SEQUENTIAL PATTERNS OF SCATTER HOARDING BY YELLOW PINE CHIPMUNKS (TAMIAS-AMOENUS)

Spatial and temporal patterns of scatter-hoarding by four yellow pine chipmunks (Tamias amoenus) were examined in the Sierra Nevada of weste rn Nevada, and the data were used to test predictions of two models of optimal scatter-hoarding behavior. Each chipmunk was allowed to scatt er hoard one load of seeds (i.e., seeds taken on one visit to the seed source) from each of 12 batches of numbered, radioactive Jeffrey pine (Pinus jeffrey) seeds presented sequentially at a feeding station. Th e caches were located with a radiation detector later the same day, th e numbers on seeds recorded and the cache sites mapped. From 96.3 to 1 00.0% of the seeds were relocated for each chipmunk, providing nearly complete data on the dispersions of caches. Chipmunks made from 2-12 c aches from each load of seeds and created arrays of 36-91 caches at th e four sites. Typically, chipmunks carried each load of seeds to a dif ferent portion of the study area, resulting in minimal overlap of cach es from different loads. Mean nearest-neighbor distance between caches from each load ranged from 1.4-4.9 m, and mean nearest-neighbor dista nces between the weighted geographic centers of sets of caches from ea ch load ranged from 5.3-10.2 m. Only one of the subjects exhibited a s ignificant tendency to begin caching near the bait station and move la ter loads of seeds progressively farther away. The nearest-neighbor di stances between caches within loads increased significantly with incre asing distance from the food source, indicating that seeds carried lon ger distances are likely to be cached at lower densities. Neither mode l of optimal scatter hoarding adequately predicted the caching behavio r of yellow pine chipmunks.