Conspecific Wounding in Free-Ranging R. Norvegicus From Stable and Unstable Populations

Abstract

The incidence and body site distribution of wounds were determined for wild R. norvegicus trapped near the border of either mature sugar cane fields (stable population) or recently harvested and burned cane (unstable population). Rats from both areas displayed recent wounds, but animals from the unstable population had significantly more. In contrast to results of laboratory tests, male and female wound frequencies were similar. Body site distributions of wounds, however, was very much like that found on male intruders into established laboratory rat colonies, with most wounds on the back and very few on the ventrum. This finding corroborates an assertion that offensive biting in R. norvegicus is targeted toward the opponent's back; it thus provides essential support for a view that offensive attack behaviors are strategies enabling the attacking animal to reach this specific target, while many defensive behaviors elicited by conspecific attack are adaptive in protecting this bite target site.