ANTIPREDATOR BEHAVIOR OF SWISS-WEBSTER MICE IN A VISIBLE BURROW SYSTEM

Swiss-Webster mice living in a visible burrow system (VBS) reacted to presentation of a live cat in the surface area of the VBS by retreat t o the burrows and reductions in nondefensive behaviors such as eating and drinking. Live cat-exposed subjects remained in the burrows 14 hr or more, while subjects exposed to a toy (plush) eat prior to live cat exposure reemerged almost immediately and made many contacts with the toy cat. However, subjects exposed first to the cat and later to a to y cat showed intermediate surface reemergence times and cat contacts d uring toy cat tests, indicating strong sensitization effects of prior live cat exposure. Previous studies indicated that rats in this situat ion show retreat to the burrows, surface avoidance, and reduction in n ondefensive behaviors. The mouse pattern was similar, with the notable exception that in the first 5-min block after cat presentation, mice rapidly alternated retreat to the burrow chambers with reappearance in the tunnel segment near the surface, to scan the surface visually and sniff. Movement during this time block involved a stretch attend post ure characteristic also of risk assessment activities in rats. Such vi sual and olfactory inspection of the cat is not seen in rats in the VB S. This difference may be related to the finding that rats, but not mi ce, emit ultrasonic ''alarm cries'' during and after cat exposure. (C) 1995 Wiley-Liss, Inc.