DYNAMICS OF YELLOW PINE CHIPMUNK (TAMIAS-AMOENUS) SEED CACHES - UNDERGROUND TRAFFIC IN BITTERBRUSH SEEDS

Fates of antelope bitterbrush (Purshia tridentata) seeds were monitore d from the time the seeds were cached by yellow pine chipmunks (Tamias amoenus) until they germinated nine months later. One thousand seeds were numbered and then radioactively labelled with scandium-46 so that the histories of individual seeds could be followed. The labelled see ds were placed under a bitterbrush shrub in the morning and by that ev ening chipmunks had gathered most of the seeds and made 110 primary ca ches within 16 m of the source shrub. During the fall, chipmunks and o ther rodents visited many of these caches and removed some of the seed s. Thirty-one caches completely disappeared, 28 other caches had some but not all of the seeds removed, and 51 caches remained intact until the time of seed germination. Chipmunks recached about 30% of the seed s they took from primary caches during the late summer and fall at 12 secondary and two tertiary cache sites. The histories of seeds were of ten complicated. Seeds survived to the time of germination at 86 of th e 124 cache sites (79 primary caches, six secondary caches, and one te rtiary cache). The population of caches from a particular source plant is dynamic. Seed-hoarding animals frequently move seeds from one stor age site to another, and this secondary dispersal has important conseq uences for the seeds being moved.