March 18, 2006

TWO MALE BLACK IGUANAS BATTLE IT OUT
The instant I arrived at my favorite iguana-watching spot I knew I was in for a show. Atop two stone pillars inside the rubble zone of the old hurricane- collapsed henequen mill, not three feet apart, two yard-long male Black Iguanas, CTENOSAURA SIMILIS, perched glaring and head-lifting at one another. A head-lift consists of throwing the head so far back that the chin points skyward. Lasting for just a second or two it displays the throat, often black- speckled on a gray background, and two big throat pouches that make hormone-juiced-up males look like they have really bad cases of mumps.

One iguana was especially skinny so I named him Wiry, and the other was full-bodied but with a bloody red spot on his back so I called him Bloody. I figured that Wiry was the dominant male in the area and Bloody was a challenger. I've seen that dominant males spend so much time guarding their harem and fighting male interlopers that they don't eat enough and loose weight, so I figured that that was Wiry's story, and maybe Bloody's bloody spot resulted from losing an earlier fight.

After a few minutes Wiry couldn't stand it any longer, descended his pillar and clambered up Bloody's, and the battle began.

Each iguana went for the other's side just behind a front leg. Each seemed about to clamp down on a large section of the other's ribcage but, amazingly, neither bit. Both could have closed their jaws on the other but both held their mouths so wide open that the tips of their teeth hardly touched the other's skin. Instead, they kept maneuvering for better potential bites -- which meant that the pair slowly circled atop the pillar, like strategizing Sumo wrestlers angling for the right moment to strike. When the terrible bites did come they happened so fast that my mind didn't register anything other than that suddenly both had big mouthfuls of the other. Soon it became clear that the goal wasn't to bite into the other's side, but rather to grab the ridge of the back right behind the front shoulders -- where Bloody's bloody spot was.

They held onto one another for three or four minutes but then they came undone, and started it all over again. At the end of the next biting Bloody fell from atop the pillar, ignominiously right onto a lolling female. Wiry slowly descended, both head-lifted at one another like bowing Sumos, and another round ensued.

Three more circlings ending in bitings took place, Bloody getting the worst of it each time. Sometimes Wiry held Bloody with his belly skyward, his legs pawing at the air. Sometimes Wiry, clamped onto Bloody's nape, shook Bloody like a dog shaking a gopher to break its neck. During the last round Wiry could only get Bloody's leg in his mouth but that leg was shaken so violently that I'm sure I saw a large tear open behind Bloody's leg.

After about half an hour, with both iguanas smeared with blood -- mostly Bloody's blood -- Bloody staggered from the arena. He left defiantly head- lifting, but he staggered as he crawled away doing it, and as he pulled himself beneath a rock his defeat looked complete, and it was terrible to behold.

Wiry mounted his front end atop a rock and began a series of head-lifts so extravagantly triumphant that his chin passed the vertical mark, curving his body into a shallow C. Then I noticed the females.

From my perspective I could see eleven females around him and there must have been more. They were positioned so that Bloody could see their entire body lengths. It seemed to me that each female was posing in a way that conveyed this message, "Wiry, I have witnessed your triumph, and I confirm your supremacy." It was like a moment in a Wagnerian opera when lesser gods emerge from the mists eerily chanting glorifications to the higher god.

At the periphery of Wiry's circle of females also I saw four or five somewhat smaller males. They were all signaling with defiant head-lifts, and they were all staring exactly at Wiry.

Clearly, the opera had just begun.

*****

A DWARF POINCIANA'S SNAPPING LEGUMES
I watched the above drama from the roof of my lodging, with a Dwarf Poinciana, POINCIANA PULCHERRIMA, right below me. I've mentioned how hummingbirds love this little tree's large, red-and-orange blossoms. These trees, watered regularly, somehow have kept blooming ever since I arrived here in October, though now they bear many more fruits than flowers. You can see the pretty flowers and feathery, mimosa-like leaves at https://www.backyardnature.net/yucatan/caesalfl.jpg.

On that late afternoon with a very hot wind blowing and the sunlight at its most ferocious, curious snapping sounds began originating inside the tree. It was about as loud as snapped fingers but with a dry, woody character. After looking several times, trying to catch the snapper, finally I saw a split-open seed pod, or legume, tumbling from the tree immediately after a snap.

So, here was another example of explosive seed pods! When the legumes' two sides had sprung apart, seeds had been slung a good distance. Many if not most pods explode with such violence that the entire split-open legume breaks from its twig. However, now I began noticing that some exploded pods, or at least one side them, remained on the tree, still coiled after the violent split. Usually such remaining pods or parts of pods remaining on the tree are empty of seeds but I found one with a few seeds still attached, showing how the seeds are arranged. You can see it, much-twisted, at https://www.backyardnature.net/yucatan/caesalfr.jpg.

