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

Tuesday: 29 May 2012

Spring Turtles Update  -  @ 05:04:10
You might remember that I'm trying to quantify the population of box turtles on a 20-acre study area of mainly hardwood forest and creek bottomland. Here are some initial results. They depend on some work I did last year, especially toward the end of the year, and a truly concerted effort to sample things this spring.

The figure below summarizes the box turtle findings so far this year. Both the red dots and green bars indicate days when trips were made to find box turtles. The red dots are for days when trips were made but no box turtles were found. Green bars indicate the number of box turtles found on successful trips. Trips were usually 2-4 hours and 1-2 miles.

This pretty much tells us when box turtles emerge here in Wolfskin. A few may make an early appearance in late March or early April, but a sustained emergence doesn't occur until the last week in April. After that there were only two trips made in which not even a single turtle was observed.

So I've had 33 encounters with turtles this year, so far. Quite a few of those were multiple observations of the same turtles, but there have been eighteen unique encounters. Of those, five were previously observed ("captured and marked") last year. With twelve unique turtles observed in the study area last year, we can apply mark and recapture equations and get somewhere around 42 turtles, plus or minus 9 turtles.

Now I typically walk a mile, scanning ten feet on either side, on average, and from that I conclude conservatively that I will almost certainly have spotted any visible turtle in a total area of about 2 acres (5280 feet x 20 feet). Since the study area is about 20 acres, I would expect to find 4 turtles on my route if all turtles were out. Since I saw an average of 1.8 turtles per trip in May, I'd guess about 1.8/4 or 45% of the turtles are out on any given day in May.

So it turns out that just under half the turtles during May are active, on average, on a given day. I've suspected that box turtles are not always roaming around, although I'm a little surprised that the percentage of active box turtles is so high. Maybe this is just their more active season. I expect to see this number go down considerably in the hot summer months, and then probably back up as things get cooler in September and October.

Notice that last - it means that the population of turtles that are active in the spring may not be exactly the same as the population that is active at the end of the season. There may be immigrants (or emigrants) involved. We'll have to wait to see if this is the case, but we won't really begin to get an idea until the end of next year at the earliest.

Thursday: 24 May 2012

Bright and Shiny  -  @ 05:43:55

On Monday night, we had a pleasant rainfall of 0.37 inches, which made for a wet turtle hunt on Tuesday morning. Down very near to Goulding Creek, I ran across two turtles which were so fresh and shiny they almost made my eyes hurt. Back home, I compared them to the several very young turtles I've found, without matches.

It was only the next day that I thought I'd better take another look at the remaining photos before pronouncing these new, previously unseen turtles. And sure enough, I'd found both of these turtles before. It was just that I'd found them before on normal dry days, and the differences in their appearances are very misleading.

Here, for instance, is Torri, who I found initially in October of last year, and then again at the end of April (left). Right, she looked thoroughly rejuvenated on Tuesday.

He doesn't have a name, yet, but I found this one initially on May 3 (left), and then again on Tuesday on Goulding Cliffs (right). The patterns could not more clearly match, but the moisture really brings out the brilliance of the coloration.

Here, by the way, is a quick map of where I found the two turtles. Torri is indicated in orange, and she's moved an amazing distance since last October. Similarly, the male, 120503m1, in purple, has moved in parallel with Torri over the last month, both ending up well separated from one another, but just above Goulding Creek.

Both turtles have migrated what seems to me to be an unusually long distance over a month's time. I've been suspecting for awhile that turtles may sort themselves into stay-at-homes, and roamers. Sylvia, who I've never found more than a hundred feet away from any previous position, seems to be a stay-at-home. These latter two may be roamers.

Wednesday: 23 May 2012

Taking a Closer Look  -  @ 04:16:34
Although I generally regard bar graphs as vulgar pretensions that can better be handled in text, I make an exception when histograms are involved. A histogram isn't just any old bar graph - it's a bar graph that reveals detail that a single number, such as an average, hides. Let's take May, 2011, last year, as an example of an extraordinary May. There are many ways last May could have been extraordinary, but a simple average temperature would not have told you much.

Last May, the average daily high temperature was 84.1 degF, where 81.5F is the average daily high. Not very different, and other Mays have certainly had higher average highs than last year's.

