Costa Rica’s Sea Turtles
Costa Rica is a sea turtle paradise. If you’re flexible with your destinations it’s possible to see them nest and/or hatch nearly anytime you plan to visit.
Sea Turtles lay eggs on beaches on both the Pacific and Caribbean shores of Costa Rica every month of the year which in turn means hatchlings are emerging somewhere every day. Some species spend most of their lives far out to sea but others are commonly seen by divers and snorkelers around the popular island and reef dive sites, especially during nesting or hatching peaks.
If you’ve always wanted to see turtles plan ahead a little and you should have a good chance when you travel to Costa Rica.
There’s a lot of information in the article below but if you just want to get on with the turtle viewing click the link to skip to Guaranteed Strategies – Show Me the Turtles.
The table shows when and where the most common species nest. Knowledge about wide variations in populations and habits also help determine the best strategy for turtle viewing.
Sea Turtles of Costa Rica
There are very few creatures whose big life events are so accessible to people.
Sea turtles are amazing spending months, years or for some males their entire life feeding in the open ocean hundreds or even thousands of kilometers from shore. But each is born on land and the females at least must return to land to dig nests and lay eggs.
A few hundred stragglers headed back to the surf just after sunrise. An arribada of than 8,000 female Olive Ridley sea turtles (by the ranger’s count) that came ashore on Valentines day to lay eggs at Ostional National Wildlife Refuge in Costa Rica.
With the ability to stay submerged for up to three hours before returning to the surface for a gulp of air they seem almost more fish than reptile. Unlike other reptiles they also aren’t strictly cold blooded and can raise their body temperature 8 °C (about 18 °F) above the temperature of the surrounding water.
Another slightly bizarre fact related to temperature is that sea turtles have temperature dependent sex determination. How warm or cool the sand in the nest is for about two weeks during the middle of the incubation of the eggs determines whether the brood will be all female, all male or a mix. If the temperature is less than 27 °C (81 °F) they will all be male, more than 30 °C (86 °F) all female and in between results in a mix.
Sea turtles can’t retract their heads into their shells but their skulls are fully roofed over with heavy bone that fits neatly under the shell protecting their necks. They all have appendages fully developed into flippers and are quite graceful in the water although as you can see from the video above ungainly on land.
In all of the Costa Rican species mating takes place in the ocean. Although we’ve seen photos of Atlantic Greens mating on the beach it’s likely that they were simply washed in on a wave. The males don’t stick around and only the females come ashore. In fact the males may not be necessary at all most mating seasons. The females can store sperm for several years and may nest many times without mating again.
Depending on the species as many as half of the eggs that are deposited will be smaller yolk-less and sterile. There’s no explanation or even a widely accepted theory as to why.
Navigation to Costa Rica’s Nesting Beaches
Leatherbacks aren’t specific about where they nest relative to where they were born but the other species have an amazing ability to return to the same beach where they hatched after years ranging across the open ocean.
“The brains of turtles contain particles of the magnetic mineral magnetite. Hatchlings are imprinted by the earth’s magnetic field as they leave the nest. Since the angle of inclination of the magnetic field varies with latitude, adults return to the natal beach to breed using the magnetic field for navigation” (p. 754 The Amphibians and Reptiles of Costa Rica – Savage).
Other scientists have proposed that they use olfactory imprinting of the water or beach and smell their way back to the same beach. It is known that they can chemically sniff salt concentrations in the sand and use this ability to determine when they have passed the normal high tide line and it’s safe to build a nest that won’t be washed away.
When and Where to See Turtles Nesting in Costa Rica
When we first started visiting Costa Rica we had no idea how to experience this incredible natural event. There are a couple of National Parks established specifically to protect turtles and their nesting habitats, but depending on when you’re traveling these may not be the best places to see nesting or hatchlings.
Most people automatically assume that since it’s namesake is the sea turtle that Tortuguero is the place to head to experience this incredible phenomenon, but except in the peak of the Atlantic Green (Chelonias mydas) nesting season July through October, you’re not guaranteed sightings.
