Native Plants, Habitat Restoration, and Other Science Snippets from Athens, Georgia

Sunday: 21 August 2011

Silkmoth  -  @ 05:52:10

Sophie found this critter, the other day, and alerted me by staring cautiously at it for an informative period of time. It's quite a monster, over two inches long, and though we don't see such giants commonly, it's probably worth mentioning. It was rooting around in the accumulation of old dead river birch leaves near the front deck. Perhaps it fell from the nearest river birch that overhangs. It could have been contemplating overwintering, but in August?

It's probably a Polyphemus moth larva, Antheraea polyphemus. I'm pretty sure I saw several polyphemus adults in the early part of the summer.

Mandibles. Really good ones. That's one description you'll find fairly frequently. They're very hungry caterpillars.

We have at least one lookalike - back in late October, 2008, I spotted a similarly large caterpillar making its way up a tree trunk. I identified it tentatively as a Callosamia angulifera, a tuliptree silkmoth. Since I've also identified an adult, in April 2006, and since we so many tulip poplars around, I'd guess that this is our most common silkmoth.

Polyphemus is pretty promiscuous - according to the Lepidopteran hostplants database it is quite happy to chow down on a very large number of host plants - but tulip poplar, Liriodendron tulipifera, is not listed. Quite a few Betula (birches) are, though.

Though they're called silkmoths, they're not the domesticated silkworm, Bombyx mori. That's the Asian lep, which isn't even in the same family. American silkmoths include Cecropia, Luna, Promethea, Imperial, and then a number of other lesser known cousins, including Polyphemus and Tuliptree silkmoths. They're all big, charismatic moths, though!

Saturday: 13 August 2011

Turtle Growth Part 1  -  @ 07:11:51

I've been thinking about box turtle growth, especially in terms of the scute rings that give only a vague indication of turtle age (why not?), and the colored patterns that persist so strongly and are located so stably on a turtle's shell (how?).

These are questions of later development, although how it works depends on some things that happen in early development. Developmental biology is mostly focused at much earlier stages than you will see here, earlier stages when the body itself is formed. The turtle story there is a strange one, since alone of the vertebrates (I think), something odd happens at the pharyngula stage of embryo development. We've talked about this before in "Turtleology," or "How the Turtle Got Its Shell" - there is an inversion of the precursor tissue that will cause the bones of the ribs to form on the outside of the body (becoming the shell), leaving the scapula, the shoulder blade, inside the body. We won't have to refer to this again - our interest is in what happens much later, and then continuously throughout the life of a turtle.

You've seen turtle shells like this one many times, but not like this. We should develop some vocabulary here. The individual polygonal plates are called scutes (and we'll talk about that white region in a moment). Scutes are essentially scales, and they cover the growing body of the turtle, and grow with it.

The descriptions I've read are a little confusing in their use of the term "scute" - is it the whole polygonal shape? I'm going to assume it is, but when I talk about each polygonal shape I'll probably refer to it as a "plate," with the term scute used to talk about the scaly growth that covers it, and is renewed and pushed outward each year, roughly.

The scute scale grows outward from an origin within each plate, and each year's new scute growth pushes the older year's scute growth ever outward. This results in the formation of scute rings that roughly track the annual growth of the plate of a turtle.

This happens on each plate, and the plates themselves grow as a result, allowing the turtle's actual body inside to grow larger.

Just as an aside, if we flip this turtle shell over (only the carapace survived here), we can see how that peculiar rib formation on the *outside* of the body results in the carapace. You can actually see how the segmented vertebra and attached ribs grow outward and expand into the rows of plates of the carapace. These bony remnants, which would be well imbedded within *your* body, are on the outside of the turtle's body.

Here is the carapace of a different turtle. In this case the brightly colored covering has flaked off, and you can see the bone underneath. This is probably how most people discover dead box turtles, since the white is so easy to see against the ground, and so it's a familiar sight.