What was different last year is revealed in the frequencies of daily high temperatures. With a histogram, we can look at the number of times during the month the high was in various temperature ranges, such as less than 60 degF, 60-69F, 70-79F, 80-89F, and 90F or above. We can immediately compare that to the average number of times the high occurs over a period of many years - say, 1948-present.

And that's why I've become enamored of presentations like the following, which shows in greater detail just where May 2011 was hotter than an average May:

Because we have 60+ years of Mays to populate those temperature ranges (red), we can also estimate the standard deviation (error bars). That shows us that many more days in May 2011 (blue) hit HIGHS in the 90F or above component than average. Moreover, that was really the only component of temperature affected. LOW temperatures, not so much: only one component in the LOWS, 51-60F, was significantly different from average, and that by only a tiny amount.

In other words, we can see *how* May 2011 was so much hotter - it wasn't so much because of extreme high temperatures, but because there were so many days in the highest temperature ranges normally encountered for May. The low temperatures, on the other hand, were fairly typical.

Simple averages don't reveal this level of detail, and with just a little practice we can intuitively grasp the extra detail without much effort.

These kinds of distributions of frequencies are also amenable to chi-square analysis. The counts for each temperature range during a particular month, along with the averages and standard deviations, make a chi-square analysis a perfect way of pinpointing unusual events. Chi-square, as you recall, determines if a particular set of *frequencies* is significantly different from an average (expected) set.

Here, for instance, are the counts for the spring (MAM) months, again with the average and standard deviations in red, with error bars. I scanned down the chi-square values on an excel sheet, and pinpointed the years that had the highest total chi-squares. 1960 had a very high chi-square total, and it turned out to be high because it was a very cold spring. (68.9 vs 73.6F average highs - again, the simple average isn't very helpful).

From the plot below, we can see that 1960 was cold not because there were so few days in the highest normal temperature ranges, but because there were so many more in the lowest daily highs (less than 60F) and daily lows (less than 30F).

So how is our May 2012 stacking up, so far?

If this May continues as it has for the first 22 days, then it will turn out to be just about as normal as possible, with all blue bars within the error bars of the average reds:

Just one additional little detail:

You might have noticed, especially for the Spring histogram in the middle above, that while the red ranges of the HIGH side of the histograms above have a fairly normal distribution, like a bell curve, the right LOW half of the histogram is definitely skewed toward the warmer LOWs.

That's my problem - it's hard to pick ranges that give good distributions, especially for long periods like spring or autumn, when temperatures change so drastically. Summer or winter - not so bad, since temperatures don't vary so much from June through August, or from December through February.

OK - one more thing, and then that's it for histograms and statistics for now. This kind of analysis is great for temperatures, because temperatures are generally predictable: cold in the winter, hot in the summer, and a smooth increase from cold to hot and back down.

It's not great for rainfall analysis, though. One reason is that rainfall doesn't follow a predictable sort of pattern during the course of the year, at least not here in Georgia, where we have no rain seasons. The other thing (I think) is that while temperatures may follow a symmetric normal (aka Gaussian) distribution around a mean, rainfall follows a distribution more like a Poisson distribution. In a poisson distribution, there are many low rainfall events, and relatively few high rainfall events, definitely not a bell-shaped curve. A chi-square test is not suitable for such a distribution (although an analogous test may be available for poisson-like distributions).

Monday: 21 May 2012

Our Pet Snake, and Other Tales  -  @ 04:59:45
The red-bellied water snake (Nerodia erythrogaster) has been something of a fixture in the ponds this spring. On Saturday, it (he?, she?) hung around the edges of the Bufo Pond basking in the morning sun. We were messing around outside, and I occasionally took a few photos as it would move to a new position. For most of the morning and early afternoon, nothing we did bothered it, and then, suddenly, it got spooked easily and took to the water. Well, water snakes are all temperamental, and that's why no one bothers them.

Saturday afternoon I went into the woods for a sit and watch. This is a variation on the active turtle hunt, but instead of walking a mile or two over two or three hours, I sit for an hour or two and wait for all the turtles to walk past me. It hasn't worked yet.

So I got up and took a walk up the west rise, and within 30 feet found two box turtles, both male. The first one was the first one of the year, on March 20, and I've spotted him again, on May 3. He's been working his way from the mid floodplain to the shagbark hickory fall west and now south to this point on the rise leading out of the study area.

