Date of Award

5-2009

Degree Type

Thesis

Degree Name

Departmental Honors

Department

Wildland Resources

First Advisor

Dr. Eugene Schupp

Abstract

Many factors affect foraging behavior of rodents, including predation risk, which is thought to influence seed selection and seed handling by desert rodents in patchy environments. Understanding forces that drive seed selection and seed fate can aid understanding of rodents' impacts on vegetation structure and dynamics. In a feeding arena study, we tested how indirect and direct predation cues influence seed selection and handling behaviors (e.g., scatterhoarding and larderhoarding) of two heteromyid rodents, Dipodomys ordii (Ord's kangaroo rat) and Perognathus parvus (Great Basin pocket mouse), foraging on three seed species. The indirect cue was shrub cover: one half of the arena had sagebrush shrubs present while the other half was free of shrub cover. Direct cues, presented one per trial, were (1) control, (2) vocalization of Canis latrans, (3) scent of C. latrans, (4) scent of Vulpes vulpes, or (5) vocalization of Asio jlammeus. We offered seeds of two native grasses, Achnatherum hymenoides (Indian ricegrass) and Pseudoroegneria spicata (bluebunch wheatgrass), and the non-native Secale cereale (cereal rye), each in separate plastic trays. D. ordii preferentially harvested A. hymenoides while P. parvus predominately harvested A. hymenoides and S. cereale. P. parvus was more likely to scatterhoard preferred seeds, whereas D. ordii mostly consumed and/or placed preferred seeds in a larder. Neither indirect nor direct cues significantly affected seed preferences. However, both species altered seed handling behavior in response to direct predation cues by leaving more seeds alive in the seed pool, though they responded to different predator cues. The two rodents are expected to have different impacts on plant recruitment in both natural and managed settings. Variation in preference, as revealed in this study, could be exploited as a component of reseeding strategies at sites where estimates of rodent community composition are available. To the extent that predator cues alter handling behavior, they provide a potential tool in developing restoration strategies that minimize seed loss.