November 2, 2014
CROCODILES
Paco's eyes focused on something below the tangle of Red Mangroves at the water's edge, he cut the boat's motor, and we coasted in close to the vegetation. Then we saw it, too, the open-mouthed crocodile swimming toward us shown at https://www.backyardnature.net/n/14/141102cd.jpg.
The croc kept his snout wide open as he moved in close, providing a good view of his upper snout, which is useful for identification purposes, shown at https://www.backyardnature.net/n/14/141102cb.jpg.
In fact, he offered a good view of everything because now, still with his mouth open, he came up to the boat's side, maybe expecting a dead fish from the guide's hand. You can see him at the boat's edge at https://www.backyardnature.net/n/14/141102cc.jpg.
I was glad to have such a close view because in the Ría Lagartos Biosphere Reserve we have two crocodile species -- the American Crocodile, and Morelet's Crocodile -- and I've been having trouble distinguishing them. Both are different species from the US's Alligator.
One reason for the confusion about their identities is that their colors and patterns are variable. Also, usually it's said that the most noticable difference between them is that the American Crocodile's snout is considerably more slender than the Morelet's. That's true, but often you see immature crocs whose snouts are shorter relative to the rest of their body, confusing the situation, plus you seldom get to see croc from directly above, from which view the snout's slenderness or wideness is most visible. On the other hand, scale configuration in the neck area varies between the species, is invariable, and now I was seeing the scales perfectly, almost from a top view.
Once the last picture was on my computer screen, at Crocodilian.Com I pulled up a diagram of the American Crocodile's head scales, at http://crocodilian.com/cnhc/cst_cacu_am_head.htm.
The corresponding diagram of the Morelet's Crocodile's head scales was at http://crocodilian.com/cnhc/cst_cmor_am_head.htm.
The most important scales to pay attention to are the larger, sharp-pointed, tooth-like ones atop the neck. Notice at the back of the neck the four large scales forming a rectangle. On both sides of this rectangle arises a smaller scale. In front of the rectangle, four smaller scales form a slightly backward-curving line. Both the American and Morelet's Crocodiles have these scales, but their configurations are different. For one thing, on American Crocodiles the rectangle of big neck scales is narrower, and the scales at the rectangle's sides are smaller than on the Morelet's.
The diagrams indicate that our boat-visiting croc is the Morelet's Crocodile, CROCODYLUS MORELETII, endemic to only lowland eastern Mexico, the Yucatan Peninsula, Belize and northern Guatemala. It likes quiet water, especially backwater lagoons, slow-moving streams and lakes, and in the Yucatan sometimes it turns up in the sinkholes called cenotes. The American Crocodile, Crocodylus acutus, also occurs in brackish water and slow streams, plus it may venture into salty ocean water. It's more widely distributed than the Morelet's, found coastally from west-central Mexico south into South America, and on the eastern coast from the Yucatan to South America, eastward into the Caribbean islands, and north to Florida and a bit up the US's eastern seaboard.
Later we ran into yet another croc, this one larger and more wary, lurking half hidden in the mangroves. Over seven feet long (2m), it's shown at https://www.backyardnature.net/n/14/141102ca.jpg.
This second individual is pale, while the previous one was blackish. Also, this one's snout appears to be much broader than the last one's. However, those big scales on the upper neck indicate that once again we have a Morelet's.
Adult Morelet's eat just about anything they want, mostly turtles, small mammals, mollusks, fish, aquatic birds, frogs and other animals. Young ones feed on insects and other small animals on or near the water's surface, including snails, crustaceans and small fish.
Though American Crocodiles definitely are present in the Reserve, having been documented by researchers who know the species well, so far, of the maybe twenty crocs I've seen here, I think all have been Morelet's.
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WOOD STORKS
In a boat in the estuary you can get closer to shorebirds than if you were on land. That's how I got the picture of the Wood Storks, MYCTERIA AMERICANA, shown at https://www.backyardnature.net/n/14/141102ws.jpg.
