Mammals are unique in that they’re practically the only creatures that take the time to chew their food. Or at least that’s what we thought. New research shows that stingrays also use chewing motions to grind down their meal. And as this video attests, it’s pretty damned weird to watch.
Chewing is a relatively recent evolutionary adaptation. It likely emerged some 60-70 million years ago when mammals first diversified, allowing them to forage on new prey, such as insects.
Other animals, such as crocodiles and great white sharks, don’t actually chew: they break apart their prey with scissor-like chomps. Apart from mammals, some lizards have been observed to chew, as well as some carp, but that’s about it. But as a new study published in Proceedings of the Royal Society B points out, we can now add another animal to this exclusive list.
Researchers from the University of Toronto Scarborough are the first to observe chewing behaviour in ocellate freshwater stingrays. Using high-speed videography, the researchers demonstrated that stingrays actually chew their food similar to mammals.
These elasmobranchs (sharks and rays) specialise in eating insect larvae, which are protected by extremely tough exoskeletons. The chewing motion allows the stingrays to grind down the larvae for easier swallowing. This may not sound very appetising, but the larvae are packed with nutritious fats.
Stingrays are able to accomplish this feat because they can extend their jaws away from their skull, while also protruding their jaws laterally, moving them left and right in a chewing motion. The researchers also discovered that ocellate stingrays lift their disk-like fins to suck prey underneath their body, allowing them to capture their prey with their pectoral fins. [Proceedings of the Royal Society B]