SALIVARY WATER-LOSS TO SEEDS IN YELLOW PINE CHIPMUNKS AND MERRIAMS KANGAROO RATS

Seeds are known to serve as sources of preformed and metabolic water f or desert rodents, but water loss to hygroscopic seeds has received li ttle attention. Salivary water loss by yellow pine chipmunks (Tamias a moenus) and Merriam's kangaroo rats (Dipodomys merriami) to Jeffrey pi ne (Pinus jeffreyi) and antelope bitterbrush (Purshia tridentata) seed s was measured to determine its magnitude and potential importance. Ch ipmunks rapidly lost salivary water to individual seeds inserted into their cheek pouches. Jeffrey pine seeds (129 mg) absorbed 9.8 mg of wa ter and bitterbrush seeds (36 mg) absorbed 4.6 mg of water when held i n the cheek pouches for 15 min. Only 3-5% of this water can be reclaim ed if the chipmunk eats the seed because most of the absorbed water re sides in the inedible seed coat, which the animal discards. The kangar oo rats, which possess external, fur-lined cheek pouches, lost no wate r to seeds held in their cheek pouches for 15 min. Chipmunk salivary w ater loss to Jeffrey pine and bitterbrush seeds was equivalent to 19 a nd 59%, respectively, of the water (preformed plus metabolic water) co ntained in those seeds. Salivary water loss is a major and previously overlooked component of the water budgets of granivorous rodents with internal cheek pouches. The presence of fur-lined cheek pouches in het eromyid rodents (kangaroo rats, pocket mice, and kangaroo mice) may ha ve contributed to the great success of these rodents in the deserts of North America by solving the problem of salivary water loss to the se eds they handle and store.