Hessy the humpback whale was struck by a ship causing fatal injuries, experts have revealed.
The 27ft-long juvenile female, nicknamed Hessy, was spotted in the River Thames near Greenhithe, Kent earlier this week, sparking international attention.
But a post-mortem revealed she suffered catastrophic injuries to her jaw and a large wound to her head, and that a ship strike was the main cause of death.
Rob Deaville, of the Zoological Society of London, said the strike is thought to have happened in open sea rather than in the river.
He added that the post mortem revealed the animal had not eaten for some time and was ‘nutritionally compromised’, but no signs of any ingested plastics were found.
Hessy died after her journey and her bloodied carcass is pictured above after it was hit by a ship. She was found dead after 5pm on Tuesday
A post-mortem revealed she suffered catastrophic injuries to her jaw and a large wound to her head (shown), and that a ship strike was the main cause of death
Rare sightings of the whale had delighted onlookers and whale watchers, who flocked to the banks of the Thames to catch a glimpse of the elusive animal (shown before its death)
The dead body of Hessy is loaded onto a trailer at Gravesend on Tuesday, on its way for dissection by the Zoological Society of London
He said: ‘ZSL’s examination revealed that it was an 8.37 metre-long juvenile female, had no evidence of recent feeding and was nutritionally compromised.
‘The whale also had a heavy burden of parasites within the intestine, and no evidence of plastic ingestion was found.
‘There was also evidence of historical entanglement or other interactions with human activity, with linear scars on the dorsal fin (located on the back of the animal) and tail flukes.
‘The main finding was a large wound on the underside of the head, associated with a fracture along the length of one of the mandibles (lower jaw).
‘Traces of blood clots around the fractured jaw and haemorrhage around the cut/torn surfaces indicate that the damage occurred before death and it was the team’s opinion that the injuries were most likely a result of ship strike and this is considered to be the primary cause of death.
‘It’s certainly possible that the whale was struck outside of the Thames and already had these injuries whilst it was seen swimming within the river at the beginning of the week – further test of tissues taken during the examination are ongoing and may shed further light on the likely timescale around the injuries.
Experts say it is likely the juvenile whale made a navigational error and swam up the Thames from the North Sea last week on a spring tide when the water level was at its highest
The Zoological Society of London dissects whales and dolphins found washed up on UK shores to dry and understand why they died
A spokesman for the Port of London authority described the recovery operation last night. He said: ‘We managed to secure the whale to the larger of the boats, the Kew, and then began dragging it. The whale was so big and heavy that the Kew was only able to do one and a half miles an hour’
A map showing how the typical migration route of a humpback whale passes the UK’s north coast. This particular whale was not following the usual pattern
‘This examination was very much a collaborative effort and could not have happened without the considerable support and efforts of colleagues from Port of London Authority and British Divers Marine Life Rescue.’
Two Port of London Authority boats and one RNLI lifeboat recovered the body at around 6.30pm on Tuesday.
A spokesman for the Port of London authority said the whale was found underneath the Dartford Crossing.
Rare sightings of the whale had delighted onlookers and whale watchers, who flocked to the banks of the Thames to catch a glimpse of the elusive animal.
Experts say it is likely the juvenile whale made a navigational error and swam up the Thames from the North Sea last week on a spring tide when the water level was at its highest.
Another humpback whale which entered the Thames 10 years ago is known to have died of starvation.
The exact cause of Hessy’s death will be determined following analysis from the Cetacean Strandings Investigations Programme at London Zoo.
It is the fifth humpback whale to be recorded stranded in the UK by the programme.
Benny the beluga whale rose to national fame when he was spotted in the River Thames last year.
Experts believe the juvenile whale made a navigational error and swam up the Thames from the North Sea last week on a spring tide when the water level is at its highest
The whale has signs of ‘historic entanglement’ scarring on its dorsal fin but looks unharmed apart from that
HUMPBACK WHALE POPULATIONS AND THEIR THREATS
Humpback whales live in oceans around the world. They travel incredible distances every year and have one of the longest migrations of any mammal on the planet.
Some populations swim 5,000 miles from tropical breeding grounds to colder, plentiful feeding grounds – this is why it is difficult to estimate population size, according to the National Oceanic and Atmospheric Administration (NOAA).
Of the 14 distinct populations, 12 are estimated to number more than 2,000 humpback whales each and two are estimated to number fewer than 2,000.
Humpback whales live in oceans around the world. They travel incredible distances every year and have one of the longest migrations of any mammal on the planet
Some populations (such as those off eastern and western Australia) are believed to number in excess of 20,000 animals—a remarkable recovery given that the same populations were almost eradicated by whaling almost sixty years ago.
By contrast, the smallest known population is one which inhabits the Arabian Sea year-round, and may number as few as 80 individuals.
Threats to humpback whales include decline in food like Krill due to a combination of climate change and industrial-scale fishing.
Humpback whales can become entangled by many different gear types including moorings, traps, pots, or gillnets.
Once entangled, if they are able to move the gear, the whale may drag and swim with attached gear for long distances, ultimately resulting in fatigue, compromised feeding ability, or severe injury.
There is evidence to suggest that most humpback whales experience entanglement over the course of their lives, but are often able to shed the gear on their own.
Inadvertent vessel strikes can injure or kill humpback whales.
Humpback whales are vulnerable to vessel strikes throughout their range, but the risk is much higher in some coastal areas with heavy ship traffic.
Underwater noise threatens whale populations, interrupting their normal behaviour and driving them away from areas important to their survival.
Sound has been shown to increase stress hormones in their system and mask the natural sounds humpback whales require to communicate and locate prey.