What's interesting about this is that the plates and scute rings we saw on the colorful layer in the first photo are also impressed on the underlying bone. So it's not just that colorful layer that's growing as a scute atop the shell, it's also the bone underneath that's growing, and apparently in synchrony with the colorful layer atop. This makes sense - the bones that form your skull grow quite a bit as you are a young child, and so also must the bones that form the shell of a young turtle. It's a little startling to see the growth rings on the bone, though, that so closely resemble those of the scute rings atop.

Now to the question of the nature of that colorful layer atop, what we normally see in a living box turtle. You saw in the first box turtle that one of the central scute plates had fallen off, exposing the bone beneath. Here I am peeling off the next pair of plates, and these are very loosely attached at this point.

Now isn't that interesting? First, that they're easy to peel off, and second, that the thin colorful covering is actually translucent - you can see my finger and the blue background through it. We can also see that the scute rings are maintained in the covering that is being peeled off. That red dot marks the natal scute, the origin of the scale that grows outward on all sides and pushes earlier growth even further outward, resulting in the rings.

This colorful thin translucent covering is keratin, a structural protein that is common in all terrestrial tetrapods. In us humans, it forms your hair, fingernails, and is a larger component of your skin. In turtles it is secreted by the cells that make up a thin layer of skin that lies between the keratin and the bone beneath.

It's analogous, and probably homologous, to your skull: you have a layer of skin lying atop the bones of your skull, and that skin produces a covering of hair atop it (more or less, depending). Same thing - the bones of the carapace have a layer of skin that produces, not hair, but the scales that form the scutes of the thin keratin covering. Scales on a reptile, feathers on a bird, and hair on a mammal are all homologous structures.

To make another analogy, the natal scute marked with the red dot in the above photo is like the root of your fingernail. More keratinous nail is produced at the root of your nail, and that growth pushes the nail outward toward the tip of your finger, and someday you must trim it if you are not to look effete. Same with the natal scute - it is the root, but it pushes outward in all directions, not just one.

How do we know that there is an epidermal layer of cells beneath that colorful keratin layer on top of the turtle? You could see how easily I peeled the keratin off the pair of plates in the above photo. I could not have done that with a living turtle, not without a great deal of difficulty, and probably with some amount of blood as well. The dead keratin layer, in a living turtle, is affixed to the underlying epidermis through its secretions just like your hair is affixed to the scalp above your skull bones. Once the turtle dies, though, that living layer quickly disintegrates and the glue that holds the keratin layer is no longer there. It can be peeled off easily. Your hair falls off the dead layer of skin when you die, too.

How about the colorful spots that are maintained so stably in position on an older turtle?

However hard it is, the colorful keratin layer isn't invulnerable to mechanical abuse. It not only sloughs off from the top, but as it nears the edge of a plate, it seems to come to an end. It must be replaced, and that's the function of the epidermal skin cells beneath it, the ones covering the white bone. The upper keratin sloughs off, but is replaced by new keratin secreted by the epidermal cells beneath. (Alternative hypothesis: the bone cells beneath the keratin secrete an actual non cellular glue, a mucilage that holds the keratin layer in place. For several reasons, this is not a hypothesis that explains a number of other things.)

Now here's the possible trick, and this is only a hypothesis: The epidermal cells under the keratin and atop the bone are not uniform in how they express their genes, particularly, let us say, colorful pigment producing ones. Much as in a spotted cat, there are spots of cells that make pigment next to regions that do not, and presto! You have a spotted cat. My guess is that as the keratin layer creeps across a spot of renovating cells, it becomes suffused with new keratin that contains pigments, bright yellow, for instance. In an older turtle this process is quite slow, and as that same layer of keratin moves over and off the pigment secreting cells, the pretty pigment is sloughed off and the replacing keratin no longer contains the pigment. The bright yellow spot you see is a function of the pigment producing cells beneath, and that spot appears to remain in place.

Another trick, and another hypothesis: The advancing scute, becoming more elderly with its older rings, eventually reaches the edge of its plate. The oldest scute portion with its oldest ring disappears, and presto! You lose information as to how old the turtle is, for that ring no longer exists.

I'll leave you with one last photo, this time of our legendary nomad Ernest, who gave permission for me to paint growth lines on each plate. I've painted four growth lines on each plate. Each originates at the natal scute, marked with a red dot, and ends at the edge of a plate. I'll leave it to you to figure out what this means, and will interpret it as best I can in a later post.

