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

Saturday: 8 June 2013

Spring Fashions  -  @ 09:07:13
Yesterday I came home, soaked, after 3.6 miles walking and 4.2 hours. Temperatures may be low, 75 to 80 degF, but humidity is stuck in the 90% range. Still, we got a little under 2 inches of Tropical Storm Andrea rainfall, and all this seems to have stimulated a little box turtle activity. I observed six box turtles (and a snapping turtle) yesterday.

Here is where we praise symmetry, along with the developmental biology it addresses. Patterning on box turtles can be seen to be roughly symmetric. This is a particularly good example. This male was a little shy, but he had equally nice pants.

In the spring, the males put on their bright colors. His carapace may not be bright, but he's doing great with the red-orange skin tones.

In contrast, yellow! This male was not intimidated by me at all. We struggled to get a weight.

What are you doing here?? She's a fairly small snapping turtle that I ran across as I walked up SBS Creek. I got the impression that she had only thought she was having a bad day. Then I showed up.

Friday: 7 June 2013

An Odd Girl  -  @ 07:37:11

On Monday I ran across Megan, who I first saw in May 2008 and then again twice in 2012. The unusual thing about Megan is the overwhelming yellow coloration. I've encountered some turtles that have a degree of this, in one aspect or another, but Megan pretty much covers it all.

This extends to her nearly uniformly yellow plastron, below left. On the right, below, is the plastron of the ever-helpful Sylvia, found for the seventh time this year on Tuesday.

It seems that I actually addressed a possible reason for Megan's yellow color, last year in April. This followed from an analysis in 2011 of the thin keratin overlay, and its definition of color patterns. Megan, it would seem, has much less brown pigmentation in her keratin layer, allowing the reflective bone beneath to shine through as a predominately yellow color. She still has enough for patterning to be evident on her carapace.

A turtle like Sylvia is a good contrast. She has either very dark keratin, or a particularly thick overlay, and it blocks the bone from shining through, except in a few places that we see as yellow or white markings. You can see this in the comparison below.

Also worth noting below, and something I failed to note in 2008, is the damage seen to Megan's front driver's side (the photograph clearly shows it, in the link above). Sylvia rounds out the comparison with her presentation of an unblemished carapace.

That damage looked about the same in 2008, so it's probably safe to say it occurred much earlier than that. I've seen (and written about) predator damage in the form of holes in the shell, and other evidence of chewing and biting. In one case (Katherine, here) the shell was so distorted that she couldn't completely close up. This reduces her effective self protection against further predator attack.

For Megan, here, the damage seems to be much more of a blunt trauma effect, although one less likely to reduce her life span because she isn't as well protected.

Tuesday: 4 June 2013

The Month of May  -  @ 07:36:46
It's The Month of May, Number 88 in a series. For us in northeast Georgia, it seemed cooler than an average May, and if it was, it was just barely.

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center. Displayed is the mean temperature anomaly. Click on it and you'll get the high and low temperature anomalies on a new page.

The much colder April for the midwest warmed to just a bit cooler than normal in May. The region of unusual warmth in the West expanded at least somewhat into the remaining western half of the US. into the southwestern corner of the country. Much of the eastern US cooled below normal, although not by more than two or three degrees.

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

The dry conditions of most of the year to date continued in the West, although there was spotty improvement, especially in the Pacific Northwest. There was no particularly obvious wet or dry trend over large areas, unless it was for continued wetter than average for the northern and central midwest. The southeast continued with at least normal precipitation, except for the Gulf Coast region, which was much drier than usual.

For the Athens, GA area:

Here is a plot of our daily temperatures excursions in May, along with precipitation amounts as experienced in Wolfskin. In December and January we had higher than normal temperatures; in February we returned to seasonably cold weather. Cold weather intensified in March, with the average temperature much below normal for much of the month. April returned us to average temperatures, and May was just below average. Rainfall was fairly uniform throughout the month, with no huge deluges or long periods of dryness.

The average monthly temperature for May was 67.4 degF, a little over 2 degF below average. We had 0 day more than 1 standard deviation above normal highs (4.5 normal). There were 7 nights with temperatures more than 1 standard deviation below normal lows (5.5 normal), and by this imbalance we had a colder than normal May. We broke no records, although we matched the record low of 1979 on May 25.

