus cutYfornicus) and composition of plant communities were compared among habitats that supported different densities of jack rabbits in sagebrush (Arlemisia tridentata)/perenniaI grass communities on the Idaho National Engineering Laboratory (INEL) in southeastern Idaho.Diets were more similar than vegetation among areas, indicating that jack rabbits feed selectively; winterfat (Ceratoides hata) and perennial grasses were staple foods, comprising about 80% of the diet in all areas.Jack rabbit densities were higher in areas having higher proportions of grass cover.Similarity between diet and vegetation was positively correlated with jack rabbit density and with the amount of grass cover in the habitat.Jack rabbits selected grassdominated areas for feeding at night and then fed as generalists on the grass species present.The black-tailed jack rabbit (Lepus californicus) is the most widely distributed jack rabbit species in North America (Hall and Kelson 1959) and has been described as flexible in habitat requirements (Vorhies and Taylor 1933).Although jack rabbits may not have rigid habitat requirements, researchers often have observed high densities of black-tailed jack rabbits in some local areas but not others (Vorhies and Taylor 1933, Phillips 1936, Wagner and Stoddart 1972).Factors promoting such patchy distributions are not understood.Some authors proposed that high densities reflect responses to environmental disturbances such as overcrowding and food shortage (Woodbury 1955); drought (Bronson and Tiemeier 1959); or the presence of succulent vegetation (Nagy et al. 1976) cultivated crops (Fagerstone et al. 1980), or abundant sagebrush cover (Adams and Adams 1959, French et al. 1965).In addition, black-tailed jack rabbit populations are thought to fluctuate sharply, cycling from low to high densities in 7 to IO-year periods (Wagner and Stoddart 1972, Gross et al. 1974).Because black-tailed jack rabbits use a variety of habitats, their diets are extremely variable.Jack rabbits are generalist herbivores (Westoby 1974); however, diets vary seasonally in response to forage maturity and availability (Vorhies and Taylor 1933, Hansen et al. 1969, Fagerstone et al. 1980).Grasses dominate the diet in spring and early summer, forbs become more important in late summer and early fall, and shrubs are selected in late fall and winter.Although general seasonal patterns of diet have been identified, recent studies in cold desert, shrub-steppe habitats (Westoby 1973, Uresk 1978, Johnson 1979) have yielded somewhat dissimilar results in terms of importance of specific food items.Johnson (1979) found that a variety of grasses comprised the bulk of the diet.Cheatgrass (Bromus tectorum)was an important diet constituent, but needle-and-thread (Stipa comata) was not.These results conflict with those of Uresk (1978), who found that needle-andthread was the most preferred food, whereas cheatgrass, though