Friday: 12 August 2011

Below the Radar  -  @ 10:36:14
The last week or so has been involved in getting our herd of cats their annual veterinary attention. For the most part this means rabies and other vaccinations.

One thing we've gradually become convinced of in the last year or so is that two of our cats, Violet and Memeow, are largely if not completely deaf. As I began to do some internet searching it became clear that there's really very little information on how to recognize deafness in cats, and how to respond to it.

This has been a post in the making for at least a month - for several reasons it's been hard to put together. And so it's just going to be a rambling post, that's all there is to it. The main reason I've pursued it is that deafness in a cat is something not likely to be on the radar of possible problems that cat owners recognize, and even when suspected is hard to confirm. Although this is entirely anecdotal, I think I have some diagnostic suggestions, along with some thoughts on alternative communications.

I'll present a capsule summary of the two cats below, but they both have some things in common. They're both female. They're both getting up in years, especially Violet who is distinctly elderly. For what it's worth they both have some hyperthyroidism issues. They're both very thin - just around six pounds, which is quite tiny for an adult cat. In their own different ways, they both have retreated into a kind of socially isolated world of their own. They both occasionally and at inappropriate times issue forth with startling loud vocalizations aimed at nothing in particular. This is apparently typical of deaf cats (one useful internet tidbit), and something to watch out for.

Statistically, because if anything we here certainly have the numbers for statistics, if I look back over the last thirty years at the 26 cats1 we've cared for, there was one more cat, who fit all these parameters, who was probably deaf and I just didn't realize it. In her case it was probably an old age thing. That makes three likely deaf cats, out of 26 randomly selected (one way or the other). That's a pretty high percentage, somewhere around 10% either congenital or age related, and so it's something to watch out for, although recognizing the syndrome and dealing with it is completely under the radar for most cat owners.

It bothers me, mostly that it took me so long to realize it. I tend to think I'm fairly observant, but cats are so damnably quiet about their ailments and problems, which can creep up because they just don't complain. Hell, they *purr* when they're in pain, and all humans ever think about is that cats are contented when they purr.

Cats respond most favorably to chatter from humans - never had one that didn't - it's a mainstay of interaction even though they don't really understand what you're saying. They like it. The sillier the better, or so it seems. So I see myself talking to them, and yes I do that, and even yelling at them when they start that odd hollering for no reason. And I failed to notice that these two were withdrawing because they couldn't, so it seems, hear me, and I wasn't substituting for that vocal communication something they could actually perceive.

Violet is 14 years old. Our veterinarian claims the records go back to 1992, but I don't think that's possible given the milestones Glenn and I know transpired on documented times. She was one of the two surviving kittens from a litter that was dumped at our fire station. Glenn rescued her and her sib Beaumont, who died a few of years ago.

Now Violet has never really socialized well, although she has her affectionate moments. She's always been extremely timid, and except in those few good moments has shied away from us. We always attributed this to kittenhood trauma, and goodness knows she had that. A few weeks ago it was clear that she was having some elimination problems, and it developed that she had a severe urinary tract infection that required a couple of days of IV maintenance, and then a regimen of antibiotics. Even before that, though, she would at occasional times begin hollering for no apparent reason. I called them night terrors, since that's when they'd happen, and usually just making an appearance and giving her a pat would be enough to quiet her down.

Memeow (her name is not our doing, but it fits, as we shall see) is the Hurricane Katrina rescue. We acquired her via a clever trick from a former firefighter who spent some time in New Orleans helping out in 2005. She's probably somewhere around 9 years old, and the story goes that she spent two or three weeks on her family's rooftop after they abandoned the residence, after which her owners suffered terrible fates. To the vet's office, she's been known as Killer since the beginning, since there's nothing more embarrasing than having to be announced for M e m e o w. All the folks with manly dogs will look at you a little alarmed, and edge away respectfully, if the office manager asks if K i l l e r needs all her vaccinations. It works.

At first she may seem ugly, but in fact she's a genetic beauty. As a tortoiseshell, she has all the intricate sectoring of orange and black on a brown background that you expect and hope for from an XoXb. She's quite a rascal.

