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

Sunday: 27 July 2014

Finally Some Turtles  -  @ 11:20:44
I haven't run across a box turtle since June 16, despite searches. Yesterday I'd already walked for two hours and expected it would be another zero added to the excel worksheet. Then I encountered Sylvia, and a hundred feet and a few minutes later, Camille.

Sylvia, on the left, is well known on this blog. I discovered her first in 2006, and have reported many of the 20 rediscoveries over the years since. She's a very active turtle who is probably one of the oldest of the many I've documented on our property. Her home range is very restricted, as you can see on the map below (I've described these maps here):

She generally stays within 75 feet of a centroid, but I found her yesterday (for the fourth time this year) under the pawpaw patch, which is the red dot most southeast of the cluster. That's about as far from her floodplain home as I usually find her. In fact, I wondered when I saw her at the foot of the rising hill toward the house, what are *you* doing here?

What is even more interesting is that our neighbors found and photographed her on June 14 as she was attempting to nest in their driveway, 1400 feet away from her usual home. I've reported before that our neighbors find quite a few females nesting around their house - it seems to be a turtle nursery. Many of these are females that I've documented as occupying territories quite some distance away.

So I was curious when weeks passed and I had still hadn't found Sylvia in her usual place. I don't think it actually took her six weeks to return (her spotting at the Gresham's came just eleven days after my previous spotting where she normally lives).

As you know, I weigh and measure the dimensions of box turtles now. Sylvia has an average weight of 446 +/- 11 grams, just under a pound. She weighed 460 grams when I found her June 3, and that was up from her 430 gram weight when I found her first this year, May 12. Yesterday she was back down to 420 grams. In between, of course, she made the Great Trip, presumably lost a half dozen eggs, and so that may explain it.

After saying hello to Sylvia, I walked up the roadcut a hundred feet, and found Camille. I first found her in 2008, and she has a somewhat larger territory. Yesterday's red dot is the northwest-most one.

Despite my fairly intensive search paths through the territories of both turtles, I've only found Camille five times. I found her last year at almost exactly this date, July 23, and she weighed 620 grams. Yesterday she weighed... 620 grams!

So why the difference in numbers of discoveries between the two? Sylvia has emerged as a particularly active turtle. Or at least she's on top of the ground a good bit more than any other, since that's both my search target and my definition of activity. Part of this may be because the floodplain where she stays has a much thinner leaf litter layer, and that's one place box turtles like to hide when they're inactive. She generally seems to hide, if that's what she's doing, under vegetation - Christmas ferns and crownbeard - rather than digging into the ground, when she's inactive. Camille stays on the north slope, which has a deep litter layer, and I'd guess that she's well hidden under that litter when she's inactive.

But there could be other explanations. Maybe the food supply is scarcer on the floodplain, and a turtle living there might need to forage more. Or maybe the turtles just have different activity patterns. I tend to do my hikes in the cooler mornings, but maybe Camille is primarily an evening turtle.

One last thing, and then we're done. It's not quite the end of July, and I'll have more to say about this. Here's the monthly activity bar chart over the last three years. Notice that it isn't just the number of box turtles per month. It's their activity, which I calculate by dividing the number of turtles found by the number of hours I've spent looking for them. That way I can compare from year to year.

That's why I say box turtles have been relatively inactive so far this year. As a hint, the summer weather this year and last have been fairly mild. Rain last year was more than plentiful, with very mild temperatures. It's been a little drier than average this year, and a little warmer, but not much different than average.

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