Relocation Nation

Blog Post By: Karoline, Sea Turtle Intern

        Something we often do during dawn patrol is debate relocations. This week, we had several members of the public approach us with questions as we were debating. We don’t take relocations lightly, and oftentimes will be on the fence as to whether or not it is in the nest’s best interest to move it. We always err on the side of caution, which means we will only relocate nests if absolutely necessary. We like to think that in general, the mother knows best, but unfortunately sometimes the nests are just too close to the water to leave in-situ (in its original location).
            Relocations are a powerful and necessary conservation tool for turtle patrols, but they come with their own risks. The main concern we have when moving eggs is rotation, as rotation of the egg can cause the embryo to detach itself from the shell. It’s up to us to decide if the benefit of moving a nest outweighs the risk of rotation or not. The most common cause for relocations is the nest being “too low”, meaning it is below the high tide line. When a nest is below the high tide line, it is at risk of being washed over by the water too many times. Too many wash overs can suffocate the nest and decrease hatching success. On dawn patrol, the main questions are usually: How many wash overs will this nest go through if it stays where it is, and how many wash overs are too many? Even though our instinct and educated debates are usually very accurate in determining the amount of wash overs a nest will receive, I was wondering if there is any research or perhaps a scientific method that could determine a nest’s wash over risk. And, as it turns out, there is!
            Researchers at Florida State University have created a model that does exactly that. The model is currently able to predict the amount of harmful wash overs a nest will receive with 83% accuracy. The model combines the beach slope and wave data to calculate harmful wash overs on the beach. With data from calculated wash overs, researchers then created a risk map, which predicted where nests on the beach were most at risk. Creating a new risk map for a nesting beach every year may sound like a lot of work, but researchers have found that the “time-averaged model” was more accurate than the most recent model from the year before. So, just creating one risk map could benefit a nesting beach for multiple years. That is, however, if the beach is not changed by big hurricanes or storms. In that case, a new map would be needed in addition to the average model.
            With a risk map, we could look at the specific percent risk of harmful wash overs for each nest, giving us more detailed data to use in our dawn patrol debates. Hopefully, the risk map model will become even more accurate and easy to obtain, making it readily available to turtle patrols everywhere!
Sources:
https://eos.org/articles/predicting-wave-wash-overs-for-sea-turtle-nests
https://www.sciencedirect.com/science/article/abs/pii/S0964569118310202?via%3Dihub