Friday, July 14, 2006

Amphibia, Etcetera

Sorry. No exciting news about Ivory-billed Woodpeckers here. This week my days off were consumed with tedious yard work and a major painting project. Not the way I wanted to spend my time, but there you are. No adventures in the swamp, no bark scaling or mysterious holes in trees, no tantalizing encounters with Pileateds, not even an intriguing double-knocky sound. Nada.

My riding mower hasn't been the same since I whacked it into an exposed tree root last year. Ever since then the blade hasn't cut evenly, creating what look like crop circles. This week it died, and decided to do so in a most inopportune location. With the rear wheels locked up I had to drag/push it all the way from the house back to the garage for proper internment. A hot sweaty miserable job. Of course the immediate problem still remained. The lawn demanded mowing, more so because I had put it off for weeks. So yesterday I went out and bought a push mower. Worked like a charm! Cut the grass and no crop circles.

While mowing I scared up yet another Southern Leopard Frog. Very pretty as frogs go. Unfortunately one didn't hop out of the path of the mower. Blade and frog intersected. The mower won. Results were messy.

While I'm on herps, I recently read in an AP News article that Mediterranean Geckos are now found as far north as Kansas. Is this more evidence of global warming, or just another example of a non-native species that has been very successful? In my old copy of A Field Guide to Reptiles and Amphibians of Eastern/Central North America (1975 edition) it states that "the speed with which this gecko has expanded its range in the southern U.S. in recent years is even more remarkable than the spread of the cattle egret." The outdated range map in the book indicates that the gecko was then distributed across South Texas, with scattered populations in East Texas, Louisiana, and Florida. Looking at the 1998 edition it appears that the gecko's range had continued to expand, with populations as far north as central Oklahoma.

Mediterranean Geckos are nocturnal. At night they crawl over the walls and windows of our house, and it's not unusual to see a dozen or more around our porch on a warm evening. We have to be careful when opening the doors at night lest one of them tries to wriggle inside. Same goes for Gray and Green Treefrogs, which are similarly fond of door sitting.

Ever since I moved here I have been puzzled by one of the common nighttime sounds that I hear coming from leafy places around my yard. I've also heard this sound at my friend's house in Spring, which is just north of Houston. I would describe it as a series of chirps or clicks, and for a long time I figured it was probably some kind of insect. There are tropical frogs that tink and click and chirp, but from the range maps in my books it didn't look like any occur this far north. Then I read that Mediterranean Geckos will emit squeaks and clicks, and because I had seen geckos while searching for the source of the clicking I concluded that I had finally solved the mystery.

But I was wrong. I described the sound I'd been hearing to John Arvin, and he told me that what I'd heard was the Rio Grande Chirping Frog, a species which has undergone a range expansion similar to that of the Mediterranean Gecko. A little online research verified that despite my outdated range maps the Rio Grande Chirping Frog has spread to Southeast Texas. Click here to hear one chirping.

There's a lesson here somewhere. Wildlife populations are dynamic and subject to change. Range maps are valuable tools, but can't be taken as gospel. Even creatures without wings, such as geckos and frogs, can undergo rapid range expansions. With birds the power of flight can accelerate things. In 1987 I saw Eurasian Collared-Doves in the Florida Keys. At that time the species had only recently arrived in the U.S., and was just beginning it's dramatic North American range expansion. Back then you had to go to southern Florida to see one. It took less than twenty years for the species to spread across the continent to California. Here in Texas they are quite common. I have yet to get one for my yard list, but it's only a matter of time. They are plentiful in Beaumont, a short distance to the south, and lately I've been seeing them in Lumberton, which is just north of us.


At 2:07 PM, Anonymous Anonymous said...

I don't mind it so much when the geckos get inside the house. They are friendly cute little critters. And aren't they supposed to eat those roaches that you complained about. Although it must be the small roaches if they do.

I also like those Chirping Frogs. They are a nice sound at night with the windows open. I'm sure with global warming they will be in Canada in 50 years.

Nice post. Good memories.

Now get back to finding the Ivory Bill. What does Arvin say? Has he found one yet?


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