Posted by admin | 10.24.2011 | Conservation, Marine Science, Turtle Talk

Arribadas: A Mass of Questions

If seeing one sea turtle nesting on the beach is a special sight, imagine the exceptionality of thousands crawling out of the ocean en masse. This is the scene that plays out on select beaches when the ridleys come for the arribadas. An arribada (Spanish for arrival) is a mass, synchronized nesting event exclusive to the ridley species: the Kemps ridley of the Atlantic and the olive ridley of the Pacific.

Over a period of 2-3 days, thousands of females come ashore to deposit eggs. Despite the enormity of this event, much of the science is unknown. Recent research pfrom Journal of Animal Ecology sheds more light on this  by studying skin samples and data loggers of olive ridleys in French Guiana. Scientists have revealed surprising information about the species’ history: while increasing in the past 10 years, they are recovering from a massive collapse that occurred in the last 2,000 years – a collapse that wiped out about 99% of the population.

One of the largest recorded arribadas took place in Ostional, Costa Rica when a calculated 500,000 olive ridleys floated in on the tide and laid eggs en masse. Due to the volume of eggs that are laid, scientists have determined that several of the approximately 10 million eggs laid in the first night of the event are destroyed due to the increased activity. Therefore, the government of Costa Rica has allowed the harvest of eggs on the first night of the arribadas by the families residing in Ostional. And with this decision comes much controversy.

Ostional is the only beach that allows poaching of the eggs, but it provides a dangerous precedent for other beaches within the country and around the world. The argument being if Ostional can do it, why can’t we? By creating a market for sea turtle eggs, it now becomes difficult to discern where eggs actually originated from. In addition, while the same per person quota remains the same since the plan was introduced in the 1980s, the number of individuals involved in the harvest has grown dramatically.

The mysteries of the arribadas still remain. What caused such a dramatic decline in the olive ridleys of French Guiana? What are the long-term effects of harvesting at Ostional? What cue allows these thousands of turtles to synchronize their behavior? Hopefully each arribada will provide a little more insight into these questions.