JIM CONRAD'S
NATURALIST NEWSLETTER
Written at Hacienda San Juan Lizarraga
one kilometer east of Telchac Pueblo, Yucatán, MÉXICO
and issued from Hotel Reef Yucatan 13 kms to the north

December 8, 2005

HOUSE GECKOS
Each night four or five minutes after I turn off the light, in that half-sleep when thinking is on the verge of becoming dreaming, then it comes:

Krrrk krrrk krrrk krrrk krrrk krrrk!

With my bare, high-ceilinged, stuccoed stone walls, the krrrking is loud and shocking. I must begin a while new cycle of going to sleep and there's a good chance that when I reach the same stage of half-sleep as before precisely the same krrrking will erupt, with the same consequences.

The krrrking critters are cream colored little geckos 2-3 inches long. They climb the walls of all the buildings here and I hear them among Hotel Reef's fancy rooms. However, last year at Komchén I never saw or heard any. I'm guessing that that's because of the several cats there. Here we have fewer cats and more buildings.

For weeks I've been wondering what gecko species I had. Therefore, when this week the long-ago-ordered book AMPHIBIANS AND REPTILES OF NORTHERN GUATEMALA, THE YUCATÁN, AND BELIZE, by Jonathan Campbell, finally arrived, the first thing I did was to open it to the gecko section. Unfortunately, my sleep- disturbing gecko wasn't there. A note in the general info section said that several alien gecko species have been introduced into Mexico, and the book presented only native species.

Back in Hotel Reef's computer room, by using Google's image option and the keywords "gecko, Mexico," I found pictures of my obstreperous roomy. Identification was particularly easy because where the reptile's tail attaches to his body several short, sharp but pliable spines appear. My sleep disturber was the Common House Gecko, HEMIDACTYLUS FRENATUS, which you can see and read about at http://www.wildherps.com/species/H.frenatus.html.

While Googling up that identification I ran across a page in Spanish listing amphibian and reptile species that have been introduced into Mexico -- Mexico's invasive species. Here I learned that my Common House Gecko is a native of islands in the Pacific Ocean, and that it's found in quite a number of places throughout Mexico. Plus, at least two other introduced gecko species occur here in the Yucatan -- and that's atop three native Yucatec species.

Ten invasive amphibian and reptile species are listed on this page, which is in chart form and thus understandable even for non Spanish speakers. It's here.  

*****

VENOMOUS SNAKES OF NORTHERN YUCATAN
The arrival of Campbell's herp book ("herp" is short for "herpetology," a study embracing both amphibians and reptiles) has cleared up the venomous-snake situation here.

In our area people who machete bushes and weeds day after day and see more snakes than anyone are absolutely convinced that nearly every snake they encounter is deadly. Still, I've been telling them that during my several months of being in this area, after encountering lots of snakes, I've never seen a single venomous one. My saying this has accomplished one thing: People here are convinced that I know absolutely nothing about the local snakes.

According to Campbell's herp book, in arid, scrubby northwestern Yucatan we have these three venomous snake species:

1) Neotropical Rattlesnake, CROTALUS DURISSUS
2) Cantil, AGKISTRODON BILINEATUS
3) Variable Coral Snake, MICRURUS DIASTEMA

This is pretty close to the situation for much of the US Southeast: There's a rattlesnake, the Cantil belongs to the same genus as the Cottonmouth, and then there's the coral snake.

Eastward and southward from here in northwestern Yucatan, average yearly rainfall increases, vegetation becomes much lusher, and the landscape supports a greater species diversity. In northeastern Yucatan, which includes the Cancun area, a fourth venomous species occurs:

4) Barba Amarilla (Fer de Lance), BOTHROPS ASPER

Farther south in much rainier, high-forest areas other venomous snakes occur: The Jumping Pitviper; the Eyelash Palm-pitviper, and; the Rainforest Hognosed Pitviper.

Twice since I've been at San Juan good fusses have erupted over "coral snakes." One was curled beneath a potted plant on the veranda when Doña Lupe the maid came watering. Both of these "corales" were Tropical Milksnakes, LAMPROPELTIS TRIANGULUM, admittedly looking very much like real coral snakes, but about as harmless and tame as a snake can be.

You can see how similar the are yourself. Our harmless milksnake is shown at http://www.cnah.org/detail.asp?id=179 while the dangerous Variable Coral Snake is at http://www.uta.edu/biology/campbell/guatemala/images/Micrurus_diastema.JPG  

*****

AN ENDEMIC HUMMINGBIRD
For the traveling naturalist few things are more agreeable than seeing an endemic organism at home in its natural environment. By "endemic" I mean an organism very limited in its natural distribution.

Medical people seem to have a different concept of the word endemic. They might say "Chagas Disease is endemic to tropical America," simply meaning that it's found here. A biologist wouldn't say, however, "That bird is endemic to tropical America," because tropical America is a vast region. A biologist might indeed say "That bird is endemic to Cozumel Island," meaning that the bird, on the whole Earth, is found only on Cozumel Island, which is a small place.