The monthly histogram below shows the breakdown of high and low temperature range counts from May 1948 on. The error bars are just plus/minus one standard deviation, which I arbitrarily set as the limits outside of which are "significantly" anomalous.

The breakdown for daytime highs showed a significantly greater number of cold days (in the 60s, F) than normal, but all the other ranges are inside the error bars. For nighttime lows, there really were no ranges that achieved significance. By this criterion it would be hard to say that we were particularly colder than normal.

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 22 years, and the river of peach shows the standard deviation.

We had the welcome blue of surplus rain, greater than one standard deviation, for most of the month, and ended up above average in the end.

Our total out here was 3.80", and the official recording in Athens (shown here) was 3.63". 3.00" is normal for May (yes, the new 30-year average for May is much lower than in past 30-year windows).

We have, in fact, stayed just above average rainfall all year since mid-February.

It's about time to take another look at our occasional figure for cumulative rainfall. The most important line here is the blue one: the deficit in rainfall since January 2005. Even with our just above average rainfall this year, the bitter truth in the long term is that we're still more than 20 inches below normal. This is an ongoing trend that began in 2006 or 2007, and was broken only in 2010, resuming a downward path in 2011 and 2012.

Prognosticator stuff:

What is the neat prognosticator telling us? A month ago, it told us the truth: in terms of both precipitation and temperatures - May was to have been cooler and wetter, grading to normal for us in northeast Georgia. As of May 28, the next month will be relatively normal in temperature and rainfall. I'm sorry to tell you that for most of the US, temperatures will be above normal over the next three months, especially for the west TX, NM, CO region. For us, at least, rainfall will be normal over the JJA summer period.

ENSO stuff:

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.

As of Jun 3, ENSO neutral conditions continue, and are expected to remain neutral throughout the Northern Hemisphere summer. We've remained ENSO neutral now for over a year. The last such lengthy period was 10 years ago, 2003-2004.

NOAA's Monthly State of the Climate product for April is available. And last year's annual report for 2012 regionally, nationally, and globally is also available.

Saturday: 1 June 2013

Spring Turtles  -  @ 06:19:51
A homely but saucy girl:

Above we have yesterday's find, a very feisty female. Some box turtles are like that, and some are very cautious and shy. She was crossing the path I'd made as far west as you can go on our property, and that's about a half mile west. She was not at all intimidated by my presence, and scampered off every time I looked away. She's a new turtle that I have not seen before, but that's not a surprise. This is the first year I've seriously canvassed the 20 acres to the west of last year's study area.

As I've been making my lists and checking them twice, it's been clear that spring box turtle activity this year is way down compared to last year, the first year I'd attempted a rigorous estimate of activity:

Box turtles were only 1/3 the activity in April, this year, as they were last year. Now that it's over, we can see that May this year has just 1/2 the activity of last year.

As it turns out, I've encountered just about as many box turtles this spring (30) as last spring (34). However, I've also greatly expanded, by a factor of two, the study area this year, and I've spent twice the time in observations. Last year my walks in April and May totaled 76.2 hours; this year it was 142.4 hours. That's why I calculate and present a box turtle "activity" index, in box turtles per hour of observation. (This simple activity index does not take into account turtle identity, in case that occurred to you. It might be worth considering though, as a kind of positive control.)

Casual note: last year I thought I was remarkably virtuous in my coverage, and that practically it couldn't, and academically it needn't be exceeded. Uh huh.

Here, I think, is the explanation: it's this year that's normal, and last year that was way above normal, not the other way around.

Histograms do a good job of showing what happened. Here is last year's breakdown. We had a great many days and nights in the warmer registers - more days in the 80s (and fewer in the 60s), and more nights above 50, and fewer below. You might recall that this all began in March 2012, with an incredible 3-week heat wave:

Spring this year has been remarkably average, with just a few more nights in the 30s or below, than average:

Up to this point, I'd been puzzled as to the lack of correlation of first emergence with early spring temperatures. The first observed turtle last year was March 20, and this year March 19. In neither case were further emergences observed until April, despite last year's very warm March temperatures. Apparently sustained emergence and activity are what is more affected by the prevailing temperatures.

For whatever reason, ticks are very bad this spring, with a drastic upturn in the last week especially.

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