The whale usually eats squid, which is likely to be scarce in the area
Conservationists are hopeful a 30ft (9m) whale spotted swimming off Dorset has swum out to sea unaided.
The northern bottlenose, which was named Gilbert after the RNLI lifeguard who spotted it, had been seen around Bournemouth Pier and in Poole Bay.
But there has been an unconfirmed report it was seen off Cornwall over the weekend on its way to the Atlantic.
It was feared that by feeding on small local fish, rather than its usual diet of squid, it would become dehydrated.
Trevor Weekes, from British Divers Marine Life Rescue (BDMLR), said : "An animal thought to be a whale has been spotted off Cornwall but the report has not been confirmed yet.
"We are trying to contact the person who made it to check it out.
"Gilbert has not been seen off Dorset since Friday night so this would tie in with the possibility he has swum out to sea.
"This would be very good news and is exactly what we hoped as there was always the fear he may beach and get stranded."
Mr Weekes believes Gilbert spent a few days feeding off Dorset to build up enough energy to swim out to the Atlantic Ocean and down to the Bay of Biscay.
The BDMLR has thanked the public who heeded warnings to observe the whale from the shore.
RNLI lifeguard Nick "Gilbert" Smith spotted the whale during a patrol last week.