January 6, 2013

RAVENS
A general rule in my life has been that I'm happiest where there are ravens in the neighborhood. That's because ravens like wild, mostly unpeopled areas, and I do, too. To me nothing sounds as promising as the raspy croaking of ravens echoing off high cliffs, or filtering through widely spaced pines of an isolated, scrubby canyon.

We have ravens here. They hang out in the rocky hills rising on both sides of the Dry Frio River Valley. Regularly they fly over the cabin I'm staying in but they never land. Overhead they keep at a safe distance looking down at things on the floodplain floor, landing only when they have rocky slopes below them. The other day one flew over the house when the camera was ready, so you can see his silhouette at https://www.backyardnature.net/n/13/130106rv.jpg.

We have two raven species in this area, the Common Raven, Corvus corax, and the Chihuahuan Raven, once called the White-necked Raven, Corvus cryptoleucus. They're hard to tell apart unless the Chihuahuan crooks his neck just right so you can see his white collar. They have different voices, but I read that young Common Ravens can sound much like Chihuahuans. The one in the picture was calling with a voice other than the hoarse croak I associate with adult Common Ravens, but I often do hear the Common's classic hoarse croaks off in the hills. The silhouette in the picture, especially with that wedge-shaped tail, certainly looks like the Common Raven, but silhouettes of Chihuahuan Ravens on the Internet look pretty much the same.

A local birder who seems to know his stuff says that in the flatlands here in northern Uvalde County, until a couple of years ago the raven to be expected -- "the default raven" he calls it -- was the Chihuahuan Raven, with Common Ravens staying in sight of cliffs and rocky outcrops. But then the historic drought we're in right now began and this area's Chihuahuans left, turning up now mostly as fall migrants.

So, because I've heard the classic hoarse croaks and know that Common Ravens are nearby, and because of that local birder's observations, I'm saying that what's in the picture probably is a Common Raven, but I'm not entirely sure.

My most vivid memory of watching Common Ravens is from when I wrote my 1996 online book A Birding Trip Through Mexico, still available at https://www.backyardnature.net/mexbirds/.

During that trip I camped at about 4,050 meters (13,287 ft.) on Nevado de Toluca Volcano in central Mexico, where each afternoon Common Ravens flew about the volcano's rim.

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BLACK SCAT
Along the road I came upon the fresh pile of scat -- animal poop -- shown at https://www.backyardnature.net/n/13/130106sc.jpg.

What animal had bestowed this interesting corporeality? Here's the thought process I went through trying to figure it out:

First, the scat's size eliminates most animals in the neighborhood, the turds being about as thick as my middle finger -- about ¾ inch in diameter (2cm). This was no squirrel or rabbit. Besides, the scat was full of animal fur. A close-up of a little pointy turd displaying lots of hair is at https://www.backyardnature.net/n/13/130106sd.jpg.

That picture shows that many of the hairs are white, so something other than black hairs constitutes this scat black. Animals eating many blackberries produce black scat, but it's not blackberry season, plus, with all those hairs the black color was surely that of digested blood. This animal definitely was not a vegetarian.

Based just on size, the presence of so much hair, and the black color, the list of local predators that came to mind capable of producing such scat was: Mountain Lion; Bobcat; Coyote, and; homeless dog. We do have Black Bears in the area but their scat tends to be even larger, is blockier, and usually has vegetable matter in it. Fox scat is smaller with the turds more strung together by hair -- ropier and with more tapered ends.

So, now the question becomes whether the scat is feline or canine.

The matter of whether turds have tapered ends or are blunt is important. In general, Coyotes and wild dogs whose diet is heavy with animal prey produce tapered prey, while Bobcats and Mountain Lions produce blunt ones. Our turds seem ambivalent on the matter, but there are more blunt ends than tapered ones.

Also, longish turds can be either "segmented" or unsegmented. Big cats tend to produce segmented ones, while Coyotes and dogs don't. Our scat is somewhat segmented, so there's another vote for "big cat."

