TORPIDITY IN THE MEXICAN GROUND SQUIRREL CITELLUS MEXICANUS PARVIDENS (MEARNS)

Abstract

Throughout a period from early November until the end of February, spontaneous torpidity was demonstrated by the Mexican ground squirrel Citellus mexicanus parvidens (Mearns) at room temperatures (17° to 22 °C), and at ambient temperatures from 3.8° to 16 °C. The oxygen consumption of individuals torpid at room temperatures was 0.2 to 0.4 cc/g hr, while at ambient temperatures from 3.8° to 16 °C, it was 0.06 to 0.30 cc/g hr. The difference between body temperature and ambient temperature was 1° to 2 °C at ambient temperatures from 6° to 22 °C; this difference increased below 6 °C. Bouts of torpor lasted from 2 to 60 hours.From the information on the seasonal activity of this squirrel, the known climatological data for its range, and our laboratory demonstration of its ability to become torpid, we conclude that C. m. parvidens is a hibernator and possibly an aestivator.