These are big birds, standing 33-45 inches tall (83–115cm), with wingspans of 55-71 inches (140–180). Seventy-one inches is 5.9 feet (1.8m). With their large size, featherless heads and necks, and massive beaks they give the impression of being very primitive. However, gene sequencing data and the fossil record don't much support that idea. Early in bird evolution stork ancestors claimed an ecological niche, exploited it, stayed in it, and through the ages have been evolving just like all other organisms. When a set of adaptations such big size, long legs, naked head and huge beak serve their purpose well, they are retained, even if they look out of date to human eyes.
In the 2010 book Storks, Ibises and Spoonbills of the World, James Hancock and others write that members of the stork tribe Mycteriini, to which Wood Storks belong, find food less with their eyes than with touch. Also, when they submerge their large, cylindrical, slightly downcurved bills they hold them open for fish to swim into. To encourage fish to swim into their open beaks they may pump their feet, flash their wings and do other fish-upsetting things.
However, in early morning, on the muddy banks of the canal cut through the barrier island in front of Río Lagartos, our Wood Storks weren't doing any of that. They were just hanging out warily watching one fishing boat after another put-put through the channel out to sea and they hardly seemed to care that our boat got close enough for the above picture.
Wood Storks are the only stork species currently breeding in North America. In the US small breeding populations are maintained in Florida, Georgia, South Carolina, and North Carolina. For thirty years conservationists have been trying to increase the US population, and they've had such success that Wood Storks were removed from the endangered species list and upgraded to threatened just this year, on June 26, 2014.
Wood Storks are mostly tropical American birds occurring along both Mexican coasts and all across the Yucatan Peninsula, and farther south through Central America to western Ecuador and northern Argentina. It's thought that the species arose in the tropics, and that they moved into North America only after the last ice age.
Our Wood Stork is different from Europe's chimney-nesting, baby-delivering White Stork, which belongs to an entirely different genus. White Storks have white-feathered heads and necks, and red beaks
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BOAT-BILLED HERONS
We already have a Boat-billed Heron page with nice pictures showing the bird's amazing boat bill, but this week out in the mangroves I got another picture, of an adult and a younger, darker bird, I just have to share. Our page about them is at https://www.backyardnature.net/yucatan/bb-heron.htm.
This week's picture is at https://www.backyardnature.net/n/14/141102bb.jpg.
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GODWITS
These days out in the estuary in front of Río Lagartos wherever the water is shallow enough, large, mostly mixed flocks of wading birds spend their time probing the submerged mud with their beaks. The birds sort themselves out very neatly according to this principle: The deeper the water, the larger the bird and the longer the legs. For example, you can see two fair-sized Marbled Godwits working into the wind as they systematically probe mud beneath about two inches of water at https://www.backyardnature.net/n/14/141102gw.jpg.
Behind the godwits, in shallower water, smaller Short-billed Dowitchers do the same work with their shorter beaks. A closer look at a godwit is provided at https://www.backyardnature.net/n/14/141102gx.jpg.
The way the various species sort themselves out according to water depth is only part of the story. Each large, mixed flock in a feeding area is much more than a random, congenial gathering of individuals wandering about picking up snacks here and there. They're finely tuned communal operations configured so that each individual and species gets all the food-energy it can while expending as little of its body's stored energy as possible. And all this in the context of avoiding predation by various enemies, dealing with social status among its own species, and taking the future into consideration.
For example, in a 2009 paper in the journal "Waterbirds," José Castillo-Guerrero and others found that during their non-breeding wintering season in western Mexico, Marbled Godwits changed their feeding behavior as the season progressed. The percentage of the birds' time devoted to vigilance dropped from 8–23% in October and November to 0.4–8% in February and March. Also, during that same period, time devoted to feeding jumped from only 12–40% to 59–74%. The authors supposed that these changes reflected the birds' change in priorities as the season progressed. Early in the season, merely surviving was most important, so they were very watchful. Later in the season it became more important to feed and accumulate energy stored as fat, in preparation for migrating back north to breed in the spring. The authors concluded that " ... habitat choice by specific individuals was complex and probably involved condition- or state-dependent tradeoffs that balanced metabolic requirements, safety priorities, and, perhaps, social status or dominance." The abstract of this study is freely available at http://www.bioone.org/doi/abs/10.1675/063.032.0304?journalCode=cowa.
