Tadpole cannibalism in Trinidad - reptilenesia

Trinidad stream frog (Mannophryne trinitatis) feeding on its conspecific. Photo by Renoir Auguste

The idea of cannibalism brings thoughts of horror movies. Yet, in the animal kingdom it occurs more frequently than we think. Cannibalism appears to offer benefits to animals. Some of these include sources of food in resource poor environments, and reduced development time. However, there are also disadvantages of cannibalism, for example increased risk of disease.

Cannibalism has been recorded in a variety of animals, including frogs. One such frog whereby cannibalism has been observed is the Trinidad stream frog (Mannophryne trinitatis); an island endemic. As the common name suggests, it is found across streams in Trinidad, abundantly across the Northern Range, but also in the Central Range. When mating occurs, the males take the tadpoles on their back and carry them to pools of water, often void of predators for them to develop. Sometimes these pools of water are large. Other times, the pools of water are small, leaving them prone to drying up, especially in the dry season. When this happens, competition for resources among the tadpoles in the pool increases.

An example of potential cannibalism was seen in 2018 (Auguste and Angeli 2018). The tadpoles were observed in a relatively small pool of water with the nearby stream dried up. It was unclear if the tadpole had already died and its conspecifics were feeding on it - or if they attacked it while it was still alive. Nonetheless, why does cannibalism persist with this species? Perhaps with further study one can discern what the contributing factors are. This may then provide insight into adaptations to the quality of habitat and to changing climatic conditions.

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