Similajau National Park’s green turtle gender reveal: Girls are hot, boys are cool

Green turtle eggs discovered on the Golden Beach at Similajau National Park, Bintulu.

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By Ling Hui

THERE may be many tips and tricks to help a human mother conceive a baby boy, but for green turtle mothers, there is only but one formula: cooler sand produces more boys!

Fun fact: the sex of sea green turtles is determined by the heat of the sand incubating the eggs, a common phenomenon which is scientifically known as temperature-dependent sex determination (TSD).

For this species of green turtle discovered at Similajau National Park, Sarawak Forestry Corporation (SFC) Bintulu Regional Manager Nickson Joseph said warmer sand produces more female hatchlings, while more males will hatch in colder temperatures.

“The eggs are gender-neutral in the beginning. Their genders depend on the temperature of the sand. If the sand is warm, then the hatchlings will be female. If the sand is cold, then the hatchlings will be male,” he said.

That begs the next question: Which gender is more desirable? The answer is both, of course!

For a balanced sex ratio, Nickson said they would ensure that the temperature of incubating sand at the hatchery is not too extreme so that both genders would hatch from one batch of eggs.

At this point, it is important to note that climate change or global warming is causing a possible crisis in sea turtle sex ratios: hotter weather means more females are hatched naturally.

According to the article titled ‘Sea turtles are being born mostly female due to warming—will they survive?’ on National Geographic dated April 4, 2019, studies found that female baby turtles outnumbered males 116 to 1 in Australia.

Decades down the road, this trend could be beneficial for the sea turtle population as there are more female turtles to give birth. But a century or more in the future, the population could be lopsided.

Maximum 1 per cent survival rate

Did you know that only one or two out of 100 turtle hatchlings get to survive in the sea and grow into adults?

Sea turtle mothers lay eggs on beaches, but many never hatch. The incubating creatures may be killed by microbes, dug up by wild boars or lizards, while those that manage to break free from their delicate shells must race past other predators to make it to the ocean.

At Similajau National Park, there is a hatchery used to raise turtle eggs under controlled conditions, before they are released into the sea after about two months. Even so, danger awaits the baby turtles in the waters.

There, fish, crabs, and all manners of marine life are waiting, eager for a baby turtle meal. So, scientifically speaking, only one per cent of baby hatchlings, and maybe less, ever make it to adulthood.

DayakDaily reporters were fortunate to have taken part in the search for green turtle eggs on Golden Beach, one of the beaches at Similajau National Park, when we were on our 2022 D’Drift Trip.

The dazzling sand that gives the beach its name at Golden Beach, Similajau National Park.

It was noon time. I remember the scorching sun, and warm steps on the golden-coloured sand while we walked barefoot along the shoreline, tagging behind five SFC rangers including Nickson, who were scouting ahead and eagerly trying to locate a turtle nest.

SFC assistant ranger Mohd Hapeni, who was also our boat operator, was leading the search party, and has been working with SFC for 10 years and is very experienced with turtle behaviour.

Along the way, we stopped at two spots, hoping to find what we were looking for. No eggs were found, so we continued until we saw trails obviously left behind by a turtle which had just laid eggs.

The straddle marks indicated that the turtle had moved from the sea toward the beach, but it had to go on a detour along a sand dune that was too high for it to crawl over. At one spot where the dune was lower, the turtle mother managed to inch nearer to land.

And under the shade was where we hit the jackpot. About three feet under the sand, there was a nest with 69 green turtle eggs.

Hapeni and Nickson moved the eggs slowly and steadily into buckets filled with sand retrieved from the nest location.

The eggs were later brought back to headquarters and buried back into the sand in the hatchery where they would be safe from human activities or wild boars and lizards.

Once the eggs hatch after about 60 days, rangers would then return to the beach where the eggs were rescued and release the hatchlings into the sea. This would be done early in the morning at about 4 to 5am, mainly to avoid natural predators from eating the hatchlings.

Thanks to artificial reef balls, turtles are coming back!

For a long time before the artificial reef ball project, the turtles never came to lay eggs on the beaches of Similajau National Park, Nickson revealed.

Perhaps due to the strong waves near shore, turtles could never land on those beaches. But several years after SFC started the Sarawak Reef Ball Project, more and more green turtle landings were recorded.

“The landing rate now is at about two or three, and sometimes up to five times a month. But not all of them lay eggs; some come onshore to scout and leave, but we are definitely seeing more (landings) than last time,” Nickson told DayakDaily.

Nickson explaining the general behaviour of green turtles on Turtle Beach I.

So, why do we need reef balls, and how do they actually help?

Before 1998, about 70 to 100 adult sea turtles were found dead along the coast of Sarawak annually, particularly in the waters and beaches at Sematan and Telaga Air. Their deaths were suspected to be caused by illegal trawling activities carried out less than five nautical miles from the shoreline.

