Friday, August 22, 2014

First report of olive ridley sea turtle nesting on Boa Vista!

In the morning hours of Sunday, 11 August 2014, our beach patrolling team on the north-west coast of Boavista, Cape Verde, made a sensational discovery: An olive ridley sea turtle (Lepidochelys olivacea) crawled ashore and started to dig her nest as if this would be the most normal thing in the world. However, this species has never been reported to have nested anywhere in the Cape Verde archipelago!


The Cape Verde islands are the 3rd largest nesting rookery of the endangered loggerhead sea turtle. Since the beginning of this year’s nesting season teams of the Turtle Foundation were patrolling every night on various beaches of Boa Vista Island to protect female nesting turtles females from illegal poaching. At 3 o’clock a.m, field coordinator of our Boa Esperanza beach camp, Ariadna Arnau from Spain, started the last night patrol for the evening for what should have be a normal tour to protect, observe, and gather data, on the beaches of Aqua Doce and Ponta de Sol. However, she and her companion, the Cape Verdean volunteer Emanuel Lima, had absolutely no clue about the stunning surprise this patrol was about to discover.

It was a clear, bright night, and the near full moon provided excellent visibility. Ariadna and Emanuel had already observed a few loggerhead turtle nesting activity from their distinctive tracks in the sand and reported them as usual into their note books. Shortly before dawn, the shift was already approaching its end, Ariadna suddenly noticed a turtle emerging from the turbulent sea and crawling directly ashore. Ariadna and Emanuel instantly freezed and sat down in the warm sand of the beach, because they know that a turtle attempting to nest can easily be disturbed and would then quickly vanish into the sea again. Thus, before they could approach the turtle to mark it and obtain some biological data of this turtle, they had to wait patiently until the turtle finished digging her nest and begins to lay her eggs. In this situation turtles fall into a kind of “egg laying trance”, and can then be carefully approached without much danger to interrupt her nesting activity. As the movements of the turtle indicated that she already started to depose her eggs, Ariadna and Emanuel slowly sneaked up from behind the animal. But wow, this turtle looked so different! Ariadna and Emanuel were quickly remembering that last year a green turtle was observed nesting on Boavista, and that was a very extraordinary incident. However, this turtle couldn’t be a green turtle, it was far too small! Ariadna and Emanuel checked the turtle again and again, judged the size and the shape of her carapace, counted its scutes, and examined the scales of the head. There was no doubt anymore: This was an olive ridley turtle!

Olive ridleys are still one of the most common turtle species in the world, however endangered with decreasing population as are the other six species. They are also the smallest sea turtles together with their close relatives, the very rare Kemp’s ridley sea turtle, and commonly weigh not more than 50 kg, significantly less than a loggerhead. Olive ridleys are worldwide distributed throughout the tropic and subtropic parts of the oceans and nest on numerous beaches with largest abundances on the Pacific coasts of Central America, and in India. In some places olive ridleys are famous for their mass nesting behaviour, called arribadas.

On the Cape Verde islands however there is definitely no arribada; instead, this turtle is the first olive ridley ever reported to nest in this area! Of course, Ariadna and Emanuel were utterly excited about their discovery, and with shaking hands they fulfilled the standard procedures of measuring and marking the animal with flipper tags and a tiny electronic transponder, recorded the geographical data via GPS, and they took a small tissue sample that should be later analysed in the lab. The turtle was dismissive about these procedures and without any sign of agitation she continued to cover her eggs with sand, steadily alternating her flipper movements in the famous olive ridley nesting dances. As Ariadna and Emanuel finally wanted to photograph the turtle to document this unique event, they suddenly realised that they didn’t carry a camera! Emanuel immediately started to run to the camp like hell to fetch one, while Ariadna stayed with the turtle. He returned completely scant of breath, while luckily the turtle was still in place. Meanwhile, dawn had already broken, and the rising sun spent sufficient light for a great photo session! Finally, the olive ridley was satisfied with covering her nest, and with a surprising quick pace, owing to her lightweight, she headed briskly to the sea, entered the breaking waves, and was gone. Ariadna and Emanuel were contemplatively looking after her for a long time – will she come back some day?

The message of an olive ridley turtle nesting on Boavista soon spread like a wildfire through our camps and was also a sensation among other turtle conservation organisations on Cape Verde. We surrounded the nest with its 120 eggs, which we counted during the egg laying procedure, with a little fence so that it was secured from predators. We are now very eagerly awaiting the emergence of the first olive ridley turtles known to hatch on a Cape Verde island – 50 thrilling days of usual egg incubation time are in front of us! We will inform you about the hatching success, please stay tuned!