Sea Lab Sidebar: Sea Turtles of the Gulf

Transcript

Angela Levins, PR Director We are joined today by Doctor Katrina Phillips. She is a senior marine scientist here at the Dauphin Island Sea Lab and an assistant professor at the University of South Alabama. And her research focus is turtles. Thank you so much for joining us.

Katrina Phillips, DISL Senior Marine Scientist Thanks for having me.

Levins First off, the difference between turtles period. Like you can’t put all turtles in the same area, right?

Phillips True. Yeah, there’s lots of different turtles out there. And there are different sort of subcategories of turtles. So the big categories turtles. And then under turtles you might have sea turtles, you might have aquatic turtles, you might have other turtles like diamondback terrapins, and you might have land turtles, which are often considered kind of called tortoises. So all of those fall under the umbrella of turtles. So, for example, tortoises are a type of turtle, but not all turtles are tortoises.

Levins Gotcha. The turtles that we are talking about that you focus on are sea turtles. And so how many species of sea turtles do we have in our waters worldwide?

Phillips There’s seven different species of sea turtles, but we only really see five of them here in the Gulf. I say only, but actually that’s a pretty big number. It’s kind of a cool place to be, to have five different species. Here in the Gulf. We have loggerheads might be the most common. We also have green turtles, Leatherbacks, Hawksbills and Kemp’s Ridleys. Those turtles all. When you say that we have them in the area, we would find them off the coast of Alabama.

Levins One thing that you talked about was that turtles are migratory. So do we always see the same turtles or are they kind of like dolphins tend to migrate, but then you have some dolphins that stay in an area. Do turtles kind of follow that same thing that some migrate but some stay within a vicinity?

Phillips That’s a good question. So turtles don’t usually migrate to follow food like some species do. But the type of migrations that sea turtles do are mainly reproductive migrations. So every two or three years, the adult female turtles will migrate to the area near where they were born to lay their eggs, and then migrate back again to the area that they normally live. And they spend most of their time there. So most of their time is spent in that area where they feed, and that’ll depend on the species where the good places to eat are.

Levins How do they determine their good places? Or do you know, I mean, you’re saying that there’s not a lot that we know about them. So when we see the little baby turtles, like scurry into the water, is there any way to know what they kind of chooses their spot? How do they know where they’re going?

Phillips That is a great question. That is one of the focal areas of my research. So I’m actually looking to see if they perhaps inherit some information about where they should migrate to. And it’s interesting, when you look at a hatchling that’s leaving the beach, it’s actually ten or twenty years away from when they’re gonna reach maturity at that moment. So they don’t need to worry about that area that they’re going to settle for another decade or two for the first few years of their life, their way out offshore, away from where the high density of predators are, and they’ll stay out there for a while. And then again, depending on the species, it might be anywhere from two to maybe up to ten years. And that’s a really hard life stage for us to study because we’re a very land based species. So that’s another area of research that there’s a lot going on right now is finding out what’s going on with those turtles in those early life stages. That is called the lost years, because we know so little about them. And then at some point they get big enough or hungry enough that they move in sort of as teenage turtles to shallower water habitats. And then they grow a lot there. And then once they’re ready, they reach maturity. They’ll head most of them off of sort of what we call the continental shelf. So the area that’s kind of close to land, but still a little bit away from shore. And that’s where they set up usually their sort of main foraging areas except for leatherbacks because they like to eat jellyfish. So they just kind of swarm around following the jellyfish all the time.

Levins That makes me think so. Do they have noses? Like. Do their noses smell the jellyfish?

Phillips They do have noses. Um, and I guess a lot of ways it’s hard to tease apart sometimes whether you’re smelling or tasting something because they’ll come up and breathe and they might smell something in the air, but while they’re underwater, they’ll also swallow water and they can taste things in the water that way, too. So they might use a bunch of different cues to kind of find where the blooms of jellyfish are.

Levins I guess that was a weird way to ask that. But, you know, we know they have noses, but do they use their noses when you say they follow the jellyfish? Or are they like sniffing? You know, I picture a cat following the treat.

Phillips There’s actually some really cool videos. So they’re also using visual cues too. And there’s some cool videos we can add some links to here that show a leatherback kind of swimming around and just munching on, on jellyfish as it goes around. And it finds this one and it finds this one. And leatherbacks are the biggest type of turtle in the world, so it takes a lot of jellyfish to keep a big body like that powered.

Levins So they eat a lot of jellyfish so they don’t have to worry about their calories.

Phillips Yeah.

Levins So we are in migration season. What do we typically see as they come up to land? I mean, a lot of people have questions about nesting sea turtles. But if we were to, you know, nail down like some of like two or three things about that period of time that they’re coming to lay their eggs, what is something that we need to think about?

