Homing in the California Vole, Microtus californicus

Homing experiments with the California vole were conducted in a grassland in Monterey County, California. Voles were primarily taken from one small area and released at specified release stations 200-1,000 feet distant from the home range. Homing success diminished with distance, and no voles returned from a distance greater than 600 feet. Homing was successful up to a distance of about six times the diameter of a hypothetical circular home range. Homing animals on the average returned quickly to their home range. Distance did not change the amount of time required to home. Trapping at release points showed that some released voles remained in areas in which there were no resident Microtus but that none remained in areas where voles were present or in areas where conditions were inadequate for support of voles. Predation may influence results in field studies of this type, but the return of voles was so rapid that predation probably had little effect here. The conclusion is reached that these voles were motivated to leave release areas primarily because of intraspecific social factors, although it is possible that innate and psychological factors may also be involved. Familiarity with a large area is unlikely in these short-ranging animals. Either navigation or simple random wandering, or a combination of these, could be involved in the ability to home, but neither means has been adequately demonstrated.