SEED WATER-CONTENT AND THE VULNERABILITY OF BURIED SEEDS TO FORAGING RODENTS

The ability of yellow pine chipmunks (Tamias amoenus) and deer mice (P eromyscus maniculatus) to detect buried antelope bitterbrush (Purshia tridentata) seed caches of differing water content was examined in an arena containing dry sand. Neither species could detect caches of air- dried seeds (6.8% water) using olfaction, but they found some caches a fter the seeds had been hydrated (exposed to almost-equal-to 100% rela tive humidity) for only 0.25 h (7.3% water). When seeds contained >8.0 % water, subjects usually found most of the treatment caches available . Search times to find treatment caches were significantly greater for caches of very low water content (<7.3-7.4% water) compared to caches of higher water content. There were no significant differences in the abilities of deer mice and yellow pine chipmunks to detect treatment caches. When seeds were moistened (41.2% water) and then were allowed to dry out (6.4% water), subjects could not find the seeds in the dry arena sand. Variation in seed water content under natural conditions i n the field may have important implications for rodent-seed interactio ns.