JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from Mayan Beach Garden Inn 20 kms north of Mahahual
on the Yucatán Peninsula's eastern coast just north of the Belize border,
in the state of Quintana Roo, MÉXICO
(N18°53'16.36', W87°38'27" )

May 29,  2011

SALLY LIGHTFOOT
At the rocky point just up the beach, three things immediately became apparent: First, it was a high tide about as high as they get. Second, atop nearly every rock barely projecting above the waves there was a crab. Third, this crab species wasn't the Ghost or Hermit Crabs we tend to see here. You can see one at http://www.backyardnature.net/n/11/110529sl.jpg.

Never had I seen crabs atop those rocks, and never since have I seen them. Obviously something was going on that day that I don't understand.

Because this was such a distinctly patterned crab species I figured that volunteer identifier Bea in Ontario would have an easy time learning its name, but she didn't. It turned out that we had a very variable species. Still, eventually we did decide that it must be what people often call the Sally Lightfoot Crab, GRAPSUS GRAPSUS.

Sally Lightfoot, who mostly eats algae on wet rocks in the intertidal zone, occurs along the coasts of subtropical and tropical America, Africa, the Gulf of California, and Chile. The species varies tremendously in color, and juveniles can look very different from adults. Ours, with its cream-colored speckles, is a juvenile. Most photos on the Internet show bright red adults.

On the other hand, descriptions of the species' behavior found on www.TheCephalopodPage.org's page for the species describes exactly what I saw:

"G. grapsus becomes frequently submerged by breakers washing over it during feeding. During this encounter the crabs press their flattened bodies to the rock and cling on until the waves recedes. They emerge from the surf and continue feeding as if nothing had happened."

At another rocky point a few kilometers away and later in the week I came upon an abandoned Sally Lightfoot shell, or exoskeleton. Crabs have the same problem as insects: They are encased in shells which periodically must be split open, crawled out of and abandoned, so that the crab can grow. A close-up frontal view of this Sally Lightfoot showing the "face" and claws is at http://www.backyardnature.net/n/11/110529sm.jpg.

*****

PASSING PLOVER
How do you get such a nice bird picture as the one at http://www.backyardnature.net/n/11/110529pl.jpg?

My approach was to go picking up trash along the beach, getting tired, deciding to take a snooze in a big bed of washed-up, dried Turtle Grass, then awakening to find the bird standing about ten feet from me already so accustomed to my presence that he didn't fly as I retrieved the camera from my pocket. More than once laziness like this has secured nice wildlife photos for me.

The bird's shortish bill with its slight bulge toward the tip meant that this was a plover, not a sandpiper, which generally have longer, more slender, straighter bills diminishing toward their tips. The black spot on the bird's side is the beginning of an extensive black bottom possessed by two plover species who migrate through here. Since the back's pale speckles are tawny or brown ("golden") instead of pure white, it was clear that this was an American Golden Plover, PLUVIALIS DOMINICA, and that was a treat to know.

For, American Golden Plovers nest in the North American Arctic, but winter in southern South America. In other words, the bird in the picture is only about halfway along on his migratory journey north; he still has a very long way to go. American Golden Plovers have one of the longest migration routes of all shore birds, over 25,000 miles (40,000kms) for a round trip.

Moreover, Golden Plovers don't migrate back south by the same route they take migrating north. In the spring, northbound birds like ours come up through Central America, then in places like Illinois stage in great numbers before making a final push northward. In the fall they return south by a more easterly route, flying mostly over the western Atlantic and Caribbean to their wintering grounds in Patagonia. During their easterly fall migration south, only a few birds rarely show up in Mexico.

Once breeding season is finished in the Arctic, adults leave in early summer while most juvenile birds remain behind until late summer or fall. With such a head start, many adults arrive back in Patagonia before the last juveniles even leave the Arctic.

