Marine Turtles

FIVE of the world's seven turtle species occur in Irish and British waters. The most frequent visitor is the leatherback turtle, followed by the loggerhead turtle. Both are usually seen regularly in late summer. The others are the Kemp's ridley turtle, hawksbill turtle and green turtle, which are only rarely seen, and most usually dead.

Leatherbacks and loggerheads have been reported every year in Ireland particularly off the west and southwest coasts, usually from August to October when the sea is at its warmest. Official sightings from sea observatories on the west coast report both individuals and groups of turtles moving past during this time.

Leatherbacks are partially warm-blooded, enabling them to survive in cooler water and at temperatures that other marine turtles may not tolerate for long. Loggerhead turtles are also cold-tolerant to some extent. In stormy conditions young loggerheads may be found cold-stunned on the coast of Ireland and Britain.

The exact origin of leatherbacks and loggerheads in the North-East Atlantic is not fully understood, but in 1997 a turtle found drowned in Wales had a tag that had been fitted on a breeding beach in French Guyana on the north coast of South America. Other breeding beaches are in the Caribbean and Gulf of Mexico. From here the clockwise currents of the Atlantic Ocean gyre bring animals east on the Gulf Stream/North Atlantic Drift. One recent estimate suggests that there may be fewer than 35,000 breeding female leatherbacks in the world, and they are known to be declining in many places.

Marine turtles feed on a variety of prey items, particularly jellyfish. Leatherbacks are known to feed on deep-sea jellyfish at depths exceeding 1,000m. They are potentially threatened by entanglement in fishing gear (nets, lines and pots), which leads to drowning, and from ingestion of marine debris — especially plastic bags which are eaten because they resemble jellyfish — leading to death from suffocation or gastro-intestinal blockage.

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