Manipulations of vasopressin alter aggression differently across testing conditions in monogamous and non‐monogamous Peromyscus mice

Differences in the distribution of arginine vasopressin (AVP) and a subtype of AVP receptors, the V_1a receptor, may explain dissimilarities in social behavior of monogamous and non‐monogamous rodents. Intracerebroventricular infusions of AVP and a V_1a antagonist were used in sexually naive males of two mouse species, the monogamous and highly aggressive California mouse (Peromyscus californicus) and the non‐monogamous and less aggressive white‐footed mouse (P. leucopus), to begin testing the interaction between the social system of a species and the effects of AVP on aggression. Two testing conditions, the resident‐intruder aggression test (R‐I) and the neutral arena aggression test, were used because they may differ in function and underlying biological mechanisms. In the R‐I test, administration of the antagonist lengthened attack latencies in California mice. In contrast, blocking V_1a receptors did not alter attack latencies in the R‐I test in white‐footed mice or in the neutral arena aggression test in both species. AVP also did not alter aggression in either species in either behavioral test. Overall, these results suggest that AVP may be more likely to be associated with offensive aggression as measured in the R‐I test than with neutral arena aggression and that the effects of AVP manipulations may differ between monogamous and non‐monogamous rodents. Aggress. Behav. 31:000–000, 2005. © 2005 Wiley‐Liss, Inc.     

Social interactions between peromyscus leucopus and P. gossypinus in captivity

In evaluating the role of behavioral interactions in the maintenance of ecological and ethological isolation in sympatric populations of P. leucopus and P. gossypinus, the interspecific behavior of 94 animals in all possible sex pair combinations was observed in 84 staged dyadic trials of 15-minutes duration. Qualitatively the patterns of behavior differed little between sexes or species. Despite a high inter-individual variability and the high proportion of amicable interactions, the mean frequency of occurrence of aggressive behavior as well as the number of trials in which aggressive behavior occurred was greater in trials of animals from areas of range sympatry in comparison with those of the control animals from areas of range allopatry. Although the dominance relationships in many trials were unclear, gossypinus nonetheless consistently dominated leucopus. These data combined with examination of the habitats of these mice where their ranges do not overlap suggest that agonistic interactions may implement species integrity either primarily by Limiting or preventing the occupancy by leucopus of areas in which gossypinus occurs or secondarily by reducing the chances of pair bond formation.     

A comparative study of rodent social behavior in a seminatural enclosure

Social behavior, aggression, and copulation were studied in six groups of two males and two females each in seven species of muroid rodents (Clethrionomys gapperi, Microtus montanus, M ochrogaster, M pennsylvanicus, Peromyscus eremicus, P leucopus, and P polionotus) in a seminatural enclosure. Data were compared to those from an earlier study with P maniculatus tested under identical conditions. There were appreciable species differences in levels of both aggressive and sexual behavior; the two were not significantly correlated. Although levels of aggression did not appear well correlated with reports of social structure in the field, patterns of weight loss and litter production during the study did appear correlated. In general, levels of copulatory behavior appeared weakly correlated with factors previously proposed as predictors of polygamous mating systems; levels of aggressive behavior were better correlated with taxonomy.