RECACHING OF JEFFREY PINE (PINUS-JEFFREYI) SEEDS BY YELLOW PINE CHIPMUNKS (TAMIAS-AMOENUS) - POTENTIAL EFFECTS ON PLANT REPRODUCTIVE SUCCESS

Animals that scatter-hoard seeds frequently dig up and recache them at new locations. The effect of the recaching of seeds on plant reproduc tive success was studied in the Sierra Nevada of western Nevada, The f ate of 1000 individually marked Jeffrey pine (Pinus jeffreyi) seeds in itially placed in 100 primary caches in a 10 x 10 array was monitored during autumn 1995 and spring 1996. Yellow pine chipmunks (Tamias amoe nus) quickly removed nearly all of the seeds and recached many of them in 377 secondary caches containing 727 seeds. Later, rodents dug up m ost of these caches and transferred them to 213 tertiary caches (283 s eeds), 75 quaternary caches (92 seeds), and 13 quintic (fifth order) c aches (13 seeds). Overall, rodents ate 15.3% of the seeds they took fr om primary through quintic caches, and an additional 71.1% of the seed s disappeared, probably to underground runways and larders. During our spring survey of the study site, 133 seeds (13.6%) from 84 caches had germinated or were about to germinate. As rodents moved seeds from ca che site to cache site, several changes occurred that potentially infl uenced the distribution and survival of Jeffrey pine seedlings. First, the number of seeds per cache decreased. Second, cached seeds were gr adually moved farther from the source area. Third, the dispersal dista nce between successive cache sites decreased. Fourth, the distribution of cached seeds became more even. Lastly, more seeds were cached bene ath shrubs, which serve as nurse plants for Jeffrey pine seedlings. Co nsequently, the movement of seeds between cache sites by chipmunks may increase the probability that Jeffrey pine seedlings will establish f rom rodent caches.