To prevent such tragedies, the Sarawak government allocated RM70 million to SFC for the implementation of the Sarawak Reef Balls Project in 2018. Artificial reef balls were randomly deployed in areas identified as the internesting swimming ground for turtles during nesting seasons.

Carved to have a sharp and rough surface, a reef ball that weighs about two tonnes becomes a tool to rip trawler nets when entangled on it. This will keep trawlers away from the sea turtles’ internesting habitats, while also helping to reduce wave heights and break waves before they reach the shore, allowing turtles to land safely on the beach.

Replicas of artificial reef balls at the Similajau National Park headquarters here in Bintulu.

On July 19, SFC dropped its final and 16,829th reef ball at Similajau National Park, marking the completion of Phase I of the project. The artificial reef balls have been deployed in 740 clusters of 20 to 30 reef balls along a stretch of 720km out of the 900km Sarawak coastline from Tanjung Datu to Lawas.

While we’re on this topic, did you know that you can take part in the Reef Ball Adoption Program at the national park? Like adopting a tree, you may raise funds to buy and deploy a reef ball as a way of protecting the endangered marine life and ecosystems in Similajau National Park waters.

The Sarawak government has already adopted over 16,000 reef balls, what about you?

The trash keeps coming, please help!

Similar to how a cat coughs up its furball every now and then, the ocean ‘vomits’ trash onto the beaches of Similajau National Park every day. Yes, every single day.

SFC staff can easily collect hundreds of kilograms of trash consisting mainly of plastic bottles, plastic containers, and polystyrene pieces with one trip along any of the beaches.

The D’Drift Team was more than glad to contribute a little to the environment by participating in the beach cleaning activity initiated by SFC during our visit. Just along Turtle Beach I, we gathered 10 large garbage bags of rubbish, while there were more left on the sands because our boats could not carry more.

SFC staff standing by bags of trash collected from Turtle Beach I together with the D’Drift Team.

While feeling somewhat content with out efforts of cleaning up the beach, we were told that more trash would be washed up from the sea the next day. Our jaws dropped. “We will never stop having to collect rubbish. It is never-ending,” they said.

Determined to keep the beaches garbage-free, Nickson said SFC desperately needs more helping hands from the public, or anyone as the matter of fact. He said once in a while, some schools or companies in Bintulu would organise beach cleaning activities at the national park, but they are not enough.

SFC strongly encourages proactivity among the local enterprises, organisations and companies to clean the beaches.

Some of the garbage washed up onto the shores of Turtle Beach I at Similajau National Park, Bintulu.

Mary, the crocodile, and trails left untrekked

“Don’t reach into the water. Mary may bite.” That was the first warning we got from SFC when our boats headed out to sea. We were reminded that the mangrove area near the dock is Mary the crocodile’s territory.

Further out, before the Irrawaddy dolphin viewpoint, is where Mary’s children would always hang out. We did not spot the reptile family, but we managed to see a pod of Irrawaddy dolphins from far.

For several minutes, we went around in circles with the dolphins as they tried to avoid our boats. Eventually, we left the mammals alone and went on our way to the beaches.

Similajau National Park has way more to offer than just turtles and beaches. If not for the maintenance works to repair damage from an earlier rainstorm during our time of visit, we would have gone on the many trails available at the national park.

These included the 450m plank walk, 600m education trail, 1.7km circular trail, 1.3km viewpoint trail, 1.35km Batu Anchau trail, 6.5 km Turtle Beach I trail, 7.6km Turtle Beach II trail, and the 10km Golden Beach trail.

The trails available at Similajau National Park.

For those who prefer an easier-going visit, a good way to get the most out of Similajau National Park is to hire a boat and be dropped off at Golden Beach and then trek back to the headquarters, or vice versa.

Boats can be hired for half a day and full day coastal and river tours, or for crocodile spotting tours at night. Camping and picnics are also allowed on any of the beaches, but visitors are advised to do so with permission and the company of a SFC guide for safety purposes.

For any arrangements, please contact the park headquarters at 019-861 0988 or the Bintulu Regional Office at 086-314 243/ 313 726/ 339 071. The park is open every day, from Monday to Sunday including public holidays, from 8am to 5pm.

D’Drift Team heading toward Similajau National Park.

Gazetted in 1978, the 8.996-hectare Similajau National Park located 30km northeast of Bintulu town, is home to 185 species of birds and 24 species of mammals, including wild boars and macaques.

In terms of accommodations, Similajau National Park offers chalets, hostels and camping in tents. There is a One-stop Customer Service Centre that houses the park office, customer reception and registration, interpretation centre and a cafeteria. — DayakDaily