Reproductive skew, cooperative breeding, and eusociality in vertebrates: Hormones
Reproductive skew, the degree of asymmetry in direct reproductive success among individuals within a social group, is most pronounced in cooperatively breeding and eusocial species. In these animals, reproductive failure in males is usually mediated by inhibition of sexual behavior, whereas subordinate females often undergo suppression of ovarian function. The endocrine mechanisms underlying alloparental behavior in nonbreeding individuals, a hallmark of cooperative breeding systems, may involve prolactin, estrogen, testosterone, oxytocin, and vasopressin. Mechanisms underlying both reproductive skew and alloparental care vary considerably across species. Identifying potential causes of this variability could be a productive avenue for future research.
