Tag: crocodilians

Leaping lizards!

May 15, 2014 • 11:53 am

Before someone corrects me, yes, I know that crocodiles aren’t lizards (they’re in different orders of reptiles), but the title of the post will resonate with you if you’re “of a certain age,” as they say.

TheYouTube notes give the location, and I’m not sure how I feel about keeping crocs in captivity and having them do tricks for people. I suspect, though, that, being sedentary, they don’t suffer from this as much as do beluga whales, porpoises, or orcas:

Thanks to http://www.crocosauruscove.com in Darwin, Australia. You can feed crocodiles, swim with crocodiles, and get really up close to them. Feeding them using a fishing rod is a really unique experience, as you can see they can jump completely out of the water.

The behavior is surprising, though. Given that they probably never do this in nature, it must be something of a spandrel (a byproduct of another evolved behavior), supported by the observation that they seem to leap by making swimming motions.

Further notes by Greg Mayer

These are saltwater crocodiles (Crocodylus porosus) at Crocosaurus Cove, a reptile zoo in Darwin, Northern Territory. “Salties” are known for their ability to jump vertically, but this is the only film in which I’ve seen them completely clear the water. (There’s a possibility that the crocodile whose tail left the water may have been hanging on to a “fishing” line, and thus been partially pulled up, but although no segment shows both the head and the tail out of water simultaneously, I think they are actually leaving the water on their own.) The usual context for seeing these vertical leaps by salties are by wild crocodiles which have become habituated to the presence of tour boats and the food proffered from them.

"Brutus", the one-armed saltwater crocodile, jumping for tourists on the Adelaide River, Northern Territory. Photo from Courier Mail, Brisbane.
“Brutus”, the one-armed saltwater crocodile, jumping for tourists on the Adelaide River, Northern Territory. Photo from Courier Mail, Brisbane.

“Brutus”, said to be 5.5 m long,  is much larger than the crocs in the film, and I don’t think he would be able to leave the water completely. (You can judge the size of a saltie by the shape of the head– they start out narrow, and get relatively broader and more massive as they get bigger.)

The way the crocs jump is by using their standard swimming motion: lateral undulation, legs tucked in, with the tail providing most of the propulsion. In jumping, they swim straight up (instead of more horizontally), and develop enough head of steam to partially or entirely break the water surface. Jerry supposes that they never do this in nature, but I’m not so sure. A number of crocodilians are known to skulk around waterbird rookeries, eating the birds that may fall out of the trees into the water, and there’s no reason to think they wouldn’t jump up to grab a bird as well. Here’s a photo of a Nile crocodile going after a grey heron from the National Geographic photo contest. (But note: the water that this Nile croc is in is much shallower, and it may be pushing off with its feet rather than its tail.)

Nile crocodile jumping for grey heron. Photo from Adelaide Advertiser.
Nile crocodile jumping for grey heron. Photo from Adelaide Advertiser.

h/t: Matthew Cobb

Cat versus caiman

September 17, 2013 • 9:07 pm

by Greg Mayer

Jaguars are the largest species of American cat, and are the top carnivore from the southwestern US to Argentina. In the Pantanal wetlands of southern Brazil, Justin Black took a series of extraordinary photographs showing just how top a carnivore it is, as a jaguar took on, and carried away to eat, an adult caiman.

A jaguar, having seized an adult caiman by the neck, prepares to carry off the ill-fated reptile.
A jaguar, having seized an adult caiman by the neck, prepares to carry off the ill-fated reptile.

Black obtained an exquisite set of photos, showing the jaguar spying the caiman from the shore, swimming out to the sand bank on which the caiman rested, sneaking up on it and seizing it from behind, and then carrying the living caiman in its jaws back across the water; the whole set of photos can be seen in the Daily Mail. It is likely that the jaguar eventually dispatched the caiman, and consumed it. Jaguars and anacondas are among the few known predators of adult caimans. This species of caiman grows only to about 8 or 9 feet. The largest species of caiman, the black caiman, reaches 13 feet or so, and there are two species of crocodile in South America that are bigger than that; a jaguar might have trouble handling these larger crocodilians.

Cretaceous crocs crunch critters

August 17, 2012 • 11:03 am

by Greg Mayer

Earlier this year my friend Chris Noto and his colleagues Derek Main and Stephanie Drumheller published a paper describing injuries to turtle and dinosaur bones from the Cretaceous that show evidence that they were preyed upon by crocodiles.  Besides the irresistible alliteration, their paper serves to show that we can sometimes learn much more about extinct animals than merely their skeletal morphology, and, with the right sorts of evidence, can learn about their behavior, ecology, and physiology as well.

Cretaceous crocodile crunching critter (by Jude Swales)

The fossils were recovered at a site in Texas known as the Arlington Archosaur Site. Modern crocodilians feed on turtles, and also on dinosaurs, if you think of birds as dinosaurs (which, in a sense, they are).  They will seize turtles side to side (as shown in the reconstruction) or top to bottom. American alligators are particularly fond of turtles, and, compared to some other crocodilians, their rear teeth are especially blunt and peg-like (sort of like molar teeth). This helps to crush the shells of turtles they are eating (which, I have been told, break with a popping sound). E.A. McIlhenny, the great naturalist of hot sauce fame, wrote:

I have seen alligators catch large terrapins and turtles of considerable size and crush their hard shells as if they were made of paper, swallowing them whole.

Tooth scars on a turtle shell (above) and a dinosaur leg bone (below).

Noto et al’s study is a nice example that shows we can learn about more than just the morphology of extinct creatures, but can also learn about thier biology and the paleocommunities they lived in, including (in other studies) ecology, behavior, and even color (see, for example, Matthew’s recent post here, and earlier posts by Jerry here and here).

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McIlhenny, E.A. 1935. The Alligator’s Life History. Christopher Publishing House, Boston. (Reissued in a facsimile edition in 1976 by the Society for the Study of Amphibians and Reptiles, with a foreword by the great herpetologist and conservationist, Archie Carr.)

Noto, Christopher R., Derek J. Main, and Stephanie K. Drumheller. 2012. Feeding traces and paleobiology of a Cretaceous (Cenomanian) Crocodyliform: Example from the Woodbine Formation of Texas. Palaios 27:105-115. (abstract)