Horns aren’t just for rhinos and cattle. A fair number of snake and lizard species have heads adorned with spiky, scaly accessories. But how the reptiles snag food may determine whether having horns is an asset or a liability.
Squamates — lizards and snakes — have repeatedly evolved horns atop their heads, on their eyebrows and jutting out from their snouts (SN: 6/9/20). Prior studies suggested these ornaments may have different functions, such as being used in courtship, defense or breaking up the body outline to evade detection. But Federico Banfi, a herpetologist at the University of Antwerp in Belgium, and his colleagues wondered whether horns’ camouflage benefits still help animals that move around a lot when hunting. If not, or if horns hinder the animal’s movements, this might discourage the protuberances from evolving in more active species.
The team compiled previously published datasets that classified lizards and snakes as either sit-and-wait predators or active pursuers, yielding 1,939 different species with 175 that had horns — defined as projections of bone or keratin on the animal’s snout, eyebrows or head.
The team mapped the presence or absence of horns and the reptiles’ hunting style onto a previously published squamate evolutionary tree, finding the projections evolved independently about 69 times. Sure enough, horns were much more common in sit-and-wait predators than in their more active counterparts. Of horned squamates, 164 — 94 percent — were also relatively stationary ambush hunters, with just 11 — 6 percent — categorized as active predators.
2023-12-12 14:00:00
Article from www.sciencenews.org