Monday, July 28, 2008

I Go For a Bike Ride With A Turtle

I know I’m supposed to get back to Utah trees, but I can’t resist just one more New England/Maine post, in part because it’s about a reptile, and I’ve only focused on reptiles a couple of times so far this year, and also because it involves a short stunt of extreme coordination on my part which gives me an opportunity to showcase my formidable 1-handed rough-road cycling skills.

Yesterday I took a short road ride from the cabin out through a couple of small villages and back. Anytime I road-bike from the cabin, the ride starts and ends with ~1.5 miles of slightly rough dirt road. One the way back, about a mile from the cabin, I came across a great sight- a Painted Turtle crawling across the road.

Turtles are cool for lots of reasons: Their shells, their egg-laying habits, and their long life-spans are some of the better-known ones. But a really cool thing about (many) turtles is that they’re slow, and easy to catch. So if you’re a dad with 3 wildlife-nut kids (Wonder Boy, Twin A, and Twin B, hereafter to be referred to as The Trifecta) and you come across a turtle a mile from home, the first thing you think is: How do I get this thing home to show the kids?

Do Not Try This Part Unless You Are (Like Me) An Expert Cyclist

Painted turtles are pretty benign as far as turtles go, and generally react to threats by retracting into their shells (as this one did) but they can also react to danger by biting, scratching or urinating. For this reason, I quickly ruled out putting her in the pocket of my bike jersey (which was sort of a shame, because it would have fit just perfectly.) So I did the only other thing I could think of: I held her in my left hand and rode home one-handed, a feat which involved steering, shifting and braking with one hand. The ride- all along a bumpy dirt road- included a quick un-nerving descent, and a brief out-of-saddle climbing effort, which I will say was probably my single-most coordinated (albeit hare-brained) biking maneuver ever.

I arrived home with that sheepish-yet-triumphant feeling of having done something really stupid but gotten away with it, and yet also felt oddly nostalgic all at the same time (probably because I’d felt that feeling much more frequently in my high school/college years) and delighted The Trifecta with my find.

Turtles are one of those kinds of creatures you really don’t think about very often unless you happen to stumble across one. Which is unfortunate because as a “design” they’ve been incredibly successful. Turtles, or turtle/tortoise-like critters, have been around for over 200 million years, and have taken on many different forms and lived in all sorts of interesting and challenging environments.

Turtles, Tortoises and Terrapins comprise the order Testudines. The Testudines are divided into 2 sub-orders: Pleurodira, the side-necked turtles, so-called because they retract their heads by folding their necks sideways in a somewhat snake-like manner, and Cryptodira, which retract their heads by lowering their necks and pulling their heads straight back in, sort of Rex Reed-(of the Fantastic4, which for the record I always thought was cool till they made that crappy movie)-like. The majority of Testudines are Cryptodira. The largest family within Cryptodira is Emydidae, which includes 40 species across 12 genera, nearly all of which are freshwater turtles.

One of those 12 genera is Chrysemys. Chrysemys contains just 1 species, Chrysemis picta, the Painted Turtle (making the Painted Turtle a monotypic species, like Blackbrush.) There are 4 subspecies of Painted Turtle (weirdly analogous to Moose in North America) and the one I picked up was an Eastern Painted Turtle.

Tangent: Painted Turtles also occur in Utah. The local subspecies here is the Western Painted Turtle, Chrysemys picta belii.

Like all turtles, Painted Turtles lay their eggs on land, typically in sandy soil, and in Maine that all too happens in the middle of dirt roads, which generally means a quick doom for the brood if not the mother. And that’s why I refer to the turtle I found as a “she”, since that was by far the likeliest reason I found her so far from the water (~60-80 feet.)

Turtles have been around so long, and been so successful, that you wonder why the grow-your-own-armor strategy isn’t more common in the animal kingdom. Armadillos do a version of it in the animal world, and a number of arthropods do something of and armor+roll-in a ball strategy (our old friend the Woodlouse, favored prey of the Black Widow, is an excellent example), but no creature seems to do it on anything near the scale of the Testudines. But the absolutely coolest thing ever about the Painted Turtle isn’t its shell- it’s its hibernation. Every winter the Painted Turtle settles deep into the mud in the bottom of a pond or lake and hibernates- without taking a single breath- for up to 6 months. There’s no other creature on the planet that can pull off that trick. Several other turtles- including the famed Snapping Turtle, Chelydra serpentina-, also hibernate underwater sans breathing, but the Painted Turtle is the endurance champion.