I walked ten feet farther uphill and ran into this fellow, who I've not seen before. His patterning is very unusual - I don't know what to make of it.

The color patterns, if they're actually there, are heavily obscured by something else. It almost looks like filagree. The closest I've come to seeing something like this is what I'm told was the result of a fungus infection (2010). But that was a clear problem that also resulted in carapace deformations, and the only real resemblance there is that it too obscured any yellow or orange markings.

Even the plastron looks scrimshawed.

Saturday: 19 May 2012

Attack of the Rolie Polies  -  @ 13:44:02
Over the last couple of weeks I've been encountering three young armadillos, as I make my way down the feeder creek into the floodplain. The first time I ran across them, or vice versa, I got these two photos of the last two in the train, just before they popped into a hole.

The only reason I presented these two long distance photos at all was to ask this question of the photo below: Is the second one holding onto the tail of the first one? I do believe it is.

So I've seen them most days that I've followed this route. The pattern is the same - they detect something about my presence, and get all panicky, and then they run straight for me, in their panic. I've had to move to get out of their way as they try to escape me.

They're really not very smart.

They're not tiny, but they're definitely much smaller than the usual adults we see. They also seem to do a lot of playing, or at least as much as armadillos might do.

And by the way, take a look at that right hind leg in the photo below. What do you see?

They hang together, but there just seem to be the three of them. And that's one of the two things you might already know about armadillos - they're one of the few examples of mammals that are polyembryonic. They give birth to identical quadruplets. So that's why I wonder where the fourth one is.

Another thing you probably already know is that armadillos can be a reservoir for Hansen's disease, or leprosy. They are one of the select mammalian species - humans are another - which provide a favorable environment for Mycobacterium leprae. Both species can get Hansen's disease, although at low percentages - the bacterium is extremely slow growing, and very difficult to transmit.

You might also be aware that armadillos have been expanding their range northward and eastward over the last century. They're now seen in Kansas, Illinois, Indiana, and Missouri, and have made it to north Georgia. Our first sighting on the property was Nov 22 2005, and they've been multiplying ever since. Earlier this year I wrote a post on holes, which have become enormously more numerous in the last three or four years.

All these things bring up a number of questions that you are probably aware of, too.

1. Why are armadillos so successfully expanding their range, now? Most of the hypotheses revolve around a combination of climate change making for milder winters, and a decline in medium size predators. See here, for instance, or here, for something a little more sensational.

2. How do new environments affect new populations of armadillos? While not foremost in my mind as the most interesting set of questions, researchers have looked at the effects of prescribed wildland burns and timber management on recently established armadillo populations. They haven't come to firm conclusions, because other factors confounded the observations, but those two practices seem to reduce armadillo populations somewhat.

3, and most importantly: What are the effects of armadillos on the ecology of a region they've expanded into? The 2008 USDA, APHIS, and WS environmental assessment report on mammal damage management deals armadillos, but also with other mammals such as raccoons, feral dogs and cats, coyotes, and opossum. It offers some statistics and tidbits, but no one really knows, yet:

A. The effects can be direct. Armadillos eat eggs of ground nesting birds, such as quail, and I'd guess whippoorwills and such, too. I think we can imagine that they'll increase the predation rate on reptile eggs, as well. That rate is already high here, given our natural populations of raccoons and opossum. On the other side of the coin, armadillos will apparently eat out a nest of fire ants, and these have also been suggested as a reason for the decline in ground nesting birds, for instance.

B. The effects can be indirect, competition for food, for instance. Armadillos are mainly carnivorous, feeding on insects, grubs, and other relatively soft arthropod and wormy types. Certainly they will then compete with other mammal species already present, as well as ground reptiles, like, well, box turtles. On the other side of the coin, coyotes, another expanding species, have been on the increase around here, too, and are likely to view armadillos as prey.

C. Finally, armadillos reorganize the physical environment in ways that may have completely unpredictable results. We've seen it here in the large increase in the number of holes dug, potentially providing hiding holes for all manner of animals: rattlesnakes, coyotes, cotton rats, and burrowing owls. Box turtles may well also occupy these holes, and consequently holes can become traps, as well, attractive nuisances.

