Mating in the monogamous male: behavioral consequences.

In monogamous mammals, males typically show selective affiliation with a single mate, high levels of paternal care, and aggression towards conspecifics to protect male and offspring. We have previously described how selective aggression and affiliation increase after mating in the male prairie vole, Microtus ochrogaster. The current studies further explored the behavioral changes that follow mating in the male of this species. The first set of experiments tested males on several behavioral measures after 24 h of either mating, social (but not sexual) exposure, or no social contact. After 24 h of mating, but not after the other two conditions, aggression and affiliation (partner preference) increased as previously reported. In addition, mated animals showed increased exploration of the open arms of a plus maze, consistent with decreased fearfulness. There were no group differences in paternal behavior (which was high in all three conditions) or analgesia (assessed by tail flick latency). To determine the minimum amount of mating necessary for the induction of aggression, males were tested in a resident-intruder paradigm after 1,6, or 24 h of mating. Although 1 h of mating was associated with a transient increase in the frequency of threats and attacks, the full spectrum of enduring aggression was observed only in the males given 24 h of mating. In a final experiment, the behavioral consequences of mating were studied in males of the closely related montane vole (Microtus montanus) which does not pair bond. Males of this nonmonogamous vole species did not show increased aggression, partner preference, or alterations in plus maze exploration following 24 h of mating. These results demonstrate the importance of prolonged mating for the induction of pair bonding in the monogamous male and they suggest that increases in aggression and affiliation are associated with decreased fearfulness in pair bonded males.