Niches

Something Up in Turtleland

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 The "vindictive" active male continued to batter at the withdrawn male, presumably frustrating its efforts to emerge and get the hell out of dodge.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.)

Five Hundred Days and Nights

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.

Sylvia Finds a Mushroom

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.

More Snapping Turtle Mysteries

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!)

Sylvia and Ernest

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.