UWA returns, aerial survey at Gnaraloo and first loggerhead hatchlings

Hi everyone,

First and foremost I’d like to thank you all on behalf of our team for following our news updates and field diaries. One of our goals here at GTCP is to engage the public in turtle and marine conservation issues, and we are delighted to be able to do this as well as inform you of the research undertaken and events occurring at Gnaraloo during this year’s nesting season!

Despite having comparatively fewer turtles nesting along our study site this month, which may indicate the end of the peak nesting period observed during late December, we have been quite busy! On 19 January 2011, the research team from University of Western Australia (UWA) arrived for their second field trip. As well as collecting new data and furthering their research, they analysed results of the work undertaken during their last trip in November. Preliminary results showed the heavy late December rains having clear impacts on the thermal properties of the nests across the study site. It was also recorded that nests with the same number of incubation days were at significantly different stages of embryonic development, demonstrating the impact of nest site selection on clutches. Of the 4 nests which were monitored by UWA researchers, 1 had been extensively predated by crabs, with only some shell fragments remaining in the nest after the incubation period. These results are of interest to the GTCP, and Lorian’s further analysis of results once she returns to the UWA will undoubtedly reveal more complex findings.

On 23 January 2011, the 3 ‘turtles’, as we are known at Gnaraloo, carried out an aerial survey along Gnaraloo station’s 65km coastline. The aim was to determine the extent and distribution of nesting female activity along beaches outside of the monitored study area, which currently represents about 10% of Gnaraloo’s coastline, and to identify any additional rookeries. During the 45min flight, 28 activities were recorded, which we estimate may have been up to 3/4 days old. The majority of these activities were concentrated along an 8km stretch of beach close to the station’s northern boundary. These findings are consistent with those of surveys carried out in previous years, indicating a consistently used, significant rookery in this area. The relatively narrow distribution of activities along the station’s coastline seems to be linked to the extent of beach exposure to the open ocean. GTCP researchers in 2009/10 found that sections of the monitored rookery with open access to the ocean have deeper water and higher wave energy than sections bordered by fringing coral reef, and tend to have a higher nesting density and overall turtle activity. The same trends have been observed during this year’s season to date.

Following the aerial survey, on 24 January 2011, while carrying out morning track monitoring, our team saw this season’s first hatchlings emerging from their nest! It takes approximately 60 days for embryos to develop, and we are monitoring the incubation period as well as estimating the number of hatchlings by counting the tracks leading from the nest to the high tide mark. All 3 of our GTCP researchers, as well as volunteers currently onsite, have been able to witness hatchlings over the last 2 days due to our presence on the beach in the early mornings. Generally hatchlings emerge throughout the night until dawn, when cooler temperatures allow them to reach the ocean unharmed by the heat of the sun. Out of a total of 9 hatchlings observed, 4 had been predated by crabs, both by the golden ghost crab (Ocypode convexa) and the running ghost crab (O. ceratophthalma). The predation of Loggerhead hatchlings by running ghost crabs had not previously been documented along the GTCP survey area, and this reinforces our wish to further analyse the impact of crab activity on nest hatching success rates in Gnaraloo. Hopefully we can research this next year!

Cheers, Marie