ROLE OF FEMALE AGGRESSION IN PREVENTION OF INFANTICIDAL BEHAVIOR IN MALE COMMON VOLES, MICROTUS-ARVALIS (PALLAS, 1779)

Infanticidal behavior of male common voles (Microtus arvalis) was inve stigated in relation to the age of unfamiliar pups. Sires from 18 pair s were removed after parturition of their offspring and replaced by un familiar males at different ages of the neonates. In group 1, containi ng six females with their offspring, the new male was introduced into the females' cages on day 1 after the parturition. In group 2 the new male was introduced on day 5 after parturition and in group 3 on day 9 after parturition. The male was removed after 3 days and the neonates recounted. Male common voles killed up to 100% of the neonates in lit ters containing neonates younger than 9 days by rapid bites to the hea d of the neonates (groups 1 and 2, mortality rates of 0.86 and 0.38). However, with older pups, a mortality rate of 0.06 was observed while 33% of the intruder males showed signs of injuries (group 3). These fi ndings show that infanticidal behavior of male common voles represents one factor of pup mortality. The results are discussed in relation to changes in the degree of maternal aggression and in the context of th e social system of the common vole for solving the conflict between po stpartum estrous mating and infanticidal behavior of male common voIes . (C) 1997 Wiley-Liss, Inc.