Sexual and aggressive interactions in a visible burrow system with provisioned burrows

The visible burrow system (VBS) is a habitat providing burrows and an open area for mixed-set rat colonies. Provisioning of food and water in the burr ows makes it unnecessary for potentially defensive animals to leave the bur rows to eat/drink on the surface, and enables evaluation of new types of ag onistic interactions that may emerge when this necessity is removed. In suc h colonies, subordinate males showed high magnitude tunnel guarding behavio r, occupying a tunnel opening onto the surface and confronting the dominant . Dominants, in response, made lunges into the tunnels, but quickly retreat ed without gaining entry, apparently stopped by contact with the defender's vibrissae. Dominants also made and continued to make lateral attacks to th e wall adjacent to the tunnels guarded by subordinates, although these were useless in terms of affording contact with the subordinate. Dominant-femal e agonistic interactions were more frequent than those of dominants and sub ordinates. These were largely initiated by the male, and involved female de fensive behavior. Nonetheless, females, unlike subordinates, failed to show tunnel guarding and continued to utilize the surface freely. They also spe nt more time in the vicinity of the dominant over days of colony formation. This apparent paradox may reflect that females were seldom wounded, and th at the initial site of male contact with females was the female's anogenita l area, findings suggesting that interactions of males and females often re flect male sexual advances, countered by female defenses that effectively p rotect nonestrus females from mounting and copulation. (C) 2001 Elsevier Sc ience Inc. All rights reserved.