'Global warming' riddle of dead baby porpoise discovered miles upstream

The metre-long animal, thought to have been less than a year old, was found dead in shallows in the River Allan in Stirlingshire on Sunday.

It is thought to have swum upriver on unusually high tides and then found itself unable to get back to the sea.

It was discovered by two teenagers fishing at Bridge of Allan and follows other unusual sightings of whales, dolphins and porpoises in tributaries of the Forth. Marine experts say the discovery may be part of a "worrying pattern" of changes in the distribution of marine mammals, which may be due to global warming.

Reports that the animal was shot have been dismissed.

Rab Graham, 18, and Paul McPhee, 15, were enjoying a weekend fishing when they spotted the harbour porpoise.

Mr Graham said: "We were fishing for trout when we saw what we thought was a big fish lying belly-up in the water next to the bank. It was about 3ft long.

"As we got a closer look it became clear it wasn't a fish, but a porpoise with a grey upper body and was smooth, with no scales. We couldn't believe a porpoise could swim that far upriver. The fishing season only began in mid-March, but people have been commenting that there are no fish. We had not even had a bite. Now perhaps we know why."

Biologist Bob Reid, from the Scottish Agricultural College, said there had been other evidence of changes in the marine life of the Forth recently, with several sightings of previously rare killer whales and Atlantic white-sided dolphins in the estuary in recent months and several sightings of harbour dolphins at Cambus. He said: "I suspect something is happening to fish movements in the Firth of Forth. Porpoises shouldn't be this far away from the sea and that's a fact."

Mr Reid, who will be carrying out the post-mortem on the porpoise later this week, was one of the authors of a report earlier this year, which reported a huge increase in the numbers of harbour porpoises dying from malnutrition and hypothermia.

He said: "The fat in their bodies is stored as blubber and used as insulation from the cold. When they start losing fat they often die of hypothermia rather than starvation."

But Mr Reid said the harbour porpoise found at Bridge of Allan was clearly underweight and may have starved to death.

Biologist Krishen Rana, of the University of Stirling Institute of Aquaculture, said he had never heard of a harbour porpoise being found so far upriver.

"Neither I nor any of my colleagues has ever come across or heard of this before," he said.

A SHORT LIFE FILLED WITH THREATS

THE harbour porpoise (Phocoena phocoena) is one of six species of porpoise and is sometimes known as the common porpoise.

They have the shortest lifespan of all cetaceans - up to 20-25 years - although most survive for only ten years. They reach maturity at about four years and females normally give birth to one calf each year.

The female is about 1.7 metres long and weighs 76kg, while the male is smaller at approximately 1.6m and 61kg. Harbour porpoises live in the coastal waters of the North Atlantic and Pacific. Their main threats are nets, pollution and the white shark. In Scotland they are often killed by bottlenose dolphins.

Their diet consists of a variety of fish, including herring, shrimp and squid.