Meeting Abstract

P1.61  Thursday, Jan. 3  Relative humidity increases pilfering success in chipmunks DOWNS, C.J.*; VANDER WALL, S.B.; Univ. of Nevada, Reno; Univ. of Nevada, Reno downsc@unr.nevada.edu

Scatter-hoarding animals store seeds and other food items when food is abundant and then use those provisions when food is scarce. Because caches are not usually defended, other individuals can pilfer them. The hoarder usually has an advantage over a na�ve forager because they can use spatial memory to located caches. A naive forager must rely on other techniques, such as olfaction, to locate buried seeds. The moisture content of buried seeds or soil affects olfaction. Evidence from a seed removal transect (a field experiment) suggests that high relative humidity events (storm systems) provide sufficient moisture to increase seed odor and facilitate olfaction by rodents. We tested this hypothesis in a laboratory experiment using 8 wild caught yellow-pine chipmunks (Tamias amoenus). The experimental arena had 96 sand-filled cups in the floor for caching. We buried 1 Jeffery pine seed in each of 10 randomly chosen cups. Subjects searched for seeds at each of five relative humidity (RH) levels: ~17, ~27, ~50, ~75, or ~95%. During the 95% RH trial, the soil was visibly wet, and mean percent soil moisture and seed recovery were significantly higher. These results support the hypotheses that relative humidity facilitates foraging for buried seeds. Thus, rodent foraging may be subject to subtle weather events and brief periods of high relative humidity may provide sufficient moisture to increase pilfering success. This role of humidity in olfaction may also be important in other contexts (e.g., scent marking, predator-prey interactions). Funding provided by The American Society of Mammalogists and UNR-GSA.