Separate vacations and other sexual differences
Three recent papers in Proceedings of the Royal Society discuss differences between males and females or, in one case, among males.
“The costs of risky male behaviour: sex differences in seasonal survival in a small sexually monomorphic primate” by Cornelia Kraus and others, is based on a 10-year study of differences between male and female behavior in grey mouse lemurs. During the breeding season, males had lower survival than females, despite any possible risks associated with pregnancy or raising young. The higher risk for males apparently resulted from their tendency to travel more, looking for females.
The sexes also differ in winter behavior: females hibernate, while males remain active. Is there something about female physiology that makes hibernation healthier for them than it would be for males? Maybe, but there was no difference in winter survival between the sexes, which don’t differ much in size in this lemur species. The authors suggest that hibernation might have longer-term benefits in females, such as increased lifespan, whereas males need to stay active to bulk up in preparation for the breeding season.
This paper reminded me of an earlier paper on albatrosses, in which "in each pair, the male spent the winter just north of the pack ice in Antarctic waters whereas the female stayed south of Madagascar." It’s not hard to understand why males and females might differ in various ways (size, color, etc.) but differences in behavior outside of the breeding season are more interesting.
The second paper addresses an old argument between Charles Darwin and Alfred Russel Wallace, who developed similar explanations of evolution by natural selection at about the same time.
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