It's not just holes in the ground. Everywhere I look, every day, ground litter has been churned up as armadillos have gone over it in previous nights (and days), searching for food. This must have an enormous effect in increasing soil evaporation rates, through removal of usually insulating litter cover. The churning effect may increase the decay of the litter itself by mixing oxygen into what is usually an oxygen poor microenvironment. All this may have conflicting effects on the populations of larger litter occupants, such as insects, worms, and grubs, which of course are armadillo food in the first place.

So what should we be watching for, as indicators of effects by armadillos?

Friday: 18 May 2012

Their August Presences  -  @ 07:42:07
So how many box turtles do you suppose are hiding under all this? Click on the image for a larger view, if you like.

Yes, it's true. I can turn anything into a box turtle post. That grass is mostly bearded shorthusk, Brachyelytrum erectum, which we've talked about before. I might take a walk through it, using a long walking stick to push the grass aside to check underneath. Mostly though I approach it quietly, and listen and watch. I've never found a box turtle this way, but I fancy that I can listen for them, and that I can watch the grass waving anomalously, announcing their august presences. Someday it will work.

In the meantime, I like this view of an interesting location just above a little fall line in the just out of sight creek that you correctly imagine winding past, to the left. The fallen tree in the back is the decaying remains of the celebrated northern red oak.

Thursday: 17 May 2012

Something Up in Turtleland  -  @ 05:42:10
Yesterday was a very active turtle day - I had three encounters with four turtles during the usual survey. Here were two of those turtles. One was inactive, and upside down. The other was as acrobatic as I've ever seen a box turtle, and very interested in the inactive one:

I haven't seen an actual interaction between two turtles until now, with an exception many years ago when I saw one turtle chasing another across the fairy ring.

The first thought was that this was a sexual interlude, but the odd thing was that the presumptive female was all closed up, which by all anecdotal evidence isn't generally the case no matter how bored she might be. Males also don't typically flip a female over on its back - this would be counterproductive. Males would flip another male though, in a dominance fight. (It also occurred to me that the inactive turtle might be dead, but that wasn't the case.)

This was probably the only situation I can remember where I saw the turtle before he saw me. Once that was no longer the case, I did the usual photography and checking. As expected, the active turtle was male. Unfortunately the inactive turtle was one of those frustrating androgynes, with just enough plastron concavity to suggest a male, and nothing clear about any of the lesser sexing characters.

The previous photos were taken under natural shade conditions, which is why they have a greenish cast. The location is under a thick canopy - the ambient light really is greenish. This one, and the remainder, was taken with flash so that explains the disappearance of green.

The active turtle quickly withdrew, and is on the right in the photo below. I uprighted the inactive turtle, left, for this photo. I watched the two for ten minutes or so. The inactive turtle was just beginning to lower the drawbridge when I took a walk to survey farther uphill. When I returned ten minutes later, both turtles were gone. After a few minutes I did locate the previously active turtle, but never found the inactive one.

Of all the descriptions I've found online, this one seems to describe what I saw exactly. I'd apply it to explain what I saw:

This was a male-male encounter, and before I came on the scene, fighting had taken place, with the inactive turtle surrendering and closing up. The "vindictive" active male continued to batter at the withdrawn male, presumably frustrating its efforts to emerge and get the hell out of dodge.

Now the linked description is from an observer who keeps box turtles. Box turtles in a pen are not in a natural situation, and especially because males are possibly kept much closer together than they'd normally get. But it does describe the behavior I saw. (There is more that could be said about the keeping of box turtles, which does require a permit, and usually involves people who know what they're doing. Certainly the majority of descriptions of all sorts of turtle behavior comes from these folks, rather than from the very few who carefully encounter turtles in the wild.)

The notion of territoriality is worth thinking about, especially since there is an anthropocentric tendency to imagine that a turtle views a territory as "belonging" to them, and "worth fighting for." It seems recognized that many (but not all) box turtles occupy a limited territory of a few acres. However they recognize this territory, a more neutral take would be that all box turtles tend to wander. Most would wander farther, but become uncomfortable as they get farther from whatever home cues are being left behind, while new unfamiliar cues begin to accrue that increase it's discomfort. The result is a drive back to the home "territory."

(This is a subtle difference in viewpoint, but essentially a turtle with a territory is a passive instinctual captive who is a slave to certain cues. This viewpoint also has interesting implications for explaining those turtles who truly wander, with no fixed territory. If you've read Isaac Asimov's robot stories, you'll know exactly what I'm talking about.)