Hawksbill turtles (Eretmochelys imbricata) do nest year round on the beaches of Tortuguero, but their numbers are so decimated that it’s very rare to see them. Leatherbacks are also extremely endangered and even at the peak of their nesting season in March and April you’d be very lucky to encounter one.
Guaranteed Strategies – Show Me the Turtles
The best chance to see turtles is to look for the right turtles in the right place at the right time. The right places are Ostinal and Nancite beaches. The right time is the few days around the new moon (any time after the third quarter and before first quarter moon) between August and November. The right turtles are the Pacific Olive Ridleys (Scientific name – Lepidochelys olivacea, Spanish – Lora, Carpintera) because they exhibit an amazing nesting behavior referred to as arribadas.
A mass arrival or arribada may involve as many as 20,000 turtles arriving on the beach to nest in a single night. Even if you don’t time the biggest landing perfectly there are usually hundreds of turtles nesting for a few days before and after the one to three night long main event and individuals are common nearly every night.
There is some variability in the predictive value of the new moon. Certainly many more arribadas occur on the darkest nights associated with the few days around the new moon but there are other factors. Sometimes rough weather and high seas interfere and reduce the numbers, but in half a dozen tries we’ve never been disappointed.
A female Olive Ridley (Lepidochelys olivacea) uses her flippers to excavate a hole in the sand near the high tide mark where she deposits about 120 small round white eggs.
Nesting is a risky business and one theory of why arribadas occur is that the predators are overwhelmed by the huge numbers all at once. They may take a few adults and consume a few thousand eggs, but the vast majority survive. If the nesting were spread over several weeks the predators and scavengers would be hungry again.
In the extremely unlikely event that there is no nesting activity at Ostional (or if they close Ostional as a result of the new popularity) you may have to drive north to Santa Rosa National Park, get special permission and hike in 21 km to Playa Nancite – the only other place in the world this occurs on the massive scale.
We didn’t guarantee it would be easy, just that there would be turtles.
There are dozens of small turtle conservation projects along both coasts and most maintain a nursery. The egg incubators are nothing more than a big sandbox with a solar powered electric fence around it to discourage pizotes, coyotes, racoons and other animals that might dig up the eggs. 24 hour human guards are typically posted as well to keep poachers from easy pickings.
Some nurseries also have a canopy or other partial shade set up to control the temperature of the sand and thereby the sex of the babies.
Conservationists watch for nesting turtles, dig up all or a portion of the eggs after the mother returns to the sea and rebury them in the egg incubator. The gestation periods are well known for the various species so it’s relatively easy to calculate an approximate hatching date for each batch several weeks in advance. There are many batches making the odds good.
Unfortunately there’s no online schedule and getting the information by any method except showing up in person can be difficult because many of the reserves don’t have phones or cell service. Asking around (concierge, taxi driver, the kid working at the ice cream shop) when you’re in turtle territory sometimes works.
Another strategy is to use the advice about nesting above and just show up when and where the odds are really, really good.
Show Some Respect
Unfortunately in late 2015 there was a mass arrival of a different sort at Ostional. The severe drought brought on by El Niño dried out the river crossings and word spread by social media resulting a mob scene as hundreds of curious city dwellers flocked to the beach.
The visitors were unaware of or unconcerned with their impact and may have precipitated the closure of the beach to all visitors.
Please be respectful of the turtles you’ve come to see. Follow all rules and regulations of every protected area you visit (ignorance is no excuse…) and minimally the following suggestions.
- Do not use lights of any kind (including camera flashes)
- Do not approach the turtles. We know that “perfect hugging a turtle selfie” is almost irresistible and they can’t escape but don’t do it.
- The area between the high tide line and the trees is where the turtles dig their nests. Do not block their access and do not drive over this area at any time or you’ll crush the nests below.
- If guides are available hire one! They will add considerably to your experience and conservation efforts depend on generating income from legal viewing to replace illegal egg and meat harvests.
The turtles may seem oblivious but they are not. They are programmed by nature to struggle up the beach and nest whatever is happening around them. That doesn’t mean they aren’t stressed by the jaguar that starts snacking on one of their sisters or the idiot tourist that decides to ride one.