Blog Post By: Ashlyn, Sea Turtle Intern
With signs plastered on every beach access, posters set up in the Camp exchange, and friendly night patrollers reminding us to only use red lights during turtle season, it’s hard to miss the fact that bright white lights can disturb our nesting turtles on the beach.
But what is the significance of using red lights as opposed to another color of light when turtles could be present on the beach?
Red light has the longest wavelength and is the first to be reflected out of the water column. Violet and blue light, on the other hand, has the shortest wavelength (and highest frequency), penetrating the deepest within the water column. Different species of turtles vary in responses in sensitivity to the color spectrum due to the prevalence of the color of light that is found in the aquatic habitats that they occupy. For example, freshwater turtles that live in shallow waters tend to have a greater sensitivity to longer wavelengths of light, such as orange and red light. In such shallow, freshwater aquatic systems, it is these long wavelength lights that are better transmitted throughout the water column. On the other hand, marine turtles have been found to be much more sensitive to shorter wavelength, blue and green, light that is better transmitted within deeper marine waters.
Sea turtles have adapted over time to respond to the light that is prevalent in their habitat. It’s no surprise, then, that the sea turtles coming to nest on our State Park Beach here at Edisto are the most sensitive to blue light that proliferates in deeper marine waters. There is still wide variation, however, in color sensitivity among sea turtles due to their life cycle habits. Loggerheads (Caretta caretta) that are the primary species seen nesting on Edisto tend to feed in shallow marine waters and have maximum diving depths of around 211-233 meters. Leatherbacks (Dermochelys coriacea) feed in the deeper open ocean and can dive to maximum depths of over 1000 meters. Research has suggested that Loggerheads have a higher sensitivity to a broad range of light wavelengths, processing blue, green, and yellow/orange, explained by their occupation higher in the water column. Leatherbacks’ sensitivity peaks at blue, with some capability of processing green, the colors that are transmitted within the deep marine water column.
Despite variations between sea turtle species in the wavelengths of light that are processed, red light is consistently processed with the least capacity among sea turtles. It is for this reason, that we as beach-goers are encouraged to use red lights when on the beach at night, as not to disturb our sea turtles that come to nest on the beach.
Kenneth W. Horch, Judith P. Gocke, Michael Salmon & Richard B. Forward (2008) Visual spectral sensitivity of hatchling loggerhead (Caretta caretta L.) and leatherback (Dermochelys riacea L.) sea turtles, as determined by single-flash electroretinography, Marine and Freshwater Behaviour and Physiology, 41:2, 107-119, DOI: 10.1080/10236240802106556
Why are sea turtle eggs round?
Blog Post By: Karoline, Sea Turtle Intern
Hello! My name is Karoline, and I am one of the sea turtle interns this summer. Before coming to Edisto, I had only ever seen one sea turtle, and didn’t know much about them. I’ve only been here a little over a week, but I have already learned so much about sea turtles. With this new information comes even more in-depth questions that I need answers to! One question I will always have when I learn a new sea turtle fact is: why? This week, something I have been wondering about is turtle eggs. As anyone who has seen turtle eggs before knows, they look like ping pong balls. So, my egg question for this week is: why are they shaped like ping pong balls?
Basically: The reasoning is up for debate…but don’t worry, there are some fascinating hypotheses out there!
The main ideas on turtle shape come from bird research. Birds with round eggs tend to be weak fliers, and strong fliers have longer eggs (making the eggs have more volume without needing to be wider). Even though turtles don’t fly (that we know of…), it’s interesting to note that weak flyers have round eggs and sea turtles do as well. Another piece of data that has been found about the shape of bird eggs is what some people call the “rolling factor”. It is exactly what you would think: the rounder the egg, the more intense the “rolling factor”. So, birds who nest on the face of a cliff would need a less round egg shape so that the eggs don’t roll off the cliff! Turtles lay eggs in egg chambers (the eggs are under the sand), so the “rolling factor” doesn’t apply, meaning that the eggs can be perfectly round without the fear of them rolling away affecting the evolution of their shape. Some relevant hypotheses I found on the egg shape of birds that seem like great ideas to apply to turtles are: conservation of warmth, space, and calcium. If you have ever done or seen a sea turtle egg relocation, you know that we have to be careful because the eggs are tightly packed together. A sphere seems to be the optimum shape for tight packing (versus a more conical shape). I would assume that tight egg packing inside the turtle is extremely important, as the turtle needs to have high reproduction rates since chances of survival are so low. Not only would tight packing be good for conserving space in the turtle, but maybe it would be optimal for the eggs to share warmth as they are close together. And, having round eggs would mean less shell surface area, which conserves the calcium used to make the eggs.
Overall, there are some great hypotheses out there, but we definitely need some more turtle specific research on egg shape. I volunteer!
We have started the registrations for the night walk program. Our night walks are held every Tuesday, Thursday and Saturday in June and July! See below for the flyer.
For more information and to register, call the Environmental Learning Center at (843)869-4430
Meet our 2021 Sea Turtle Interns!
We are excited to be joined by three summer interns for the 2021 sea turtle nesting season! Meet Chase, Karoline & Ashlyn!
They have already been doing great with turtle training and finding their first few nests. The interns will be assisting with our dawn patrols, night walks and assisting at the ELC, so be sure to say hi. They will also be posting to this blog, so stay tuned to future posts!
Our nest adoption program is back!
Since we have found our first nests of the season, that means that our nest adoption program has returned! For a $50 donation, you can adopt a nest at Edisto Beach State Park! For each adoption you will receive:
- A turtle plush toy
- A certificate
- Your name on our adoption board
- A digital photograph of your nest
- An email update on your nest when it hatches!
The money from the nest adoption go towards our turtle program so we can continue to protect our nesting loggerheads! The money raised goes towards purchasing new supplies for our patrols. We are so thankful for all of the support for our turtles!
Our first nest of the season!
We found our first three nests on May 15th! We found our first crawl on May 13th but it was a false crawl. A false crawl is when the turtle turns around without nesting. With that first crawl, we knew the turtles were going to be nesting soon. We are so excited that our nesting season has begun and we look forward to finding more new nests every day!
Be sure to say hi if you see us on the beach and come on up if we are working away at some fresh turtle tracks!
Turtle Patrols are Back!
With the arrival of May, it means our turtle patrols are back! We are excited to patrol our beach in search of our first nest. When do you think team EBSP will find the nest?!
The first nest in South Carolina was found yesterday at Seabrook Island!
A large portion of our patrols at the moment is dedicated to picking up trash. We use the app, "Clean Swell" through the Ocean Conservancy to document all of our trash finds. I always encourage individuals to start using it! It is a fun way to document all of the items you pick up. My app shows that I have picked up 13,345 pieces of trash since I started using the app! At the end of the season, our patrol can identify how many pieces of trash we pick up and what types of trash. It is really interesting information to have.
Stay tuned to the blog for when we get that first loggerhead sea turtle nest! It could be any day now.
Sea Turtle Biologist