The effect of livetrapping on the movements of Peromyscus

The movements of P. leucopus in small island populations were studied by means of nightly smoked-paper tracking supple- mented by occasional livetrapping. The mice left enough track records on nights when trapped to show that they often do not enter the first trap encountered and usually move through their home ranges for some time before being trapped. This suggests that in livetrapping studies there may be little or no bias in favor of traps located near the. nest. On the other hand, the movements of mice for several nights after being trapped were markedly altered. There were many more track records than usual on such nights, probably partly because of increased activity and perhaps partly because of an altered response to the track shelters (heightened exploratory behavior). Results with P. maniculatus show that much of this increased activity occurs in daylight immediately after release from traps. P. leucopus sometimes traveled far outside their former home ranges on nights after being trapped, sometimes resulting in a permanent shift in range. Because of these effects of livetrapping, this is not a satisfactory method of studying home ranges or activity patterns, but there is little indication that the results of previous studies have been seriously affected by the after-trapping effect.