New research has uncovered patterns of biological, genetic and developmental change in marine turtles of the Kimberley that could change the way the region is managed.
Marine turtles in the Kimberley nest throughout the year, with flatback turtles stocks separating into distinct summer or winter nesters; generally separated by the Dampier Peninsula.
During breeding season, female turtles emerge from the water and crawl up the beach to dig a nest for a clutch of eggs. Flatback turtles will lay about 50 eggs per nest, while green turtles will lay around 100 eggs per nest. Typically, each female lays between three to five clutches of eggs a season before making the journey to a foraging ground to replenish energy until the next migration 2-4 years later.
|Overlap of summer and winter tracks occurs between Lacepede Islands and Dampier Peninsula (WAMSI)|
Distribution and Abundance by Parks and Wildlife (Marine Science and GIS Units), and Pendoley Environmental researchers
Aerial counts of turtle tracks along island and mainland beaches found the winter track counts highest at Cape Domett, South Maret, Parry Island and Vulcan Island. The summer track counts were highest at the Lacapedes Islands, Eighty Mile Beach, Maret, Cassini and Oliver Islands.
|Ground view of turtle tracks at Cape Domett. Photos (Parks and Wildlife)|
Genetic Analysis by Griffith University and CSIRO researchers
Previous genetic studies recognised four major flatback population stocks in Australia. However, the early results from the Western Australian Marine Science Institution’s (WAMSI) Kimberley Marine Research Program discovered five genetic breeding stocks in Western Australia alone.
The previously recognised stocks included the Pilbara and Cape Domett stocks. Three newly recognised stocks are provisionally referred to as the Eighty Mile Beach, Ecobeach, and Maret Island stocks.
The green turtles of the Lacepedes were also a different genetic stock than previously recognized. The research team of Nyul Nyul rangers and CSIRO are taking a skin biopsy from a day-time nester. (Parks and Wildlife)
According to project leader Dr Scott Whiting from the Department of Parks and Wildlife, the new WAMSI data is also updating the thinking about the green turtle populations.
“Of particular interest was the relationship between turtles from the coastal Kimberley (Lacepede Islands) and Northwest Cape,” Dr Whiting said. “An earlier analysis, based on limited genetic sampling, indicated that these distant regions (>1000km apart) should be considered a single stock. In a new analysis with more data, green turtles nesting at the southwestern extremity of their Australian range (Barrow Island & Northwest Cape) were significantly genetically distinct from those at the Lacepede Islands and so could be considered distinct stocks.”
Effects of Temperature by The University of Western Australia researchers
Another aim of the WAMSI turtle project is to understand the effects of a changing climate on turtle populations. Climate change has the potential to significantly alter the balance of populations as incubation temperature determines the sex of the incubating turtle embryos.
To investigate this question the researchers incubated summer and winter flatback and summer green turtle eggs to record the temperatures that produced mixed sexes, and the temperature producing an equal number of sexes. Predictions based on global climate models were used to adjust temperatures to allow for future projections.
Traditional Knowledge by the Kimberley Indigenous Saltwater Science Project and established ranger groups
A fourth component being developed is to incorporate traditional knowledge about turtle populations from 11 Traditional Owner groups on Country to improve outcomes for management activities in the region’s Marine Parks and Indigenous Protected Areas.
Flatback turtle with satellite tag attached in Eighty Mile Beach Marine Park. Eighty Mile Beach is a newly identified new flatbacks genetics stock determined in the WAMSI study. Participants included the Nyangumarta, Ngarla, and Karajarri rangers, Marine Park staff, Marine Science program staff and Murdoch faculty and students. (Parks and Wildlife)
The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley.