When baby sea turtles hatch on a beach at night, their instinct is to head to the sea. The beach slopes down, which is one directional clue they follow. Another is light: The horizon over the sea is brighter than the horizon over land.
(From New York Times/ By James Gorman) — But lights from towns and beach developments can distract the hatchlings. The sky glowing above a city can be disorienting, leading them to wander. And particularly bright lights can draw them away from the sea.
You’d think the extra time crawling might wear out hatchlings, which need energy once they get in the water to swim for about a day to get to their destination, the warm current of the Gulf Stream. In a normal sprint from nest to waves, the babies have been shown to build up chemicals that indicate they’ve been pushing themselves.
Sarah L. Milton, an associate professor of biology at Florida Atlantic University, and Karen Pankaew , a graduate student in biology, collected 150 loggerhead and green turtle hatchlings as they came out of the nests on beaches in Boca Raton, Fla. The researchers took the hatchlings to a lab, where they ran on a little treadmill and swam in a tank while their blood and breathing were monitored.
The surprise finding: As the researchers reported in the Journal of Experimental Biology, even after a couple of hours scrabbling the equivalent of about 500 yards, the turtles were fine by all measures and swam as well as turtles that didn’t have an extended crawling period.
The reason, apparently, is that they pause frequently in crawling if they are doing it for a long time, unlike the uninterrupted sprint they make when headed straight to the water. So disoriented turtles are not worn out.
Dr. Milton answered questions in a telephone interview about the research. Our interview, below, has been edited for clarity and length.
Q. This required a lot of late night work. Is that all on the part of your graduate students?
A: I’m always up for the first few nights because I have to train the graduate students. After that it was all on them, and they had a few volunteer undergraduate students to help as well. We actually had planned to have the turtles do an entire kilometer, but it just took so long. It turned out that the turtle could go that distance, but the graduate student couldn’t hang in there that long.
The turtles are snatched up right away and go to the lab where they’re on a treadmill. Do they get a rest before you release them?
They were held at a nearby nature center that we work with. They take them out, along with other hatchlings that have been mis-oriented that people bring to the nature center. Actually, they get a ride out on a boat when some of the local dive masters volunteer, and they take them out all at once and basically drop them off in the Gulf Stream.
How did you make such a small treadmill?
It’s a belt sander. We put a power coupling on it so that we could slow it down. Obviously, we don’t really want to be sanding the turtles. The crawling surface is actually hair scrunchies, so it would be soft and give them some traction.
It was tough on the graduate students, because they had to watch them the entire time. When the turtles were crawling, we’d have the treadmill on, but as soon as they stopped, you had to turn the treadmill off. And then as soon as they started crawling, you had to turn it on again. So it was very labor intensive to do the experiment.
What do the hatchlings do when they get to the Gulf Stream? …