In the process of a wander, though, one turtle may encounter another, as seems to have occurred here. The reaction then would not be the silly view of one turtle explicitly taking arms to defend his territory, but rather two male turtles simply reacting upon spotting one another.

It seems like this would be susceptible to experiment. It would be difficult to work out in the wild, where subject turtles would have established their home locations naturally. But there would also be drawbacks in using captive turtles kept in enclosures and already out of place to demonstrate much other than that two males fight.

(ADDED: BTW, neither of these two turtles had ever been encountered before, by me. Both were on that part of the property that is not in the study area, and which I've only recently began to visit as a kind of control survey.)

Wednesday: 16 May 2012

Five Hundred Days and Nights  -  @ 04:58:05

One third of the year is over now, and it seems reasonable to kind of summarize it, for our local area, anyway. Briefly it has, on balance, been much warmer than usual this first four months, and much drier. We've had just over 50% normal rainfall, which is a lower rate than we were seeing in 2007, although not sustained for as long as yet.

I can summarize that with some reasonable confidence at a glance. Beginning in 2008, following our annus horribilis of 2007, I've kept an ongoing daily diary of temperatures recorded half a dozen to a dozen times a day here at Wolfskin, and combined them with our precipitation events. I've tinkered with the presentation many times, and have settled for the moment on this one (as of May 1):

Hard to see that one, so I've cropped a May 11 version of the rest of the year so it will all be visible without reducing the size too much:

There are two sets of data here. The blue and red are temperature data for 2012 (blue) and 2011 (red). The dots are individual measurements, and here the lines are 25-point running averages. The purplish line is the Athens KAHN average for each day.

The second set of data, down at the bottom in green, is for precipitation. The vertical bars are individual events (tied to the left axis), the bright green solid line is cumulative rainfall for 2012 (tied to the right axis), and the dotted line is the average accumulation over many years.

Let's look at our temperatures, the blue and red. I like including the individual points, since averages don't give an impression of short term extremes, and the cloud of points doesn't really get too much in the way. For instance, even though you can tell that the last 2/3 of March was really warm (blue line), you can see by the dots that there are virtually no temperatures recorded below the usual average during the last 2/3 of March this year.

I also like the 25-point running average. This takes the 12 measurements earlier and later than each given measurement, and averages them together to take the place of each measurement. Ideally the blue and red lines would represent the average, to be compared directly to the purple line. I do try to be representative during the course of a day, but in practice manual measurements don't make that possible. It's best just to read the lines in a relative sort of way, and not worry too much about the absolute numbers being perfect averages. They're close enough.

For April, then, you can see that we had generally about equal areas of blue above and below the purple average, and so we'd conclude that April should be about average, temperature-wise. However in the last week of April we began to get March-like extreme warmth again, with one blue dot above 90, and the presentation reflects this nicely. In the last week, we've had some cooler weather which has brought the running average down below the mean for the first time in three weeks.

I like including the precipitation data as well, because rainfall is the other major influence on plant growth, creek conditions, and fire weather around here.

You can tell from the vertical bars that since January our rainfall events and their intensities have declined markedly in the first four months. It rained just five times in April, and three or four of these were so paltry as to hardly being meaningful.

The bright green cumulative line has plateaued off beginning in March, and we haven't even reached 10 inches in the first 1/3 of the year. You can see in comparison with the dotted average that we've had just slightly above half the rainfall we'd expect for a normal year.

So all that's a kind of daily early morning ritual for me. It doesn't take very long to enter in the last 24 hours of measurements, and it's a kind of relaxing, fun thing to do.

Although 25-point running temperature averages are very useful for visualizing the fluctuations in temperature, even they can be too noisy to see long term trends easily. Increasing the window in the running average smoothes things out more, at the expense of some detail.

Here is a presentation of the same data, this time run through a 100-point running average filter. Given the number of measurements I take each day, this would be the average of measurements made over three or four days of measurements taken before and after each measurement.

This smooths things out quite a bit, but also depresses the absolute averages, so again, look at the trends, not the absolute numbers implied by the curves.

You can see in red the extraordinary number of days last year with average temperaures above the mean purple line beginning in April 2011 (or, arguably, even in mid-February), and lasting into September - the most number of days with above 90F highs of any on record here. Truly average weather would be more like the red line tightly following the purple average from September through November.

