Development of selective partner preferences in captive male and female meadow voles, Microtus pennsylvanicus

Intraspecific social systems vary considerably as a function of environment al parameters (Lott 1984, Behaviour, 88, 266-325). For example, nonmonogamo us species may engage in facultative partner preferences and parenting to o ffset the costs associated with harsher breeding conditions. Because no fie ld or laboratory research has examined nonmonogamous meadow voles under sub optimal conditions (e.g. low-density summer populations or during colder mo nths), it was not known whether meadow voles could form affiliative prefere nces for a specific partner. The aim of this experiment was to identify whe ther meadow voles develop selective partner preferences and if so, under wh at circumstances. We assessed partner preferences using a choice apparatus in which the test animal chose to spend time with a familiar mate or strang er. We paired and tested males and females (within photoperiod) under one o f five different conditions: after 24 h, 10 days, or 23 days of cohabitatio n with mating or after 24 h or 10 days of cohabitation without mating. Male and female meadow voles rapidly formed selective partner preferences for a familiar mate when compared with controls in nearly every condition, regar dless of photoperiod, cohabitation duration, or whether mating did or did n ot occur. Within 24 h, males directed significantly more aggression towards unfamiliar animals, and mating enhanced this effect. For females, 24 h of social cohabitation was sufficient to decrease aggression towards partners, but stranger-directed aggression appeared later, following delivery of the litter. These data suggest that meadow voles are capable of developing sel ective partner preferences and stranger-directed aggression and may have ev olved these abilities to maximize reproductive success during the colder mo nths of the year or under low population density during the summer breeding season. (C) 2001 The Association for the Study of Animal Behaviour.