‘Not related to the lockdown’

 

Once hatchlings break out of their shells and climb up the steep wall of their nest, they skitter across the sand toward the ocean, guided by the moonlight. During this journey, these tiny animals memorize the sand and shoreline, enabling them to return to this same spot when, a few decades later, it’s time for them to build their own nests.

Humans tend to be the biggest disturbance to sea turtle nesting. Something as simple as walking on the beach at night can scare away a nesting mother, and result in what’s called a “false crawl.”

“The turtle will return to the ocean, leaving just tracks, without laying any eggs,” Perrault said. “Sea turtles may expend precious energy reserves crawling onto the beach without actually laying their eggs. Furthermore, sea turtles have a window of time when they can lay their eggs, [and] if they false crawl at the end of this window, they may even drop their eggs in the surf or the ocean, causing embryonic mortality.”

As for hatchlings, they often get blocked, or completely stopped, by litter, man-made holes, and even footprints. Light pollution can make them travel in the wrong direction.

Sea turtle hatchlings. Image by Daphne Sánchez / Flickr.

“If you think about it in a world without humans, the only lights are going to be moonlight reflecting off the water, and so the hatchlings are evolutionary primed and geared towards crawling down the beach … toward the moonlight on the water,” said Kyle Van Houtan, turtle expert and chief scientist at the Monterey Bay Aquarium. “But if there’s a bunch of development and hotels and cities with all sorts of light, they could draw the turtles inland where they get run over or picked up by birds.”

COVID-19 lockdowns could provide short-term benefits for nesting mothers and their hatchlings, but Perrault said he doesn’t expect the pandemic to make a significant impact on turtle populations in the long term.

“Sea turtles are a long-lived and highly migratory species, so a temporary shut down only provides sea turtles a healthy break from some human-related disturbances, and we do not expect many long-term benefits to population recovery due to this short shutdown,” Perrault said. “The hope for survival comes from continued vigilance of local beach-goers and local, national, and international protections for these imperiled species.”

In Phuket, Kanokwan Homcha-aim, supervisor of Maikhao Marine Turtle Foundation, a local group that educates the community about turtle conservation, told Mongabay the return of the leatherbacks “is not related to the lockdown” since they were already nesting before the pandemic hit.

Loggerhead turtle hatchlings in South Africa. Image by Jeroen Looyé / Flickr.

According to Van Houtan, a bumper nesting season tends to be influenced more by the availability of food and the ability of female sea turtles to get enough nutrition to produce eggs.

“Female sea turtles don’t nest every year; they nest every three to seven years, depending on the excess amount of calories that they have,” he told Mongabay. “Their parenting essentially goes into the yolk which makes those eggs, and they’re only going to do that if they have the excess calories and the metabolic energy to allocate to that, and that means that they’ve been eating a lot and the place where they forage has been producing enough food. And this is something that is months in making … and so this is reflecting something that happened before the pandemic.”

If the pandemic does yield any benefits for sea turtles, Godfrey says it will take a long time to see.

“It’s possible that some additional hatchlings will survive this year that otherwise might have died,” Godfrey told Mongabay. “In short, we may see increased survivorship of nests this year. However, given that it takes about 30 years for hatchlings to mature and nest themselves, by the time we get three decades down the road it will be impossible to ever determine if a change in nesting rates was due to the pandemic. Too many variables at play that far in the future.”

‘Sustained conservation efforts’

 

The more likely explanation for boosted nest counts is the introduction and strengthening of conservation programs, fishery management practices, and local and international laws.

“[It’s happening] because of over 60 years of sustained conservation efforts in many countries around the world,” Godfrey said. “Stopping the harvesting of sea turtles. In the US this has been accomplished through the Endangered Species Act. Internationally, many countries have enacted similar laws preventing the killing of turtles and the taking of their eggs, and we also have banned international trade by the Convention of International Trade in Endangered Species (CITES). Through these and other actions, we have given sea turtles the chance to start recovering.”

