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

Saturday: 22 October 2011

Box Turtles of the Year  -  @ 06:49:31

I still have a couple of posts to make about box turtles, but with morning temperatures in the 30s for a couple days running, and daytime highs in the 60s over the last week, it seems likely that I've seen the last of the turtles until next year.

So how did we do on the box turtle census this year?

To preface, since 2005 I've had 39 turtle encounters involving 29 unique turtles in the study area. (Since I've been walking through the new property, which is not a part of the study area, I've actually seen 9 additional turtles). Six turtles have been observed more than once, and three of these have been observed four times.

This year I had twelve encounters. Nine of these involved new turtles in the study area, and three were old turtles previously observed.

The last turtle I saw was Ivan, once again this year, playing in the creek last week after a good rain:

What did we learn this year?

Population estimate:

I took the turtle observations and used them as numbers for a mark and recapture analysis, and estimated somewhere around 40 turtles, which in the 20 acre study area is around 2 turtles per acre.

I did a re-estimate after encountering four new turtles in a row, here, and increased the estimate to 50 turtles, or 2.5 turtles per acre.

If I use 2011 as the recapture year, and all previous years as the marking years, then I'd estimate about 70 turtles, or 3.5 turtles per acre.

It was the last two re-estimates that cause me to suspect that turtles from the outside may be migrating into the study area in advance of hibernation.

Turtle movements:

I've already mentioned the interpretation of the last month's observations suggesting an influx of end of season turtles, perhaps returning to their hibernacula.

Last year our neighbors discovered a lot of nest building turtles, and several turned out to be some of the ones I'd observed here. One of these was Ernest (oddly, a male). This year I found Ernest back in his old place, indicating a full round trip.

The nesting sites our neighbors have observed, and the one we observed in 2009, were all located well upland from any natural source of water - not much less than a thousand feet. This is a lot of distance to expect a tiny baby to cover, and baby box turtles have a semi-aquatic habit for at least a couple of years. Very strange, and I don't know to make of it:

We could just be location biased. That is, we're seeing something happen in a location that we spend the most time in, and not seeing what's happening elsewhere in places we don't go as often. That would imply a huge amount of turtle nesting, if so.

There could be some kind of selection strategy going on, similar to the weird and seemingly pointless nesting treks of Antarctic penguins (on a much smaller and more modest scale, of course).

Or these nesting turtles we've observed could have gotten themselves into a programmed nesting instinct entirely by accident, by some foolish ancestor whose progeny just happened to have survived despite all odds.

Turtle growth:

I still have to write up one more post, at least, but I did some scute ring counting and comparisons and showed very little change in the rings of older turtles over several years. We also took a good look at external carapace morphology - the bone structure beneath the keratin layer, and how it appears to grow.

All in all, a pretty good year for box turtle observations, with lots of suggestions for next year's goals.

Friday: 21 October 2011

Sassafras  -  @ 09:53:22

In the last couple of weeks we've had warm dry weather with two periods of fire watches alternating with two periods of significant rainfall. Totals since Oct 10 have amounted to a low of 2.5" in north Oglethorpe County to 4.6" in parts of Clarke County west of us. We had 3.68" here in Wolfskin (southwest Oglethorpe County).

The rain has been very welcome! Only one extreme characteristic of the rain of the past few days: on Wednesday air pressure dropped to 995 millibars 6am-7am, which is the lowest I've seen it. It remained below 1000 mb most of the day, and I've only seen that once or twice. Otherwise the rains fell over a period of several days, with very little runoff from the very dry soils. The creeks saw a little more filling, and a little extra flow, but there were no raging torrents.

A few days ago I was out watching for (guess) box turtles, and near the bottom of the northwest slope just above the floodplain, saw this pretty fallen leaf.

It's one of the two leaf shapes that Sassafras (Sassafras albidum) is known for - the other is of a two-lobed mitten. "Sassafras" can also be typed solely with the fingers of the left hand!

I've walked this route for years now and didn't know the tree was there. Although rather skinny, the tree is 40-50 feet tall. This isn't that unusual in the south, according to the always interesting Fire Effects Information System. For a number of years, we'd had a colony of tall trees along the neighborhood road, quite distant from this find, hidden under the canopy of mostly leftover pine. But they gradually fell and disappeared, and this too is not all that unusual. Sassafras individuals may colonize disturbed land for a time but are not very long lived, especially when on drier locations.

