Vocal communication regulates sibling competition over food stock

Abstract

Animals resolve conflicts over the share of resources by competing physically or signalling motivation with honest signals of need. In some species, young siblings vocally signal to each other their hunger level and the most vocal individual deters its siblings from competing for the non-divisible food item delivered at the next parental visit. This so-called sibling negotiation for forthcoming food has been studied only in this context. It therefore remains unclear whether siblings could also negotiate access to a pool of divisible resources, a situation that is similar to a group of individuals competing for an accessible food resource. To tackle this issue, we placed barn owl (Tyto alba) nestlings singly in artificial nests containing several mice, and we simulated the presence of a sibling calling at low or high rate using playback experiments. If nestling barn owls vocally negotiate over a divisible food stock, we propose the following two predictions. First, nestlings would vocally signal before eating from this stock of food, and second, numerous playback vocalizations would inhibit feeding. Accordingly, singleton nestlings vocalized just before consuming food stored in their artificial nest and they delayed the consumption of the food stock if hearing many playback calls. The production of such food-associated vocalizations has been observed in foraging adults in various birds and mammals, but never in young animals and when resource is divisible and easily accessible. Our study raises the possibility that vocal communication could evolve in a variety of competitive contexts. Significance statementWe present here the first experimental evidence that sibling barn owls use food-associated vocalizations to compete over the preys stored in the nest. Owlets emit calls just before consuming an available food item and broadcasting calls induces nestlings to temporarily refrain from eating from the food stock. This raises the possibility that vocal communication can mediate the share of a food stock accessible to all competitors.

Corticosterone release in very young siblicidal seabird chicks (Rissa tridactyla) is sensitive to environmental variability and responds rapidly and robustly to external challenges

“…Second, the differences in HPA activity could be driven by post-natal behavioral cues from parents or siblings. While chick body condition indicated that parents seemed to be meeting the nutritional needs of their chicks at this early age regardless of the supplemental food treatment (but see 4.2), differences in competition from siblings or responsiveness of parents to begging may impact corticosterone secretion (Braasch et al, 2014; Dreiss et al, 2016). Finally, other aspects of interannual environmental variability could modulate the relationship between food availability and corticosterone by imposing additional energetic challenges.…”

Kind to kin: weak interference competition among white stork Ciconia ciconia broodmates

“…A nestling was assumed to win a dispute if it ended swallowing the food item and to lose it if the food was eaten by its opponent. In the case of food assaults, we also recorded any behaviour by receivers to avoid being robbed, such as concealing food, attempting to hide from the actor, or performing communicative displays (Roulin et al , Dreiss et al ).…”

Avian vocalisations: the female perspective

“…This framework also distinguishes song from vocalisations that are socially selected ( sensu Lyon & Montgomerie, 2012) outside the context of sexual competition (e.g. sibling competition in barn owls Tyto alba ; Dreiss et al ., 2016) and vocalisations that may function in cooperation (e.g. chestnut‐crowned babblers Pomatostomus ruficeps ; Crane et al ., 2016), and hence avoids blending the selective processes underlying vocal signal design.…”