Temperature Regulation, Hibernation, and Aestivation in the Little Pocket Mouse, Perognathus longimembris

Abstract

The little pocket mouse, Perognathus longimembris , was selected for a study of temperature regulation because (1) it is one of the smallest North American rodents (adult weight, 6.5 to 10 grams); (2) it is a member of the highly specialized family Heteromyidae; (3) it is locally very abundant; (4) it is readily maintained in captivity; and (5) nothing was previously known about its temperature regulation. Despite the abundance of pocket mice, very little has been published on the physiology of any member of the genus Perognathus . Hall (1946) adduced circumstantial evidence for the occurrence of hibernation in some species of pocket mice and its absence in others. Scheffer (1938) found that Perognathus parvus showed an irregular dormancy during the winter but he determined no body temperatures. We are unaware of any other published information concerning temperature regulation in the genus. P. longimembris occurs commonly in eastern and southern California, extreme northwestern Mexico, and throughout much of the Great Basin, reaching the northern limit of its distribution in southeastern Washington. It lives from below sea level in the Salton Sink to an altitude of at least 6500 feet in the Sierra Nevada. The present study was made between June and September, 1955, and is based on 23 adult animals trapped in the Antelope Valley and Walker Pass areas of the Mohave Desert of southern California. The captive animals were individually housed in glass jars or plastic boxes partly filled with fine sand. They were given no water and remained in excellent condition throughout the study on a diet of mixed bird seed. All temperatures were measured with 30 gauge copper-constantan thermocouples coated with baked insulating enamel and connected to a recording potentiometer. Oral and rectal temperatures were taken with thermocouples inserted to a depth of at least 2 cm.; …