If you start with red December 2011 at right, and take a jump back to the left into the blue at January 2012, you can see that we've been above average since December, with just a little cold weather in mid February. Against last year's red backdrop, the blue of the last two or three months is even more extreme to date.

I could (and did, actually) write a fair amount on why I do this. It probably suffices just to say I like to do it.

Tuesday: 15 May 2012

Sylvia Finds a Mushroom  -  @ 07:54:23
I spotted Sylvia again, yesterday. She was up to something.

It was May 3 when I saw her last. She contributed to my mark and recapture data for this year, since I saw her last year, but only on that first May 3 encounter. I don't count a second observation in a single time period as relevant to the M&R estimate.

However I do count it as important when I see a turtle two or more times in a short time period, as was true for the four times in encountering Corey last month, or Ivan last year. It means that I'm achieving positive hits consistently. When I stop seeing the turtle, it suggests that it's because the turtle is no longer available to be found, for whatever reason.

So it turned out Sylvia had found a mushroom, and was snacking on it. Look at those delicate little bites! I've been taking note of mushrooms in the last couple of days, since we had a little rain. Looks like those are the turtle marks I should be looking for.

A couple of things about this new female I found yesterday. First, she's the first turtle I've found in the upper pine-hardwood mix that is found in the east quarter of the property. It's not a part of the "study area," so I can't count her in M&R results for this year (although she can form the data base for an extension of the study area if I include that area in my periodic surveys).

I admit I don't spend nearly as much time in the boring upper piney woods as I do in the much more interesting creek and floodplain areas. Still, I have spent *some* time there, and yet have only run across this turtle. And she's new - I've never seen her among the other turtles that are part of the study group.

Her driver's side looks pretty good, although I noted some lumpiness about the carapace that doesn't come through well in the photos. It's her passenger side that's quite damaged. There are what look like punctures, scute separations that have been filled in by repair growth (I guess), and loss of keratin and of marginal scute portions. I'd conclude that this was more of a predator attack, as opposed to a mower, because of what look like punctures and because of the heterogeneity in the damage.

At first, though, it seemed to me that the plastron was remarkably unscathed. but as I looked a little more closely, it seemed that there were several puncture wounds, which seem generally healed. Still, there are not as many on the plastron, nor as deep, as I might have expected, given my assumption of how a predator might tend to grab and bite a turtle.

Most of the box turtles I encounter are seemingly healthy and undamaged. There are perhaps a half dozen out of three dozen (let's say) that show something more traumatic than normal aging wear and tear. The three main sources of damage to adult turtles are predators (natural or not), lawn mowers, and cars (this last isn't so important with the turtles I see, although it's not out of the question). The last two, and possibly at least part of the first, are human associated.

Saturday: 12 May 2012

More Snapping Turtle Mysteries  -  @ 07:20:13

When I'm walking through a particular area, I often do think about the turtles I've found there. This is especially true if it's a turtle like Sylvia or Ernest, who I've found multiple times. Where is Ivan, for instance? I haven't seen him at all this spring, and I found him several times last year.

Snapping turtles are not easily identifiable in the way that box turtles are, and they're not as loveable either. That is, until I watched in fascination the one who was cavorting in Goulding Creek the first day of spring, this year. That probably set me to remembering the one I'd found last year, on May 25. She had been on the bank above SBS Creek beginning nesting operations.

So though it seemed a very unlikely possibility, I'd been keeping an eye out for nesting snapping turtles. And on Tuesday, there one was, same place, although 17 days earlier.

The nesting activity was taking place in exactly the same spot, on the edge of the bank four feet above creek level, and right next to the fallen shagbark hickory.

On Wednesday, I stopped by, and noted that something had already dug up and eaten the eggs. So it goes.

(Just out of curiosity, I checked last year's May 25 (top) and this year's May 8 (bottom) photos to see if this was the same turtle. I used the sawtooth posterior marginals to see if I could make any comparison. Other parts of snapping turtles don't have much in the way of easy features. Unfortunately the posterior marginals were salvageable only to a certain extent - the camera angles are different enough to be uncertain. However, I don't think these are the same snapping turtles. Odd, if true!)

