Pup contact promotes paternal responsiveness in male meadow voles

Male meadow voles, Microtus pennsylvanicus, were tested with unrelated pups to determine the social factors that affect the initiation of paternal responsiveness and the inhibition of infanticide. Adult males were initially more responsive to pups if they had been reared as neonates with their fathers rather than with unfamiliar males. Decreased aggression and facilitation of paternal responsiveness occurred most reliably after extensive exposure to pups, even if exposure had occurred more than 2 months before testing. Unlike house mice, neither copulation nor exposure to females enhanced male responsiveness to pups. Given that male meadow voles only nest with females and young during the colder parts of the breeding season, it may be adaptive for paternal responsiveness to be triggered by pup exposure, rather than by some aspect of earlier contact with the female.