Feature

From crocodiles to sea-turtles

Karin Theron

With a management plan and nesting sanctuary in place for the threatened Nile crocodile (Crocodylus niloticus) population of the Okavango Delta in Botswana, Stellenbosch University's Crocodile "dundette", Dr. Alison Leslie, continues with her crocodile research in Zambia, but is now focusing her research on sea-turtles.

Dr. Leslie has now embarked on a sea-turtle research project with the aim of contributing to a management plan for the conservation of Leatherback and Loggerhead sea-turtles in Kwazulu/Natal, where one of the only major nesting colonies on the east coast of Africa occurs.

The primary nesting area is a 56 km stretch of beach between Kosi Bay and Mabibi and the research site currently being monitored by MSc student Chris Boyes spans 30km of this coastline. This site is the only major Leatherback (Dermochelys coriacea) nesting colony on the east coast of Africa and in the eastern Indian Ocean.

Leatherbacks are the largest of the sea-turtles and have the widest range, even entering polar waters, but, according to dr. Leslie, their nesting activities are still limited to a few very specific breeding beaches usually in tropical and subtropical regions around the world. Dr. Leslie completed her masters' thesis on the nesting ecology of Leatherbacks way back in 1993 in Tortuguero National Park in Costa Rica.

"The worldwide state of sea-turtle populations is dire at this moment in time, and without concerted research and conservation efforts, these populations will fast disappear. Of the seven turtle species in the oceans, the Leatherback is one of the three species classified as critically endangered," she explains.

Monitoring of these two species started along this coast in 1963 by the former Natal Parks Board. "This colony is a seemingly healthy population. Few populations in the world display such signs of stability, making it important to understand as much as we can about this population in order to know why this population is more successful than others, specifically from a management point of view."

More recently Wilderness Safaris (one of the concessionaires to the area) was given a permit to assist with a monitoring programme in the research area. As a result the monitoring programme has intensified substantially. During the nesting season (October to mid-March), turtles are tagged and various measurements are recorded.

"No detailed study has however been undertaken in this research area on nesting ecology where nests are monitored for the duration of the incubation period. Consequently we currently have a rough estimate as to how many nests are laid per season, but we have no idea as to what is actually happening to each of these individual nests. This is an essential ingredient when it comes to managing a population of an endangered species," she says.

"Although the monitoring has provided valuable information for management actions, more baseline data with regards to nesting ecology of both species is required. We need to know how many of the nests are actually surviving to hatching, what the hatching success of these nests is, what percentage of hatchlings are in fact entering the ocean (recruitment), and with current global climate change issues, what is the estimated sex ratio of hatchlings and how predicted global warming may affect these ratios."

Dr. Leslie and her students' research have so far found that the mean hatching success for loggerhead nests was 85,5% and 79,9% for leatherbacks. However, not all of these hatchlings were able to leave the nest. A higher percentage of leatherbacks were not able to leave the nest, most probably because their nests are deeper. It then seems that honey badgers, ghost crabs, jackal and dogs were the main culprits for predating emerging hatchlings and those on their way to the sea. Scientists estimate that only approximately 2% of hatchlings survive and return to the breeding beaches.

Dr. Leslie urges turtle watchers to adhere to the international code of conduct:

• Limit groups of turtle watchers to no more than 20 people per turtle. The group must remain together.
• Drive/walk along the beach a few hours either side of low tide looking for tracks. Never drive/walk above the high tide mark.
• Do not approach or shine lights directly on turtles leaving the water or moving up the beach, either with vehicle lights or flashlights.
• Use red lights as they have the least impact on the turtle's eyes.
• Avoid excess noise and sudden movement at all times.
• Position yourself behind the turtle and stay low. If you are getting covered in sand as she digs you are too close!
• No contact with the nesting female is permitted except for research purposes.
• Be patient. She may abandon the nest and dig another one for a variety of reasons including hitting an obstacle or the sand being too dry.
• Wait until she is about halfway through the laying process before moving closer, shining your torch, taking photos from behind or carrying out research actions. She is then usually in a comatose state, but still no flash photographs may be taken of the turtle standing directly in front of her. Flash photography must be ceased as soon as she starts moving towards the ocean.
• Give her enough space to camouflage the nest.
• Let her return to the ocean without interruption.

More information:

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