Thursday: 10 May 2012

Sylvia and Ernest  -  @ 07:30:07

Last Thursday I encountered Sylvia (060512f) for the fourth time. She was the third turtle I'd documented, May 12, 2006, and the first one I rediscovered in October that same year. She started the tradition of naming rediscovered turtles.

I hadn't seen her since April 2009. But there she was, on Thursday, as she's always been, within 50 feet of her original location on the west side of the roadcut near Goulding Cliffs. And who can blame her, when the lighting is so nice?

Perhaps it was just a coincidence, but yesterday, in the middle of a rain, I ran across Ernest for the fourth time, exactly four years after my first encounter with him, May 9.

Ernest is, simply, one of the prettiest turtles I've ever found. His plastron is no exception - it shows some of the nicest patterning and color coordination that I've seen.

He's also a female - I was suspicious of this two years ago when our neighbors Tom and Gisela photographed him during nesting season at their place. He wasn't nesting, but he was the only male (sic) among the seven other turtles they've observed in the process. Last year when I saw Ernest I checked him out for other characteristics. He does have a very slight concavity to the plastron, but he lacks the flared carapace edges that males tend to have. Preponderance of evidence.

Ernest is also quite small. She, for I must get used to it, has the upper limit in scute rings, so perhaps she isn't just young and small.

Twice it's been suggested I rename her Ernestine. Please. That is so too obvious. There is importance in her being Ernest.

Monday: 7 May 2012

Fuzzy Feathered Friend Photos  -  @ 06:23:50
Early early this morning, around 3am, there was some sort of confluence of barred owls not too far off. They cackled and hooted and conversed in startlingly diverse language for at least half an hour before drifting off to the northwest.

That was a convenient reminder of yet another owl encounter that took place last week. As usual, I got a few photos of questionable quality, but rather than view these as desperate efforts to display a fuzzy owl, consider them an ongoing mystery play in which owls stalk me while I try to keep an eye on them.

Because of course they're fascinated by me, since I am a human and therefore it is by definition all about me.

So late morning last Thursday, last week, I was on my way back from my turtle walk when I spotted some movement off to the side, and up. It was a barred owl coming to an abrupt stop on a white oak branch several hundred feet away.

This isn't the first time a barred owl has come to perch nearby, and in all cases that I've detected the owl is clearly watching me. I have no idea how many times this has happened and I just haven't noticed.

I did slowly and obliquely close about half the initial distance, which still wasn't close enough to get a quality photo. It never is close enough.

I apparently crossed some sort of line of toleration, and the owl took off, again allowing me only the fuzziest of distant photos. It landed in another white oak nearby, but between me and the morning sun. I thanked it for the little adventure and went on my way.

Sunday: 6 May 2012

Out of the Blue  -  @ 06:07:45

On my turtle walk on Friday, after one of our few pissy little rains in the past six weeks, I was surprised to see this lone milkweed flowering in the open beech and white oak forest of upper SBS Creek. It turns out to be White-flowered Milkweed, or Redring Milkweed, Asclepias variegata.

And indeed it does like dry, upland woods with partial shade. How it got there is anyone's guess, but I love the little surprises that crop up now and then, and hope this single plant will start a trend in this area.

The Range Map, from USDA Plants, shows this to be a widely distributed species in the eastern US and parts of of Canada. Don't worry, though, there are tons of western species that are at least as nice!

Let's take a look at the inflorescence up close. Unlike the straggly florets of Common Milkweed (A. syriaca), these florets (I count in excess of 30) form a tight dome. The business parts sit raised above the flattish petals, five per customer, and these petals along with the unseen sepals form the floor of the dome.

Here is a nice side view of an individual raised floret, and the violet-red ring that surrounds the base of the working part of the flower and gives the plant one of its names. I would guess there are probably nectaries and other glands in this region.

The structures you see here are complex fusions of modified male and female parts. Milkweed flowers have a five part symmetry, and we've talked about this before, a long long time ago. The five "hoods," the structures that look a little like molar teeth, each receive a "horn." These are fusions of stamen parts, such as modified filaments. This weirdness is typical of milkweeds, and each part has its own name. At least one.

Here we have a top view of the floret - the liquid that is apparent is just raindrops, I think.

You might recall that the unit of pollination in milkweeds is not just a single pollen grain, it's a sac of thousands of pollen grains, called a pollinium. A pollinating insect must be encouraged to snag one of these sacs and then deliver it to a receptive flower.