Also via the same FEIS article by Janet Sullivan, this was interesting:
An unusual pure stand of sassafras was reported by Lamb [59] in 1923. This stand appeared to have remained essentially pure and intact for over 100 years. The trees were described as fully mature, slow growing, and the soil was very fertile. It is possible that the persistence of this stand, and the competitive success of sassafras in pioneer communities are related to the presence of terpenoid allelopathic substances in sassafras leaves.

And along those terpenoid allelopathic lines, of course, sassafras is well known for its herbal and medicinal properties. It has a lot of ethnobotanical and commercial connections, which a simplistic google search will turn up in such numbers as to hide anything else, so I'll leave others to sift through them at their own pleasure.

From USDA Plants, sassafras is an eastern plant, with occurrence over the entire range up into Canada. It's remarked that sassafras has special concern issues in Maine.

Saturday: 15 October 2011

Break Out the Orange Vests  -  @ 09:45:08
Deer hunting season with firearms begins today in Georgia - primitive firearms for the next week and then starting on the 22nd and going through Jan 1, all firearms. Here's the short form - not all counties allow deer hunting. Refer to the website with the unnecessarily massive PDF for the full 2011-2012 schedule and regulations.

If you're in another state, a good place to find hunting regulations is your state's DNR - Department of Natural Resources. North and South Georgia have somewhat different regulations.

Hunters - familiarize yourselves with your boundaries. Watch out not to trespass into private adjoining properties, and don't shoot into them either. Non-hunters - don't go into private properties that may have private agreements with hunting clubs, at least not without contacting the owner. And wear your nonfashionable but legally necessary orange vests when walking in the woods, wherever you are. We think about these things because Glenn often botanizes in privately held areas. He's careful to keep contact with owners, but a lot of folks aren't.

FYI, CYA, hopefully not KYAG!

Friday: 14 October 2011

Contact  -  @ 07:41:11
The Turtle Gods must have decreed that Wayne could only find one box turtle a day, and that within the first ten minutes of a 3 hour walk, just enough to whet the appetite for more. The Turtle Gods are cruel, but the Snake Gods were kinder yesterday.

Here's why you keep your eyes on the ground, especially on pleasant sunnyish days in October. Here's who I ran into on Goulding Cliffs, just before the roadcut fording Goulding Creek:

I had my eyes on the ground, but they were in the back part of the back and forth mode I use to scan for box turtles. It's inconsistent with good strategy to continue walking forward while looking away. When I looked forth, there at my feet was about a meter of fat timber rattlesnake, Crotalus horridus.

In fact, I do believe I kicked him, just a little, before realizing he was there.

This was a very polite snake, especially in response to such rudeness on my part. He merely lifted his head. He didn't adopt a strike position, and he didn't rattle. He was probably thinking what a ninny I was, and how he could have scorched me good if he'd wanted to.

There is general agreement, not to minimize the danger, that timber rattlers have a mild disposition, and it takes quite a lot of harassment to provoke them to go beyond positioning, rattling, feinting, and striking. That's not to say he couldn't have been in a bad mood to start with and skipped all the foreplay; in that sense I was fairly lucky. Just an inch more and I would have stepped right on him, trespassing beyond mere rudeness.

And it is probably a male. Here's the typically black tail - in a male it tapers gently and in a female the tail constricts abruptly, as in these examples.

He has only three buttons, besides the baby one, and so is only 3-6 years old, a fairly young one, and an impressive size for that.

Our newest firefighter, Charleen, was very interested in the photos. She did not ask, as is almost always the case, if I had killed it. Her assumption was correctly that I had left it unmolested, and isn't that nice? Timber rattlesnakes aren't rare in our part of the Georgia Piedmont, but they are fairly uncommon. I've only seen four, now, in twenty years, and two of those were on our little neighborhood road (where one had been killed by a neighbor).

As usual, the Forest Service's Fire Effects Information System has its typically interesting take on timber rattlers.

Now if that wasn't thrilling, then what else is?

Monday: 10 October 2011

Influx of New Turtles?  -  @ 06:51:47

Today and tomorrow are binary days - in YYMMDD format, 111010 and 111011. Next month we'll have 111101, 111110, and 111111 and those will be the last binary days of the century.

Yesterday I predicted I wouldn't find any box turtles, but the humidity was marginally good, the temperatures warm, and I found this fellow making his way across SBS Creek. He wasn't happy to see me.

