70 to 80 per cent of turtle hatchlings normally make it out of their nests at Bells Beach. (ABC News: James Liveris)
In short:
Turtle hatchling numbers are significantly down in WA's Pilbara region this season.
Heavy rain from Tropical Cyclone Sean and hot temperatures have been cited as the main reasons.
What's next?
Authorities are monitoring events in the Ningaloo Reef area with laying expected to continue for another two months.
There has been a significant drop in survival rates of turtle hatchlings in two locations in Western Australia's Pilbara region following two extreme weather events.
West Pilbara Turtle Program coordinator Sarah McDonald said the rain and larger tides caused by Tropical Cyclone Sean in January led to nests being inundated.
Some turtles in the Pilbara began nesting as early as August this year. (Supplied: DBCA)
"A heavy amount of rain also creates [a surface similar to] a concrete crust on the top of the beach, which means the hatchlings find it really hard to dig their way out," she said.
Nest excavations by the team in recent weeks illustrated the low survival rate.
"Usually for Bells Beach at Wickham, 70 to 80 per cent of the hatchlings make it to the surface," Ms McDonald said.
"This year half a dozen of the 50 eggs would have hatched and made it to the surface for pretty much all the nest we've dug up.
"We've had a couple of really good years and lots of hatchling success — unfortunately this year [that] hasn't been the case."
Sarah McDonald is the coordinator of the West Pilbara Turtle Program. (ABC News: Amelia Searson)
The conditions at Bells Beach were similar to those seen in 2020 with Cyclone Damien.
Impact of heat
At Port Hedland's Cemetery Beach, 200 kilometres north of Bells Beach, the heat is believed to have led to a major reduction in surviving hatchlings.
Kelly Howlett from Care for Hedland said hot temperatures between December 20 and 23 had a significant impact.
"We found this year with the heat we had substantial drop off to the extent that we didn't see any more hatchling emergence, no little tracks on the sand, from Christmas," she said.
"That's incredibly unusual, we are normally celebrating, posting lots of pictures, getting everyone to come down and see the hatchlings over Christmas and into the school holiday period." Â Â
A turtle nest in the Pilbara. (ABC News: Amelia Searson)
Ms Howlett said the survival rate for the previous two seasons was about 65 to 68 per cent, but this year it was around 29 per cent.
"We've had 29 per cent before in 2015, 2008, 2009, so we've had it before," she said.
"The concern is that with climate change … instead of having these bad years every five or 10 years, we might get them more frequently."
Early nesters
The peak nesting period for hawksbill turtles on Rosemary Island, off the Pilbara coast near Karratha, was significantly earlier this season.
The females laid their eggs in August instead of October because the temperatures were as high as normally seen in October.
"Usually when we go out in October we would find maybe two or three hatched nests, but this year we had 75 hatched nests," Department of Biodiversity, Conversation and Attractions Pilbara marine programs officer Kathryn Bates told the ABC.
Volunteers help monitor the turtles on Rosemary Island. (Supplied: DBCA)
"They've shuffled their season just for this year," she said.
Ms Howlett said it would take time to see the true impact of this year's season, but it was concerning.
"Generally you get one in 1,000 hatchlings survive to maturity to come back and nest in 20 years," she said.
"We're estimating we might have only had about 3,000 hatchlings this season so we have got three turtles survive, when normally we're around that 60,000 [hatchling] mark."
Thousands of turtles hatch each year at beaches in the Pilbara. (Supplied: DBCA)
Ms McDonald said early hatchlings at Bells Beach and also some more recent arrivals offered some hope.
"Usually our peak nesting [period] is November/December and our peak hatchling [period] is January/February, but we did have loads of hatchlings come out in November and December," she said.
"We thought we would see nothing this week, but we actually saw a couple of eruptions where half a dozen to a dozen cracked through the concrete and got out."
Positive outlook for Ningaloo
Further south on the North West coast in Exmouth, there have been more than 2,700 nests this season with beaches south of the Vlamingh Head Lighthouse prime turtle rookeries.Â
Exmouth DBCA marine program officer Dani Rob remained hopeful their season would be more successful than what has been seen in the Pilbara.
There are more than 2,700 turtle nests in the Exmouth region so far this season. (ABC Open: Peter Wandmaker)
"We are still seeing them laying for another couple of months," she said.
"Provided we don't see any more cyclones, touch wood, we should still see decent numbers of turtles hatching and going out to the population."