Friday, June 24, 2005

ENV: Not-Really-a-Cat-Friday

Last week i was brought a lizard in a zip-lock bag from the clinic here. I posted earlier that, before i even saw the thing, knowing where it was from, i deduced it was likely a Texas Alligator Lizard, Gerrhonotus infernalis. It was.

A couple of days later one of the kids brought me another lizard, this one trapped inside a green valgene water bottle. It was the same basic size (about five inches in body length, minus the very different length tails), and the same basic bulk, but otherwise the two lizards were about as different as lizards can be. This second lizard was a Texas Spiny Lizard, Sceloporus olivaceus.

While both are inhabitants of our rocky areas, about there the differences end. The Alligator Lizard prefers horizontal slab-like zones of limestone, a bit higher humidity, and shade -- thus it's being found at our clinic, a rock cabin of natural limestone laid in slabs, the natural humidity of an abode, and the shade of Escarpment Black Cherry and Texas Red Oaks. Before rock cabins the lizard would be likely limited to the one wetter canyon on our place.

The Spiny Lizard on the other hand is a denizen of bouldered slopes, where it may sun on exposed rock. Mostly it is arboreal though, it climbs trees well and can be seen on Plateau Live Oaks, Pecans, and Arizona and Mexican Walnuts in our area, all of which typically have angled trunks.

The Texas Alligator Lizard has only recently been split from the more widespread Mexican species Gerrhonotus liocephalus (many old guides will list our critter as G. liocephalus infernalis). Compared to the other lizard, Alligator Lizards are relatively smooth, a characteristic of the family Anguidae. They also have somewhat prehensile tails that may be equal to or longer than their body length.

It is basically a lizard of the Edwards Plateau in Texas, though it is also known from the Chisos and Christmas Mountains in the Big Bend, and down into Coahuila, and perhaps Chihuahua. There is also an isolated locality east of the plateau.

Update: Regular reader Jeanette Scott (nee Carignan) sent an email to say that there is a Brewster County record from well north of the Chisos and Christmas Mountains -- in the Del Norte Mountains, east of Alpine -- and she has published the record: Carignan, J. M., 1988. Geographic range extension for Gerrhonotus liocephalus infernalis (Texas Alligator Lizard). Herpetological Review, Volume 19 (3): 60.

The Texas Spiny Lizard is a member of the family Phrynosomatidae (although until recently, the spiny lizards were considered to be in the family Iguanidae), and displays the typical familial character of rough, keeled scales -- in this case, projecting ones which give it its nomer. Texas Spiny Lizards occur from southern Oklahoma down into Mexico, including a wide swath of central Texas.

Largely these lizards are insect and small arthropod eaters, although the Alligator Lizard will take small rodents, and likely ground-nesting birds' eggs as well (it can grow to 20 inches). The Spiny Lizard hunts by watching and then running down its prey. The Alligator Lizard is a stealth hunter that stalks then lunges at its prey in the final millimeters.

Be sure to check out the weekly Friday Ark at The Modulator

Texas Spiny Lizard, Sceloporus olivaceus

Texas Alligator Lizard, Gerrhonotus infernalis

And some miscellaneous at my window things last night
included two species of Mayfly and an inch-long Cicada.


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