Perhaps it was because we'd never met before. He's a new turtle, the fourth such in a row that I have found for the first time in the last few days.

And that brings up a new point - what is the probability that I would find four turtles in a row that were not turtles I'd seen before?

First, given the data since mid July of this year, I've reevaluated the mark and recapture results I wrote about at that time. At the time I estimated 40 turtles on the 20 acres under study. With the discoveries since then, I'd now up that to about 50 turtles, four or five of which are rediscoveries in the "recapture" period.

Second, in the last six years of observation, I've discovered 28 unique turtles. So the probability that the next turtle I'd find would be one I've found before would be 28/50 or about 56%. That means the probability that the next turtle I'd find would be a new one would be 100-56 = 44%. Finding four new turtles in a row is a probability of about (0.44)4, or 4%.

It depends on what you consider an acceptable probability but the most rigorous standards usually require a 5% cutoff to reject random coincidence. It just seems very unlikely that this could be a coincidence, everything being random (and I see no reason why it's not).

One tentative explanation for this is that there are a lot of new turtles invading the study area, all of a sudden. This makes it much more likely that I'd pick up a new one rather than an old one.

It turns out that toward the end of the warm seasons, many box turtles will leave their summer residence (where I would not discover them during most of the turtle season) and return to their hibernacula, their winter residence which might not be the same place they spend most of the summer. The hypothesis here is that here in October is an influx of turtles that have spent May-September elsewhere, and are just coming home for a winter rest. I'm now finding them.

The hypothesis suggests a plan for a new census schedule, much more rigorous than the last few years when I've just been farting around. I'm thinking four periods of a week of daily searching. Two of these periods would be at the beginning and end of the season, and two would be in the middle. Next year would be my "capture and mark" year, and the following year would be my "recapture" year. The early spring and late fall periods would test the winter residents, and the two mid season periods would test the summer residents.

It looks like the weather is developing as planned ; - )  , with rain just beginning and lasting through Wednesday, and warm temperatures continuing through the weekend. If so, I should be seeing more turtles on a daily sampling.

Sunday: 9 October 2011

Confused Box Turtles  -  @ 07:57:32
The temperatures have been very pleasant for the last week. They did dip down below 40 degF on the 2nd and 3rd, but lows have been steadily increasing while highs have remained in the upper 70s most days. Poison ivy and virginia creeper have turned bright red, and now's the time to document all the sourwood as it begins to blush:

The warm temperatures have been made perfectly liveable by the extreme dryness. Last Sunday, the relative humidity got down to 17-18% late afternoon, with temperatures around 80F. That's extraordinarily low for us - it's always of fire watch note when we dip below 25%, which we have for most of the past week. I did check August 2007 and found that we had 10% RH on several days, but the temperatures were also in the 100s - so that's not so surprising. Desert people may laugh scornfully at us when we blanch at such circumstances, but they don't have the enormous load of parched fuels that we do (as you can infer from the above photo).

The last ten days or so, and the overall hot summer rainfall deficit, has resulted in a KBDI of about 700 for our local area. KBDI is an index which measures soil moisture content. This value is near the top of the 0-800 scale, where 0 represents nice wet soil with no moisture depletion, and 800 represents total soil moisture depletion. While you might not have known that (and I had to refresh my memory), box turtles are going to be very much aware of this already.

Our 10-hour fuel moisture yesterday was at 5-10% saturation, which is extremely low. You can think of 10-hour fuel as 0.25"-1" sticks of wood - it takes 10 hours of moist conditions for them to reach full water saturation. We have a LOT of 10-hour fuel, and so that's why these sorts of things worry us. Box turtles may be a little fuzzy on 10-hour fuel moisture - they should read this page on fuels.

To complicate things, we're also coming down to the wire with End of Turtle Season - the latest I ever saw a box turtle was Oct 10 2008. That was right after a 4" rain, with similarly warm temperatures, for a few days after. It's a hint that abundant moisture coupled with warm temperatures might just prolong the active season a bit.

Despite the dry weather, I've been spending two hours a day, crunching around in the parched leaf litter, doing deliberate searches for box turtles. I've tried out some new strategies - using binoculars, for one, to expand the zone of observation. That slows me down quite a bit, so I'm also able to listen for the pitter patter of tiny box turtle feet. Actually, neither of those approaches netted me anything. I found nothing from Thursday Sep 29 until Thursday Oct 6, when I found two male turtles in my path. And again on Friday, and in my path, I found a female. All three turtles were new to me.

