Posted for Katharine Sanderson

Alligators have developed a special pelvic thrust to help them roll over.

So say researchers at the University of Utah and I am slightly disappointed that the headline “Croc and roll” has not been used by a single press outfit. You’ve got to love a good cliché now and again.

Alligators work the muscles in their diaphragm, pelvis, abdomen and ribs to shift their lungs, and so change their buoyancy. This allows them to perform the devastating dives and rolls that they use to kill their prey without the use of flippers or fins. Sneaky, no?

“The secret to their aquatic agility lies in the use of several muscles, such as the diaphragmatic muscle, to shift the position of their lungs,” says researcher C.G. Farmer (press release). “The gases in the lungs buoy up the animal, but if shifted forward and backward cause the animal to pivot in a seesaw motion. When the animals displace gases to the right or left side of the body, they roll.”

To check the mechanism of the diving crocs, the researchers strapped weights to their noses with duct tape, then checked how much less they used their muscles when they dived. They then repeated the process by taping the weights to their tales, and finding they needed to use the same muscles more.

The finding is exciting the world’s press. PA says it shows crocodiles and alligators “behave like sophisticated submarines”. Both Reuters and AFP use the phrase “nary a ripple” to describe the alligators’ movement through the water. And ‘rock and roll’ which almost sounds like croc and roll has been favoured by others.

The study will be published in The Journal of Experimental Biology in April.

Photo: Study author T.J. Uriona holds a juvenile American alligator / Hannah Chirillo.