Early development of climbing skills in harvest mice

The tiny harvest mouse, Micromys minutus, is skilled at climbing among grasses. Owing to the short lactation period of 15-16 days, young harvest mice need to achieve this climbing skill very rapidly. We examined the early development of five components of climbing behaviour and the final climbing pattern of harvest mice from birth to weaning. During the lactation period, the pups' climbing ability developed rapidly and they were able to climb a vertical bar by the time they first emerged from their nest. Climbing skills were acquired in the following order: hand grasping at 3-7 days; foot grasping at 6-9 days; quadruped stance at 6-11 days; tail prehension at 10-11 days; and righting at 10-12 days. The ratio of foot digit length to foot length was greater in harvest mice than in laboratory mice, Mus musculus, indicating a better grasping ability in the former. Copyright 1999 The Association for the Study of Animal Behaviour.