*****

A FRESHWATER SPRING IN THE SEA
This week I was invited to go on a day-long ecotour offered by an association of underemployed fishermen at the coastal town of Dzilam de Bravo, about half an hour northeast of here. My task was to write up the trip in English so they can better market the tour to the English-speaking public. It is true that during our trip if I had not translated what the guides told me the group of Canadians I was with would have missed many of the highlights.

From the picturesque little Dzilam de Bravo we took two boats up the coast. It was a very windy, sunny day and we all got a little wet from salt spray. However, with seagulls and big flocks of White Pelicans above us playing with the wind, the pleasing rhythm of the boat slapping into the waves, the stinging sunlight and the coolish breezes, we all felt more than content.

About half an hour east of Dzilam de Bravo, maybe 200 yards/meters from shore and in about two feet of water, we came upon a spot maybe five feet across where water was surging up from below. It was an underwater, freshwater spring.

"People from the National Geographic Society measured the outflow at 3500 liters (925 US gallons) per minute," the guide said. "This spring is connected to the big cenote (sinkhole) we're about to visit inland now where you'll get to swim in clear freshwater with tropical fish all around you. The people from National Geographic dove from here through a cave to a point inland where they encountered a hole through which all this water was pouring, but the hole was only about a foot across and the divers couldn't continue. However, they dove into the inland cenote we're about to visit and followed the streaming water seaward, to the other side of the same foot-wide hole they'd seen coming from here. That way they knew that these two freshwater sources were connected."

It all makes sense. The entire Yucatan Peninsula is basically a big slab of limestone very shallowly tilting toward the sea. No rivers flow on northern, inland Yucatan's surface because the peninsula's limestone bedrock is highly fractured and filled with solution features such as underground caverns. Here water drains into cracks and sinkholes, then runs beneath the land's surface. The Yucatan has a never- ending, peninsula-wide river of freshwater beneath it running from its interior toward its coasts. At the hacienda, wells about 20 feet deep stay filled with freshwater even when we're watering plants all day or filling the pool. If a tree can get its roots down to groundwater, it has it made.

By the way, the peninsula's shallow tilt also explains why hundreds of yards/meters from the beach the water still was only a couple of feet deep.

On the Web you can read a somewhat technical history of the "Yucatan Platform," provided by the Quintana Roo Speleological Survey, with an emphasis on how caves and cenotes were formed, at http://www.caves.org/project/qrss/geo.htm.

*****

BOAT-BILLED HERONS
For me the most interesting species seen during the Dzilam de Bravo trip was the Boat-billed Heron, COCHLEARIUS COCHLEARIUS. All of the 16 members of the Heron Family found in Mexico are found in North America, except the Agami Heron, two tiger herons, and this, the Boat-billed Heron. Boat-billeds are truly tropical-habitat specialists, distributed from Mexico to Argentina. The closest we have to them in North America are the two night-heron species.

Like night-herons but unlike most other heron species, Boat-billed Herons have short, thick necks, very large eyes, massive but relatively short beaks, and they are nocturnal (thus the oversize eyes). Boat-bills are even more strictly nocturnal than night herons.

I wouldn't have seen these birds if the local guide hadn't pointed them out. They perched wing to wing next to their nest deep inside a shadowy mangrove thicket, four or five feet below a very exposed, bush- top nest of Great Egrets with fuzzy nestlings begging for food. The Boat-bills moved not an iota and remained perfectly quiet. Yet even in silhouette their big, flat "boat bills" distinguished them from all other herons. You can see the boat bill at http://www.chaffeezoo.org/animals/boatBilledHeron.html.

Across the lagoon we could see hundreds of American Flamingos feeding, showing us how those birds used their large, banana-shaped beaks. With their heads upside down beneath the water's surface so that the bill's bent part acted like a scoop dragged along the lagoon's floor, it filtered out algae and small marine life such as snails and bottom-dwelling insect larvae. However, as far as my books and I know, no one can say why Boat-billed Herons need their kind of bill, which is so like a huge, pointed duck-bill.

*****

MORELET'S CROCODILES
As soon as our van had pulled up to the dock at Dzilam de Bravo we saw a good-sized Morelet's Crocodile, CROCODYLUS MORELETII, floating in the much-boated canal right beside our busy road. The guides said it was a Morelet's but the reptile rode so low in the water and was so silhouetted that we couldn't distinguish it from an American Crocodile, which might conceivably appear in this area, or even an alligator, which shouldn't.

My herp book doesn't mention Morelet's Crocodiles existing in the northern Yucatan, so I asked the guides if maybe these crocs had been introduced here for the benefit of tourists. No, it was true that until a few years ago no crocodiles lived along this coast but then a big hurricane came along, Gilbert if they remembered correctly, and since then the crocs have been reproducing and spreading.

