A Testosterone-Mediated Trade-Off Between Parental and Sexual Effort in Male Mongolian Gerbils (Meriones unguiculatus )

Effects of testosterone (T) on parental behavior of male Mongolian gerbils (Meriones unguiculatus) were examined. After undergoing gonadectomy, castrated males were implanted with empty capsules or capsules containing T; sham-operated males were implanted with empty Silastic capsules. Subsequently, each male was paired with a pregnant female, and after delivery, families were observed 15 min/day for 20 days. Gonadectomized males without T spent more time in contact with, huddling over, and licking pups than did either sham-operated males or gonadectomized males with T. When given a choice between nest sites and displaced pups, females and males with low T preferred pups, whereas intact males and castrated males with T preferred nest sites. The findings are consistent with E. D. Ketterson and V. Nolan's (1994) hypothesis implicating T in mediating trade-offs between parental and sexual effort.