18 October 2008

Crawling Lessons, or .74% Really Can Make A Difference

I think my boss was a little amused when Sally and I brought back just two eggs from the assessment of Santa Rosa 8061 the other day. After candling the eggs, we knew one had stopped developing very early, but one had a rather large turtle in it. We weren't too sure about the little embryo, but kept it safe and warm in the fire cache to give it a chance at survival.

When I returned from a morning bird survey today, I was thrilled to see one little loggerhead crawling around in his cooler full of sand! S/he must be rather lonely without all those siblings. You might be able to see just a tiny bit of his sand covered egg in the photo above.

This little turtle represents 0.74% of the total eggs in the nest -- that's our hatch percentage for this nest. We usually have hatch rates of about 90% or better in relocated nests, so this was strangely low. The tiny loggerhead seemed fine though; in a short time, s/he was trekking around the cooler, dragging a little bit of yolk sac with him.

In a natural nest, it would likely take a day or two for the hatchlings to crawl through the several inches of sand above the egg chamber. These yolk remnants would be absorbed or rubbed off in the rush of tiny turtles attempting to reach the surface. With a hundred hatchlings tripping on each others flippers and stepping on each others heads, there's no way s/he would have emerged with this bit of egg left.

I was inspired while watching this lone ranger wander in his cooler... Normally, s/he would have a hundred more hatchlings crawling around with him. It's a good thing we dug this egg out of the nest on assessment - s/he would have died trying to crawl out of the natural nest on his own, exhausting the energy reserves in his yolk sac, and leaving him/her lacking in resources for the swim through the waves.

We're not sure why 134 of 136 eggs showed no development at all. Perhaps they were infertile. Maybe something happened on day one that stopped all development. Maybe it was too cold or too wet or too dry. There's so much we still don't know about turtles! All we do know is that one hatched, and s/he has no obvious anomalies :)

With just one tiny turtle in the cooler, I was able to get some great shots of s/him learning how to crawl... They're a bit out of focus as I couldn't get in the cooler with my camera, so I had to trust auto focus while the camera was suspended (with the flash off) just above the sand.

First, you reach, stretching as far as your tiny flippers will allow...

then grab a flipper full of sand, (I love how his/her little flipper curls under the layer of sand)

push the sand back while reaching forward with your head and neck,

then repeat! There, now that's easy, isn't it?

One turtle may not seem like much, but who's to say this little loggerhead, representing 0.74% of his nest, might just be the far less than 0.1 to 0.01 percent that survives to maturity? S/he's beaten the odds so far!

1 comment:

Robert V. Sobczak said...

Really great photos: they really convey what you are saying. And yes, the numbers are mind boggling: on the one hand depressing (so few make it), on the other hand inspiring (for the ones that do), and 100 percent evolutionary reality (from a population dynamics perspective)!

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