The green turtle, which is listed as endangered by the IUCN, is one species that’s recovered substantially due to conservation and fishing moratoriums, Van Houtan said.

“We … have seen numbers rebound in South Florida, in Hawaii, in other places in the U.S., where there are bans on green turtle fisheries, which is the species of sea turtle that’s been commonly consumed for its meat,” he said. “Those bans have been in effect for almost 45 years now, and there’s been dramatic population growth in those time periods. So that’s been really impressive.”

A green turtle nesting in Florida. Image by FWC.

In Florida, green turtle nests have increased eighty-fold since 1989, according to data compiled by the Florida Fish and Wildlife Conservation Commission (FWC). While these numbers are encouraging, Simona Ceriani, a turtle nest expert and research scientist at FWC, says that an increase in turtle nesting doesn’t equate to population growth. Nest surveys only look at female turtles of a certain age, and don’t take into account what’s happening to other demographics.

“An increase in nest count is good but [it’s an] indirect measure of breeding females,” Ceriani told Mongabay. “It’s something obvious that we all know, but if you look at the published literature, there is a lot of confusion about terminology. Folks report trends in nest count, but then when they discuss their results they talk about ‘population’ because they use nest counts as a direct proxy of adult females. Nest count and female count … are not synonyms and that should be emphasized.”

There can also be huge fluctuations in turtle nesting from year to year that experts can’t really explain, Ceriani said.

The best way to assess population, according to Van Houtan, is to conduct underwater surveys, which is what he and a team of researchers did over a 13-year period. To collect data on sea turtle populations, trained scuba divers were towed behind a slow-moving boat at 53 reef sites in the Pacific Ocean, including Hawaii and the Marshall Islands, to count green sea turtles and hawksbills.

“You’re looking at a much broader swath of the population,” Van Houtan said. “You’re not just looking at adult females — you’re looking at males and females, which is really key. And then you’re looking at very young juveniles, maybe three to four years of age, all the way up to the adults that are breeding.”

After navigating more than 7,300 km (4,500 mi) and counting 3,400 turtles, the team found that green turtle populations were indeed going up, but that hawksbill turtle numbers remained low. They published their results in PLOS ONE.

‘They’re survivors’

 

Sea turtle species might be making a slow and steady recovery, but this doesn’t mean conservation efforts should be eased, Van Houtan said. Despite an increase in nests in Thailand and Florida, leatherback turtles continue to struggle. This may have to do with the fact that leatherbacks spend their entire lives in the ocean, only coming to shore to nest.

“Many sea turtle biologists believe that their offshore geography and forage habits may expose them more to fishery interactions, such as longline bycatch, and climatic variability that can create boom and bust cycles in their food, like [jellyfish],” Van Houtan said. “Recently in northern California, where leatherbacks come to forage on jellies in the boreal late summer, there has been concern about entanglement in offshore crab fishing gears — the same kind of gears that entangle whales.”

Leatherbacks also travel long distances between their foraging sites and breeding sites, and they can encounter further threats during these migrations, Van Houtan said.

“Their numbers, from Mexico to Indonesia, have dropped significantly over the past several decades,” Van Houtan said.

A leatherback turtle nesting at night on Juno Beach, Florida. Image by Loggerhead Marinelife Center.

On a global scale, it’s estimated that leatherback populations have declined 40% over the past three generations, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).

But with continued conservation efforts and better fishery management, Van Houtan says he believes that even leatherbacks can persevere.

They’re survivors,” he said. “Leatherbacks are literally dinosaurs. They’ve been around for millions of years, and they’re very resilient and can adapt.”

Citations:

Becker, S. L., Brainard, R. E., & Houtan, K. S. (2019). Densities and drivers of sea turtle populations across Pacific coral reef ecosystems. PLOS ONE, 14(4). doi:10.1371/journal.pone.0214972

Banner image caption: Green sea turtle hatchlings in Papahānaumokuākea Marine National Monument in Hawaii. Image by Mark Sullivan / NOAA.

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