People have been urged to avoid getting too close to Wally the Walrus as he is struggling in the heatwave.
The mammal has been in the Isles of Scilly since June 17 and has proved popular with visitors and locals alike.
But animal experts say he is likely to be suffering in the hot temperatures and needs to be left alone.
A spokesperson for Cornwall Seal Group Research Trust said: "This heat is not something he is adapted for so it's more important now more than ever to give him rest and space. The hot weather is challenging him."
Wally was first spotted in Cornish waters in May, but is believed to be from Svalbard - which is between mainland Norway and the North Pole.
A customised pontoon marked with his scent has been built for him while he stays near the Isles of Scilly, to allow him to rest safely.
He is particularly fond of clambering on people’s boats, though the Seal Trust have urged owners to keep their distance.
"All boats-owners and water-users have been asked to give the walrus space and refrain from actively moving towards him, but the temptation has proved too strong for many,” they added.
“The walrus is a highly protected species and disturbance of this nature is a criminal offence. Even a lift of the head means his rest has been interrupted.
“Please stay away from him.”
The seal trust spokesperson added if he is continually distracted, he will not gain the weight and energy required to travel long distances.