THE EFFECT OF AGE ON TEMPERATURE SELECTION BY LABORATORY MICE (MUS MUSCULUS)

Abstract

Adult animals have been used for most of the previous mammalian temperature selection studies, and relatively few systematic observations have been made with young animals. In this investigation, laboratory mice (Mus musculus), ranging in age from 1 to 84 days, were studied in a horizontal temperature gradient established along a 5-ft copper bar. Despite poorly developed locomotion and cold immobilization, it was shown that the temperature selection response is present at birth. The initially high level of selection appeared to be maintained for about 2 weeks, after which it began to decrease, rapidly at first, and then more slowly until the adult level was reached.