July 29, 2005

Tiny Tracks

I spotted them on the second day -- light marks in the sand about two inches wide. At first I assumed they were sand crabs, and wondered why so many sand crabs had been out overnight and why they had all run in the same direction. Later that day I was inside, writing an email about how bummed I was that I wouldn't see hatchlings, when it suddenly hit me what the marks were. I ran outside with a camera and had a closer look. Sure enough, they weren't crab tracks. They were miniature versions of the big tracks. Hatching started about three weeks before our arrival, according to one of the turtle patrol guys.

I've used my flip flop (size 8) for size reference. Here's a newly hatched nest from the night before.



This photo shows a single track of a baby that ran along a tire mark. You can see the little alternating flipper marks. Notice that this tire track is the same size as the tire marks in the previous blog entry.



And here's a shot that shows baby tracks with adult tracks, for size contrast.



It was obvious the babies were tinier than I realized. After the second night I spent a lot of time trying to see hatchlings. Apparently they are much harder to spot than adults. They're tiny and have cryptic coloring, and they move pretty quick. I read that baby turtles have about 45 minutes to make it to the sea before they get dehydrated. For three nights I looked, wandering over the dry sand where the high nests were, as well as by the waterline. No luck. On the last night I stayed out longer than I intended, and walked several miles along the beach. I thought, I'll just go along this dark stretch of sand here and then I'll go home and throw in the towel. A loggerhead had come up and was cresting the dune. I walked slowly behind her. And that's when I saw them. Several dozen tiny little disks, all the same size, scattered on the hard sand, pausing then skedaddling toward the water. It took me a minute to realize what they were, and when I did, I gasped out loud. "Oh my God! You guys are so cute!!" This apparently startled the big turtle behind me, who heaved her massive carapace back over the dune and slipped back into the water. I felt bad for a moment, then turned my attention back to the little ones. They were disappearing quick. Those little guys can move. Each little turtle had a shell about the size of a Nilla wafer, tiny yet disproportionately large flippers, and a tiny head with big black dots for eyes. All the better to see in the dark. I picked up one tiny turtle between my thumb and forefinger just to prove to myself that it was real. The underbelly was brown, like the top. Loggerhead. The turtle twisted its little head and flippers. I gently turned it back over and set it down, then watched it run to the water's edge. A few laps of seafoam and the baby floated away like a tiny leaf. In five minutes, all the babies were gone. I decided to look for the opening of the nest to see if anyone was still there, but I couldn't find it. There didn't seem to be any lost hatchlings either. Seeing those tiny turtles make it into the water was the highlight of the whole trip.

I couldn't take pictures of hatchlings at night, but some people are lucky enough to get daytime photos. Check out these hatchling photos taken by a turtle patrol volunteer in South Carolina.



From looking at tracks, it seemed as if hatchlings that had emerged close to the water were better off in terms of navigation. These little guys all went the right way.



Further from the water, I saw a lot more of this: tracks going every which way. These little guys were lost. I wonder if apartment lights left on by careless residents screwed them up.



If you're interested in seeing the turtles for yourself, you should think about taking a guided walk. There are many organizations offering these walks along both coasts of Florida, as well as other coastal areas of the Southeastern US. I joined a walk led by the Sea Turtle Preservation Society, which is based in Melbourne Beach. The volunteers were knowledgeable and well trained, and they teach people how to observe turtles while disturbing them as little as possible. The tour guides also have permission to open a loggerhead nest while she is laying eggs, so that visitors can watch the eggs being deposited. It was an amazing experience and I highly recommend it.

Finally, I leave you with a photo of the turtle hunter herself, who was coaxed and cajoled to actually go out on the beach in daylight hours every now and then.

July 22, 2005

Big Tracks

Every morning during nesting season, there are dozens of new tracks in the sand. I got up early and went for a walk every morning to see who had come to visit the night before. It was fun to get a close look at the tracks left by turtles I saw on shore. After a few days without rain, the beach starts to look like someone's been doing construction work with heavy machinery.

Click on this or any other image to see a larger view. The tire tracks you see in many of the photos were made by the ATV used by the Turtle Patrol.



Scientists refer to the tracks as "crawls." The classic crawl has a horseshoe shape. The turtle exits the water, crawls up the slope of the beach, chooses a spot above the high tide line, then starts to dig her nest, which is a couple of feet deep. She deposits her eggs in the egg chamber, then carefully covers the nest with sand and packs it down. Once satisfied with her work, she turns around and crawls back down the beach to the water, sometimes resting on the way. Once she reaches the water, a few waves break over her, she pushes off, and disappears. Although most turtles crawl straight up and down the beach, some seem to wander a bit, perhaps to find sand to their liking. And there are numerous "false crawls", or tracks left by turtles who emerged from the water and went back in without having laid any eggs. This could be a sign that the turtle was spooked. One Turtle Patrol volunteer told me he thought some of the false crawls this year might be due to changes in the sand from recent dredging. Some turtles are very particular about the sand they choose, apparently.

Most of the tracks are left by loggerheads. Loggerheads walk on land by using an alternating diagonal gait, which some would call the default quadruped gait. The marks they leave in the sand are characterized by a wavy portion left by the belly, and alternating scooped marks left by the front flippers. Occasionally, a loggerhead also leaves what looks like a wavy tail mark in the middle of the track, but this is left by the cloaca.

How do you tell which direction the turtle was going? Flipper marks always point backwards.