Here's the first male on Thursday, right at the confluence of SBS Creek and Goulding Creek. Nice yellow markings on his head, but look at the shell on the rear end.

It's probably one explanation for the relative dullness of his carapace markings - he's having a little trouble with the fungus that we occasionally see. I asked Kenneth Dodd about this and he said that the fungus was fairly benign as far as he could tell. It really shows up when things are very dry.

Definitely a male, with a nice concavity in the middle of the plastron, but look at that circular chunk out of the lowest section of the plastron. I have no idea how that got here - it's not a regular anatomical feature, as we'll see with the second turtle.

And here he is, 111006m2. He's also fairly dull with redder markings on both head and carapace.

He has a little of the fungus on his marginal scutes, but the dullness is probably more that his carapace is very dry.

Another nice indentation to the plastron, indicating he's male, and a more normal plastron appearance without the scarring you could see on the previous turtle of the day.

Turtles don't like low humidity, which may be surprising given the terrapene name and the desertish connotation we associate with the word tortoise. Captive turtles have to have relative humidity at 50% or above, or they get respiratory, eye, and ear problems. The humidity at the time I was finding these three was 40-50%, with temperatures in the upper 70s. Wild turtles can seek out detritus and bury themselves to increase local humidity conditions.

Here's the third turtle, found Friday. It looks like he/she's down in a little crater, but that's just a shadow flat on the ground.

The plastron is one of those that gives muddled sex identification. There's just the tiniest bit of concavity, but not nearly as much as the two males of the previous day. I'm going with a tentative female ID on this one.

And she was a feisty one. She wouldn't withdraw completely even when held upside down. I took the opportunity to gently poke my finger at her face, and she several times opened her mouth just the tiniest bit in response.

She has three weird looking knobs on her upper carapace. This looks like biting or chewing damage some time ago.

Here's the thing: we're at the cusp of this area's box turtles going into hibernation, or brumation.

The air and soil moisture conditions are terrible, but temperatures have been warm. Turtles stop eating before hibernation, anyway, so as to empty their GI tracts, so there isn't that to motivate them to risk their necks getting out and about. However, they're all for sex this time of year, so that might get them moving.

There's also this: box turtles are moving toward their hibernacula, and many box turtles use the same exact location winter after winter. Further, this might not be their usual summer habitat. (This might explain why I've seen three new turtles in the last week.)

We are at a confluence of a lot of conflicting urges and signals right now.

But that might be coming to an end. We're due for a change in the weather beginning tonight through Wednesday, and it will be interesting to continue this daily canvassing. Today will be a little more humid, and slightly cooler but still in the mid 70s. I expect nothing, but tonight, Monday, and Tuesday we should have some rain. Temperatures in the mid 60s might be a little too cool Monday and Tuesday, for much turtle activity (they prefer 70F or above, preferably much above).

Wednesday through Friday, warming up into the mid 70s with continuing fitful rain, and all three days may support turtle movements if they're so inclined. My plan is to continue looking for a couple of hours each day until I haven't seen any more turtles for a few days. I can then more rationally peg conditions and timing for the onset of hibernation.

Friday: 7 October 2011

The Month of September  -  @ 06:51:20
It's The Month of September, Number 68 in a series. September will be remembered fondly here, for a time at least, for its kindly temperatures, the first in five months. It was dry, though, but you can't have everything.

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.

There was a switch in temperature regimes over much of the US. The big news was the much cooler temperatures in and around Texas, while a lot of the Pacific northwest averaged quite a bit hotter.

The northeast US was hotter in September, but the central part of the country was much cooler, as was most of the southeast.

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

Dry weather and continued drought continued across the southern states of Texas and surroundings, but most of the southeast and the Appalachian states got a good soaking. Dry weather continued for much of the Pacific northwest, along with their warmer temperatures, in September.

I've circled that little smudge of brown in Georgia, lonely in its abnormality, because it sits right over us.

For Athens:

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

How pretty the damped harmonic oscillator is! It's like someone finally got the brakes working. We had two major fronts finally break through the high pressure that's been sitting over us over the last four months, and exert some significant effects.