These features change enormously depending on the food the animal has eaten so by no means is any particular feature determinative. They are just hints at the pooper's identity. The diet of big cats is usually nearly entirely of flesh, while Coyote scat typically contains at least some vegetable matter, but that situation also varies from poop to poop.

If I'd been lucky, the animal's tracks would have appeared next to the scat, or maybe there would have been signs of the animal scraping the ground after pooping, but this scat resided on hard-backed clay with no dust on it showing signs of post-defecation activity.

Felines sometimes but certainly not always cover their dung with material scraped together with their forepaws, or leave it in scrapes created with their back paws. However, canines also sometimes scrape vigorously and somewhat haphazardly with their hand legs after pooping.

Big cats often mark territory with their scats by leaving them in conspicuous places, as at crossroads. Coyotes might also do this, but do so with less intention, their scat often appearing alongside roads, like ours.

Big cats also tend to mark their territories with multiple scat deposits. In fact, a stone toss away there was indeed another pile of similar scat similarly right beside the road's pavement, but white, as shown at https://www.backyardnature.net/n/13/130106se.jpg.

That scat is more clearly blunt-ended and segmented than the other. Bobcat scat is known to turn white after a few days of exposure to the elements. I think the main reason it turns white is that the blackness is produced by the remains of blood, which easily decomposes and leaches out with rain. Also there's a lot of bone in Bobcat poop, which contains much calcium carbonate, the semidigested past of which turns white when dry, plus the bone itself is white.

Maybe a more experienced tracker than I could come to an absolute decision about the identity of our poop-leaver, but I can't. Mostly because the turds are fairly segmented, have ends more blocky than tapered, we have two deposits close together, and Mountain Lions are pretty rare around here, I suspect that we have Bobcat poop. This notion is supported by the fact that one night our wildlife camera took a very blurry picture of a Bobcat not a hundred yards from where the scat turned up, plus ranchers around here tend to shoot Coyotes and I'm told that Coyotes are seldom seen.

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SWEETGUM TWIGS
Sweetgum trees are one of the most commonly occurring trees in most of the eastern US. Around my old hermit camp in Mississippi they were the most numerous woody species. Here we're well west of their natural distribution in the US, but there's a planted one next to the cabin. It almost died during our droughty last two summers, but somehow it's still holding on.

I find myself drawn to that tree, less from sentimentality than from the fact that our low, scrubby forest here is so dominated by two tree species -- Ashe Junipers and Texas Liveoaks -- that it's just a pleasure to see a different tree.

The tree has lost all of its star-shaped leaves, which just before they fell were prettily crimson and yellow. What's left is reddish-yellow twigs with buds pleasing to look at. I suppose it's the promise of spring in each of those buds that attracts me, knowing that just inside the buds' armor of shiny scales there's green, very fragile, embryonic material from which later will arise spring's new leaves and twigs. You can one of our Sweetgum's twig tips at https://www.backyardnature.net/n/13/130106lq.jpg.

Really it's beautiful how bud scales protect such easily harmed embryonic material through winter's extremes. Of course they protect from the cold, but also they keep the green matter inside from drying out. Also, sometimes even in winter, a whole day's sunshine can douse a twig with dangerous amounts of ultraviolet radiation and even heat, and bud scales need to protect against those, too.

In the above photo you might notice the leaf scar at the base of each bud. When a deciduous leaf naturally breaks from its twig in autumn, it leaves a leaf scar. Leaf scars come in many shapes and sizes. You can see the Sweetgum's leaf scar at the base of a bud at https://www.backyardnature.net/n/13/130106ls.jpg.

