Effects of cold on activity and exploration by wild house mice in a residential maze

Summary Wild house mice,Mus musculus, were bred in environments kept at 23 °C (warm-reared) or 3 °C (cold-reared). Males of the fourth generation in each condition were observed for 4 days in a residential maze with a central nest box and four arms radiating from it. One maze arm contained food, one contained water, and two were empty until Day 4, when one had soft (balsa) wood. Mice of each type were run in a maze at each temperature.Mice of all classes responded to the novel environment of the maze with a high rate of visiting the arms on Day 1. The novel presence of balsa wood also provoked extra visits to the arm that contained it, and a longer stay in that arm on Day 4 than on Day 3. Visits to the arms were fewer in the cold than in the warm, and time spent in the arms was less.Cold-reared mice in the cold environment spent more time outside the nest on Day 1, that is, were more responsive to novelty than were the warmreared. Hence for the cold-reared mice the competitive balance between exploring and energy conservation was altered. This difference, we suggest, is an aspect of cold-adaptation.These experiments were done in part while JLW held an award from the National Science Foundation under the US/Australia Agreement for Scientific Cooperation. We are also grateful to Rhondda G. Dickson for help with the statistical analysis.