May 31, 2015

SIDEWALK RAIL
It's clear that our stubborn dry season, lingering later this year than it should, is affecting wildlife, because certain species are turning up in unexpected places. The other day a tourist told us that at dusk she'd been sitting in a restaurant in town when she looked down the street and saw a blackish cat much too large to be a house cat. Her description sounded like a Jaguarundi. Around mud puddles that used to be large ponds you can see many kinds of tracks, especially of peccary, raccoon and sometimes large cat paws, again probably Jaguarundi.

Among birds, most of the winter when we got to see Gray-necked Wood-Rails, it was something to get excited about, but it's nothing to see them along the road leading out of town through the mangroves.

Still, I was surprised to see a pair of Gray-necked Wood-Rails strolling down the sidewalk along the Malecón, where it extends south a bit on the town's southeastern shore. You can how pretty that looked at https://www.backyardnature.net/n/15/150531wr.jpg.

Our Gray-necked Wood-Rail page is at https://www.backyardnature.net/yucatan/woodrail.htm.

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TIGER-HERONS UP CLOSE
During most of the year when a Bare-throated Tiger-Heron turns up we regard it as something special. Nowadays they're fairly common and easy to approach during trips up the estuary, probably because of our especially long dry season, which already should have ended.

Whatever the cause, a recent shot of a tiger-heron close up is at https://www.backyardnature.net/n/15/150531tu.jpg.

A close-up of patterning on this one's back is shown at https://www.backyardnature.net/n/15/150531tt.jpg.

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RACCOONS WITH SLENDER TAILS
At dusk Wednesday night a pair of Raccoons wandered down a beach sniffing the white sand. We see lots of Raccoons at the mangrove's edge, so this was nothing special. Still, every time I see one I'm reminded of how small the ones here are, and how slender their tails, compared to those seen farther north. You can see one of our slender-tailed ones at https://www.backyardnature.net/n/15/150531rc.jpg.

Raccons are allowed to be variable, however, for they come in a variety of subspecies. The 2005 edition of Mammal Species of the World recognizes 22 subspecies of PROCYON LOTOR, which is the same Raccoon species found in Canada and the US, all the way south to Panama. Four of those subspecies occur only on small Central American and Caribbean islands, and one of those is thought to be extinct.

Subspecies, if given enough time, evolve into species, and one Raccoon form that most experts agree has graduated to being a full species lives a bit east of here. It's the Cozumel Raccoon, Procyon pygmaeus, also called the Pygmy Raccoon, regarded as critically endangered on Cozumel Island just off the Yucatan Peninsula's eastern coast.

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YUCATAN MOLLIES
I was watching fish in a shallow pool beside the mangroves where saltwater streamed through a culvert beneath the Malecón. The culvert connects the estuary with the mangroves, and the direction its water flows depends on what the tide is doing. Thousands of tiny, brownish, guppy-like fish swam at the water's surface, often seeming to gulp air, though it was hard to see how the water could be oxygen poor. Within the multitude of tiny, brown fish, from time time a small flash of powder blue ignited among the pool's sparkles and ripples. It took awhile to pinpoint the powder blue's source, which turned out to the top part of tail fins of a tiny minority of the little, brown fish, as seen at https://www.backyardnature.net/n/15/150531ym.jpg.

These fish of an obviously different species from all the others were about 1½ inches long (4cm), a little larger than the others. The picture doesn't show enough detail to see the fins well, much less count the number of spines and rays in each fin, which often is needed to properly identify a fish. Therefore, I used a very untechnical identification technique: I Googled images of every fish listed for Ría Lagartos Biosphere Reserve, looking for small species with powder blue spots on their tails, and the kind of tiny, highly ordered speckling displayed by the fish in our pictures.

There was only one such species, one described as living in marshes, lowland streams, swamps, and estuaries just like where these were found. It's POECILIA VELIFERA, the Yucatan Molly, endemic to the Yucatan Peninsula. The EoL.org (Encyclopedia of Life) website's distribution map indicates that the species is found only along the Peninsula's northern coast.

On the Internet, when I searched for other images of Poecilia velifera, the vast majority found looked nothing like our fish. They displayed different colors, including entirely red, yellow and white bodies, and the powder blue spotting of some covered their bodies entirely instead of being restricted to the tops of their tails. Some of their spotting was of other colors than powder blue, plus many pictures showed fish with outrageously tall, splendiferously colored top, or dorsal, fins.