She's very well socialized around people, but hates the other cats and is very effective in using the fast paw, claw, and a hellacious shriek, to enforce her privacy. She goes to Defcon 1 at the drop of a hat, sort of the North Korea of kitties.

Periodically, Memeow is also very, very loud, and not infrequently. This was, btw, the reason for her name (me meow, me me me meow... get it?). For years, she dogged Glenn upstairs with these frequent wails, and, exasperated, he'd put a little food in her bowl, maintained especially for these occasions. Now I see that it's likely that she'd look at him and think something like, "oh no, it's the food man again," when that's not what she was asking for at all. She was always polite enough to eat a mouthful, and then ten or twenty minutes later, same thing. Either she was training Glenn or he was training her.

Apparently it's not uncommon for deaf cats to use their voices as a source of comfort - though they can't hear, they can feel the vibrations of the sounds they're making.

Once I began to get it, because humans can take awhile, I conducted a long, long series of tests with Violet and Memeow, and the other cats as controls, and began to conclude that the two were hearing impaired. Such tests with cats are difficult to interpret - one reason, as everyone knows, is that a lack of response may well be because the cat doesn't care to respond.

(You might remember the efforts to demonstrate that cats can see color. It seemed clear that they should, because they have retinal cone cells, but did they? It turned out that eventually you could demonstrate that they would distinguish different colors, but they had to be trained to see color as a tool before they could associate color with, for instance, the container with the food in it.)

Although it's a charming anthropomorphism, I don't buy the conceit that cats deliberately ignore you. I pretty much think that they're naturally whatever the opposite is of ADHD. Autism, maybe, but they're inclined to focus on one thing exclusively for significant periods of time. Humans have to take every perceived slight so personally. Even so, the controls show that even when a cat is otherwise focused, there will still almost always (it's that "almost" that makes these things so hard) be some tell that says they can hear you - a flick of an ear or a twitch of the tail, even if they don't toss candy and flowers at you when you beckon.

Further, and this is largely how I now catch the attention of Violet and Memeow, positive responses were to be had by tapping on the floor, when vocalizing or snapping of fingers had no effect. There were just too many occasions when they were responsive to floor tapping when calling was ineffective. They were a little puzzled at first, but now respond immediately, able to sense vibrations from the tapping through their feet. I do this a lot.

I've also substituted the occasional (cautious, because you don't want to grab a deaf cat unless he or she knows you are there) hug, stroking, and even just some momentary touching for the chatter I always direct at cats, since, after all, they can't sense the latter at all. So there's a lot more touching and holding, and of course I still talk to them while I do it, because that's my habit. It's fine to continue to talk to a deaf cat, though it may seem useless, because to be silent while engaging in this misinforms the touching and stroking aspect. They can tell.

This seems to have made all the difference. They still have the yelling episodes - but I can quiet those quickly with a pat or stroke. And Violet's personality has completely changed. She's now apparently fearless, rather than timid, and she doesn't run away when I approach her. She appreciates the physical touching, and I think it's a result of the tapping on the floor that I use to catch her attention or even just acknowledge her presence.

The food man seems to realize that Memeow wasn't always just asking for food - all she ever wanted was acknowledgement of her existence. Or so I think.

1Note on the cats: Another reason I've had trouble finishing this post is that I really don't like to make cat posts. Or I do, but the responses can, once in a while, usually by email, be so thoroughly mean spirited. It's usually just not worth it. So to summarize for those encountering for the first time that "26 cats in the last 30 years:"

We didn't set out to have a steady state population of ten cats at a time. I'm allergic to cats, and I never had cats when I was growing up so was completely unfamiliar with them. Our cats come to us - we don't seek them out. They're the discarded and abandoned, and most of them aren't cute kittens when they come to us, but they have all been gentle and in great need. And we don't leave them feral, either - they are neutered immediately, they get their vaccinations (particularly rabies) on time, and they are individually cared for with great concern.