Once it's realized that what at first looks like a big picnic of gypsy-like birds is actually a gathering of individuals and species engaging in a life-or-death competition for extremely limited resources, even as they have to deal with enemies who want to eat them, higher ranked individuals who might take a jab at them, and with preparations for the eventual exhausting and dangerous journey back north, the way we see our birds changes. In fact noticing how the belly feathers of the godwit in our last picture are so disordered and waterlogged, how the bird is in a water depth exactly matching the top of its legs, and noticing the somehow grim-looking expression on the bird's face as the entire head is about to be thrust below the water so that the beak can be stabbed blindly again and again into mud... one can almost feel sorry for that bird.
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SHEARTAIL EATING SPIDERLINGS
In some places where Río Lagartos butts up against the mangroves there's a chain-link fence. In the mesh opening at the top of one fence, dozens of tiny spiderlings had hatched from their silken egg case and now clustered, suspended in a maze of silk strands spread across several mesh openings. A hummingbird was so occupied with plucking spiderlings from the cluster that I was able to stand ten feet away (3m) and take the picture shown at https://www.backyardnature.net/n/14/141102hb.jpg.
The hummer would hover for a few seconds stabbing into the cluster, then zip to a perch atop the fence or inside one of its holes, presumably deal with its mouthful of spiderlings, and then quickly return and repeat the process. You can see the bird at the moment of one of its lift-offs at https://www.backyardnature.net/n/14/141102hc.jpg.
This is the most commonly seen hummingbird species in and around Río Lagartos, plus it's the most interesting for visiting birders. It's the Mexican Sheartail, CALOTHORAX ELIZA, endemic only to the Yucatan Peninsula's northern coast, and with a small population in central Veracruz state, across the Bay of Campeche. If you want to add this species to your life list, you just need to come here.
The bird in our picture is a female. In the northern Yucatan, any hummer with such a curved beak and a completely white throat is a Mexican Sheartail. Species with very similar females live in other parts of Mexico, but not here. The male's throat, or gorget, is glittering rose-pink, and its tail is long, slender and very deeply forked. The female's tail is only shallowly forked. You can see her green back and stubby tail at https://www.backyardnature.net/n/14/141102hd.jpg.
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THE SMALLEST NORTH AMERICAN BUTTERFLY
Out among the wind-swept dunes where sunlight on the whitish, salt-encrusted soil is blinding, you're likely to spot a butterfly so small that you wonder how it deals with the wind. If you watch it awhile you see that it keeps close to the ground, so that's one way. A picture of this tiny butterfly is at https://www.backyardnature.net/n/14/141102bf.jpg.
Though the wings' undersides are mottled and eyed, the wings' open to reveal plain rusty color.
When volunteer identifier Bea in Ontario identified our little butterfly as the Yucatan's own subspecies of the Western Pygmy-blue Butterfly, BREPHIDIUM EXILIS YUCATECA, I was thrilled. One reason was that not only do our dune butterflies constitute a subspecies endemic only to the arid coastal zone of the northern Yucatan Peninsula. Another was because the Western Pygmy-blue species is recognized as one of the smallest butterflies in the whole world, and the very smallest in North America, with a wingspan of only 1/2 - 3/4 inch (1.2 - 2 cm).
The Western Pygmy-blue species with its various subspecies is common and widely distributed from Central California east to southern Nevada, central Arizona, central New Mexico, and western Texas, south through Mexico to Venezuela, plus in the US it migrates to Arkansas, Nebraska, and Oregon. It's just the subspecies yucateca that's endemic here.
Western Pygmy-blue caterpillars feed on members of the Goosefoot Family, the Chenopodiaceae, which in our salty dune area mainly means Saltbush (genus Atriplex), Glasswort (genus Salicornia) and Seepweeds (genus Suaeda).
