Hello, my name is Mr. Hill. Please join me as I travel to Costa Rica to study sea turtles!

Friday, February 4, 2011

Day Six: Late-afternoon

It was about an hour ago, and I had just sat down to update my blog when the call went up: an Olive Ridley turtle had just come ashore to nest. Those of us here in the bunkhouse immediately scampered down to the beach. Very thoughtful of the turtle: she chose to make her nest right near the hatchery.

By the time we got to the site, the turtle was putting the finishing touches on her egg chamber. She then began to lay her eggs. By the time she finished -- about 8-10 minutes later -- there were 79 eggs in the nest. She then covered the eggs, tamped down the sand with the characteristic Olive Ridley tamping dance, camoflauged the nest with loose sand, turned herself towards the ocean, and quickly crawled back into the water. The whole process took about 1/2 to 2/3 the time it takes the leatherback to do pretty much the same thing, and that, in part, is because the Olive Ridley weighs about 150 pounds -- not even a quarter of what the leatherback weighs -- and digs a nest that's about half the depth of the average leatherback nest (see question 2.6 below).

Olive Ridleys are the only species of sea turtle that comes ashore to lay during the daytime; consequently, we got to see in full daylight a process similar to what we see at night with only red-light illumination. Nice.

Now to answer a few more posted questions from all y'all.

1. (from 4M) If the babies hatch during the day, do they wait until the night to emerge from the nest and head to the water? Most often, yes, but, if they don't make it all the way out of the nest at night, they will most likely be subjected to the heat of the day, and, as you can figure out, that's not good -- they usually end up dying because it's way too hot for them 'up there' and they have no way of cooling themselves off. If you see a hatchling, why not just pick it up and take it to the water? Depending on where the hatchling is in relation to the water, and whether or not there might be predators around, we do sometimes pick up the hatchling and help it on its way. That said, it's important for the hatchling to get itself into the water because, in doing so, it 'warms up' the muscles the hatchling needs in order to take its maiden voyage in the ocean! How do leatherbacks eat jellyfish without being stung? The leatherback is not affected by the toxin of the jellyfish, so that makes it a-OK for a leatherback to scoop up a jellyfish without thinking twice about what its ingesting.

2. (from 3S) How big are leatherback eggs? About the size of a billiard ball. How much do hatchlings weigh? On the average, approximately 45 grams (or just under 1.5 ounces). How many hatchlings make it to the ocean? As you can imagine, that depends on all kinds of factors (temperature of the sand, predation, etc.), but the vast majority of the hatchlings in each nest make it to the ocean. How long does it take a hatchling to get from the nest to the ocean? Tough to say precisely: some nests are closer to the water than others, and some nests hatch closer to high tide than others. How long does it take the eggs to hatch? Approximately 60-65 days. How deep is the nest? Approximately one meter.

3. (Alvin Lee) How does the hatchery keep eggs warm? The hatchery is outside, so the sun and sand keep the eggs warm -- there's no artificial heat or light source in the hatchery here. Is the heat in the hatchery ever manipulated to produce more of one gender of hatchling than the other? See answer to prior question. But to elaborate a bit, one of the biologists is conducting research into the area you ask about, Alvin. Because of global warming, there is concern that eventually, if it hasn't already happened, there will be an increase in the number of females and a decrease in the number of males, so the biologist is watering with varying amounts of water a certain number of empty plots in the hatchery and recording the temperatures of those plots at various times during the day to see how those varying amounts of water could affect the temperature of a nest. Do the bioligists there name the turtles? Why, yes they do -- not all of them, but some of them. 'Bootsy' came ashore last night to make her 11th nest this season. She's called 'Bootsy' because one of her back flippers has a slice in it and the flipper therefore is now shaped like a -- you guessed it -- boot. At the beginning of the nesting season, the first six turtles ashore are entered into an online 'race', and you can vote for which one of those first six you think will lay the most eggs during the season. In order to keep track of which turtle is which, the Big Six are named. This year there's Esmerelda, La Famosa Tom, Esperanza, Tamy, Tamarinda, and Baulitica in the running. Esmerelda's presently winning, though the aforementioned Bootsy has actually been ashore one more time than has Esmeralda and, as a result, has laid more eggs, but Bootsy was not one of the first six, so she can't be in the race. Sorry to disappoint you, Alvin, but there is no turtle named 'Shelly'...

4. (Ben Miller) Do leatherbacks ever nest in the Galapagos? No, they don't. They go there only to eat!

Because high tide is getting later and later (or, depending on how you look at it, earlier and earlier), tonight's the last night of one six-hour shift. Tomorrow, we go to two shifts: 7-11:30 p.m. and midnight to 5:00 a.m.. Can't decide which shift I'd prefer -- but my preference doesn't really matter since Tera makes up the duty roster!

1 comment:

  1. hey Hill,
    how do you know when there is a turtle on the beach?
    Jack Hogan

    ReplyDelete