Why some male Mongolian gerbils may help at the nest: testosterone, asexuality and alloparenting

In previous studies we have shown that those male Mongolian gerbils, Meriones unguiculatus, that as fetuses resided in intrauterine positions (IUPs) located between two female fetuses (2F males) have lower circulating levels of testosterone, less well-developed genital musculature, and lower reproductive success than males gestated in IUPs between two male fetuses (2M males). We have also found that such 2F males spend more time caring for …