Most nesting concentrated in very few locations
Olive ridley populations are in sharp decline due to a familiar list of causes including poaching of eggs, beach development, fishing, and pollution.
The belief that turtle eggs have aphrodisiac properties is a major threat to olive ridley populations in Central and South America. Like the Kemp's ridley turtle, the olive ridley will always be vulnerable because such a large proportion of its reproductive effort is concentrated in only a few locations.The abundance of olive ridleys at a few rookeries has led to the impression that these turtles may not be endangered. But human-caused or natural disturbances to nesting beaches and inter-nesting areas can have huge repercussions on the whole population.
For example, Hurricane Pauline destroyed nearly half a million nests, the equivalent of 40 million eggs and 10 million hatchlings, on La Escobilla beach, in the state of Oaxaca, Mexico, in 1997. A species already under intense threat from human activities can scarcely afford such heavy losses.
Directed take
The Galibi Nature Reserve, Suriname, hosted the largest and most important olive ridley nesting population in the western Atlantic. Thousands of females were nesting there in the 1960s, but nearly all the eggs were harvested by local villagers. Conservation efforts were resisted forcibly by the local villagers. In 1989 only about 450 females came ashore. A survey in 1995 counted just 335 olive ridleys nesting in this area.
The illegal nature of the turtle egg trade makes it difficult to estimate the impact on olive ridley populations but seizures of eggs are not uncommon. The largest on record occurred in October 1996 in Mexico City, when a lorry was seized containing over 500,000 olive ridley eggs, taken from a single beach. The size of this haul indicates a large demand for eggs in Central America and the Hispanic communities of California and Florida.
Olive ridleys were once killed in large numbers for meat and leather. There were many economically important slaughterhouses on Mexico's Pacific coast, where officially over 1 million turtles were killed each year during the 1960s. This slaughter was reduced when legal quotas were introduced, but an illegal industry still does occur, although fortunately not to the extent of the earlier years.
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Indirect take
Perhaps the most threatened nesting site is located on India's eastern coast at Gahirmatha, in the state of Orissa. There, no 'arribadas' occurred in 1988, 1997, 1998 and 2002. The number of dead olive ridleys found stranded on the Orissa coast increased from 5,000 per year in 1994 to 13,000 turtles per year in 1999, which represents a total of 46,000 dead turtles in 6 years. Current mortality rates are estimated at 15,000 turtles per year.
The main cause of this mortality is thought to be in-shore mechanised fishing, in particular shrimp trawling, which is actually illegal in that area. Mechanised fishing is illegal within 5 km of the coast and within 20 km of the Gahirmatha coast (35 km). But reports suggest that fishing intensity has gone from approximately 1,000 mechanised boats in the late 1980s to approximately 4,000 boats by 1996.
Moreover, these turtles are threatened by widespread coastal development for industry and private use, predation by domestic dogs and stock, and upstream abuse of rivers that affects the estuaries close to nesting sites. Mangrove forests that have in the past protected the Orissa coast from erosion are being cleared to make way for a missile testing range and shrimp ponds.
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