In fact, at the edge of one lagoon up the coast we saw a mound of sand about the size of a melted Volkswagen, and that was a crocodile nest. A few feet away at the water's edge, well camouflaged among mangrove stems, rested several babies maybe 15 inches long. At the reedy edge of one lagoon we saw where a very big adult had slid from the water onto dry land, smoothing mud and knocking down vegetation. Not one of the group could resist glancing behind us.

The guides told us that during the nights the hundreds or maybe thousands of flamingos across the lagoon flew elsewhere to roost. It's supposed that they go to crocodile-free lagoons.

You may be interested in looking over the tourist blurb I wrote about the Dzilam de Bravo trip at https://www.backyardnature.net/n/06/060318x.htm.

Also, I've put together a selected list of plants and animals of the Dzilam de Bravo Conservation Zone at https://www.backyardnature.net/yucatan/dzilamff.htm.

*****

A MIDDLE AMERICAN SMOOTH-SCALED RACER
It's been a good week for reptiles. One morning back at the hacienda Darwin approached wearing his snake- at-the-big-building smile so off I went to see what it was this time. It was a slender, reddish, big-eyed species about two feet long, its body encircled by numerous narrow, pale bands, and it was hiding behind a potted plant on the patio at ground level. At first glance it looked like a coral snake, but it didn't have the right head markings. You can see it at https://www.backyardnature.net/yucatan/ss-racer.jpg.

My herp field-guide by Jonathan Campbell identified it as the Middle American Smooth-scaled Racer, DRYADOPHIS MELANOLOMUS. It occurs from northern Mexico to Panama and it feeds mostly on reptiles, especially lizards, as well as reptile eggs, frogs and small mammals. It's not too closely related to North American racers, which belong to the genus Coluber. They do share the smooth scales typical of northern racers, however, and are just as eager to bite as any cornered northern racer.

Thank's to Vladamir's digital camera I'm especially glad to be able to post this snake's image because it comes in different basic colors, from olive-tan to reddish brown to reddish orange, like ours. The book says that the specialists haven't figured out what causes the various color forms, so now, whenever a researcher Googles "Dryadophis melanolomus" anyplace on Earth. he or she will find this page and this picture, and that'll help explain the mystery.

*****

A SCHMIDT'S STRIPED SNAKE
Then the next day, Roberto the gardener, while cleaning up a weed-overgrown junk pile, ran into yet another snake species I hadn't yet seen. This one was like a brownish garter snake, with narrow lines running the body's length. It was a Schmidt's Striped Snake, CONIOPHANES SCHMIDTI, and its picture is at https://www.backyardnature.net/yucatan/stripsn.jpg.

Schmidt's Striped Snakes are distributed from here, the northern Yucatan, south into Guatemala and Belize, so their distribution area is much smaller than the former species'. The species feeds on lizards and frogs.

I'm even more pleased to post this snake's picture because a debate among specialists is going on as to whether this is a distinct species or just a subspecies of the more generally distributed Cope's Striped Snake, Coniophanes piceivitis. Maybe this picture and geographic note will help clarify matters.

What a pleasure to feel like I might be contributing to the understanding of these species. This is the traveling naturalist's dream.

*****

IGUANA FIGHTS, MONEY & ENLIGHTENMENT
Back to those fighting iguanas.

During the half hour Wiry and Bloody fought I found myself thinking about this question: Why did nature create this species so that males must fight, and subordinate males on the periphery must suffer such frustration?

Of course I knew Darwin's answer, for here I was seeing "survival of the fittest" at work -- evolution being powered by "natural selection." The strongest, most dynamic male would get to pass on his genes to the next generation, while the weaker or less adapted males would not.

Since I am on record as regarding "Nature as Bible" -- as believing that enlightened human behavior should be harmonious with paradigms observable in nature -- one might assume that witnessing this iguana fight might convince me that human competition of all kinds is good. Since the iguana fight was natural, maybe I should champion the highly competitive free market system, and maybe I should even agree with the claim made by many evangelical Christian groups that material wealth is a reward from the Creator for hustling.

There are different levels of interpretation for everything. At one level, two male iguanas fighting over territory and females are indeed like two capitalists competing over resources and customers. On the other hand, fighting iguanas and consequent rewards and punishments are not ends in themselves. They are no more than the means by which the evolutionary process fuels itself through natural selection. Evolution is the greater thing here, with greater implications for my philosophy of life, not fighting. Therefore, what is the meaning of evolution?

The only way I can set my teeth into that question is to try to identify trends in the examples of evolution I see around me every day. After all these years of reflecting about the matter, I think I can list at least these three important trends of Earthly evolution:

Viewing my own society from the perspective of these three insights, I find that I must condemn some of its dominant features. For:

Therefore, fighting iguanas mean this to me: That I have a mind and a spirit perfectly capable of seeing beyond images of instinctual aggression -- be it battling iguanas or consumption-focused society. I can aspire to higher meanings and principles.

*****

Best wishes to all Newsletter subscribers,

Jim