You can download for free the 1970 journal paper in which the yucateca subspecies of the Western Pygmy-blue butterfly was first described, with interesting notes, at http://images.peabody.yale.edu/lepsoc/jls/1970s/1970/1970-24(1)3-Clench.pdf.
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WOLFBERRY
Last week we looked at a knee-high, woody-stemmed bush with succulent leaves like those of the North's sedum plants, growing in salty mud at the side of mangroves. This week we have another plant looking very similar to that one -- despite not being related to it. It grew on salt-encrusted levees separating big salt ponds at the salt-exporting town of Las Coloradas on the coast about 15kms east of Río Lagartos. You might enjoy seeing how similar the two unrelated plants can look. Last week's Saltwort with sedum-like leaves is at https://www.backyardnature.net/yucatan/saltwort.htm.
This week's bush with similarly slender, whitish, woody stems and sedum-like leaves is shown at https://www.backyardnature.net/n/14/141102ly.jpg.
The main reason these two unrelated shrubs are so similar is that they employ similar adaptations to deal with extremely salty soil -- they're "halophytes." In both cases, succulent leaves (more cylindrical than flat in order to cut down on water evaporation from leaf surfaces) retain water during those long periods between rains when water can't be taken in through the roots because of the salty soil (unfavorable osmotic pressure). Whitish stems reflect intense sunlight bouncing off white, salt-encrusted soil.
The most noticeable difference between the plants is that last week's Saltwort bore yellow-green fruits while this week's plant produces bright red ones. A close-up of this week's plant's fruits is shown at https://www.backyardnature.net/n/14/141102lz.jpg.
When you squash that red fruit, little white, flat seeds pop out, looking very much like tiny tomato seeds, as shown at https://www.backyardnature.net/n/14/141102lx.jpg.
Seeing the fruit's resemblance to a tomato, already we can guess that this week's plant is a member of the Nightshade or Tomato/Potato Family, the Solanaceae. Once we know that, our plant is easy to figure out, because only a very small percentage of Solanaceae species produce succulent leaves.
This week's plant is variously known as Carolina Wolfberry, Carolina Desert-thorn, Creeping Wolfberry, Christmas berry and by other names. It's LYCIUM CAROLINIANUM, described as inhabiting ditches, ravines, depressions, swamps and marshes. It's distributed along most of Mexico's coastlines and here and there inland, and extends north into the US along the Gulf Coast from Texas to southeastern Georgia.
Wolfberry's red, tomato-like fruits are described as edible. I find them so small and seedy, and not particularly tasty (thought not unpleasant) that there's not much cause to nibble on them. Last week's succulent Saltwort leaves were worthy of sprinkling in salads to add a little salty crunch, but I'd hesitate to try that with Wolfberry's leaves, since members of the Solanaceae often contain powerful toxins, as with the case of Deadly Nightshade and the Tobacco plant.
Pictures on the Internet show that Wolfberry flowers are fair-sized, usually purplish, and typical of the Nightshade Family. Our plants bore only fruits at this time.
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COTTON ON THE DUNES
Just beyond the Las Coloradas salt ponds on the coast about 25 kms east of Río Lagartos a sandy road runs behind dunes along the shore. The dunes are thickly vegetated with grasses, yuccas, Goat's-foot Morning-glory and other low-lying plants. You can see a typical stretch at https://www.backyardnature.net/n/14/141102cq.jpg.
On the right side of that picture notice that some plants bear egg-sized, whitish flowers. A close-up of the plant's flower and leaves is at https://www.backyardnature.net/n/14/141102co.jpg.
That looks like cotton. A side-view of a broken-open flower showing how the stamens' filaments all attach to a cylinder around the ovary's style is at https://www.backyardnature.net/n/14/141102cp.jpg.
The flower's stamens confirm the plant's membership in the big Hibiscus Family, the Malvaceae, to which cotton plants belong. Also, notice that vegetative sepals below the corolla are sprinkled with black dots, and that the ovary is a big one causing a bulge at the stamen column's base, all like cotton. And when I looked around, some plants bore old flowers from which the corollas had fallen, leaving behind egg-shaped ovaries developing into black-spotted "bolls" nearly surrounded by the enlarging, leafy calyx -- all like cotton -- as seen at https://www.backyardnature.net/n/14/141102cr.jpg.