For those who gnash their teeth, these cats are essentially out of the environment where they would have had a short, brutal lifespan with a painful end. They will not make new cats. I think that we've made the world just a tinier bit better place for it. It's not because rescued animals makes the world a better place intrinsically, but because somehow their companionship has made me feel a lot better about my fellow human beings. They have calmed me in my cynicism and anger. They've caused me to get involved with things that actually do have to do with people, to our mutual benefit, that I wouldn't have done otherwise. I don't know how that works, but it did. And that's all I have to say about it.

Thursday: 11 August 2011

Out of Balance  -  @ 04:10:20
Since May 1, if predictions hold through August 17, we will have had 85 days with high temperatures at or above 90 degrees F, out of 109. The normal number of such days would be 41, so for some time now we've been working through our second summer in the length of time normally spanned by one. Up to this point, I've simply been noting that, with some amazement admittedly, but now I'm really offended. If I'd known this back in May, it would have been a shoot me now moment.

We can't complain about unduly high temperatures - we've had just 5 days 100 degF or above (2 such days normal), nothing like the extremely high temperatures the central US has experienced. It's just the *persistence* - it's gone on for so *long*.

As was true yesterday when the prediction was for a high of 94 and we had a couple of hours of 100+, I feel much more comfortable when the temperatures get really hot like that. I didn't even have to use a fan out on the porch. The relative humidity drops, and when it drops to 25% at 98F, it's actually much more comfortable than temperatures in the 80s with 60% RH. You really have to live in the southeastern US to appreciate the difference between the two extremes, because we can get both in a 48 hour period.

Of course, once you get below that 30% relative humidity, 25% is the trigger here, you get red flags - wildland fire watch. We maybe should have had one yesterday, but it wasn't issued.

Sunday: 7 August 2011

Round Trip  -  @ 09:11:24
Friday afternoon brought several waves of thunderstorms through our area, for the first time in a while. The temperature dropped 25 degF, we had several very close lightning strikes, and a half inch of rain which we are not complaining about at all. Saturday morning seemed like a good morning to go look for box turtles.

Imagine that one day you, with only the mental faculties of a box turtle, decided to set out on what to you as a human would be a 30 mile trip1. And then return those 30 miles to your starting point, again aided only by your box turtle brain. No GPS, no itinerary or maps allowed, just what we can only imagine is an urge.

That's what I found yesterday morning, when the lighting was fairly dim under the canopy. I don't know how I found him2 - he was well hidden, some distance from me, under long cutgrass right on the edge of the bank of what's left of SBS Creek, and he had quite a coating of mud on his carapace. This photograph has been zoomed in and enhanced in contrast so you can see him.

That's Ernest, now discovered for the fourth time. The first discovery was May 9 2008, about 100 feet away from where he is right now. The second discovery was a week later, just by chance, and only 100 feet away from the first one.

The third discovery was by our neighbors last June 30, in their driveway, 30 miles away as a human would have to have walked.

That in itself was remarkable, but now I find him a year later, just about at his original starting point. He traveled the box turtle equivalent of 30 human miles to a specific location that we all by now know is special because of its nursery aspect, and then traveled back to his starting point.

One thing I noticed this time around was how small Ernest is. He has 20-25 scute rings, so I know he isn't a very young turtle. But he's only about 2/3 the size of the turtles I typically find. This was something I hadn't noted in the 2008 posts, and I do wish now I'd been measuring turtle dimensions, if not mass.

He has quite a handsome plastron.

And a handsome carapace, too, once the dirt was washed off. All box turtles are pretty and special when they're wet and clean.

1 A human movement forward with all its legs is around 5 feet, I'd guess. A box turtle's similar movement forward is perhaps an inch. That's a ratio of 60:1, and so with a distance of about a half mile traveled one way, 30 human equivalent miles. More to the point, it isn't 30 human equivalent miles randomly, it's 30 such miles to a destination which we can only peg as specific, since several other box turtles previously identified have traveled and been discovered there too. And for the first time, we've found one that has made the 30 HE miles back to the original starting starting location. Without our neighbors' observations, I couldn't have made this unique and remarkable documentation.

