Abstract
DBA/2J and androgen-deficient C57BL/6J mice were examined for their response to newborn (1–3 day old) Rockland Swiss (R-S) albino mouse pups. Significantly more 70–90 day old C57BL male mice killed young as compared to similarly aged DBA males (80% vs 30% respectively). Adult, 70–90 day old, female mice of both strains typically retrieved newborn young to the nest site. Adult castration significantly reduced infanticide in males of both strains while exposure to testosterone (T)-containing silastic capsules restored it. Treatment of adult ovariectomized female mice of both strains with T-containing capsules significantly elevated the exhibition of pup killing. When tested for infanticide at 25, 35, 45, 55 or 65 days of age, few males of either strain killed young at 25 days of age. However, beginning at 35 days of age, significantly more C57BL males killed young at every age as compared to DBA males. Moreover, C57BL males exhibited an earlier developmental onset of adult-like levels of infanticide than DBA males (45 vs 65 days of age respectively). Finally, older (4.5 to 7 months of age) DBA males exhibited levels of pup-killing identical to that of younger (2 months of age) C57BL males (70%). The findings are discussed in terms of their relationship to other sexually dimophic T-dependent masculine behaviors. The potential importance of infanticide for rodent reproductive strategies and population regulation is also considered.
Published Version
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