Paternal responsiveness in biparental dwarf hamsters (Phodopus campbelli) does not require estradiol.

Males of the biparental hamster species Phodopus campbelli act as midwives and are responsive to an experimentally displaced pup. Males also have peripheral estradiol concentrations that are similar to conspecific females. Castration reduces peripheral estradiol, yet does not affect paternal responsiveness despite the known role of estradiol in maternal behavior. Synthesis of estradiol within the central nervous system, however, might not be affected by castration. Males received implants of osmotic pumps containing the aromatase inhibitor letrozole to reduce both peripheral and central estradiol concentrations. Though estradiol was effectively reduced, it had no effect on paternal responsiveness or reproductive success. Neither testosterone nor aggression directed towards an intruder was altered. Results support the emerging conclusion that estradiol is not required for the exceptional paternal behavior of male P. campbelli.