The beluga whale swimming in the Thamesthousands of miles from its natural Arctic habitat is still feeding and there are no plans to try and move it, conservationists have said.
The whale was spotted on Gravesend, Kent, on Tuesday and is being monitored by the Port of London Authority (PLA) and the British Divers Marine Life Rescue (BDMLR).
The PLA manages shipping and tourism in the Thames as well as monitoring the health of the marine environment.
Nicknamed "Benny" by the media, the whale has stayed in more or less the same spot and is displaying behaviour consistent with foraging, a spokesman for the PLA said.
The spokesman said: "We are not planning to intervene – it’s moving around freely but in the same location."
He continued: "It appears to be exhibiting what scientists would call ‘foraging behaviour’ and it’s likely to be feeding.
"Its behaviour is consistent with that of a healthy animal that’s feeding – no one knows if it is feeding normally or adequately, but it’s behaviour is consistent with that."
Rescue teams have been on standby in case the animal gets into difficulty and have urged people to keep their distance.
Beluga whales can grow up to 20ft in length and are usually at home in the icy waters around Greenland, Svalbard or the Barents Sea.
On Thursday, a porpoise was spotted in the same area, although they are a common sight in the Thames, the BDMLR said.
BDMLR director Gavin Parsons said they would work with the PLA to plan for “possible assistance scenarios” but currently did not see any reason to step in.
The whale was first spotted on Tuesday by ecologist Dave Andrews, who tweeted footage of the white animal.
“Can’t believe I’m writing this, no joke – BELUGA in the Thames off Coalhouse Fort,” he said.
The last reported sighting of beluga in UK waters was in 2015, when two were spotted off the Northumberland coast and one in Northern Ireland.
One theory of how the whale ended up in the Thames is that it followed a shoal of fish into the waterway and fish such as herring, capelin and cod are the species usual diet.
In 2006, a whale died after it swam up the river into central London despite rescue efforts.
But the PLA spokesman said that whale, a northern bottlenose, had not been feeding and by the time it reached London it was starving and very dehydrated.
He said there is evidence to suggest beluga whales are more diverse feeders that the northern bottlenose.