by Greg Mayer
Last month Matthew asked me about herbivory in reptiles, and part of my reply was that there are few or no reptiles that are exclusively herbivorous. The ones that came closest that I could think of were the true land tortoises (family Testudinidae, sensu stricto). I wrote, “some true tortoises are pretty close to vegetarian, but I’d still say they are at least facultatively omnivorous.” And sure enough, shortly after I ran into the following:
The video, of a giant tortoise (Aldabrachelys giganteus) on the island of Fregate in the Seychelles eating a noddy (Anous tenuirostris, a member of a genus of common tropical terns), accompanied a paper on the incident published last August by Anna Zora and Justin Gerlach in Current Biology. Wikipedia makes an amusing observation about noddies:
Anous is Ancient Greek for “stupid” or “foolish”. Noddies are often unwary and were well known to sailors for their apparent indifference to hunters or predators.
The sailors were right– the noddy, it seemed to me, though not fledged, could have gotten away. Perhaps it had a strong aversion to moving away from the immediate vicinity of its nest.
We’ve encountered island biologist Justin Gerlach before here at WEIT, where I noted his paper on an Aldabran tortoise’s ocean journey.
We’ve encountered Justin Gerlach before here at WEIT, where I noted his paper on an Aldabran tortoise’s ocean journey (picture just above). The Fregate tortoises are probably introduced from Aldabra, but the systematics of Indian Ocean tortoises is not entirely settled, and there have been a number of claims of tortoises surviving from the Seychelles populations that are usually thought extinct.
As far as reptile feeding in general goes, snakes, crocodilians, and the tuatara are exclusively carnivorous (in the broad sense of feeding on any kind of animals, including carrion), lizards range from carnivorous to omnivorous with a large herbivorous component (e.g. iguanas), and turtles are omnivorous, ranging from mostly carnivorous (e.g. snapping turtles) to mostly herbivorous (e.g. true tortoises).
Gerlach, J., C. Muir and M.D. Richmond. 2006. The first substantiated case of trans-oceanic tortoise dispersal. Journal of Natural History 40(41–43): 2403–2408.
Zora, A. and J. Gerlach. 2021. Giant tortoises hunt and consume birds. Current Biology 31: R989-R990.