An Olive Ridley turtle roams the ocean. Photo courtesy WWF

We like it local: Sea turtles prefer to mate within their local ocean currents

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Very little is known about movement patterns and mating preferences of large marine animals, many of which move across entire oceans and cross a variety of habitats during their lifetime. Now marine biologists from Flinders University have discovered that turtles found across vast oceanic regions (over several 1000 km) show movement and mating preferences influenced by small differences in current circulation (just a few 100 km).

Journal/conference: Proceedings B

Organisation/s: Flinders University, The University of New South Wales

Media Release

From: Flinders University

New research has revealed how an endangered turtle capable of traversing big distances to find a mate may not do so due to seasonal ocean currents.

Contrary to other species of sea turtles, Olive Ridley turtles show high nomadic behavior and very low fidelity to the beach they are born - however they’re less likely to journey large distances to find a mate when currents aren’t favourable, a world’s first study published today in Proceedings Breveals.

Researchers lead by marine biologists at Flinders University in Adelaide have studied Olive Ridley turtles across a large coastal region of the tropical eastern Pacific Ocean known to have complex ocean circulation.

They generated DNA data for over 600 turtles collected at 27 nesting beaches in five countries, from Mexico to Panama.

Then, they compared the connectivity across the region inferred from genetics with patterns predicted by models of current circulation for different seasons of the year.

“Surprisingly, we showed that connectivity is largely reduced in these turtles because of the influence of dynamic ocean circulation during the migration and mating seasons, but not in other periods of the year”, says one of the authors Professor Luciano Beheregaray.

It shows that turtles found across vast oceanic regions show movement and mating preferences influenced by small differences in current circulation.

This suggests that turtles follow the currents and are adapted to seasonal oceanographic differences across the region, providing cost–benefit solutions that might be particularly advantageous for females during the breeding season.

Very little is known about movement patterns and mating preferences of large marine animals – some can move across entire oceans and cross a variety of habitats during their lifetime.

This behavior spreads their genes and reduces differences between animals born in different regions. This was thought to be the case for the Olive Ridley sea turtle.

This is the first study to show that these sea turtles, despite being capable of moving across very large distances, show connectivity reduced by their ocean environment. “This finding is very relevant for the conservation management of this endangered species in the eastern Pacific, a region that represents the main area of reproduction of the species in the world”, says author Dr Clara Rodriguez-Zarate.

Sea turtles and other large marine animals are threatened by multiple human activities, including fisheries, pollution and climate change. “Understanding how marine animals perceive their environment and how this impacts on their movements is essential for addressing human impacts and for informing conservation management”, says Professor Beheregaray.

Researchers from University NSW, Imperial College London, Mexico (National Council for Science and Technology) and Nicaragua (Fauna and Flora International) supported the study.

This work has been published in the Proceedings of the Royal Society of London B:

Rodríguez-Zárate CJ, Sandoval-Castillo J, van Sebille E, Keane RG, Rocha-Olivares A, Urteaga J, Beheregaray LB (2018) Isolation by environment in the highly mobile olive ridley turtle (Lepidochelys olivacea) in the eastern Pacific. Proceedings of the Royal Society of London B http://dx.doi.org/10.1098/rspb.2018.0264

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