Phillips Well, so nesting season starts May first in our area. And this turtles probably start migrating a little bit before that because it’ll take some them some time to get here. So the female turtles migrate over to lay their nests for the season. And I think one thing that people don’t always realize is that when a turtle comes and it’s her, it’s her season to lay nest. She doesn’t lay just one nest. She usually lays five or up to seven or eight nests in a season. So a turtle will come up and lay a nest, and then she’ll swim away for about two weeks. And then she comes back and lays another one, and then she swims away. And then she comes back and lays another until she’s laid all the eggs that she has for the season. And then she’ll migrate back to where she spends most of her time. And that’s one of the reasons why most sea turtles take a year or two off between their migration and reproductive seasons, because it takes a lot of energy to do that long migration and to lay all those eggs. So it takes some time to recuperate that energy and build it up again so that they’re ready for the next season. Each nest that they lay is about one hundred eggs or so, and they’ll lay those eggs. And then the next follicles are already starting to develop and get ready for the next nest. That’s going to be in a couple of weeks.

Levins That’s very fascinating. That is one thing that I did not know about turtles. I thought they came up and just set their eggs out and they were like, we’re done.

Phillips Which is a pretty cool adaptation when you think about it, because turtles come up and lay their eggs in basically hurricane season is a huge overlap between that. So if a big storm came and washed out one of their nests and they only laid one nest, then they would lose all their reproductive activity for the season. But when they lay multiple over the course of the season, if a storm hits one, there’s probably other nests that’ll still be okay for the season.

Levins Do we think they strategically place them like, okay, here’s one here and here’s one there.

Phillips There has been some research that individual turtles kind of vary in how specific they are to a site. So some will go almost to the same place over and over and over, year after year and year. And then some of them will spread their nests out away more. Some of them are using the all the eggs in one basket strategy, and some of them are spreading them out. But if you spread them out through time, through a season, then your nest that laid in May might be okay. Even if the one you laid in August gets washed away.

Levins Fascinating. It really is like, these are things that I didn’t think about with turtles. It just adds another level to them.

Phillips Another fun fact about sea turtle migrations is that we still know very little about what male turtles are doing. We can study female turtles pretty well because they come up on the beach, and then we can put a satellite tag on them. Or we could take a little skin sample and learn about them. But the males generally never come up on the beach again after they hatch and they go out to sea. So we’re still there’s still a lot we need to learn about males. We think that they also migrate to about the area that they hatched from, but we’re not sure about that. And we think that they probably do that every year instead of taking year off, because they don’t have to invest so much energy in creating eggs and that sort of thing. As far as we can tell, the males will migrate to the area where the females were going, but only at the beginning of the season. So you might have seen some male loggerheads. Loggerheads are the most common nesting turtle around here. You might have seen them at the end of April, beginning of May, and then usually by the middle of May, end of May, they’ll leave. So even though the female turtles continue laying nests, they actually have a way to store the sperm at the beginning of the season and hang on to it and use it throughout the season.

Levins There is so much more to turtle reproductive biology than I’ve probably ever put my thought into. Moving away from the nesting side of things. And you know, you’re talking about the lost years and the lost years. That’s a big part of your research, and that is working to figure out what happens after they scurry into the water. What is one or two things that you have been able to find in your research?

Phillips So one thing that we found is that a lot of times people thought about the lost years as only happening way, way, way far off shore and away from that continental shelf. That’s sort of shallower area closer to shore. But what we were seeing is that turtles that were in this lost years stage and in that life stage, they spend most of their time at the surface, and at least in the Gulf, they’ll, they’ll associate with that floating seaweed that you might see sometimes sargassum. So they spend their time floating at the surface with Sargassum, and they might actually come in over the shelf sometimes and then out again. So that was something new that we didn’t think we would find. We thought they would only stay way, way far offshore, but they actually came kind of close to shore in a way, again. And we also saw, though, that if they got really close to shore, there was a clear like slowing down in their trajectory and turning away from shore. So they definitely don’t want to get too close to shore. And we’re not exactly sure what, cuz they’re using to know that they’re actually getting close to shore. And one way that we knew that they were doing that is that when we would, we would find turtles out in the Gulf, and we would put a tag on them to see to track where they were going. And we would also release a passive, just drifter that drifts with the currents. And we found that a lot of our drifters would wash up on shore, but the turtles didn’t. So at some point they had some sort of cue that said, oh no, I need to turn away from shore now. And they would do that.

Levins Katrina, this has really been fascinating with the migration and the reproduction and all the different pieces to it and your research with the lost years. And it seems like we could talk forever and ever about this. So promise me you’ll come back and chat with me on some of the things that we haven’t had a chance to chat with.

Phillips Absolutely, I promise.

Levins Well, we will put some of those videos and stuff that you mentioned on the page with this, and we will chat with you soon. Thank you. Katrina.

Phillips Thanks.