Dorset's favourite flipper, Danny the Dolphin, has returned to Weymouth harbour following a three-month stint near Poole.

Since last year, numerous videos have been appearing online of Danny the bottlenose - he even has his own Facebook page - but now a dolphin expert is worried for his safety.

Liz Sandeman, co-founder of dolphin and whale charity Marine Connection, has been studying in this field for more than 25 years and specialises in so-called 'solitary' dolphins.

She said that while Danny does not have any particularly distinguishing features, it is clear that all these sightings are of the same dolphin because these solitary animals are quite rare.

"The coast of Cornwall, Devon and Dorset tends to attract quite a lot of solitary dolphins," she said, "but at any time there are only between two and ten solitary cetaceans [marine mammals] in the world.

"The problem with solitary dolphins is when they stay in one area over a period of time they become what we call habituated. This is not a good thing because we don't want him being too comfortable around humans and boats."

Numerous videos have shown Danny being very comfortable around swimmers, divers and boats. A recent video showed him playing under a jet ski.

Ms Sandeman said: "In the video with the jet ski I know it is Danny going to the jet ski rather than the other way around but ideally the driver should have switched it off.

"It's quite dangerous because if he starts getting too comfortable with jet skis then he will start doing it around boats and a propeller can be lethal to a dolphin.

"It is vital that people keep their distance from these animals. We see too many times boat owners chasing them or people swimming with them and stroking them.

"These are wild animals and they need to be kept wild. If people start swimming with him and interacting with him or feeding him, he will become habituated and lose his natural instincts and put himself at risk of harm."

Marine Connection says the dolphins exhibiting the highest degree of interaction with humans are at the greatest risk of injury, illness and death.