These results do not square with expert predictions_其他

These results do not square with expert predictions

But there’s a catch: While females adopt relatives to increase the copies of their genes, adding additional young may reduce the rest of the litter’s odds for survival. Indeed, we discovered that surrogate females do in fact become more selective when they have more mouths to feed. That is, as her litter size increases, she requires that orphans be a closer relative to her before she’ll adopt them.

For example, if a female already has two pups, then she might adopt her niece or nephew. But when she has three pups, she would only adopt her grandchild or younger sibling, as they share more genes than her niece or nephew would.

Females, then, are forced to calculate the costs and benefits of adoption in a sophisticated way: They only adopt when the proportion of shared genes is high enough to make up for lowering the odds for survival of their young.

This suggests that what looks like altruistic behavior at first glance may not in fact be purely altruistic. If squirrels simply adopt to “be nice,” why do they not adopt unrelated orphans? By adopting only orphans related to themselves, red squirrels force us to consider that perhaps being nice may simply be a selfish means to increase one’s genetic fitness. Essentially, you can pass on your genes by having young of your own or by helping your relatives raise their young.