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

Infanticide is widespread across the animal kingdom. However, the physiological mechanisms underlying infanticide versus care or neglect are relatively unexplored. Here, we identified salient environmental and physiological antecedents of care and infanticide in the mimic poison frog ( Ranitomeya imitator ), a biparental and monogamous amphibian in which female parents feed their tadpoles with unfertilized eggs. Specifically, we explored potential environmental cues by evaluating changes in the frequency of food provisioning and tadpole mortality after cross-fostering tadpoles within and between morphs and displacing tadpoles within the terraria of their parents. After analyzing trophic egg deposition and observing tadpole mortality in the latter condition, we concluded that changes to offspring location reduce care and increase infanticide. Following this observation, we investigated whether steroid hormones relate to infanticide in an unfamiliar, resource-limited setting. Infanticidal behavior towards fertilized eggs and hatchlings included cannibalism and was associated with lower testosterone concentrations upon displacement to the new environment, while corticosterone concentrations did not correlate with infanticide at any sampling event. Ratios of testosterone to corticosterone were overall lower in infanticidal individuals. Overall, these findings support earlier investigations of environmental cues for offspring-directed behavior in poison frogs, while offering a novel perspective on temporal endocrine correlates of infanticide.