Early filial cannibalism revisited from an endocrinological perspective
Offspring desertion by parents generally occurs at an early stage of parental care, which is considered to minimize the time and energy costs of parental care prior to desertion and ensure an opportunity and time for future reproduction. In addition to these conventional reasons, we investigated the effects of endocrinological constraint on early total filial cannibalism in fish in which care-giving males eat all eggs and restart reproduction when tending a small number of eggs. The occurrence of total filial cannibalism in male Rhabdoblennius nitidus, a paternal brooding blennid fish with androgen-dependent brood cycling, was strongly associated with decreased plasma 11-ketotestosterone levels, suggesting that males in which it was difficult to exhibit courtship behavior began to cannibalize eggs. Moreover, the additional mating probability at the beginning of parental care may delay the timing of total filial cannibalism; at the same time, the costs of parental care may shift the timing earlier than expected based on androgen decline. These results suggest the potential importance of considering endocrinological constraints with respect to the adaptivity of behavioral traits.