Science and Health

Tracking the rare Indian Ocean humpback dolphin in Pemba waters

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Dr Gill Braulik (left), head of Wildlife Conservation Society dolphin team in Pemba conducting a survey. PHOTO | RUPI MANGAT

Dr Gill Braulik (left), head of Wildlife Conservation Society with a team of researchers scanning the waters of the Indian Ocean in Pemba for humpback dolphins. PHOTO | RUPI MANGAT 


Posted  Thursday, April 7   2016 at  11:25

In Summary

  • The Indian Ocean humpback dolphin occurs in the western and northern Indian Ocean.
  • The species occurs very close to shore, making it particularly susceptible to the effects of human activities.
  • The Wildlife Conservation Society project is setting up a photo ID catalogue of the dorsal fins to compare with already existing catalogues of dorsal fins from Unguja set up by the University of Dar as Salaam and Newcastle University, and in Kenya with the Watamu and Shimoni catalogue compiled by Watamu Marine Association under the same project.
  • Once the dolphin researchers have evidence of whether humpback dolphins move several hundred kilometres between Kenya and Tanzania, they can look at the core areas where high numbers regularly occur and work with governments on protecting those locations.

Dolphin researchers with the Wildlife Conservation Society have been scanning the waters of the Indian Ocean between the islands of Pemba and Misali for humpback dolphins since dawn, when suddenly a pod surfaces for air.

The excitement is palpable. Straightaway, the team starts taking pictures of the dorsal fins and record the exact sighting location with their GPS. The exercise will continue for two weeks, 11 hours a day, using a local dhow, come rain or shine.

Gill Braulik, head of the WCS dolphin team, has been studying dolphins for most of her adult life. She set up a dolphin research project in Pakistan, to study one of the world’s most endangered species — the Indus River dolphin.

In Tanzania, the focus is on the humpback dolphin — the rarest of the dolphin found in the western Indian Ocean.

Dr Braulik says the project is the first complete survey of dolphins and whales in the Pemba Conservation Area.

“The Indian Ocean humpback dolphin is endangered throughout its range in the Indian Ocean. When we first started the survey, we didn’t even know we would find any, but the habitat was good so we were hopeful,” she says. “I was relieved when we found humpback dolphins here.”

From our vantage point, the pod of four humpback dolphins surface every few minutes to breathe, gliding in and out of the blue waters in bursts of speed within metres of the coastline, where local fishermen spread out their fishing nets.

The humpback dolphin lives in very shallow water always near the coast. PHOTO | AFP

The humpback dolphin lives in very shallow water always near the coast. PHOTO | AFP

“They live in very shallow water, always near the coast,” the dolphin scientist adds.

In contrast, the following day far out at sea, spinner dolphins — almost 400 in several pods leap and spin out of the water. They are more common and much less elusive.

The gill nets are the marine mammals’ greatest threat. As mammals, dolphins need to surface for air, so should they get caught in the nets, they drown.

“It’s still a mystery to us why they get caught in the nets,” says Dr Braulik.

One theory could be that at the speed they move, they may not see the nets until it is too late, or perhaps they just get careless and don’t realise the risks, she adds.

Another intriguing aspect of this research is to find out if this population of humpback dolphins ever leave Pemba island for Unguja island (popularly called Zanzibar Island) or the African mainland coast of Kenya, given that Pemba island and its smaller islands are isolated, separated from Africa by the 1,000-metre deep Pemba Channel.

“We think that they could be trapped here but we have no proof of that yet,” Dr Braulik says, adding: “We want to find out if this is an isolated small population.”

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