It turns out that Poecilia velifera is a favorite aquarium fish and as such many spectacular forms have been bred, often by hybridizing with other molly species. Aquariests often call forms with oversized dorsal fins Giant Sailfin Mollies. Beyond that, the fish has been introduced into waters of numerous tropical countries, and pictures of them might show forms ranging from the most bizarre to our relatively subdued-looking ones. In the US they turn up, often in large numbers, in coastal wetlands from North Carolina south all along the Gulf of Mexico. Poecilia velifera introduced into California have caused a decline in populations of the federally endangered Desert Pupfish, Cyprinodon macularius.

Much in contrast to that, in Ría Lagartos Estuary, Yucatan Mollies are "specially protected" because of two distinctions: First, they are among the estuary's species most tolerant to the least salty water, and; second, they are listed by Mexico's CONABIO as endemic and threatened.

I read that they can reach six inches in length (15cm) so our fish definitely are juveniles. Sometimes I see adults hanging around the submerged parts of stilt roots of Red Mangrove along the estuary's sides.

Yucatan Mollies eat algae and other plant materials, as well as aquatic invertebrates, including mosquito larvae.

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YUCATAN PUPFISH
Sometimes after looking at flamingos we pull up to the edge of levies enclosing the salt ponds at Las Coloradas, so visitors can see the operation. At the base of one levy, on the estuary side, there was a car-size pool of water less than finger-length deep inside which schools of small, silvery fish were swimming back and forth. The fish were no more than an inch long (25mm). You can see them at https://www.backyardnature.net/n/15/150531pp.jpg.

What interested me was that the fish were swimming in exceedingly salty water. Sea water's salinity is rated at about 35.5 PSU (Practical Salinity Units), with water of the famously salty Dead Sea being around 40 PSU. A 2004 study by Valdes and Real, published in the Indian Journal of Marine Sciences, found that during the dry season, when salinity in Ría Largartos Estuary is at its maximum, salinity averages over 69 PSU. In some parts of the Estuary's inner zone it can soar to over147 PSU. That's over three and half times saltier than sea water. And these fish -- here at the dry season's absolute peak when the estuary's water should be the saltiest and right beside the salt ponds famed for their salty water -- appeared to be doing quite well.

But, what where they?

In a 2010 study of fish in Ría Lagartos Estuary, Peralta-Meixueiro and others found that of the 63 fish species they identified in the estuary, two species predominated in the estuary's most saline waters: Cyprinodon artifrons and Floridichthys polyommus.

The fish in our photograph were only about an inch long (25mm) and their color pattern was not yet well developed. However, seven or eight dark, vertical bands can be discerned along their sides, their eyes can be seen surrounded by pale zones, and the fishes' head shape can be made out. These features all correspond to those of young CYPRINODON ARTIFRONS, one of the estuary's two most salt-tolerant fish. With age the banding in this species becomes much more conspicuous and the fish's body shape changes. Cyprinodon artifrons often is known as the Yucatan Pupfish.

Studies indicate that Yucatan Pupfish don't necessarily prefer very salty water -- the species tolerates a wide range of water, including freshwater -- but rather the young seek out very salty water probably because most other fish species can't tolerate it. Thus in very salty water Yucatan Pupfish young find less competition for food from other species, and there's less threat of predation by larger fish of other species.

Not only are Yucatan Pupfish found in Ría Lagartos Estuary's very salty waters, but also it's one of the most numerically abundant species throughout the estuary, even in the least salty zone near the estuary's mouth.

Mature Yucatan Pupfish average about 1½ inches (4cm). The species seems to be endemic just to waters of the Yucatan Peninsula and Belize.

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THE HIGHLY EDIBLE CROWN CONCH/ CHIVITA
At least at the eastern end of Ría Lagartos Estuary where the water is shallowest, saltiest, and broad mudflats emerge at low tide, one seashell-producing, gastropod-type mollusk is by far the most commonly encountered of all fair-sized species. If you walk barefooted in shallow water, with almost every step you feel them buried in soft mud beneath your feet, and along shore, bleached, empty shells abound. During the winter I seldom saw living individuals, only their shells. But now at low tide you find thousands scattered across freshly emerged mudflats, such as the two-inch (5cm) one shown at https://www.backyardnature.net/n/15/150531cf.jpg.

