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First Major Genetic Study of Elusive South African Dolphin Reveals a Species in Peril

The views expressed are those of the author and are not necessarily those of Scientific American.


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Heaviside-DolphinIn 1828, in a short paper in the journal Spicilegia Zoologica, British zoologist John Edward Gray reported six “new and undescribed” marine animals, among them a small dolphin found off southern Africa’s Atlantic coast. The specimen had been brought to him by Thomas Haviside, a captain for the East India Company, who encountered the dolphin off the coast of Namibia. Gray dubbed the species Haviside’s dolphin.

Unfortunately, Gray and those who followed him made a slight mistake in describing this species. They confused Capt. Haviside with the similarly named Capt. Heaviside, a British surgeon who collected cetacean species. The name Heaviside’s dolphin (Cephalorhynchus heavisidii) has since stuck.

Precious few scientific studies of the Heaviside’s dolphin have been published in the nearly 200 years since its first description. One paper in 1977 described its underwater sounds, a topic a few other studies have echoed. Another project in 2004 tracked six dolphins via satellite to learn about their range and movements. A 2006 study looked at genetic variation within the species, which suggested a high level of homogeneity within the dolphin’s populations but made few conclusions. A 2008 study tried to estimate the population size for the species, but it suffered from a lack of data.

That was about it—until now. A new genetic study conducted by Keshni Gopal as part of her doctoral research at the University of Pretoria in South Africa has revealed some bad news for these poorly understood dolphins. They are all related and the removal of as few as 15 individuals per year from the total population could have dire consequences on future breeding and population size.

For her study, Gopal collected samples from 395 individual dolphins, a difficult task that took four hot summers. “Since these dolphins come inshore in the early hours of the morning, I had to be out at sea very early,” she says. Over time she developed the coordination necessary to collect biopsy samples from the fast-moving dolphins with a pole-spear called a Hawaiian sling. “The dolphins sometimes made it extremely difficult for me to take a sample,” she says. “When I was unsuccessful at taking a sample, they were more wary of me.”

Once she finally had enough skin samples, Gopal tested them for molecular markers such as microsatellite loci, which are genes inherited from both parents. The results show that Heaviside’s dolphins live in two major metapopulations that have little to no migration between them. The southern metapopulation, in South Africa’s Table Bay and Saint Helena Bay, had the greatest level of relatedness. She was also able to identify six smaller subpopulations, which show signs of interbreeding but to a lesser degree.

Gopal says this genetic information is important because so little is known about the dolphins’ social biology. In particular, scientists don’t know how often they breed, which would be an indication of how quickly they could recover from population losses. The species faces a potential threat from the nearby hake fishing industry, which uses longlines and trawling nets that could entangle the dolphins. “The amount of Heaviside’s dolphins and other marine mammals caught in these nets are unknown, as it has not been recorded,” she says.

Gopal, who is currently taking time after graduation to travel and write up her research for publication, says she looks back on her Heaviside’s dolphin research as an incredible experience. “It was amazing to be out at sea during that time, as I have seen many things—inquisitive southern right whales coming up to the boat, being surrounded by a school of common dolphins and dusky dolphins, moving through waters with millions of bell jellyfish and sunfish, and, when the water clarity was superb, looking down to the bottom of the inshore coastline.” She also made connections with local recreational and subsistence fishermen who use small boats and dinghies to catch crayfish and who value the Heaviside’s dolphins. They report back to her whenever new individuals are spotted.

Obviously there is still much to learn about the Heaviside’s dolphin. Hopefully it won’t take another few decades before that happens.

Photo: Jutta Luft via Wikipedia. Used under Creative Commons license

John R. Platt About the Author: Twice a week, John Platt shines a light on endangered species from all over the globe, exploring not just why they are dying out but also what's being done to rescue them from oblivion. Follow on Twitter @johnrplatt.

The views expressed are those of the author and are not necessarily those of Scientific American.





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