Different views of loggerhead tracks are shown here:







Green turtle tracks are less common, but I still saw some every morning. Green turtles use a completely different method of locomotion. Instead of crawling, these turtles use a gait I don't even know the name of. Using all four flippers at once, they lift the flippers, bring them down, and drag themselves a few inches forward. The difference was very noticeable when I finally got the chance to see a green crawl down the beach. There is no lateral movement, and this leaves a wide, smooth track with symmetrical flipper marks. "They" say that you can tell a green's track because there is a tail drag mark. I think a lot of people see the cloaca mark in a loggerhead track and think it's a tail mark. From observation, it appears that the loggerhead cloaca mark tends to be wavy, whereas the green's tail leaves a thin, straight mark down the middle of the track. I also noticed that when the turtle drops its body in the sand and briefly rests after every step, the body backslides a bit and the tail leaves a little divot in the sand. This is visible in both pictures, below. Notice also that the turtle that left this track doubled over her incoming track when she reentered the water.





Next: Tiny Tracks

July 20, 2005

On the Beach

First things first: That beach is dark. Because sea turtles use light to navigate, artificial lights are illegal on the beach. This means no flashlights, camera flashes, spotlights, or indoor lights in buildings that face the beach. Loggerhead turtles are threatened, and Green turtles are endangered, which means that interrupting their nesting is a felony. Therefore, I could not take pictures of nesting or hatching, which take place at night. I was fortunate enough to be visiting while the moon was in its waxing phase, so there was enough light for me to walk on the beach without tripping on an adult turtle, stepping on a baby, breaking my neck or accidentally drowning. It's still a little spooky, though. There are always other people on that stretch of beach, and there's no way to know whether those dark figures in the distance are nice people or not.

I walked along the water's edge for two reasons: It's the best way to spot fresh tracks, and it's the least disturbing to females that are already nesting on the beach. Fresh tracks were very easy to spot as I was walking at low tide. Incoming turtles are harder to see. They first look like a dark shape in the surf which could be a trough of a wave. If the shape is persistent, chances are it's an incoming turtle. When turtles first come ashore, they are quite skittish and prone to turning around and getting back in the water if they are the least bit spooked. I was told that when I spot a turtle in the surf, I should stand very still and wait for the turtle to come ashore until she feels secure. In the case of loggerheads, once they are over the high tide line, they seem to commit to the nesting process, and it's ok to keep walking and eventually even approach the animal. Green turtles, on the other hand, are extremely skittish and will abandon egg laying at any time if they feel threatened. Most of the turtles coming ashore are loggerheads, but this year there is a large number of greens nesting. I saw several each night I went out. They were, indeed, very skittish. I saw two of them walk over the high tide embankment and go halfway up the beach before getting spooked and turning around. On the flip side, I saw a drunk guy stumble right behind a loggerhead coming out of the surf and it didn't seem to bother her in the least.

Speaking of the drunk guy, it turns out that most people on the beach are nice people who are interested in the turtles, and don't want to hurt or bother them. But there are also a whole lot of jerks out there carrying flashlights, taking flash pictures, making noise, and even poking the animals. Since I was alone on the beach in the dark, I didn't think it was safe to approach people who were doing bad stuff. But man, I wish I could have given them an earful. And that doesn't even include people leaving lights on in their beachside houses.

Getting out of the water and up the bank seems to take five or ten minutes for the average turtle. An uninterrupted walk along the beach at night is pretty much out of the question at this time of year, if you're into walking beaches in the dark. When I was visiting, on a mile long stretch of beach, there would usually be half a dozen turtles in various stages of egg laying. I could only walk a few minutes at a time without having to stop for a crossing or nesting turtle. All in all, in my four nights in Melbourne Beach, I saw about 40 adult turtles on the beach.

Next: Big Tracks

July 16, 2005

Chelonia Mobile: The Turtle Moves



Back in Melbourne Beach, Florida for a much needed summer vacation. It's turtle nesting season!


From the Archie Carr Refuge site:

The twenty mile section of coastline from Melbourne Beach to Wabasso Beach in Florida is the most important nesting area for loggerhead sea turtles in the western hemisphere and the second most important nesting beach in the world. Twenty-five percent of all loggerhead sea turtle and 35% of all green sea turtle nests in the United States occur in this twenty mile zone. Nesting densities of 1,000 nests per mile have been recorded. Approximately half of this area is available for acquisition and four parcels totaling 9.3 miles make up the core area.


I spent the last two nights on the beach, and unlike last year, there was no shortage of turtles. Green sea turtles are on a biennial nesting schedule. Although they were previously laying eggs in even numbered years, last year saw few nests. This year they are back, suggesting that the greens may have altered their cycle.



Thursday night, I walked about 3/4 mile up the beach and back, and confirmed 10 turtles. I assumed they were all loggerheads, but after going to the Sea Turtle Preservation Society headquarters and talking to a representative, I learned about the difference between loggerhead and green turtle tracks. Loggerheads have asymmetrical tracks, and tend to wiggle from side to side as they pull themselves up with alternate flippers. Green turtles tend to have wider tracks which are relatively straight, as they drag themselves up the shore with both flippers together. After learning this, I walked along the beach and was able to identify a number of green turtle tracks. Years ago, at Cornell Vet School, I was lucky enough to dissect a juvenile green turtle that had died accidentally. The turtle's unusual skeletal anatomy and elegant form made it one of my favorite dissections of all time; so I have a bit of a soft spot for green turtles.

I met quite a few people on the beach who were also looking for turtles. Unlike certain MTV reality shows, I try to follow proper turtle etiquette. This means no lights, no flashlights, walk along the waterline, and no disturbing a turtle as she is emerging from the water.

Turtle images are from the STPS website. My own pictures of tracks will follow when I return to Virginia.

My Ice Cream Flavor of the Week: Caramel Turtle, at Moo's in Melbourne Beach
My Beach Reading: Small Gods, by Terry Pratchett