Rare, pregnant dolphin dies

14th December 2007

Much to the concern of researchers monitoring cetaceans in Cornwall, the body of another rare dolphin has washed ashore on the Lizard. The female bottlenose dolphin measured around 3.2m in length and weighed 370 kg. She was carrying a female calf 80 cm long, weighing 6.2 kg.

"We were very concerned to see this dolphin because, although we record so many, it's always particularly sad to find pregnant females, especially when it's one of this species. It means that we've lost two generations of a scarce animal in one stranding," said Jan Loveridge, one of the coordinators of the Marine Strandings Network for Cornwall Wildlife Trust.

"We received a call via our Hotline coordinator, Maddie Precious, that the dolphin had been reported dead on the beach.

We went down right away, as the tide was still coming in and we were anxious that it didn't get washed out again. It was a foul day with very strong winds and huge seas, so we could never have retrieved it safely if it did float off again."

 

A team of 10 volunteers was mobilised to retrieve the animal, which had apparently died only a short time before. It was taken to be examined at the Veterinary Laboratories Agency in Truro. "Luckily, the dolphin was quite close to the slipway, but we still had the problem of how to get it up off the beach, especially with the surf lapping at our feet" said Mike Lord, another CWT volunteer.

"Fortunately one of the team, Rory Goodall, was able to reverse his four-wheel drive down the slipway. We laid a path of slippery kelp, which made a perfect slide and protected the animal from being damaged, and towed the dolphin over the rocks and straight up into the trailer. It was fantastic team work and having a tow meant that we could secure it safely and quickly," said volunteer Lesley Jarvis. "It was a really beautiful animal. She had lots of very distinctive notches on the dorsal fin, tail fluke and flippers and getting up close to her, you realise just how huge and how powerful these animals are. There were lots of rake - or bite - marks on her made by other dolphins. Some of the marks were nearly a metre long, which shows how aggressive they can be towards one-another. They aren't always the friendly, gentle animals we assume them to be."

Jan Loveridge continued, "It's quite possible that the dolphin stranded alive, but there was no obvious cause of her death. However, she was only in moderate nutritional condition, which often indicates disease, and this, together with the extremely bad weather at the time, may have resulted in her stranding. We'll have to wait for the full post mortem test results to come through before we can be more certain."

Nick Tregenza is a local expert on cetaceans and studies bottlenose dolphins in particular. "We can’t be sure whether this female comes from a tiny group of bottlenose dolphins that are struggling to survive around the coast of Cornwall, or from a large group of this species that lives much further from our coast. Although we obviously don't want to see animals lost from either population, even a single animal lost from the inshore group threatens its long term survival. Over the last 10 years, the group has been just hanging on to survival and three have been recorded dead this year alone. Despite their very small numbers, they are the animals that so many people have seen while visiting the Cornish coast." He went on to say, "They face many threats to their survival and several of those most recently examined by the Marine Strandings Network volunteers have been thin and malnourished, possibly due to being diseased. The Network does a great job in retrieving these important animals for veterinary pathologists to examine to help us learn more about why they die and what we can all do to help protect them. So I urge the public to support the team in any way they can."

The public are asked to report stranded marine animals to our Network’s Hotline on 0845 201 2626 but for health reasons, are advised not to touch dead dolphins or allow their children or dogs to get too close.

UPDATE - Parasites found on dolphin

Closer inspection of photographs taken at the time the dolphin was retrieved have revealed that it carried a particular parasite that only lives on cetaceans. Known as 'whale lice', these unusual creatures are actually crustaceans which hide in external skin lesions, genital folds, nostrils and eyes, clinging on by their hook-like claws. They don't live freely in the water but spend their whole life on a cetacean and move from one animal to another when the dolphins interact or between mother and calf. Some species are specific to a particular species of cetacean. The species found on the bottlenose dolphin were about 5mm long and are believed to be Isocyamus delphinii.