That picture shows that the mollusk's flesh is white but that its operculum is brown -- the operculum being the "lid" or covering that seals the shell's opening when the body is withdrawn into the shell. Most commonly you find empty shells, however, often broken ones, as shown at https://www.backyardnature.net/n/15/150531cd.jpg.

A distinctive feature of the shells is their blunt "teeth" arranged in spirals that are best displayed when a shell is viewed from behind, as seen at https://www.backyardnature.net/n/15/150531ce.jpg.

Volunteer identifier Bea in Ontario pegged this abundant species as MELONGENA BISPINOSA, usually called the Crown Conch. Around here they're known as Chivitas, maybe because a chiva is a goat, and goats have horns like the shells. Earlier the species was considered a subspeciess of the widely distributed, common and highly variable Melongena corona. Just by looking at the shells I can't see any difference between the two species, but Mexican researchers refer to Melongena bispinosa, Chivitas, as the common species found here, so I'm using that name. Melongena bispinosa is endemic to estuaries along the Yucatan Peninsula's coast.

Sometimes you find masses of Chivita shells along shore, as shown at https://www.backyardnature.net/n/15/150531cc.jpg.

That's where people have thrown shells after removing their fleshy contents, to be eaten. I'm told that at low tide sometimes people go collecting large numbers of them, set up their kettles there in the tidal flats, drop their Chevitas into boiling water, gouge out the fleshy contents, leave the empty shells in piles, and take home the edible part. More commonly, a family or one or two guys show up walking along the estuary's shores picking up Chivitas and dropping them into bags, as shown at https://www.backyardnature.net/n/15/150531cb.jpg.

In a 2003 issue of Mexico's Ciencia, poetically entitled "La nobleza, belleza y via crucis del recurso pesquero caracol 'chivita' en Yucatán," Vicoria Patiño Suárez and others report that just in the small coastal town of Chuburná Puerto, NNW of Mérida, with a population of 1720 in 2005, 70% of the people collected Chivita during part of the year, removing an incredible 256 tons of them. That translates to an annual loss of about 77 million Crown Conch individuals, which, the authors suggest "... can't be considered as subsistence fishing, and which requires control in order to be sustainable."

The study also points out that other mollusk species also are vigorously collected as food, including Queen Conch (Strombus gigas), the Milk Conch (Strombus costatus), Horse Conch (Pleuroplaca gigantea), West Indian Chank (Xancus angulata) and various species of whelk (Busycon sp.) That study in Spanish can be freely downloaded in PDF format here.

An interesting inclusion in that study is a chart showing that compared with pig flesh consisting of 16% protein, beef flesh of 18% and chicken flesh of 20%, Chivita's flesh consists of 39% protein.

On a recent flamingo viewing trip our boatman saw so many Chivitas wandering the mudflat onto which our boat was pulled that he couldn't resist gathering some for himself. He took them home and made the locally popular dish "civiche." He filled the container normally used for bailing water from the boat with muddy Chivitas, as shown at https://www.backyardnature.net/n/15/150531cg.jpg.

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YELLOW RED-MANGROVE LEAVES
We've seen that Black Mangrove and White Mangrove take up seawater through their roots, then excrete excess salt through pores, or salt glands, on their leaves and/or petioles. I'd been told that the Red Mangrove's technique for ridding itself of excess salt was by simply dropping its older, salt-saturated leaves, at which point the leaves would have turned yellow. Here at the end of the dry season when the estuary's waters are most salty, I'm seeing more yellow leaves on Red Mangroves than during rainier times, so I've been assuming that there were more yellow leaves because now the trees have more salt to rid themselves of. You can see a typical Red Mangrove branch with yellow leaves at https://www.backyardnature.net/n/15/150531mg.jpg.

But, I like to confirm things I hear, and I can't confirm this neat little story about Red Mangroves disposing of excess salt by dropping yellow leaves. On the other hand, I've found reference to plenty of evidence that Red Mangroves filter most salt from saltwater before it enters their roots.

Instead of relying on salt excretion, Red Mangroves practice salt exclusion.

So, who knows why nowadays more yellow leaves appear on the Red Mangroves than usual?