Well, it IS cotton, GOSSYPIUM HIRSUTUM, the species usually called Upland Cotton or Mexican Cotton, the very species constituting 95% of all cotton produced in the us, and about 90% of cotton planted in the rest of the world. Our dune plants are the wild race known as Gossypium hirsutum 'yucatanense,' limited in distribution to the Yucatan Peninsula's northern coast. The importance of the wild-growing cotton along the Yucatan Peninsula's northern coast is made clear in a study by d'Eeckenbrugge and Lacape published in September, 2014, where it's stated that "... upland cotton domestication was very probably initiated in its largest native population, in northern Yucatán."
So, a preponderance of the world's cotton industry is based on genes supplied by our northern Yucatan dune plants. These northern Yucatan plants are known to be exceedingly genetically diverse, and this genetic diversity may be of special importance to the world's cotton growers as new cotton cultivars must be developed to deal with global warming, growing salinization of irrigated land, and other unforeseen future challenges.
Unfortunately, all populations of wild races of cotton may be threatened by extensively planted, genetically modified cotton. GMO cotton plants all bear the same genetic material, and their genes have been modified to serve industrial purposes, not to help the plants survive in the wild. Wild cotton populations already may have been contaminated with human-manipulated genetic material. Also there's evidence suggesting that wild cotton populations in Hawaii, Brazil and the Galapagos are in danger of extinction by hybridizing with domesticated cotton. The GMO threat and the problems with hybridization are discussed in a 2013 paper by Ana Laura Wegier, entitled "Diversidad genética y conservación de Gossypium hirsutum silvestre y cultivado en México," freely available at http://www.biodiversidad.gob.mx/genes/pdf/Wegier2013_AR.pdf.
It's good that these genetically diverse cotton plants in dunes along the northern Yucatan coast are protected within the Ría Lagartos Biosphere Reserve.
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RUSTY FLATSEDGE, YUCATAN STYLE
During our recent stay in arid southwestern Texas we got to know the Rusty or Fragrant Flatsedge, CYPERUS ODORATUS. You can see the dinky little Texas plant we profiled at https://www.backyardnature.net/n/h/cyperus2.htm.
I certainly didn't have that plant in mind when I set out to identify the robust, chest-high heap of vegetation shouldering its way onto the street at the corner of the lot where I live now in Río Lagartos, shown at https://www.backyardnature.net/n/14/141102od.jpg.
At https://www.backyardnature.net/n/14/141102of.jpg you can see how the spikelets of our Río Lagartos plant cluster in bristly little heads in a compound inflorescence with each bunch of heads bunched together on their own stem, or ray. This is the same configuration employed by our little Texas plant, so when I saw this here, I figured our streetside plant might belong to the same genus as our Texas Rusty Flatsedge, the genus Cyperus, but that's a big genus so even still I didn't make a connection between the two plants.
But then I looked even more closely at our Yucatan spikelets, saw how they were roundish in cross-section instead of the usual flattened way, and that's unusual for the genus Cyperus, though it's exactly the way our Texas Rusty Flatsedge was. Now my brain started percolating a little. You can see the spikelets at https://www.backyardnature.net/n/14/141102og.jpg.
The short story is that my big, bushy plant here in Río Lagartos is in fact regarded as the same species as the ankle-high little herb we profiled earlier in Texas. Working it all out in keys of the online Flora of North America, I could hardly believe it, so I teased some achene-type fruits from some spikelets, and they turned out to look exactly like achenes of Rusty Flatsedge, as shown at https://www.backyardnature.net/n/14/141102oh.jpg.
