Humpback whale dorsal fin

The whale has been identified due to the distinctive shape of its head and dorsal fin © Luis Alejandro Bernal Romero/Flickr 

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A humpback whale has been spotted in the river Thames

This is only the second humpback whale observed in the Thames since records began over 100 years ago.

Update: Unfortunately, after not being spotted for 24 hours, the whale was found dead floating near Greenhithe, Kent. 

Over the weekend of 5-6 October 2019, a young humpback whale (Megaptera novaeangliae) was spotted swimming in the Thames near the Dartford Crossing. Over the following days reports of the whale have been coming in from Dangenham and Rainham in London, as well as Greenhithe in Kent.

As reports came in, the whale was confirmed to be a humpback due to the distinctive shape of its head and dorsal fin. So far, it has been suggested that the animal may be a juvenile, based on estimates that it is only around five metres long, although its size is yet to be confirmed.

Richard Sabin, curator of marine mammals at the Museum, has been keeping an eye on events in the Thames.

'This is not actually the first time there has been a humpback in the Thames,' says Richard. 'There was an occurrence in 2009, which was the first humpback observed in the river since the UK strandings records began in 1913.' 

That means this is only the second humpback whale to have been observed in the river Thames in 106 years. 

The images seem to show that the whale is in good health and behaving normally as it surfaces and then dives to search for food in the estuary.

'The good thing about humpback whales is that they are seasonal feeders and have a broad diet,' explains Richard. 'They will eat anything from krill to herring and other small schooling fish, but they won't find much in the Thames itself. To find the quantity of food they need requires moving into the estuary and out to sea'

Where did it come from?

Humpback whales have a global distribution - they are found in all major oceans. 

Historically, they would migrate from feeding grounds near the poles to breeding grounds closer to the equator. Growing up to 16 metres in length and 30 tonnes in weight, they were also heavily targeted by whalers.

'Humpback whales travel around the UK coastline as they migrate up to Norway and Iceland,' says Richard. 'There has been an increase in reports of sightings of humpbacks for several years now, in both UK waters and elsewhere in the North Atlantic, which is obviously a good thing as it suggests that their numbers may be recovering.

'There was a report about three years ago of a bowhead whale that had been seen off the Cornish coast. That is a long way away from the edge of the pack ice in the Arctic, where they are normally found. It could be that as whale populations increase they are exploring and returning to areas where they were once found, prior to large-scale human exploitation. This could be what we are seeing here.' 

Humpback whale underwater

Humpback whales sightings have been increasing, suggesting that their populations may be recovering © Christopher Michel/Flickr

What are the whale's chances of survival?

Despite the fact that the animal looked healthy and was seemingly behaving normally, the lifeless body of the whale was found floating near Greenhithe, Kent, on 8 October. 

The UK Cetacean Stranding Investigation Programme and experts from the Zoological Society of London will now conduct a post mortem on the whale. They will take samples of its tissue to test for parasites and pollutants, while at the same time trying to ascertain a cause of death.

Whales in the Thames

In addition to the humpback that swam into the Thames in 2009, there have been a number of other notable cetaceans making their way up the river over the last few decades.

In 2018, Benny the beluga made headlines around the world as it spent over three months living in the estuary before it is assumed to have made its way back out in the North Sea in the new year.

Possibly the most famous whale that made its way up the Thames in recent years was the northern bottlenose whale that swam as far up as the Houses of Parliament in 2006. It drew thousands of people to the banks of the river as they watched the attempt to save the animal

It is likely that, as whale number continue to recover, this will not be the last cetacean to swim into the Thames.

In the event that it does occur again, Richard has some advice for what to do: 'The best piece of advice that we can give to people is if you are planning on going down to the area to see a whale, then stay on the shore and don't go onto the water.

'The last thing you want to do is cause the whale any kind of distress by having too many vessels in the water, and create logistical problems for the Port of London Authority.

'Observe and enjoy the whale from the shore, and of course share your photographs online.'