Intrinsic and Extrinsic Factors Modulating the Shift from Paternal Care to Filial Cannibalism

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Nontechnical descriptionMany animals provide care for their young that is critical for early development, but disruption of this relationship can lead to neglect, abandonment, and death of offspring. In some species, parents can even take the extreme step of eating their own young. Cannibalism of offspring has long fascinated scientists, but little is known about the environmental factors that provoke this behavior or the physiological changes that underlie the decision to care for or eat one's young. Answering these questions will provide insights into how and why adults terminate parental care in a broad range of species. This study will examine the switch from parental care to cannibalism in a fascinating study system, the eastern hellbender. These giant salamanders were once common in streams across the eastern U.S., but have experienced drastic population declines across much of their range in the last 30 years. Unlike many species, male hellbenders provide exclusive care for their young for an extended period (7 months). In some circumstances, however, male hellbenders cease providing care and consume all of their young. This study will employ underwater nest boxes in streams across a gradient of habitat characteristics to determine what hormones trigger this switch in behaviors and what environmental factors promote cannibalism. Not only will this advance knowledge of parental care, but the study will also employ high school science teachers in an integrated outreach effort to conserve of one of the largest and most fascinating amphibians in the world. Technical descriptionParental care is a fundamental aspect of the life history of many animals. Paradoxically, in some invertebrates and vertebrates the parent(s) providing care engage in filial cannibalism, the consumption of one's own viable young. The adaptive basis for filial cannibalism remains an unresolved evolutionary conundrum, and the physiological basis for the behavior is unexplored in wild animals. In addition, few studies have considered the possibility that filial cannibalism may be maladaptive in some contexts or that there could be multiple drivers of filial cannibalism within a species. These critical knowledge gaps exist, at least in part, due to a scarcity of tractable wild animal models for simultaneously identifying environmental and physiological aspects of this life history decision. Hellbender salamanders exhibit paternal care as well as filial cannibalism and possess a suite of characteristics that make them an ideal system for addressing previously untested hypotheses related to the modulation of this fascinating life-history decision. Using a highly integrative framework that includes underwater nest boxes deployed in streams across a gradient of habitat quality and parasitism, coupled with genetic analyses and analysis of serum components collected from individuals throughout the paternal care season, this study will: 1) Identify the physiological modulators (i.e., hormones, serum components) that underlie the decision by a parent to either care for or cannibalize one's young, 2) Determine what key factors (i.e., per capita resources/body condition, multiple paternity, and parasites) influence this trade-off, and 3) Determine if habitat degradation increases the frequency of filial cannibalism. This award was co-funded by the Animal Behavior and the Integrative Ecological Physiology Programs within the Division of Integrative Organismal Systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.