Defensive behaviors in wild and laboratory (Swiss) mice: The Mouse DefenseTest Battery

The development of laboratory rodent models for elicitation and measurement of a range of defensive behaviors raises the question of the relationship between defense in these animals and those of their wild congeners. To eval uate this relationship for mice, defensive responses to an anesthetized rat were compared for fourth-generation laboratory-bred wild mice and Swiss CD -I (Swiss-Webster derived) laboratory mice in a Mouse Defense Test Battery. Wild mice showed enhanced levels of both freezing and flight, fleeing from distant approach of the predator in several situations and fleeing more qu ickly than the Swiss mice. However, Swiss mice did flee upon contact with t he rat and also showed levels of several other defensive behaviors (risk as sessment, defensive threat, and attack) that were often reliably higher tha n those of the wild mice. However, when wild mice were prevented from fleei ng, their levels of defensive threat and attack were as high as, or at very short prey-predator distances higher than, those of the Swiss mice. These findings suggest that flight and freezing are the major defensive behaviors reduced in Swiss mice and that these reductions allow the appearance of hi gher levels of additional defensive behaviors in the laboratory animals. Ho wever, although Swiss mice do show lower levels of flight and freezing, the ir patterns of defensive behavior are sufficiently similar to those of wild mice that they provide adequate subjects for research on the biologic base s of defensive behavior. A final experiment indicated that when wild mice a re familiarized with a chamber providing a place of concealment, they flee directly to this chamber on presentation of a rat, indicating that flight i s a targeted response and not simply an abrupt increase in forward locomoti on. Over IO rat presentation trials with a blocked chamber entrance, howeve r, this response declines. (C) 1998 Elsevier Science Inc.