Our Red Mangrove Page is at https://www.backyardnature.net/yucatan/mang-red.htm.

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WHITESEED MANGA FLOWERING
Though most afternoons around five o'clock the sky toward the south darkens and it's clearly raining there, so far here in Río Lagartos we haven't had a single rain this month. The landscape is crispy-dry. Still, in the scrubby thorn forest south of town several woody species now are flowering and sometimes even leafing out, apparently in anticipation of eventual rains. You wonder just how they do it.

One such tree caught my eye this week because it was clearly an acacia or something close to it whose powder-puff-like flower clusters were different from any I'd noticed before. New leaves and stems were emerging along with the flowers. The tree's slender branches grew intermingled with neighboring trees and shrubs, so a portrait of it would just show a jumble, but you can see one of its flowering and leafing-out branches, its smallish flowering head fuzzy with long stamen filaments and perched atop a long stem, or peduncle, at https://www.backyardnature.net/n/15/150531ch.jpg.

The flowering head is very much like an Acacia or Albizia, and its emerging leaves were twice-compound, also like species in those genera, as shown at https://www.backyardnature.net/n/15/150531ci.jpg.

Also its legume-time fruits were typical of those species, as shown at https://www.backyardnature.net/n/15/150531cj.jpg.

I'd about convinced myself that this was an Acacia or Albizia species when I noticed that the tree's trunk was smooth and blotchy, with peeling-off, curling flakes of bark, which wasn't like those species in those genera at all, as shown at https://www.backyardnature.net/n/15/150531ck.jpg.

This kind of trunk I'd seen before, in the woods around Chichén Itzá ruins south of here. Back then I'd found that the trunk had been so distinctive that just it and its twice-pinnate leaves leaves had enabled me to identify it as an Albizia close relative, CHLOROLEUCON MANGENSE. It's a widely distributed but often overlooked species occurring in dryish forests throughout most of Mexico south through Central America into the northern half of South America. An English name sometimes used for it is Whiteseed Manga. Here the Maya call it Yax-ek.

The Maya recognize Whiteseed Manga as a general source of wood, as producing young leaves and stems that livestock can browse, and as a good source of nectar for honeybees.

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DROPSEED GRASS
Beside Río Lagartos's storm wall, along the pretty, windswept, sun-baked Malecón, sand had piled up along the curb and a certain small, wiry grass somehow not only was living in it, but flowering. It was an environment as dry, salty, and inhospitable as you ever meet, and I wondered how any plant could live in it. It's shown at https://www.backyardnature.net/n/15/150531sp.jpg.

When I tugged at a leaf, the whole plant popped out of the sand as if its roots penetrated nothing more substantial than the sand itself. You can see the whole plant's general form, shown against the estuary's waters just beyond the storm wall, at https://www.backyardnature.net/n/15/150531sq.jpg.

That picture shows that the grass's blades cluster toward the stems' bases and that flowers are held in narrow, panicle-type inflorescences. Notice a feature that later was important during the identification process, that even though the panicles spread open at their bases they stay closed, or "compacted," at their tips. Another good field mark is shown at https://www.backyardnature.net/n/15/150531sr.jpg.

That shows the lowest secondary branches arising from the inflorescence's main stem, or rachis, in a whorl. It's slightly unusual to have so many branches. A close-up of a cluster of individual spikelets is shown at https://www.backyardnature.net/n/15/150531ss.jpg.

Here we can see that each spikelet, which is uncommonly small, contains a single floret, and that there are no needle-like appendages and no hairiness.

We've seen grasses structured like this before, usually in species of the big genera Sporobolus and Muhlenbergia. A difference between these two common genera is that the ligule -- the tiny, wall-like thing often occurring between a grass's blade and its stem -- is composed of tiny hairs, or cilia, in Sporobolus, but is "membranous," or like cellophane, in Muhlenbergia. You can see this plant's ligule at the base of one of its salt-speckled blades at https://www.backyardnature.net/n/15/150531st.jpg.

Our grass's ligule is composed of tiny, white, sharp hairs, so at this point I began thinking we might have a Sporobolus, species of which commonly occur worldwide, and often are known as dropseeds.