Clarification Tangent #1: Just to be clear, Turtles are reptiles, have lungs and breathe air like we do. They cannot breathe underwater.

Clarification Tangent #2: Technically, they don’t actually “hibernate”. Hibernating is something that mammals do. Reptiles “brumate”.

Scientists have studied just how it is that Painted Turtles can survive so long without oxygen. They’ve found that C. picta has evolved two important tricks. First, they can lower their metabolism- and specifically both the production and consumption of ATP- to an extremely low level, particularly in brain tissue through a chemistry and molecular/synaptic architecture very alien to that of a mammalian brain, such as ours.

Quick Backgrounder on ATP: ATP (Adenosine triphosphate) is an organic compound (specifically a nucleotide) that is the most important energy transfer mechanism in living things. Pretty much everything living things do- move, think, whatever- is powered by and consumes ATP. Animals make ATP by metabolizing food; plants also make it by metabolizing food, but in their case it’s overwhelmingly food they’ve produced themselves via photosynthesis.

Tangent: The actual methods involved in this research are a bit repugnant. Researchers basically asphyxiated turtles and rats, then sliced up their brains and analyzed the slices…

Part of that metabolic slowdown is a reduction in heart rate. My typical resting pulse is in the mid 50’s BPM (beats-per-minute.) When I’m walking around it’s typically between 70-90 BPM, when I’m biking between 120-150BPM, and the highest it’s been in the past year is 191 BPM. A Painted Turtle’s typical “active” heart rate is ~40 BPM. When it’s hibernating its heart beats once every 10 minutes, or an incredible 0.1 BPM.

Special Bonus Action Video

Here's a video of the turtle on the move across the cabin deck. (Pretty lame until last few seconds, when she hauls ass...well for a turtle anyway...)

The other trick is even cooler. Part of what kills most animals when deprived of oxygen is the build-up of metabolic waste, namely lactic acid. A hibernating Painted Turtle actually sequesters excess lactic acid within its bones, including its shell, until springtime, when it can safely extract it back from the bones/shell and process it with fresh oxygen. This feature is cool for 2 reasons: First, it’s yet another great biochemistry story, and second, it’s a great example of evolution making use of a structure that evolved for some other purpose. It’s pretty clear that turtle-shells evolved primarily for protection, but the evolutionary ancestors of Chrysemys later leverage this excess bone mass to evolve the sequestration technique.

After our little show-and-tell, we freed the turtle. Although Painted Turtles are the turtles most commonly kept as pets, my wife and I- as I’ve mentioned before- are not pet people. For my wife, this position is mainly driven by her continual and admirable quest for Less Needless Hassle. For me, it’s probably really pretty much the same deal, but I dress it up in an overblown “theory” about livestock and sociobiology and a bunch of other baloney that I’ll go off on a tangent about in some other post, but not right now. The plane is getting ready to land back in Salt Lake, and it’s time for me to get back to the Wasatch.

4 comments:

SLW said...

Trust you let her go close to where you found her (though not IN the road)... Cool story and critter, but why an EASTERN painted in your neighborhood?

And yes, it IS an awesome graphic! Nice job...

Watcher said...

SLW- answers to your questions:

This was the third of 3 posts I did while on vacation back in Maine, hence the Eastern painted turtle. The 2 preceding posts give some of the background of the trip.

Second, of course we returned her! I took her back to the same spot (in a car, not on a bike- I wasn't trying that trick twice), put her on the other side of the road, since that's where she was headed. Hopefully she completed her journey.

My brother says I should put that graphic on a T-shirt!

Michelle said...

I saw an eastern painted turtle and she was next to my house,she layed three eggs then left.so i was wondering how long until her eggs hatch?

Watcher said...

Hi Michelle- sorry for the late reply, just catching up on comments to some older posts now...

I think about 10 weeks is normal. Their sex is determined by the incubation temp of the eggs. The hotter the they are, the more likely they'll hatch as females, and vice-versa.