The Flora of North America grants that Rusty Flatsedge is an "exceedingly variable" species with stems up to 130cm tall (4.3ft). Also, it's very widespread, occurring just about everywhere except really cold areas and in Europe, so much variation is to be expected. The spikelets of our Yucatan plants appear to be more numerous in the heads, and more closely packed together than most illustrated on the Internet, but a few plants in hot tropical regions do look like ours. Also, the Flora of North America says that "Numerous segregates have been named, some of which may deserve recognition when the species is studied in detail worldwide." In other words, we may actually have something different here from what's commonly seen in North America, but so far taxonomists haven't figured that out yet.
Anyway, I'm glad to document what we have here for those future folks who will study this Rusty Flatsedges "in detail worldwide." One last detail to mention to them, when they find these words, is that I find Rusty Flatsedge growing in town, as shown in our picture, but not in more natural areas outside of town.
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FAST EVOLUTION
Jarvis in North Carolina sent a link to an article in the October, 2014 edition of Science Magazine documenting incredibly fast evolution among the lizards called Green Anoles. We have a good bit to say about Green Anoles at https://www.backyardnature.net/n/a/anole.htm.
The study took place on small islands off Florida's coast. There, an exotic Caribbean species of anole was introduced, which invaded the native Green Anole's habitat, driving the Green Anoles higher into trees. This resulted in the Green Anoles evolving larger toepads after only 20 generations, or 10 to 15 years. Larger toepads enabled the Green Anoles better to adhere to the more limber and wind-agitated branches at the tree's higher levels. The abstract of this paper is available for free at http://www.sciencemag.org/content/346/6208/463.
This study is important because such fast evolution among organisms as complex as anoles is poorly documented. To give the study some context, one of the researchers, Harvard's Yoel Stuart, said, “if human height were evolving as fast as these lizards' toes, the height of an average American man would increase from about 5 foot 9 inches (1.75 meters) today to about 6 foot 4 inches [1.9 meters] within 20 generations."
I'm way past needing more evidence that the Universal Creative Impulse constantly evolves the Universe, making it ever more complex and with the parts ever more interdependent, with each tiny change causing the need for other changes everyplace else. Still, learning about the study refocused my thinking about evolution in general, and before long the thought arose that, at least as experienced here on Earth, at least three great rivers of evolution flow through time and space.
The first grand river of evolution started with the Big Bang gushing out dead matter -- everything from atoms, subatomic particles and electromagnetism to stars, planets and galaxies, creating the Universe we now behold.
Second, as soon as enough reactive dead matter was in place here on Earth, life arose. Then the evolving river of life flowed until now Earth abounds with diverse life. It continues to flow, and probably evolving life or something like it permeates the entire Universe.
Third, once there was life, at least some living things began thinking, and thought, over time, is itself a river. For, thought, as in Nature, builds upon earlier realizations. Nature came up with the idea of a flower, and the galaxy of flowering plants, or angiosperms, gushed forth. In the same way, someone came up with the notion of electronically encoding information in zeros and ones, and today we have the world of computers and cyberspace.
A question arises: Are these three great streams of Universal evolution the only ones? Or might there be a fourth river possible, one arising from thought, as thought arose from life, and life arose from dead matter? If another great river of evolution is about to spring forth, I'm betting that it will be the River of Spirituality. And, if that's so, what will that spirituality be like?
Will it be as Maya shamans visualize, a return to when super-enlightened mystics built pyramids using their minds to move great stones through the air? Or, might another of their beliefs, that events eternally repeat themselves in cycles, assure that what ultimately arises from incisive mentality will be a return to whatever nothing-seeming state preceded the Big Bang? Or, something unimaginable beyond these possibilities?
What a pleasure to be currently occupying this random plot of furiously evolving Planet Earth, and hear from an old friend about anoles who speak wisdom to us, if only we pay attention, and wonder about the meanings of things.
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FEATURED ESSAYS FROM THE PAST:
"Weed-Slip" from the December 10, 2007 Newsletter, at https://www.backyardnature.net/n/p/071210.htm
"Weedy Kids" from the August 22, 2004 Newsletter, at https://www.backyardnature.net/n/p/040822.htm
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Best wishes to all Newsletter readers,
Jim
All previous Newsletters are archived at https://www.backyardnature.net/n/.
