Triprion petasatus is a modest frog. Medium in size with a little snoot, these polite looking animals are found in Mexico, alongside the Mexican treefrog Smilisca baudinii. The two don’t look much alike but they both begin life in water where they hatch into tadpoles and later metamorphose into frogs. Tadpoles conventionally feed on algae, invertebrates, eggs, and other tadpoles, but consumption of frogs is extremely rare. A Natural History Note published in the journal Herpetological Review tells of the surprising discovery by a group of researchers in Mexico who discovered several T. petasatus tadpoles feasting on Mexican treefrogs. Limited food sources could explain the shocking discovery but whether or not the predatory behavior is beneficial to the tadpoles remains to be seen.
The team was working in Calakmul Biosphere Reserve, Mexico, when they discovered the body of a deceased Mexican treefrog that was in the process of being slowly gnawed upon by a T. petasatus tadpole inside an artificial water tank. These tanks had been brought into the region to try and support amphibian populations as in recent years temporary pools have been shrinking, making a water-born start to life all the more treacherous.
Under these conditions, food supplies can run low and previous research has found that T. petasatus tadpoles will cannibalize members of the same species when times get tough. However, these findings were observed in an experimental setting where tadpoles were isolated from other anuran species. This new discovery could therefore indicate that when hungry these ambitious tadpoles will go one step further in the pursuit of a snack and take on a fully metamorphosed frog of a different species.
Nutrients in early life has a big influence on the growth rate of tadpoles, with a high-quality diet leading to a faster rate of metamorphosis. This is a very good thing for the developing tadpoles, which are extremely vulnerable to predation when they are but wee babies.
The T. petasatus tadpole found grasping the dead S. baudinii metamorph in a tank was the first of six carnivorous tadpoles found in a 4-hour search of the area. The researchers posit that the behavior is likely either the result of near-starvation or an effort to accelerate metamorphosis by feasting on something a little more substantial than algae. To their knowledge, it’s the first time a tadpole has been recorded killing and feeding upon the metamorph of another anuran species. Badass.
“Due to their cryptic lifestyles, herpetofauna are often overlooked and so our understanding of the majority of species basic life history is limited – every bit of information helps fill in our mosaic of the natural world,” said author Alexandros Theodorou in an emailed statement. “Being opportunistic feeders will reduce the amount of time spent in the vulnerable larval stage. This is extremely useful information to have about survivorship, predator-prey interactions, and conservation.”