So, for a long time I lay there in my Turtle Grass bed looking at this hand-sized little bird gazing out into the ocean, wondering what he thought and felt. Finally he looked over at me and for no reason I could discern issued a loud PEEP! and flew off down the beach.

*****

ORIOLE NEST
Up at Hacienda Chichen usually we only saw the Black-cowled Oriole when he was fighting his image in the outside rear-view mirrors of cars in the parking lot. Here a pair has hung a pendulous nest beneath a Coconut Palm frond about ten feet above the kitchen door, and on Wednesday the eggs hatched. You can see a parent feeding a nestling over the nest's rim at http://www.backyardnature.net/n/11/110529or.jpg.

Everyone seeing the nest believes that at any time it must fall, since the palm's frond constantly heaves in wind that's always blowing in from the sea, sometimes mightily. But in years past Marcia has seen such nests much closer to the door and rocked much more vigorously than this one, so she's not worried.

Just what would it be like being a babe in that little nest beneath the yellow-green-translucent frond ceiling, being hatched into wind and the sound of ocean breakers and slamming screen doors, and having food delivered by hidden providers over the rim?

*****

CHITONS
At the rocky point below us a ringed or segmented object about two inches long (5cm) was either stuck to or else protruded from an algae-covered rock regularly swept by waves. It looked so rocklike that I thought it was a fossil. Scratching it with my fingernail, it felt so dense and flinty I grew convinced it was. Then I noticed a kind of hairy-leathery fringe around the protrusion. Between waves I got the picture shown at http://www.backyardnature.net/n/11/110529ch.jpg.

Before long I'd found a dozen or so of these creatures, all on rocks or sand in very shallow water or submerged only when waves swept in. They were like slugs with stony, straight, segmented shells.

On the bike ride back home, the name "chiton" suddenly dawned on me. It was a word from Biology 100 class many years ago. Chitons are primitive "living fossils" appearing at least 400 million years ago, during the Devonion Period. That was very long before dinosaurs, in fact the first fish with hinged jaws were just arising in the oceans, and on land the first gymnosperms were just getting around to forming the Earth's first forests.

Soon the Internet confirmed that they were chitons. In fact, my picture matches the appearance of what often is called the West Indian Fuzzy Chiton, ACANTHOPLEURA GRANULATA, commonly distributed throughout the tropical Western Atlantic. In English speaking Caribbean countries sometimes chitons are referred to as "curb," and their fleshy parts are eaten. The "hairy-leathery" ring surrounding the stony segments is known as the girdle. It's not clear what girdles do for the chiton, since some chitons get along well without them.

About a thousand chiton species are recognized. Wikipedia's page all about them is at http://en.wikipedia.org/wiki/Chiton.

*****

HAWKWING CONCH
A seashell picked off the beach here this week appears at http://www.backyardnature.net/n/11/110529hk.jpg.

An underside view showing its upturned front tip is at http://www.backyardnature.net/n/11/110529hl.jpg.

Volunteer shell identifier Bea in Ontario pegs the shell as belonging to a Hawkwing Conch, STROMBUS RANINUS, found throughout the Caribbean, including southern Florida.

We've already seen another conch, the Queen Conch, Strombus gigas, which is illustrated and described at http://www.backyardnature.net/yucatan/conch.htm.

All members of the genus Strombus are thought of as "true conchs," and characterized as medium to large sea snails. About 50 Strombus species exist, but only six live in the greater Caribbean region. Earlier in evolutionary history many more species existed, but most species went extinct. Today most true conchs survive in the Indian and Pacific Oceans.

Like the Queen Conch, Hawkwing Conchs are favored foods of some. They themselves eat mostly algae.

By the way, consensus among folks who should know, including those at conchworld.com, say that "conch" is pronounced with a hard K: "Konk."

*****

GULLFEED
During a garbage-picking-up hike up the beach Marcia walked over to a handsome, flowering and fruiting, woody shrub with succulent leaves and asked what it was. Nearly always if I have flowers and fruits I can recognize the family a plant belongs to, and often the genus, but I didn't have the slightest idea who this one was. You can see Marcia conferring with the plant at http://www.backyardnature.net/n/11/110529go.jpg.