Here's the same image as above with a few names attached. The five hoods and horns are the most visually dramatic parts of a milkweed flower. It seems that they could provide some direction to an incoming insect bearing a pollinial gift. Land here, on the stigmatic surface of the gynostegium.

The gynostegium is another fusion of the male and female parts, with the anthers and their modifications arranged around the outside of the gynostegium. The corpusculum is a knob that joins two pollinia - this flower only has one remaining. The translators are threadlike arms that connect all five parts, and provide the snag that will connect a pollinium to an insect.

It's always good to have native milkweeds around - they're great insect attractors. I had never seen this species before. You can find a nice review of flower terminology here. The portion devoted to milkweeds begins about 1/3 down. And here's a treatment of Common Milkweed, along with flower dissections and explanations.

Saturday: 5 May 2012

The Month of April  -  @ 04:42:12
It's The Month of April, Number 75 in a series. For large parts of the country, April was the fifth month in a row, since December, with higher than normal temperatures. Still, for most of us, it was not quite as warm as March was!

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

The high temperature anomalies flipped to the other side of the continent in April, with much of the West seeing higher temperatures than normal, while the East was much milder. Ominously, the regions centered around north Texas that received brutal heat treatment last summer are showing the highest temperatures in April.

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

The northern midwest finally got a break from a half year or more of dry weather. There was little relief in the east, and the south and southeast continue a drying trend that's deepened since the beginning of the year. Florida peninsula got a little relief in most places, but still not an abundance of needed rainfall. California got quite a lot of precipitation, nearly twice as much as normal except scattered areas in north CA.

For the Athens, GA area:

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

Temperatures moderated during the first week in April, even became a little cool now and then in the middle two weeks, and then ramped back up in the last few days of April.

Our high temperatures averaged out to be 77.3 degF, compared to a 30-year average of 74.0F. While nothing singular about this, it's still over 3F higher than normal. Similarly our average low was 2.3F above normal.

We had 9 days with high temperatures greater than one standard deviation above average (4.7 days is normal). We had only 4 nights greater than one standard deviation below the average low, where 5.2 such nights is average.

Here is a histogram that shows the breakdown of high and low temperature counts from April 1948 on:

In only two cases were our April 2012 categories significantly outside the norms: we had significantly more days with temperatures in 80s, and significantly fewer with temperatures in the 70s. We did have one day that achieved a high above 90F, which is very unusual, but not unheard of in April.

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 four rainfalls here in Wolfskin, amounting to 0.62". Three of these were so trivial as to be irrelevant. Since this is official Athens data, the month shows us ending with Athens' 1.36" of rain, compared to an average April rainfall of 3.37". Athens' total was just above the critical one standard deviation below average, and Wolfskin's was well below it.

I haven't presented my rainfall accumulation in Wolfskin, plotted year by year, in a while. In the plot below, each color represents a different year, and we're represented since 2005. For a particularly dry year, see 2007. At present, 2012 (black) is at the lowest of any year at the beginning of May: almost 50% below normal rainfall by this time.

What is the neat prognosticator telling us? It says that for the next two weeks we can expect cooler than normal temperatures here in the East, and warmer in the West. After that, and for the next two or three months it will be warmer than usual here in the southeast at least.

Precipitation will continue to be lower than normal for the next two weeks, and then after that an equal chance of normal rainfall. HOWEVER, I've noticed this prognosticator relies heavily on the current ENSO regime, and I'm betting that this transition in two weeks has more to do with historical trends after recently ended La Niñas, than with any modeled forecast.

Prognosticator stuff:

Finally, the folks at CPC have a version of PDF or HTML that is much different from their previous presentations, but at least it's there and the link isn't broken.

La Niña has ended, officially, and impacts are expected to continue to wind down. Just remember that last year we were ENSO neutral only for a short period before falling back into the La Niña from which we are just now emerged. This could happen again, and hurricane season could easily be ramped up by a La Niña reappearing.

The US Drought Monitor continues to have us in extreme to exceptional drought, depending on where you are in Georgia. Only in northwest and along the top tier of of counties is it merely abnormally dry or normal. There is little expectation of relief.

NOAA's Monthly State of the Climate product for March is available, and it's a fascinating read. The summary for 2011 regionally, nationally, and globally is also available.

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