Evidence for begging as an honest signal of offspring need in the biparental mimic poison frog

Whether begging behaviour mediates food provisioning has been extensively studied in birds. However, begging behaviour occurs without direct offspring competition in some species and thus may be driven exclusively by intrabrood dynamics. We studied begging behaviour of individually housed offspring of the biparental mimic poison frog Ranitomeya imitator. We tested whether (1) begging is an honest signal of need or hunger, (2) begging is costly and (3) parents allocate food according to offspring need. Under manipulation of long-term diet, food-limited tadpoles increased begging effort over the course of development. Tadpoles that were induced to beg suffered a cost of taking longer to reach developmental stages and showed a marginal cost on growth rate. Finally, parents were more likely to feed the tadpole that was exposed to a nonsupplemented diet over its food-supplemented sibling. In R. imitator, begging behaviour appears to signal offspring need honestly and thus may predict differential food provisioning among offspring.