The three pale, horseshoe-shaped features inside this leaf scar are bundle scars. To understand what bundle scars are, remember that inside a woody stem there's a vascular system that carries water and nutrients from the roots up to the leaves (the xylem part of the system) and photosynthesized carbohydrates from the leaves down to the rest of the plant body (the phloem part). When the vascular system encounters a part of the stem from which a leaf arises, strands of xylem and phloem depart from the main vascular system and unit into bundles that enter the leaf stem, or petiole. In some species only one bundle enters a leaf through its petiole, in others there may be several bundles. You can see that Sweetgum leaves have three. When the leaf falls in autumn, it breaks across a well defined abscission zone, also called a separation zone, at the base of the petiole. When the petiole breaks off, it leaves a leaf scar, and inside the leaf scar there are bundle scars.

Not only do different woody species bear leaf scars of many different sizes and shapes, but also the numbers of bundle scars within the leaf scars is consistent within species, but highly variable between them. And the patterns made by the dispositions bundle scars vary, and the bundle scars' shapes.

Often but not always, Sweetgum stems also bear "wings," or corky ridges of a kind seen on few other species, as shown at https://www.backyardnature.net/n/13/130106lr.jpg.

Maybe such wings make the stems stiffer and less vulnerable to breakage; maybe the wings help regulate temperature in the stem. Whatever the case, it's clear that the typical twig bears very many interesting field marks that help us identify and admire leafless, flowerless, fruitless, winter-stuck trees.

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PRAIRIE THREE-AWN GRASS
I'd hoped that winters here would be so mild that at least a few plants could be found flowering year-round, but this week I haven't seen a single blossom. Except for the hills' wooded slopes populated with evergreen Ashe Junipers and Texas Live Oaks, which lose most of their leaves at winter's end, the landscape is dun colored, the color of straw, of dead annuals and of perennials not yet issuing spring sprouts. Though grasses are much more in evidence here than back East, possibly there's less species diversity among them. The same prairie grasses appear again and again, and in this Newsletter we've already looked at the most common ones.

However, one annual, knee-high clump grass we haven't looked at yet is shown at https://www.backyardnature.net/n/13/130106t2.jpg.

Vegetatively it's similar to several other species found here. Only when you come close enough to see the fruiting heads against a black background provided by a friend with black trousers can you see this grass's most distinctive field mark, shown at https://www.backyardnature.net/n/13/130106t3.jpg.

That fruiting head bears mature, caryopsis-type grains and atop each grain there are three long, widely spreading, needlelike bristles, or "awns." Each awn is about 2½ inches long (6cm). In our area there's simply no other grass with its grains topped by three long, spreading awns.

We do, however, have other grasses whose grains are topped by three spreading awns, just that their awns aren't nearly so long. In our September 23rd Newsletter we looked at the Purple Three-awn Grass, structured very much like our present grass, except that its grains' awns were less than half as long. In fact, about 19 three-awn grass species -- 19 members of the genus Aristida -- are listed for Texas, so the present one with its very long awns is our second species for this area. Awn length in none of our other Aristida species even comes close to that of this one.

This long-awned species is ARISTIDA OLIGANTHA, in English often called Prairie Three-awned Grass, though other species of Aristida also occur in the prairies. It's also called Oldfield Threeawn, which probably is a good name because here I find it in disturbed, sometimes eroded soil like you might find in old fields. The species occurs in prairies and on limestone soils throughout most of North America and arid parts of northern Mexico.

Though Prairie Three-awned Grass's dense clumps protect against soil erosion, most folks around here don't care much about it because with those long awns its grains work into sheep wool and can injure the eyes of sheep and cattle. The awns serve the plant by helping with seed dispersal when they tangle in the hairs of passing animals.

Prairie Three-awned Grass provides nesting sites and/or material for small animals, and of course seed-eating birds have their way of feeding on its grains without bothering with the awns.

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POTATO EARTHBALL
During the dusk walk, at the thin edge of the asphalt road, something egg-sized was pushing up from beneath the pavement causing the asphalt to buckle and crack. I lifted away a loose asphalt plate and exposed what you can see at https://www.backyardnature.net/n/13/130106pb.jpg.

