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Results of previous studies in our laboratory have shown that testosterone (T) inhibits parental response in adult male Mongolian gerbils. Here, we examined developmental changes in parental responses of male gerbils before, during, and after a naturally occurring surge in T that peaks on Day 75 postpartum. On the hypothesis that T inhibits parental response in male gerbils, we predicted that (a) 75-day-old male gerbils would be less responsive to neonates than would either younger or older male gerbils, and (b) young male gerbils whose T titers were rising as the litters that they were helping to rear matured would show a decrease over days in parental effort relative to older male gerbils whose T titers were falling as the litters that they were helping to rear matured. Both predictions were confirmed, providing evidence consistent with the view that naturally occurring, developmental changes in circulating concentrations of T play a role in age-related changes in the level of parental response of male Mongolian gerbils.

Adult. --- Developmental-changes. --- Gerbil. --- Gerbils. --- Laboratory. --- Level. --- Male mongolian gerbils. --- Male. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Neonates. --- Parental behavior. --- Parental responses. --- Play. --- Prediction. --- Response. --- Responses. --- Testosterone. --- Young.

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Following either a) castration or b) both castration and implantation with capsules releasing a constant, physiological dose of testosterone, adult male Mongolian gerbils that had matured in intrauterine positions between two male fetuses still scent marked with greater frequency than did male gerbils that had matured in intrauterine positions between two female fetuses. We also found significant positive correlations between the relative frequency of scent marking exhibited by individual male gerbils when intact, after castration and after both castration and implantation with capsules releasing testosterone. Each of these findings is consistent with the view that differential exposure to testosterone, as a consequence of fetal intrauterine position, has lasting effects on the organization of scent-marking by male gerbils

Adult. --- Castration. --- Exposure. --- Female. --- Fetuses. --- Frequency. --- Gerbil. --- Gerbils. --- Implantation. --- Intrauterine position. --- Intrauterine positions. --- Male mongolian gerbils. --- Male. --- Marking. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Organization. --- Physiological. --- Position. --- Positions. --- Scent marking. --- Scent-marking. --- Scent. --- Territorial marking. --- Testosterone. --- Time. --- Uterine position.

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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

Behavior. --- Biparental care. --- Choice. --- Contact. --- Female. --- Females. --- Gerbil. --- Gerbils. --- Individual-differences. --- Inhibition. --- Intrauterine positions. --- Male mongolian gerbils. --- Male. --- Males. --- Maternal-behavior. --- Meriones unguiculatus. --- Meriones-unguiculatus. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Nest. --- Parental behavior. --- Paternal behavior. --- Peromyscus-californicus. --- Pups. --- Reproductive success. --- Scent marking. --- Sexual. --- Testosterone. --- Time. --- Unguiculatus. --- Voles microtus-ochrogaster.

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In 4 experiments, the authors explored effects of interaction, with both sexually active adult female and unfamiliar adult male Mongolian gerbils (Meriones unguiculatus) on young female gerbils' ages at first parturition. Presence of a natural mother retarded development of her daughters. However, presence of a-natural mother had no greater effect on her daughters' development than did presence of any other familiar animal, either male or female. Further, exposing young female gerbils to an unfamiliar male accelerated their development even when their reproductively active mothers were present. The data indicate that maintaining young female gerbils in stable family groups results in both inhibition of sexual maturation (caused by exposure to familiar individuals) and failure to activate sexual development (caused by lack of exposure to unfamiliar males)

Adult. --- Age. --- Animal. --- Colonies. --- Cotton-top tamarins. --- Development. --- Experiment. --- Experiments. --- Exposure. --- Failure. --- Female mongolian gerbils. --- Female. --- Females. --- Gerbil. --- Gerbils. --- Group. --- Incest avoidance. --- Induced infertility. --- Inhibition. --- Interaction. --- Male mongolian gerbils. --- Male. --- Males. --- Maturation. --- Meriones unguiculatus. --- Meriones-unguiculatus. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Mother. --- Natural. --- Oedipus. --- Parturition. --- Pheromones. --- Puberty. --- Reproduction. --- Sexual development. --- Sexual maturation. --- Sexual-maturation. --- Sexual. --- Suppression. --- Time. --- Unguiculatus. --- Young.

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We housed male Mongolian gerbils, their mates, and foster litters of standardized size and sex ratio in enclosures that provided cover in two locations. Males had been gestated in known intrauterine positions. either between two females (2F males) or between two males (2M males). From Days I to 20 postpartum, we examined the frequency with which both males and females were in contact with the pups they were rearing. We Sound that 2F males spent more time with pups than did 2M males both during entire observation periods and when females were away from the nest. Further, when pups were moved from the nest site, 2M males spent more time than did 2F males in the vacated nest site. We concluded that 2F male gerbils spent more time with pups than 2M males not because of a greater attachment of 2F than 2M males to places of concealment, their male, oi their nest site. Rather, 2F males were more attracted to pups than were 2M males. (C) 1998 John Wiley & Sons, Inc

Attachment. --- Care. --- Contact. --- Female. --- Females. --- Frequency. --- Gerbil. --- Gerbils. --- Intrauterine position. --- Intrauterine positions. --- Male mongolian gerbils. --- Male. --- Males. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Nest-site attachment. --- Nest. --- Observation. --- Parental behavior. --- Periods. --- Position. --- Positions. --- Pups. --- Rearing. --- Sex ratio. --- Sex. --- Sexes. --- Size. --- Sound. --- System. --- Time. --- Uterine position.