Olive Ridley turtles choose mates of similar size, reveals new study

A study published in the journal Ecosphere by scientists from the Kolkata-based Zoological Survey of India (ZSI) and the University of Michigan revealed that olive ridley sea turtles—a vulnerable species listed on the IUCN Red List—prefer mating with partners of similar size.
Some species of animals where males maintain a territory, are bigger in size as compared to females. In contrast to these animals, Olive Ridley females are bigger in size to accommodate the eggs inside their body. The Olive Ridley Sea turtles do not mate with random sized mates. They are mating with a preferred sized mate, the research finds.

The research, conducted over two years at Odisha’s Rushikulya rookery, one of the world’s largest mass nesting sites for the species, involved capturing, tagging, and measuring 134 mating pairs. The study found a strong positive correlation between the sizes of male and female turtles, indicating size-assortative mating behaviour.
“This preference may be shaped by biological advantages,” said Dhriti Banerjee, ZSI director. “Larger females tend to lay more eggs, and larger males may have a competitive edge during mating.” The team also recorded signs of intense mating competition, including bite marks on females and instances of multiple males attempting to mate with a single female.
Olive Ridley turtles are important because they are crucial in maintaining healthy marine ecosystems. They are a vital part of the food chain, helping regulate populations of other marine organisms, like jellyfish. Additionally, their nesting habits on beaches enrich coastal ecosystems and contribute to biodiversity.
Their nesting on beaches enriches the environment by contributing to the nutrient cycle and providing habitat for other species.
The research was led by Basudev Tripathy and Anil Mohapatra of ZSI, along with Anshuman Swain from the University of Michigan and Ashis Kumar Das and Sandeep Kumar Mohapatra from ZSI’s Gopalpur-on-Sea centre.
The study not only sheds light on a previously little-understood aspect of olive ridley behaviour but also underscores the importance of targeted conservation. “There are many unknown aspects of the biology of olive ridleys. Monitoring and reducing high sea mortality is essential for their long-term survival,” added Banerjee.
The Rushikulya rookery, discovered in 1994, has shown a steady rise in nesting females thanks to sustained conservation efforts. Tripathy, who has monitored the beach for nearly three decades, noted the positive trend: “The number of nesting females has been growing due to our persistent protection and habitat monitoring work.”
The need to protect Olive Ridley turtles and their nesting grounds underscores the importance of their role in maintaining healthy ocean ecosystems.