It was a kind of puffball mushroom, about the homeliest looking one you could imagine, looking like a dirty, smooth-skinned, malformed potato cracking open here and there. However, you can see that the pavement it was pushing up was a good half inch thick (2.5cm), so you have to give the little being credit for its strength and persistence.

The working fungus body, the network of hyphae gathering water and nutrients, was in the ground below and alongside the road, so I felt little guilt about plucking the little puffball for study, for it was nothing but the fungus's ephemeral reproductive structure. The ball was mature and full of spores, and I figured that after I'd studied it, on a windy day I'd crumble the spore-filled interior and toss it into the wind, helping the spores disseminate into new territory much more effectively than if the puffball were to stay there mostly covered by asphalt.

At home I broke off one corner of the puffball to see what the spongy, spore-filled interior looked like. You can what I saw at https://www.backyardnature.net/n/13/130106pc.jpg.

In that picture the knobby protuberance at the puffball's bottom is the rudimentary stem, which in this species doesn't develop much more than you see here. The puffball's white skin covers a dry, spongy mass called the gleba. Millions of spores are suspended in the gleba. Though one description I find of this species say that its gleba is black, and another says it's deep purple-brown, you can see that our mushroom's gleba is dark brown.

This mushroom is SCLERODERMA BOVISTA, often called the Potato Earthball. It's widespread in Europe and North America. You don't eat this potato because it's poisonous, causing severe problems in the gastrointestinal system.

Reading that Potato Earthball spores have an unusual appearance, I looked at them under the microscope, and you can see them yourself at https://www.backyardnature.net/n/13/130106pd.jpg.

The fuzzy, round items are the spores, and the fuzz, or spines as they're called in the literature, are part of what makes the spores unusual. You can barely make out the other unusual feature on a few spores, which is that the spore surface is reticulated, a little like the windowed surface of a honeycomb. The spores are about 13 microns across -- 0.013mm, or 0.0005 of an inch.

"Puffball" and "earthball" are both informal terms without technical distinctions. Some would say that the Potato Earthball is not a puffball. Generally, puffballs are more lightweight and softer, while earthballs are heaver and harder. The Potato Earthball doesn't puff out its spores through openings in the skin, but rather fractures irregularly so that its spores get distributed rather haphazardly.

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JUICE VESICLES
Each day I spend a couple of hours digging a ditch for pipes to be placed in. Especially in this cool weather when the sun shines and a nice breeze blows, I look forward to the work, though I'm glad there's only two hours of it each day. The ground is rocky, sometimes solid rock. My favorite time is after working the first hour when I sit on the trench's bank and have a snack. In mid-snack the other day I saw the lovely thing you can see at https://www.backyardnature.net/n/13/130106gf.jpg.

I'd noticed the same thing many times before, but somehow that time the place and time were perfect for me to see more deeply, to luxuriate in the colors, textures, the attendant odors and tastes, and meanings. A good while I sat there just looking, marveling that such a commonplace thing on such an ordinary day could be so utterly astonishing.

The picture shows the face of a split-open red grapefruit. The shiny, elongate, baglike items are filled with grapefruit juice and are called juice vesicles.

So, thinking about fruit anatomy of such simple fruits as grapefruits, we can say that seeds are surrounded by masses of tissue known technically as pericarp. The pericarp itself is typically made up of three distinct layers: the exocarp, which is the outside layer or peel; the mesocarp, which is the middle layer or pith, and; the endocarp, which is the inner layer surrounding the seeds.

In grapefruits and other citrus fruits the exocarp forms the tough outer skin of the fruit, which bears oil glands and pigments.

The mesocarp is the white, pithy, somewhat bitter material immediately below the exocarp or peel, and is commonly removed before eating.

The endocarp is the part we eat, the part shown in the picture, formed of juice vesicles closely packed side by side.