This week I saw an endemic hummingbird endemic to the northern Yucatan Peninsula's coastal zone, plus there's a tiny, mysterious population across the Gulf of Mexico in the state of Veracruz. The pleasure in seeing the bird was much diminished, however, because it was dead, having been hit by a speeding car on the beach road near Hotel Reef.

The hummer was the Mexican Sheartail, CALOTHORAX ELIZA, easy to identify because of its long, black, conspicuously down-curved bill, its glittering, rose- pink throat, or gorget, and -- most strikingly -- its very long, deeply forked tail. You can see one at http://www.surfbirds.com/media/gallery_photos/20050205051118.jpg.

The habitat of Mexican Sheartails is described as arid scrub, semiopen mangrove edge and gardens, so coastal northern Yucatan is perfect for it.

*****

COOPERATIVELY SINGING MELODIOUS BLACKBIRDS
Melodious Blackbirds are common from central Mexico to Costa Rica. We have lots of them at the hacienda. They are like the US's Red-winged Blackbirds except that they are totally black. You can see one at http://world.std.com/~eva/belize/Cockscomb/bze_melodious_blackbird.jpg.

I'm astonished that my field guides do not mention something remarkable I am seeing these birds do every morning: They are "cooperatively singing." Two birds cooperate in making a call that sounds like it is coming from a single bird.

The songs are very varied but a classic case arises when two birds are perching together high in a tree preening as the rising sun warms them up. One bird suddenly makes itself taller and stands stiffly, enlarges his chest and ruffles his feathers, and opens his beak.

His companion, seeing these signs, does the same. Then follows a two-bird-made song in which one bird makes a piercing POING call, which can sound a little like a much amplified drop of water in a bathroom sink.Another part of the call is a loud CHRRR or maybe a metalic-sounding ping, which may begin the call. The two birds alternate their calls for several seconds and it sounds exactly as if one bird were making a single very melodious call. As the birds call they pump up and down on their legs, alternating with one another.

Sometimes the cooperating birds can be 50 or more feet apart, in different trees, but then the complementary effect is not nearly as coordinated. The calls are usually out of phase and often the birds don't bother to pump their legs with such vigor. They need to be about two feet apart to really do a good job. Often, especially later in the day, birds sing alone, performing just one part of the song, and sometimes lone birds call with other sounds not incorporated in the POING CHRRR or PING POING call. Lone birds don't seem nearly as enthusiastic about their calling as birds in a pair cooperatively singing.

Apparently these callings are at least partly meant to defend territory, because when a couple nearby calls I can hear far away another couple responding.

*****

MILKSNAKES, TREESNAKES, HOOPSNAKES & GEORGE BUSH
When I told Roberto the gardener that the "coral snakes" he'd so often killed had actually been harmless milksnakes, I also told him that as a farm kid in Kentucky I'd been taught that milksnakes steal milk from cows. Then he volunteered his own snake- and-milk story:

"We have a snake here in Maya called Xay Kam. It's very big and dangerous looking, and it can smell the milk of a mother who has just given birth, and whose breasts are full of milk. When the snake smells the milk, it goes looking for the mother. When it finds her, it waits until she's asleep, then it wraps itself around her so tightly that she can hardly breathe, and at the same time it sticks its tail up her nose so she can't inhale. Then the mother dies of asphyxiation and the snake takes her milk. At that big hacienda just north of here, that's exactly what happened a while back. They found the mother all sprawled out and dead, and everyone knew what had happened."

Roberto wasn't sure whether two snakes were needed to plug both of the mother's nostrils, or whether the tail entered one nostril, bent around inside her head, and then came out the other nostril. However, looking at pictures in my new book he did finger as the Chay Kam the harmless but mean-looking Tiger Treesnake, SPILOTES PULLATUS. He said that we have a couple of them here hanging out in some big Neem trees.

I have to admit that as I listened to Roberto's story I felt a little smug, for I am from a culture that has evolved beyond entertaining such superstitions. However, then I remembered that as a child not so long ago not only was I was taught, and seriously believed, that milksnakes steal milk, but also that I needed to watch out for hoopsnakes.

Hoopsnakes take their tails into their mouths, form themselves into hoops, and roll down hills. The instant before they reach a person they straighten out and stab their tails through your body like poisoned spears.

In fact, maybe Roberto's culture is slowly abandoning its superstitions while my own is returning to a time when misinformation confuses and terrorizes average people. If that is true, no agency is more responsible than the current US administration.

Once again I refer you to the Union of Concerned Scientists' document called "Scientific Integrity in Policymaking: An Investigation into the Bush Administration's Misuse of Science." The page where you can read and download the 2004 report and an update, plus find other links of the same sort, is here.

The Tiger Treesnake is either a herpetological curiosity or a demon in the night. The presidency is either a position of leadership, or what it seems to be, judging from evidence at hand.

*****

Best wishes to all Newsletter subscribers,

Jim

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