Celebrating student science: track that turtle!

One of our recent alumni, Nick Goldsmith (Marine Zoology – BSc (Hons) 2015), is currently one of four Scientific Interns working on a sea turtle conservation program in remote Western Australia. This year, the program will be using satellite technology to track the long-term movements of these mysterious creatures and you can follow along with the free “Turtle Tracker” App!

Sea turtles are amazing creatures that have been around for millions of years, yet there are still plenty of things we don’t know about their biology. The South-East Indian Ocean population of loggerhead sea turtles (Caretta caretta) is the least well studied of the seven populations around the world. With information on the status of this population still limited, it is critical that scientists get their feet on the ground to answer basic questions such as: How many females in this population nest in a given year? How many clutches do females lay per year? Where do turtles go in between nesting attempts? How often do females migrate to their breeding grounds to nest? How old are turtles when they mature?

 

 

 

The temperature of incubation determines the sex ratio of the offspring, with more males being produced at lower temperatures

This is where the Gnaraloo Turtle Conservation Program (GTCP) comes in. The GTCP is a research, monitoring and community engagement program located on a remote part of the WA coast approximately 1,100 km north of the city of Perth. Each year, the GTCP patrols the coast for 120 consecutive days (1 November – 28 February, including Christmas Day!). The GTCP monitors two rookeries, the Gnaraloo Bay Rookery (GBR) and Gnaraloo Cape Farquhar Rookery (GCFR), both of which are roughly 7 km long. To qualify as a significant loggerhead turtle rookery, there needs to be at least 300 nests laid annually; with an average of 417 in the GBR each year since the program was initiated, this is a significant rookery and is the largest confirmed mainland loggerhead turtle rookery in Western Australia.

Alongside the plentiful loggerheads, green turtles (Chelonia Mydas) and hawksbill turtles (Eretmochelys imbricata) are also present but in much smaller numbers. While surveys of the GCFR were initiated in 2011/12, they only cover part of the nesting season so it is still too early to determine the number of nests laid in this rookery each year.

In addition to conducting annual monitoring of turtle nesting activities, this year the GTCP will also be satellite tracking nesting female loggerhead turtles to reveal their long-term movements, and conducting sand temperature analysis to assess the vulnerability of these rookeries to climate change.

Beginning in the first week of December, ten loggerhead sea turtles will be fitted with satellite tags at Gnaraloo Bay. These devices will regularly fix and transmit a GPS location when the turtle comes to the surface to breathe, allowing us to see where they have traveled. What is so exciting about this opportunity is the fact that a FREE App has been created to allow anyone, anywhere in the world, to follow these females on their journey. The App will be up and running a few days after release of the first turtles, so you can follow them throughout the nesting season and beyond. We are hoping to discover how these turtles move while on the breeding ground near Gnaraloo and identify where they go to feed once they are done nesting! Feeding grounds are where turtles spend 75% of their time as adults, so it is critical to know where the females that nest at Gnaraloo go when they aren’t nesting. The free App is called “Turtle Tracker” and can be downloaded for Apple, Google and Windows phones now. So, when you are tucking into your festive meals, open up the App and see where the turtles have got to!

TurtleTracker1

Early-morning beach surveys are the primary method the GTCP uses to monitor sea turtle nesting. By counting and interpreting tracks that turtles leave on the beach (they typically emerge to nest at night), researchers can estimate the number of nests laid and evaluate when and where turtles choose to nest. A turtle can achieve three different activities when she emerges from the sea. First, and what we like to see for this endangered species, is a Nest. This is when a female successfully deposits her eggs into a pit dug in the sand. Second, she could achieve an Unsuccessful Nesting Attempt, where an attempt was made to dig but no eggs were deposited. Finally, a U-track is one where no digging activity occurred and the turtle simply returned to the sea after emerging. These data are analyzed to determine the nest success rate overall, among species and between different sections of the beach, which can lead to adaptive management being implemented.

In addition to early morning surveys, the GTCP uses night surveys (direct observation of nesting turtles) during a subset of the nesting season to assess how successful we are at accurately interpreting turtle tracks.

In addition to conducting annual monitoring of turtle nesting activities, this year the GTCP will also be satellite tracking nesting female loggerhead turtles

Track interpretation is challenging and even for the most experience turtle biologist, error in track assessment will occur. We therefore run night surveys, which are more time-intensive and logistically challenging that day surveys, for roughly six weeks to determine what our error rates are and improve our accuracy. We conduct night surveys until a statistically significant number of activities have been verified (i.e., directly observed) on night surveys.

The final part of the GTCP 15/16 research program looks at beach sand temperatures at differing depths. Sea turtles are like other reptiles and the temperature of incubation determines the sex ratio of the offspring, with more males being produced at lower temperatures and more females at higher temperatures. This is a very important, and potentially challenging, characteristic in the context of climate change (i.e., likely increasing sand temperatures over time). This year, led by a researcher from Deakin University, we are using sand temperature loggers to determine the temperature profile of the beach and compare these data with air temperatures from our weather station to determine how closely associated these temperatures are. Once we know this relationship, we can use historical atmospheric data to reconstruct nesting beach sand temperatures back in time and look for any potential trends. This way, we will be able to assess the vulnerability of Gnaraloo rookeries to climate change and gain additional insight factors influencing hatching success in this region.

To keep up to date with all the exciting activities that Gnaraloo Turtle Conservation Program are up to, give them a ‘Like’ on Facebook and see if they can break the 2009/10 nesting season record of 522 nests!

www.facebook.com/gnaralooturtleconservationprogram/?fref=ts

Or visit the website:

www.gnaraloo.com/conservation/gnaraloo-turtle-conservation-program

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