Unexplained rise in attacks by dolphins off Sussex coast

Until February 2, 2024, Rob Deaville and his team at the UK Cetacean Strandings Investigation Programme had only recorded two cases of dolphin attacks on porpoises off the Sussex coast since the scheme's launch in 1990.

But since then, some seven out of eight porpoises recovered from beaches between Pagham and Brighton have been diagnosed as bottlenose dolphin attack cases.

This article contains graphic images of deceased animals throughout.

The marine biologist conducts post-mortems on the cetaceans which wash up on beaches around the UK to establish a cause of death and find out what is impacting marine life off the coast.

"My wife calls it CSI of the sea," said Rob. "I think it captures what we do quite well.

"Every case is interesting and unusual and potentially unique. But the bigger question is to find out what these animals are dying from normally, so we can create a baseline."

Rob leads the CSIP programme in England and Wales (Image: ZSL)

Rob noticed an uptick of porpoises dying with traumatic injuries such as rib fractures, blubber tears and teeth marks this year.

"I have been recovering animals in the area for 25 years now, and first diagnosed a case of a bottlenose attack in 2020 - and then another in 2021.

"This year there has been an extraordinary number, with seven out of eight porpoises we have discovered being diagnosed as bottlenose attack cases. It is a pretty significant increase.

Teeth marks, known as rake marks, on a porpoise's tail (Image: Rob Deaville / ZSL)

"We don't know at this stage, but speaking with colleagues we think the dolphins could be coming from further afield, or perhaps there has been a change in the distribution of bottlenose dolphins and porpoises together."

Elsewhere in the country, bottlenose dolphin attacks are a common cause of death, with roughly 15 per cent of porpoises found in the programme dying from this, but this has rarely been the case on the south coast.

A cross section of the porpoise's blubber shows the 'v' shaped tear (Image: Rob Deaville / ZSL)

"Bottlenose dolphins are massive animals in the UK, much bigger than Flipper on the telly. They hit the porpoises with the tip of the beak, the rostrum, and smash into the side of them. That'll knock them out of the water and fracture their ribs.

"Once they kill them, they will swim off and lose interest, so it isn't for food," Rob said.

During the post-mortem investigation, Rob will take a cross-section of the impact site, which shows where the porpoise was hit, finding torn blubber and rib fractures beneath the surface.

Rake marks on a porpoise in Pagham (Image: Rob Deaville / ZSL)

Beside investigating dolphin attacks on porpoises, Rob also investigates other causes of death out of his lab at the Zoological Society of London.

"We are also interested in chemical and noise pollution, ship strikes, we picked up a dolphin outside Fatboy Slim's house last year which was hit by a propeller.

"These animals are hard to study in the wild, so we use strandings to learn more about their lives, not just their deaths."