Mammal monogamy still a mystery, but maybe more than a numbers game

National Public Radio Morning Edition “For Some Mammals It’s One Love, But Reasons Still Unclear”

Although brief, I appreciate how this article lays out the three hypotheses for monogamy:

1. Monogamous co-parenting increases the survival rate of offspring as compared to parenting by the mother alone;
2. Monogamy results from the pattern of resource distribution: if resources are highly dispersed so are females, and males gain no advantage by trying to travel from female to female; and
3. Breastfeeding creates greater reproductive delays, which creates greater incentive for male infanticide of unrelated juveniles, which incentivizes fathers to “stick around” and provide care and/or protection.

What is interesting is that hypothesis #1 is not favored by either of these studies: this seems to be the prevailing explanation of monogamy in birds, and it is the hypothesis that has stood the longest test of time. But I have always found this hypothesis somewhat unsatisfactory because it does not make it clear why these monogamous parents are more successful in raising offspring than non-monogamous parents: is it predation risk, or competition for food, or is it risk of infanticide? What actually drives the success of dual parenting is what makes monogamy interesting, and potentially mutually exclusive of hypotheses #2 and #3.