New study into turtle mystery

Aliza Khatun is researching why baby turtles aren’t surviving to join the adult population. Photo by David Bell.

NESTING season has started for Hyde Park’s oblong turtles, and UWA researcher Aliza Khatun is calling on parkgoers to report any turtle nesting movements so next years’ hatchlings can be monitored.

“We need people’s help especially in the nesting season from October to February…to let us know if they see any turtles laying eggs,” Ms Khatun says.

“It’s not an easy task to find nests” if the laying turtles aren’t spotted and reported, as the turtles cover them over and they are nearly invisible.

Sex imbalance

Vincent council is funding UWA’s ongoing research into the lake’s turtles supervised by Roberta Bencini and Gerald Kuchling. It started in 2015 after reports of fewer hatchlings being sighted, and in previous years studies looked at whether the hatchling shortage could’ve stemmed a sex ratio imbalance among the adult turtles, or from fertility problems. But trapping and examining the adults showed a pretty even ratio and the females appeared fertile, and they were found to still be nesting. 

Ms Khatun is undertaking this new study for her PhD and says “my main objective is to determine the factors that affect survival and recruitment”–the hatchlings joining the rest of the population. Some eggs may not be hatching, and the ones that do could be being eaten by dogs or birds. 

She will also investigate the huge variation in egg incubation times. Usually these turtles’ eggs hatch in 60 to 230 days. But some of the nests that were laid last November didn’t hatch until September, around 300 days after they were laid. 

“It may depend on air temperature and soil temperature, humidity, and rainfall,” Ms Khatun says.

She has also found nests with no viable eggs: Some may have been eaten by ants, others appeared to be unfertilised. 

Once the nests are located they can be carefully monitored next hatching season when the babies emerge. 

This season Ms Khatun monitored 26 hatchlings that came from three nests. 

“We weigh them, measure them, and release them to observe the movement of the hatchlings and monitor if any predators attack them.”

Ms Khatun is from Bangladesh and hopes to use the findings here to help the endangered turtle population back home. 

“In our country, we need to take action and find management strategies to protect our turtles,” she says. The Bangladesh turtles are shorter necked but otherwise very similar, so it’s likely the same factors are affecting both populations.

The turtle is an important component for the ecosystem, both for its role in controlling insects through its diet, and because of what they can say about the ecosystem’s health: If there are no turtles, there may be a problem. 

The turtles will be regularly making their way out of the lake to nest, preferring to come out in the afternoon. If you see any, give them plenty of space but note where they’re headed and call 6488 2521.

by DAVID BELL

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