11.04.2019: Not only males, but also females of the poison-arrow frog Allobates femoralis exhibit cannibalism of conspecific clutches. A recently published study by Vetmeduni Vienna now shows that there could be good reason for this behaviour from an evolutionary perspective.

Cannibalism is widespread in the animal kingdom. This includes the consumption of juvenile animals by adult conspecifics. Although it may not be obvious at first, this seemingly abhorrent act does in fact have a deeper evolutionary advantage. Possible reasons for cannibalistic behaviour include the acquisition of nutrients, decreased competition for one’s own offspring, and increased mating opportunities. Yet many questions with regard to cannibalism among animals remain unanswered.

Known cannibals: male poison-arrow frogs

This prompted a team of researchers from Vetmeduni Vienna to more closely investigate the – non-poisonous – poison-arrow frog Allobates femoralis, which have been observed cannibalising conspecific clutches. Past experiments with A. femoralis have shown that males care for clutches inside their own territory, even if they aren’t their own offspring, but become cannibalistic when they take over a new territory. Cannibalism by females had not previously been observed.

Brood behaviour closely scrutinised

The aim of the recently published study was to investigate if, and under which circumstances, female A. femoralis would cannibalise clutches of other females. As study director Eva Ringler from Vetmeduni Vienna’s Messerli Research Institute says: “We conducted several behavioural experiments in the laboratory in which we manipulated the presence of the father with foreign clutches, the reproductive state of the female, and the familiarity of the female with the surroundings – familiar or unfamiliar terrarium.” After they hatch, the tadpoles are usually transported to small pools of water by the males. Females only transport tadpoles if the male is absent. Previous laboratory experiments have shown that females are able to recognise their own clutches by the exact location and that they can remember the location over a period of several weeks.

First proof of cannibalism among female A. femoralis

With their research work, the scientists from Vetmeduni Vienna have now been able to prove for the first time that cannibalism is also common among female poison-arrow frogs. According to their findings, A. femoralis females clearly cannibalise eggs of other females. “This occurred more often in our study if the female had not previously produced her own clutch and the father of the foreign clutch was not present. Whether the females were in their usual or a new terrarium had – in contrast to the males – no influence on the occurrence and frequency of cannibalistic behaviour,” says Sandra Spring, the first author of the study.

Evolution of parental care: Important role of male territoriality

Possible reasons for the observed cannibalistic behaviour may include nutritional benefits through the consumption of conspecific clutches and the enhanced fitness that results in comparison to other females. The fact that the father’s presence is sufficient to reduce cannibalism by females suggests that male territoriality plays an important role for the evolution of brood care. Ringler: “The finding that the mere presence of the father was enough to reduce cannibalism by females underscores the important role of territoriality for the evolution of male parental care.”

The article “Oviposition and father presence reduce clutch cannibalism by female poison frogs” by Sandra Spring, Marion Lehner, Ludwig Huber and Eva Ringler was published in Frontiers in Zoology.