Almost 5,000 dolphins, porpoises and whales have been found washed up dead on shores around the United Kingdom in a single seven-year period.
The findings, published by the UK Government, were collected by researchers from wildlife conservation charity the Zoological Society of London.
Researchers said that 4,896 underwater mammals were reported as having been washed up between January 1, 2011 and December 31, 2017.
This is a 15 per cent rise over the previous seven-year period.
Causes of death included infection disease, exposure to pollution and litter, entanglement in fishing gear and being struck by ships.
Monitoring programmes like these allow scientists to learn how populations of different species are changing and why — which can better inform their protection.
Scroll down for video
Almost 5,000 dolphins, porpoises and whales have been found washed up dead on shores around the United Kingdom in a single seven-year period. Pictured, a mass stranding of long-finned pilot whales on a beach in Durness, Scotland, in the July of 2011
Marine mammal expert Rob Deaville of the Zoological Society of London and colleagues conducted the review.
They noted 21 species — nearly a quarter of all marine mammals known to science — as well as six marine turtle species and several species of large-bodied sharks.
The highest number of recorded strandings in a single year, which exceeded 1,000 was recorded in 2017 — the biggest count since 1990.
The team also investigated several large-scale mass stranding events involving multiple animals.
These included one during which 70 long-finned pilot whales became stranded together in the Kyle of Durness, Scotland in the July of 2011.
‘We routinely produce reports like this for Defra and the devolved governments of Scotland and Wales, who co-fund the programme,’ said Mr Deaville.
‘4,896 is an increase of about 15 per cent on the previous seven-year period.
The researchers also conducted 1,030 post-mortem examinations in order to determine why individual animals had died.
They found that two of the most common causes of death were infectious diseases and accidental entanglement in fishing gear — a phenomenon known as ‘bycatch’.
Bycatch accounted for around 23 per cent of common dolphin deaths and around 14 per cent of harbour porpoise.
In addition, experts found 25 animals that appeared to have died as a result of being struck by a passing ship, as well as a single Cuvier’s beaked whale that died, in 2005, of stomach complications following the ingestion of marine litter.
The findings, published by the UK Government, were collected by researchers from wildlife conservation charity the Zoological Society of London. Pictured, two sperm wales stranded on a beach at Gibraltar Point, Lincolnshire, in 2016
Researchers said that 4,896 cetaceans — including proposies, pictured — were reported as having been washed up between January 1, 2011 and December 31, 2017
Causes of death included infection disease, exposure to pollution and litter, entanglement in fishing gear and being struck by ships. Pictured, a sperm whale is stranded on a beach at Skegness, in Lincolnshire, in 2016
‘It’s difficult to say conclusively what’s driven this rise,’ said Mr Deaville.
‘It’s potentially associated with multiple causes — including increases in local reporting effort and seasonal variation in the population density of some species.
‘As both nets and propellers can cause characteristic injuries, we can readily diagnose causes of death which are directly related to human activity, such as bycatch and ship-strike.’
‘However, the total proportion of deaths linked to the impact of humans is actually likely to be higher over the period covered by this report,’ he added.
‘For example, cases of infectious disease may be associated with exposure to chemical pollution, including legacy pollutants such as polychlorinated biphenyls (PCBs), which can have immuno-suppressive effects.’
Marine mammal expert Rob Deaville of the Zoological Society of London and colleagues conducted the review. Pictured, a sperm whale beached at Pegwell Bay, in Kent
The highest number of recorded strandings in a single year — which exceeded 1,000 — was recorded in 2017. Pictured, a common dolphin that was washed up on the shore
The researchers, led by the Zoological Society of London’s Rob Deaville, pictured, conducted 1,030 post-mortem examinations in order to determine why individual animals had died
‘Although in some respects the data paints a bleak picture, there are still positives to be drawn,’ Mr Deaville noted.
‘Between 2011 and 2017 we recorded 21 cetacean species, including one — the dwarf sperm whale — that had never been previously seen in the UK.’
‘That’s nearly a quarter of all currently known species, reflecting the range of diverse habitats around our coast.’
‘Although in some respects the data paints a bleak picture, there are still positives to be drawn,’ Mr Deaville noted. ‘Between 2011 and 2017 we recorded 21 cetacean species, including one — the dwarf sperm whale — that had never been previously seen in the UK’
‘It may be that, as the climate continues to change, the pattern of strandings around the UK may also change but we’ll have to wait to see what future reports find,’ Mr Deaville added.
‘That’s the value of monitoring programmes. We produce long-term, continuous data that picks up changes in the UK’s marine biodiversity that other approaches might miss.’
‘By investigating stranded cetaceans, we can also gain a real insight into the wider health of the marine environment and the frankly extraordinary wildlife that can be found around our shores.’
The full findings of the report can be downloaded from the DEFRA website.