Parent–offspring cannibalism throughout the animal kingdom: a review of adaptive hypotheses

Abstract

Parents that kill and consume their offspring often appear to be acting against their own reproductive interests. Yet parentoffspring cannibalism is common and taxonomically widespread across the animal kingdom. In this review, I provide an overview of our current understanding of parent-offspring cannibalism, which has seen a proliferation in adaptive hypotheses over the past 20 years for why parents consume their own young. I review over four decades of research into this perplexing behaviour, drawing from work conducted on fishes, reptiles, insects, birds, and mammals among other taxa. Many factors have been hypothesised to explain parent-offspring cannibalism in nature, including poor parental energy reserves, small or large brood sizes, low or uncertain parentage, and high brood densities, and additional factors are still being uncovered. Parent-offspring cannibalism does not appear to have a single predominant explanation; rather, the factor, or set of factors, that govern its expression is largely taxon specific. Parents may either consume all offspring under their care (fullbrood cannibalism) or consume a fraction of their offspring (partial brood cannibalism). These forms of cannibalism are thought to provide adaptive benefits to cannibals under a range of circumstances, primarily by allowing parents to allocate parental efforts more optimallyenergy from eating (some of) one's current offspring can be redirected to other offspring, or to parental growth, survival, and ultimately to other future reproductive endeavours. Thus, parent-offspring cannibalism is a phenotypically plastic trait that responds to changing environmental, social, and physiological conditions. The expression of parent-offspring cannibalism in any given system is intimately linked to the reproductive value of current young relative to parents' expectations for future reproduction, and also to whether parental care is predominantly depreciable or non-depreciable. Furthermore, parent-offspring cannibalism has the potential to generate conflict between the sexes, and I briefly discuss some consequences of this conflict on patterns of mate choice. Finally, there still remain many aspects of this behaviour where our understanding is poor, and I highlight these topics to help guide future research.

The Fall Armyworm, <em>Spodoptera frugiperda</em> (Lepidoptera: Noctuidae), Influences <em>Nilaparvata lugens</em> Population Growth Directly, by Preying on Its Eggs, and Indirectly, by Inducing Defenses in Rice

“…FAW larvae are omnivorous, and intraguild predation brings nutritional and energy benefits, increasing the size, growth and development of individuals [46][47][48][49]. Hence, the fast growth rate of FAW feeding on BPH eggs is probably related to the high nutritional and energy benefits of the eggs.…”

Ant queens cannibalise infected brood to contain disease spread and recycle nutrients

“…Filial cannibalism, where parents eat their own offspring, is a taxonomically widespread behaviour with a multitude of potential adaptive explanations [1]. Of these, the impact of parasites on the expression of filial cannibalism is particularly poorly understood.…”

“…Of these, the impact of parasites on the expression of filial cannibalism is particularly poorly understood. On one hand, cannibalising young with low survival probability may enable parents to reinvest valuable resources into future reproduction [1]; on the other, cannibalising offspring harbouring parasites that can potentially also infect the parents may select against this behaviour. Although disease-induced cannibalism of eggs has been reported in fish [2], the benefits of consuming infected brood to contain infections – as an explanation for the evolution of filial cannibalism – remains largely unexplored.…”

“…resources into future reproduction [1]; on the other, cannibalising offspring harbouring parasites that can potentially also infect the parents may select against this behaviour. Although disease-induced cannibalism of eggs has been reported in fish [2], the benefits of consuming infected brood to contain infections -as an explanation for the evolution of filial cannibalism -remains largely unexplored.…”

Androgenic shifts and external cues mediate parental care versus infanticide in mimic poison frogs

“…Therefore, parents provide a valuable framework for studying flexible social decision-making at multiple levels. While behavioral ecologists have reported numerous adaptive rationales for infanticide across diverse taxa, including mammals, fish, amphibians, insects, and birds (Hrdy, 1979;Ebensperger and Blumstein, 2007;Bose, 2022), efforts to link this behavior to its hormonal substrates is limited, especially beyond mammals. By connecting endocrine states to the performance of parental care versus infanticide, we can clarify how evolutionary innovations in physiology enable rapid responses to social challenges.…”