Concerning hibernation, Bailey (_loc. cit._) remarks that animals of this species in Oregon, become fat in early autumn and lay down excess adipose tissue under the skin, over the muscles, and in the abdominal cavity. Svihla and Svihla (_op. cit._:133) noted that captives from the Olympic Peninsula, Washington, gained weight in September and October and became extremely fat. With the additional weight they were more listless and drowsy, often spending days curled up in the hibernating position with the head between the hind legs and the long tail curled completely over the head and body. Warmth aroused the animals to activity, but when the temperature dropped they again hibernated. Flahaut (1939:17) reported the discovery on February 23, 1939, at Henderson Inlet, South Bay, Thurston County, Washington, of two nest cavities inhabited by jumping mice that were hibernating. The nests, four inches apart and 30 inches below the surface of the ground, were approximately five inches in diameter and made of shredded paper. Both mice were dormant, covered by nesting materials and curled up in the aforementioned hibernating posture. Dalquest (1948: 371) writes that in the lowlands of Washington this species disappears by late July but that in the mountains it remains active until the middle of September. Edson (1932:56) records an individual taken on April 20 from its place of hibernation beneath the roots of a decaying stump. This animal quickly roused in the warm mid-afternoon sun but became dormant again when the temperature dropped to 45° F. It seems that animals near the end of hibernation become active on warm days and return to the torpid state on cold ones. _Enemies._--Little is recorded concerning enemies of _Z. trinotatus_, but Bailey (1936:233) lists owls and other nocturnal birds, weasels, skunks, and badgers as preying on this mouse. Smith and Hopkins (1937:191) found _Z. t. orarius_ in barn owl pellets obtained in Elk Valley, Marin County, California. _Food._--Bailey (_loc. cit._) remarks that in Oregon, these mice feed mainly on small seeds of grasses, small grains (wheat, barley, oats, and rye), and other plants. These seeds are obtained by cutting the stems, drawing the stems down and biting off lower sections until the seed-laden heads are reached. Bailey (_op. cit._:234) found that _trinotatus_ utilized also the seeds of the western skunk cabbage. Near Seattle, Washington, according to Dalquest (_loc. cit._), the principal food of _Z. trinotatus_ was velvet grass (_Holchus lanatus_), broad-leaved dock, and the seeds of other grasses. Dalquest reports also that the fruit of the blackberry (_Rubus macropelatus_) is eaten and that an occasional jumping mouse has its chin stained a deep purple by juice from these berries.