Early filial cannibalism revisited

<p><span>Offspring desertion by parents generally occurs at an early stage of parental care, which </span><span>is considered to minimize</span><span> the costs of parental care </span><span>prior to</span><span> desertion. </span><span>T</span><span>his study</span><span> investigated the effects of endocrinological constraint on early total filial cannibalism by male Rhabdoblennius nitidus in </span><span>the </span><span>field, a paternal brooding blennid fish with androgen-dependent brood cycling. In brood reduction experiments, </span><span>cannibal</span><span> males showed low </span><span>levels of </span><span>plasma 11-ketotestosterone (KT</span><span>) relative to non-cannibals, and also similar levels of 11-KT to males in the parental care phase</span><span>. Since 11-KT regulates male courtship intensity, males with decreased courtship activity </span><span>would exhibit</span><span> total filial cannibalism. However, there is a possibility that </span><span>a </span><span>transient increase in 11-KT levels at the early stage of parental care delays total filial cannibalism. </span><span>In contrast</span><span>, total filial cannibalism could occur before a decline to the lowest 11-KT levels, at which males might still be able to exhibit courtships, probably to reduce the costs of parental care. To understand how much and when </span><span>caregiving</span><span> males exhibit mating and parental care behaviors, it is important to consider not only the presence of endocrinological constraint but also its intensity and flexibility.</span></p>