Here is my plot of high temperatures for the month of September 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 just slightly over the 84.0 degF average for September, although we did very nearly break a high record on September 2. Our low temperatures averaged a degree or so below the long term average. Everything averaged out at about, well, average, BUT:

We still had 8 days more than one standard deviation above the norm (4.7 days normal). We also had 8 nights more than one standard deviation below normal (5.7 nights is normal). The simple monthly average obscures some fairly significant swings in temperature, as we have seen so often before.

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.

Sadly we must report that the rain picture was not so benign as the temperatures. Out here in Wolfskin we improved our August 1.99" somewhat with 2.48" in September, but that was still far below the 3.94" expected. Rainfall was quite heterogeneous in our local area - the official Athens rainfall was 1.55", nearly an inch less than we got 14 miles east.

It is appropriate at this time to take a look at our drought situation, and we'll update our old friend the accumulated rainfall plot. Here we plot the actual rainfall total since Jan 2005 and compare it to the accumulated expected total if everything in the world were average. The blue line is the difference between what we'd have expected by now, and what we've actually gotten.

Some water conservation measures have been put in effect in our area - lawn watering days in particular. And that's because we've been on a decline in our rainfall differential, the blue line in the plot below, since April, after maintaining a level plateau for 18 months or so.

And according to the neat prognosticator we are indeed in an extreme drought, with likely persistence over the next few months. It did a little better for our anomalous September warmth, a little worse in predicting more rain than we got.

Perhaps more interesting is that it predicts essentially normal temperatures and rainfall for the next month, maybe the next three (however, see below about La Niña).
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.

The La Niña that began mid 2010 and apparently ended in February has revved back up after a few months at ENSO neutral. La Niña is expected to continue through the northern hemisphere winter. Even in the earlier part of the year these atmospheric conditions (and La Niña-like weather patterns) never really left us.

NOAA's Monthly State of the Climate product for August has been considerably augmented, and is worth a read for your region. September should be appearing soon.

It addresses the high temperatures this calendar summer. Of considerable interest is this statement:
For the second consecutive year, the end of August marked one of the warmest meteorological summers (June-August) on record at several locations across the Southeast. Locations that experienced their warmest summer on record in 2011 included Tallahassee, FL, Augusta, GA, Athens, GA, Columbus, GA, Savannah, GA, Charleston, SC, Columbia, SC, and Cape Hatteras, NC.

Sunday: 2 October 2011

Something New  -  @ 06:57:47
The temperature just dropped below 40F, as I write, and probably won't make the two degree difference that would tie the 38F record of 1924. Still, it suggests that our Long Hot Summer is truly over, as we'll be discussing soon. Pleasant weather notwithstanding, it's very very dry around here, with no likely rain in the next week, and we've had two red flag days already - today will be the third. (Red flag are fire danger days, prompted when the fuels become dry enough and the relative humidity drops in the neighborhood of 25%; we've had both conditions plus unusually strong sustained winds in the late mornings to early evenings.)

Yesterday's two hour hike did not net any box turtles. The day was pleasantly warm enough for them, so it could be the low humidity that kept them hidden away. They like on the order of 50%, which we were definitely not after air temperatures reached their cruising altitude of 70 degrees.

Yesterday afternoon this little pretty bounced off the kitchen door and onto the ground. His claws curled tightly around my finger, which seemed to me to be a good sign, and he held himself upright but showed no panic.

It's a male hooded warbler, Wilsonia citrina, and I've never seen one before. That's not too surprising - there are probably quite a few species of warbler around here that I've never seen.

Such large eyes, apparently for warblers, anyway. It seems that they migrate nocturnally, something which had never occurred to me.

So is he just passing through on his way to the Caribbean or Central America, or has he been here all the time? No way to know, of course, but he hasn't got his dull fall plumage yet, if that means anything. Apparently our mature hardwood forests and dense undergrowth here and there are ideal breeding ground, so there's no reason to think that he hasn't been a seasonal resident.

I left him on the upstairs deck, and Glenn reported that after five minutes or so he flew off.

We seldom have trouble with birds flying into windows. I haven't fed the birds in a couple of years - not that I have any strong opinions one way or the other as to the wisdom of bird feeding - but that may have something to do with it. We just don't keep a large concentration of birds scavenging around the house, therefore, fewer collisions.

This one would not have been interested in a seed-bearing feeder at all, in any event.

And if that isn't nice, then what is?

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