CHS Blog

Otter and loon fall for fake turtles

May 29, 2020
Grégory Bulté, Department of Biology, Carleton University

As part of our research on the mating habits of the northern map turtle, we used 3D printed turtle decoys to woo wild turtles and recorded their behaviours with action cameras. Our fraudulent turtles worked their intended goal admirably well, but they also attracted the unwanted attention of peckish neighbours.

Adult turtles have few predators in Canadian waters but otters are a notable menace as Matt Keevil, Ron Brooks and Jackie Litzgus from the Algonquin snapping turtle project have clearly shown. Knowing this, we were not extremely surprised to see an otter nibbling at our male decoy.

An attack by a loon was more surprising, however. Even the relatively small map turtle males seem too big of a bite for a bird swallowing its prey whole. Apparently, this loon doesn’t think so and struck three times at our model before giving up.

This video was captured at a communal hibernation site which is adjacent to a small island hosting a nesting pair of loons since at least 2004. If a loon can figure out how to gobble small map turtles, this would be the spot to do it. This could be an example of individual specialization, but it could also just be a singular behaviour from a loony individual.

These two predation attempts are the only ones we captured in roughly 380 hours of video recordings involving turtle decoys and both were directed at males. We used male decoys in only about 20% of the recordings while female decoys were used in all of them. These numbers suggest that predation attempts on adult map turtles, although seemingly rare, are more commonly directed toward males than females. This is not very surprising considering the much larger size of females.

Whether our decoys give a fair appreciation of predation risk is unclear, however. Decoys are sitting ducks and can be expected to overestimate predation risks. On the other hand, decoys will underestimate predation risk if predators see these imposters for what they are or learn to ignore them after having taken an unsavoury bite at them. What is clear is that the underwater lives of turtles still have many secrets.