Using satellite tags to track Hawksbill turtles after nesting on Arnavon Islands
IF YOU look carefully on Solomon Island beaches you may see turtle tracks; distinctive lines in the sand that are made by female turtles as they crawl up the beach to lay their eggs.
Recently a team of scientists, community members and staff from the Ministry of Environment Conservation, Climate Change and Disaster Management went to the Arnavon islands to study turtles, but on this occasion they were hoping to track turtles across the water – by attaching satellite tags to their shells.
The Arnavon islands are located in the Manning Strait between Isabel and Choiseul Province, with this small island group supporting the largest remaining nesting grounds for critically endangered hawksbill turtles in the Western Pacific.
Harvesting of hawksbill turtles for their shells commenced in the Arnavons in the mid-1800s, and 150 years later in the early 1990s the number of nesting hawksbills at the Arnavons was critically low.
This pattern of severe decline followed global trends, and excessive hunting of hawksbill turtles for their shells has resulted in this species being listed as critically endangered under the International Union for the Conservation of Nature (IUCN).
When a species is listed as critically endangered it means it is at very high risk of global extinction in the near future if efforts are not made to conserve it.
While hunting has caused global declines in hawksbill turtles, their biology is also partly to blame.
Hawksbill turtles grow very slow, with females not having their first clutches of eggs until they are 30- 35 years old.
Furthermore, most baby turtles die, with only 1 in 1000 surviving to adulthood.
Turtles have inbuilt compass in their heads and that they will only come back to nest where they are born.
This means that the turtles that are nesting in the Arnavons islands crawled down those beaches over 30 years ago, and were able to survive numerous ordeals to come back to nest in the Arnavons again.
The genetic studies have also proven that turtles in the Indo pacific are ocean specific, meaning that they will never travel to another ocean in the world for breeding.
Fortunately for the Arnavons hawksbill population, the Solomon Islands government banned the sale of all turtle products in 1993, and in 1995 the Arnavon Community Marine Conservation Area (ACMCA) was established, a partnership that involves the communities of Kia, Wagina, Katupika, The Nature Conservancy, The Ministry of Environment, Climate Change, Disaster Management and Meteorology (MECDM) and Isabel and Choiseul provincial governments.
Since protection in the mid-1990s the numbers of hawksbill nest laid in the Arnavons have doubled, providing early signs of recovery.
To study turtle movements of hawksbill turtles that nest on the Arnavons the tracking team conducted their work from 12 – 21 April.
With the help of ACMCA rangers, ten female turtles were captured from the beaches of Sikopo, Kerehikapa and Maleivona, the islands that make up the Arnavons group.
Capturing ten turtles required teams to walk each beach throughout the night, waiting for nesting females to crawl up the beach.
Once a turtle was found, it was left alone to nest, then after nesting it was captured and taken to the field station at Kerehikapa for tagging.
The following morning fibreglass was used to attach a satellite tag onto a high point on its shell, and six hours later, when the fibreglass was dry, the turtle was released.
When the turtle comes up to the surface to breath, the satellite tag comes out of the water and communicates with satellites in the sky, and the precise position of the turtle is identified.
The Director for The Nature Conservancy’s Melanesia Programme Richard Hamilton explains the purpose of the tagging “April is the start of the peak hawksbill nesting season in the Arnavons and in any one season a female turtle may lay between 3-5 clutches of eggs, with approximately two week interval between each clutch. By tagging early in the season we hope to answer three questions; 1) how much time does a female turtle spend within the Arnavons protected area during her entire nesting season? 2) Do the turtles always nest at one specific beach in the Arnavons, or do they also lay some clutches in the outer islands in the Manning Strait, and 3) where do the turtles migrate back to once they finish nesting in the Arnavons?”
This is not the first time satellite tagging has occurred on the Arnavons.
In July 2001 two hawksbill turtles that were nesting at the Arnavons were fitted with satellite tags, with information from these tags showing that one tagged turtle swam back to its feeding grounds in Milne Bay, Papua New Guinea, and the other swimming back to the Great Barrier Reefs in Australia.
But in the past 15 years satellite tagging technology has become far more advanced, with satellite tags now having the ability to collect very accurate location information on a frequent basis.
“By tagging ten turtles with latest state of the art satellite tags we will be able to learn a great deal more about the Arnavon Islands hawksbill population than ever before” says Simon Vuto, Marine scientist for the Nature Conservancy’s Solomon Islands Programme.
This research was very successful, with ten female turtles being fitted with satellite tags as hoped.
On 2 May, seven of the turtles were still swimming around the ACMCA, while three had finished nesting and had begun migrating back to their feeding grounds.
All three turtles that have finished nesting swam across the Isabel Trough to the southern end of New Georgia, and the turtle that has swum the furthest is named Dora.
Currently Dora is over 100 km south of New Georgia, on her way back to her feeding grounds most probably in Australia or Papua New Guinea.
The Conservancy plan to have a live feed on their website soon in order for people to be able to follow the movements of these ten turtles, and shortly the winners of the primary and secondary school turtle naming completion that was recently advertised will be announced.
The two students who win this completion will have their winning entries published in the paper and will get to name two of the turtles that had a satellite tag placed on it.
Finally, Henry Kaniki, ACMCA Co-ordinator had this to say “If you are fisherman and you see a hawksbill turtle with a satellite tag on its back, please don’t kill it. Hawksbill turtles are an important part of Solomon Islands culture, and this study is helping us learn more about them. By learning more about their biology hopefully we can ensure that the hawksbill turtle remains a part of our culture well into the future”.
— TNC PRESS
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