A close-up of the plant's leaves and black, half-inch wide (1.3cm) drupes, which are topped by scars where the corolla fell off the flower's inferior ovary, is at http://www.backyardnature.net/n/11/110529gq.jpg.

A white flower a little less than an inch long (22mm) oddly split along the top and with its thick, stiff style arcing from the split above the corolla is shown at http://www.backyardnature.net/n/11/110529gp.jpg.

The style also is curious because of the two-lobed, flattish stigma tipping it -- the stigma being the female part where male pollen is supposed to land, germinate, and send the male sex germ down to the ovary in the bottom of the flower. Notice the fuzzy area below the yellow stigma. That fuzzy zone, known as the "pollen cup," or indusium, concentrates pollen, assuring pollination.

The reason this common shrub stumped me is that it belongs to a plant family I've never been introduced to, and seldom even heard of, the Goodenia Family, the Goodeniaceae, a family of some twelve genera and over 400 species, occurring mostly in Australia. One of the twelve genera is "pantropical" -- found throughout the world's tropics -- and that's what we have here. Our seaside bush is SCAEVOLA PLUMIERI. Since it's also found coastally in Florida, Louisiana and Texas, it has English names, including Gullfeed, Beachberry and Inkberry.

I identified the bush by recognizing the flower's similarity to lobelia blossoms, then by checking unrecognized plants listed for this area in plant families closely related to the lobelias. On the Evolutionary Tree of Life, Goodeniaceae does occupy a branch near the lobelieas, but it's even closer to the Composite Family, with its sunflowers, goldenrods and asters.

What a pleasure to meet something completely new to me like this, to see novel new ways of doing things -- to experience yet another "variation on the theme" of the "average wildflower" carried in my head.

*****

BIG TANGLES OF DODDER
Often along roadsides you see large, orange tangles spreading atop many kinds of plants, as shown at http://www.backyardnature.net/n/11/110529dd.jpg.

There the tangle covers a dense population of Coastal Ragweed. A close-up showing the tangler's wiry, orange stems, some spikes of tiny, hardly open, white flowers and, in the upper, right corner, a white fruit, is at http://www.backyardnature.net/n/11/110529df.jpg.

Folks into wildflowers up North will recognize this as a dodder, of which there are many species. Weakley's flora covering the US Southeast lists about 18 species for that region, but here in the Yucatán we appear to have only this very common one, sometimes known as American Dodder. It's CUSCUTA AMERICANA, spottily distributed throughout much of tropical and subtropical America, including southern Florida.

The thing about dodder is that it's parasitic. It's a member of the Morning Glory Family, so presumably its ancestors were similar to present-day morning glories. Once they evolved the practice of robbing water and nutrients from plants they grew on they no longer needed leaves and chlorophyll for photosynthesis, so they lost both, transforming themselves into nothing but orangish stems sometimes bearing flowers and fruits.

Dodder steals its food by wrapping around a plant host and producing rootlike appendages known as haustoria that penetrate the host's stem, tapping into the stem's vascular system. You can see haustoria emerging from the side of a twining dodder stem at http://www.backyardnature.net/n/11/110529de.jpg.

Once the dodder plant has tapped into a host, the dodder's original roots in the soil die, leaving the dodder totally dependent on stealing sap. Up North dodder plants are annual but here in the tropics they can grow more or less continuously, often growing high into trees or covering swaths of vegetation much larger than in our picture. Some dodder species contain a little chlorophyll and can photosynthesize at low levels while other species have no chlorophyll at all and are entirely dependent on their parasitism. American Dodder's stems are sometimes green so apparently it does some photosynthesizing.

Studies have shown that dodder seedlings are more likely to grow toward plants releasing certain chemicals than plants not releasing those chemicals.

*****

YUCATÁN'S RAINY SEASON
As a kid on the Kentucky farm I thought of being someplace in the tropics with a rainy season about to break as about the most exotic and desired experience I could imagine. Kipling had taught me how rainy seasons arrive in Indian villages. There'd be long- lasting, debilitating heat and humidity, a sky's blinding, silvery glare, a community's stunned quietness and an awful tension preceding the first thunder clap... Then, the downpour, the first cool air in months, streets and fields awash, kids, dogs and wide-eyed cattle ecstatic, old men in streets, their trouser legs rolled up, sipping hot tea in cold rain and laughing through toothless gums.

For years that mental image of a breaking Indian monsoon was so deeply rooted in my mind that I had to experience several rainy seasons here before it occurred to me that our rainy seasons aren't like what Kipling described.

Our rainy seasons begin and end more gradually, beginning about now and reaching a peak of frequency and severity in September or thereabouts, and then piddling out by late November or so. Hurricane and almost-hurricane storm systems also peak during the rainy season, in their own way making rainy seasons rainier.

Yucatán's rainy-season afternoon storms -- at least those in the interior -- are caused by the land growing frightfully hot from the sun shining almost directly down from above. All that solar energy dumped into a humid atmosphere creates enormous convection currents of unstable air that start curling around like big cats with increasingly upset tempers. These currents gather strength until they gurgle up through the landscape's steam and sweat like bubbles in cooking gravy. With such heat, humidity and unruly rushing air at play, rainstorms just happen.

But, that's what happens in the Peninsula's interior. Here on the Yucatán coast perpetually blessed with much cooler ocean air, something else is happening. I've already seen several storms develop inland and at sea, while we remained dry here. I'll have to watch things here a while longer before I can figure out how coastal Yucatán's weather works.

*****

WAITING FOR THE RAINY SEASON
Several times this month I've thought that the rainy season was about to break. One heavy-feeling morning the sky hung silvery opaque and the Caribbean's surface was leaden and sullen. I sweated profusely and deer flies left red blood streaming down my legs. Surely nothing but the season's first storm could undo such pressure and tension! But, that afternoon the sky and ocean turned blue again, the waves' white crests grew playful, and there was no rain.

One afternoon a certain low rumble began unsettling my chest, a feeling I recognized as thunder from so far off that it couldn't be heard beneath the beach's roar of breaking waves. In about half an hour real thunder developed and inland toward the west a storm formed, but not here. Over the sea there were widely spaced, summery, white clouds, like little sailboats in a city park, but when they sailed over us on the coast they were drawn into the western storm. And then dusk came, a dry and crisp one for us.

One day dawned looking like all other days, except for the wind blowing like crazy. Out beyond the reef enormous sawbacked waves mounted into hills that for a minute or two would trouble the horizon's usual straight line with impossible aberrations. Foam off beach-breaking waves rolled across sand and slopped into buildings, and every couple of minutes I had to wipe white salt-spray off my glasses. The wind kept howling all night, whistling around the building corner just outside my door. But, next morning, the wind had brought nothing, except just another day.

All these false starts make days feel a little off center, even irritating. Why do these grand, self- important thunderheads on the horizon keep fizzling out?

But, of course, it's all in my own head, the way all my aggravations are. The weather is just being the weather, with no script to follow, no promises to keep, no reason at all, really, to be anything other than what it is. If the days feel off center, it's because of the cockeyed frame of reference I myself choose. If these false starts are maddening, it's because I choose to think in terms of beginnings and ends, and favor one state over the other.

Yet, I do also claim my own right to be idiosyncratic, and to be myself assertively, whether consistent and reasonable or not.

For, how I love a rainy season that just won't come, and how I love poetizing inconstant winds, malicious waves, conspiring colors and sounds and odors and tastes, all just being themselves with me inside them!

*****

Best wishes to all Newsletter readers,

Jim

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