In some fruits figuring out what is what can be tricky. For instance, most of the edible part of a peach and a considerable part of a tomato is mesocarp, which in citrus fruits is the white, pithy stuff right below the peel. Often I can't figure it out myself. I read reports from anatomists who have watched embryonic cells differentiate into the various parts.

Whatever things are called, the names or lack of names are hardly relevant when you're sitting on the edge of a trench you're digging through rock, the sun is shining, the air is cool and fresh, and a friendly breeze is passing through. What a pretty thing is the interior of a grapefruit. And what other everyday things do we underappreciate simply because the right time and place never arise for taking a good look?

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DIATOMS
Scanning a thin smear of mud from the little Dry Frio River behind the cabin, beneath the microscope I found lots of what's shown at https://www.backyardnature.net/n/13/130106di.jpg.

Using the excellent, free-to-use "Pond Life Identification Kit" at http://www.microscopy-uk.org.uk/pond/ I found that despite the organism in the picture not being green, it's an alga. On the Pond Life site's algae page, then it was easy enough to discover that our colorful little being is a diatom, which the page describes as "usually brownish, silica cell wall in two parts, solitary or colonial, some have a slow gliding motion, < 0.5 mm."

Browsing through various diatom pages I was reminded that diatoms are unicellular organisms who photosynthesize with yellow-brown chloroplasts instead of green ones. Diatom cell walls are made of silica so they're almost like glass houses -- silica being silicon dioxide, SiO2, and Si02 being the formula for quartz and pure sand, from which glass is made. The diatom's cell wall, called a frustule, consists of two silica valves that fit into each other like little pill boxes. If you look closely, you can see this construction in our photograph.

Traditionally, diatoms have been divided into two main groups -- those with radial symmetry and those configured bilaterally, like ours. In freshwater environments the bilateral ones, often referred to as the pennate type, are the most commonly encountered.

The earliest diatom fossils are from about 100 million years ago. Over time, as incredible numbers of diatoms died in the oceans, their silica shells sank to the sea floor forming thick layers of mud. Because silica is hard and chemically stable in seawater, the shells were preserved, and eventually geological processes created thick deposits of diatomaceous earth, a sedimentary rock that can be crumbled into a white powder also called diatomaceous earth, which nowadays is used in many ways.

Powdered diatomaceous earth is used in filters, as a mild abrasive in products such as toothpaste, as an insecticide (When the insect cleans its legs, the sharp-edged shells enter the gut, cutting it to pieces like ground glass), to absorb liquids (used in cat litter), as a matting agent for paint coatings, to reinforce plastics and rubber, to stabilize dynamite, as a thermal insulator, and much more. Under the microscope diatomaceous earth shows diatom skeletons and parts of skeletons, some of which are similar to our Dry Frio one.

Even having learned all this long ago, until now I've been unclear as to whether diatoms could be found someplace like the little Dry Frio River behind the cabin.

Now we know that they can be, and that they are abundant. In fact, there are more than 200 genera of living diatoms, in which about 100,000 surviving species are recognized, and those species occupy habitats ranging from the open ocean to freshwater and beyond, including soils and a huge variety of generally damp surfaces.

Using the freely available "Diatoms of the United States" resource at http://westerndiatoms.colorado.edu/ I find that possibly our diatom is an "asymmetrical biraphid," but I can't say which one. You might enjoy trying to figure it out yourself at http://westerndiatoms.colorado.edu/taxa/morphology/asymmetrical_biraphid.

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FEATURED ESSAYS FROM THE PAST:

"Walking as Therapy," from the October 6, 2006 Newsletter, at https://www.backyardnature.net/n/p/061006.htm  

"Walking with Carl Jung," from the July 20, 2007 Newsletter, at https://www.backyardnature.net/n/p/070720.htm  

*****

Best wishes to all Newsletter readers,

Jim

Visit Jim's backyard nature site at https://www.backyardnature.net