Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
A photograph of an alligator on the back of an inflatable alligator is making the rounds of a variety of news media.
An alligator supposedly sunning itself on an inflatable alligator in Miami-Dade Co., Florida.
This is a stuffed alligator. The splayed legs, open mouth, and curled tail are typical of the poses used for souvenir stuffed alligators, and atypical of the way a live alligator would pose, especially atop a floating object. The body and tail are overstuffed, and do not look at all like a live alligator. The posterior half of the tail hovers above the float, and the coup de grace is that both visible limbs are sticking out stiffly, perpendicular to the body, and casting shadows on the float. As Monty Python would have put it, this is an ex-alligator.
Note in the enlargement below the shadow, and how you can see a spot of sunlight reaching the float behind the crook of the knee.
Another Florida correspondent sends this picture of several American alligators (Alligator mississippiensis) in Oviedo, Florida.
American alligators
They’re at a combination bar, gift shop, and wildlife refuge (the kind of place Florida specializes in, I gather!) on the shore of Lake Jesup. Alligators are said to be abundant in the lake, and a few are kept on display near the gift shop. You can still see on the alligators’ flanks some remnants of the yellow stripes typical of young alligators. These look to be somewhere in the vicinity of 7 feet (the one back right is smaller), but that’s just a guess. There are well authenticated records of alligators 19 feet long, but none that big has been seen in a long time.
Like the Brown Pelican, American alligators are also a conservation success story. Greatly depleted by both the draining of swamps and hunting for the leather trade (boots, handbags, etc.) through the 19th and 20th centuries, they received federal protection in the 1960s, and by 1987 they had recovered sufficiently so that alligators are now subject to endangered species regulation only because they can easily be confused with species that are endangered. (In federal jargon, that means they are “threatened by similarity of appearance”.) They are now common in many areas, and hunting/trapping them, and selling alligator products, is once again broadly legal. (Much commercially marketed alligator meat and other alligator products comes from alligator farms, not from wild alligators.) Live alligators, mostly through the pet trade, pop up all over the US.
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.
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).
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)