2 Ernest's plastron is definitely concave, but not as distinctly so as some males. His maleness is of interest because of his trip to the Gresham's nursery. Almost all the turtles they've found have been at least digging nests with their back feet, along their driveway. Ernest was not making a nest, just ambling around, but there he was. We might call Ernest's sex into question, given the preponderance of females that have made this trip and were engaged in female nesting activities. But that's the only reason I can think of for imagining that Ernest is a female, and he certainly was not engaged in female activities at the time.

Friday: 5 August 2011

The Month of July  -  @ 06:38:48
It's The Month of July, Number 66 in a series. The word for July was hot, and in many places, not just hot but dry.

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center. The mean anomalies can be had on a new page by clicking on the image below.

The westernmost West continued cooler than usual for the fourth month in a row. The northern midwest, which had been cooler than usual since February, began to experience warmer than usual temperatures in July. The south and Atlantic states were once again warmer than usual, continuing a trend since near the beginning of the year.

The south had much warmer high temperatures, but nighttime lows were also warmer than normal for much of the eastern half of the country.

It's the big red blog centered around TX, OK, and KS that has occupied much of the weather attention in July.

We find the National Weather Service Climate Prediction Center's precipitation plots here.

Dry weather and continued drought continued across the southern states from TX to FL but it was highly scattered in the deep southeast. The big red blob above also coincided with continued drought. A strip of western states from AZ and NM northward got some relief with normal to surplus rainfall, but drier than normal conditions extended northward in northern CA and western OR and WA.

For Athens:

Here is a plot of our temperature swings in July, along with precipitation amounts as experienced in Wolfskin:

The unusual number of days with 90+ high temperatures in May and June continued in July, with 27 days receiving 90+ high temperatures. In July the absolute highs never broke a record, but their persistence tied us for third place in the number of days in July with 90+ temperatures. On 1993 and 1986 had more than 27 such days, since 1948.

Here is my plot of high temperatures for the month of July in Athens. As usual, the black dots are for the years 1990-2009 (black dots), 2011 (green line), and 2010 (red line).

Our high temperatures were much higher above July's average 90.2, by 4.5 degF. This isn't record breaking, but similarly to June our 94 degF average high ranks up there: the sixth highest since 1920. In June only 1925, 1931, and 1933 were higher. In July it was those years as well as 1932 and 1993.

In July, there were a 10 days more than one standard deviation above the norm (5.0 days normal). We had only 2 nights more than one standard deviation below normal (4.5 nights is normal). So even our nighttime lows averaged higher than normal, by 2.9 degF.

While it's true that we didn't break any records in July, the degree of persistance of daytime high temperatures since May is unprecedented. As of this writing, in the 96 days since May 1, 72 days have reached 90 degF or above.

The figure below shows the Athens precipitation data which are official for our area. As usual the green line shows our actual rainfall, the red shows the average accumulation expected. The black dots are rainfall over the last 20 years, the vast river of peach shows the standard deviation.

We had only two periods of real rain in July. The plot below, of Athens data, shows a lower total than we got in Wolfskin. We had 1.96" here in Wolfskin, Athens official rainfall was 1.46", and the average is around 4.3" expected for July.

The neat prognosticator largely failed in its predictions for April and May, and were so-so for June. It did a little better for our anomalous July warmth. And I'm afraid it predicts continued higher than normal temperatures for at least the next month, and maybe for the next three.

As far as rainfall, the next two weeks will be below normal, and after that there's an equal chance of normal rainfall.

ENSO stuff:

The ENSO PDF update at this page still chokes on download - wish the Climate Prediction Center at NWS would get that fixed! The power point option is ok, though.

La Niña ended in February, after a nearly year-long manifestation, and normal ENSO conditions are in effect, just in time for hurricane season! ENSO neutral conditions are expected through our northern hemisphere summer. The current update suggests the possibility of a return to La Niña conditions in the autumn.

NOAA's Monthly State of the Climate product for June is now up, and addresses the high temperatures this calendar summer. It confirms that Georgia had its 3rd highest temperature average in June.

July should be appearing soon. Detailed explanations for weather events occurring during whatever month is current can be found for the several sections of the US under the National Overview. There are many interesting weather- and climate-related items to be found here.

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