Our plant is SPOROBOLUS PYRAMIDATUS, whose most common English names seem to be Whorled Dropseed and Madagascar Dropseed. The "whorled" in the first name relates to the whorl of secondary inflorescence branches shown above, and the "Madagascar" in the second name is inappropriate, since the species is native from Kansas and Colorado south through the Americas to southern South America. It it indeed invading other parts of the world, however, because it's such a tough survivor. Frequently it occurs in sandy, salty, human-disturbed environments exactly like where we found it.

As global warming takes out the Earth's organisms adapted for moderate and stable ecological niches, it's good to pay attention to these beings who survive in extreme, unstable environments. Eventually they may become the planet's dominant life forms.

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MEXICAN FLAME VINE
Nowadays here and there across town you find spectacularly flowering examples of the fence-climbing vine shown at a neighbor's house at https://www.backyardnature.net/n/15/150531sn.jpg.

Around here you get so used to visual explosions of red produced by bougainvillea vines that it's easy to overlook this one, which isn't a bougainvillea. Up close you see that its crimson flowering heads aren't bougainvillea-like at all, as seen at https://www.backyardnature.net/n/15/150531so.jpg.

They're daisy-like flowers of the Composite Family! Look how long, Y-shaped styles of a head's many crammed-together disc flowers form a bushy "eye" surrounded by radiating ray flower corollas at https://www.backyardnature.net/n/15/150531sl.jpg.

Seen from below, the head's green, cup-like structure -- the involucre -- consists of scale-like bracts, or "phyllaries," arranged side by side, instead of overlapping like roof shingles, as it is in most composite flower involucres, shown at https://www.backyardnature.net/n/15/150531sm.jpg.

Having just one series of bracts that are not joined at their margins helps a lot with identification.

Breaking open a flower, other good field marks are found, shown at https://www.backyardnature.net/n/15/150531sk.jpg.

Note that the white, egg-shaped, cypsela-type fruits bear at their tops "pappi" consisting of many slender, white hairs. Also, no chaff-like "paleae" separate the disc flowers.

To a northern wildflower expert this combination of features brings to mind the big genus Senecio -- the groundsels. But who's ever seen a Senecio that's a woody-stemmed vine?

But, that's exactly what we have here, SENECIO CONFUSUS, often known as the Mexican Flame Vine or Orange Glow Vine, native to northern and central Mexico, but not to here in the Yucatan, though it's frequently planted here.

Senecio is a big genus, embracing over a thousand species, and they take every form, from delicate herbs to giant trees -- though the field marks mentioned above for the flowers apply to their flowers, too. If you want to expand your mind relative to groundsels, do a Google image-search on the keywords "senecio trees."

Some experts split Mexican Flame Vines from Senecio, insulting it with the despicable name Pseudogynoxus confusus.

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RAMSAR WETLAND #332
On the two-lane extension of Río Lagartos's broad, seaside avenue, the Malecón, along the estuary's shore on the east side of town, right beside the mangroves there's the sign shown at https://www.backyardnature.net/n/15/150531rm.jpg.

The sign welcomes us to a "wetland reserve of importance especially for the conservation of aquatic birds," in accordance with the Ramsar Convention on wetlands that was signed in Ramsar, Iran, in 1971. The sign's fine print goes on to explain that this "Ramsar site" extends from the municipalities of San Felipe in the west to Lázaro Cárdenas to the east, in Quintana Roo -- basically describing the boundaries of Ría Lagartos Biosphere Reserve.

The sign says that under terms of the Ramsar Convention, the site was inscribed on July 4th, 1986, as Ramsar Wetland #332...

Mexico is home to 141 Ramsar wetlands, and Ría Lagartos Biosphere Reserve was the first to be declared. Only the United Kingdom hosts more Ramsar wetlands. The US is home to 30.

The official Ramsar website is at http://www.ramsar.org.

There you can click on a map and read about all the world's Ramsar wetlands. On their Río Lagartos Biosphere Reserve page, our site is described as:

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FEATURED ESSAYS FROM THE PAST:

"Stumbling" from the May 4, 2003 Newsletter, at https://www.backyardnature.net/n/p/030504.htm

"Sprawl" from the April 25, 2006 Newsletter, at https://www.backyardnature.net/n/p/060425.htm

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Best wishes to all Newsletter readers,

Jim

All previous Newsletters are archived at https://www.backyardnature.net/n/.