Polar bears fail to adapt to lack of food in warmer Arctic

Polar bears are unable to adapt their behaviour to deal with the food losses associated with warmer summers in the Arctic.

Polar bears across the Arctic region face a shortage of food in the summer due to increased melting of ice

Scientists had believed that the animals would enter a type of 'walking hibernation' when deprived of prey.

But new research says that that bears simply starve in hotter conditions when food is scarce.

The authors say that the implications for the survival of the species in a warmer world are grim.

Back in 2008 polar bears were listed as a threatened species in the US. At that time, the Secretary of the Interior noted that the dramatic decline in sea ice was the greatest threat the bears faced.

Polar bears survive mainly on a diet of seals that they hunt on the sea ice - but increased melting in the summer reduces seal numbers and as a result the bears struggle to find a meal.

Some researchers have argued that polar bears would deal with a reduced calorie intake by entering a low-activity state termed 'walking hibernation', similar to the way that many species of bear cope with winter.

To test this idea, scientists embarked on a dangerous and expensive trial where they attached satellite collars and surgically implanted logging devices to track the bears' movements and to record physiological details.

They studied more than two dozen bears in the Beaufort Sea, north of Alaska.

Researchers studied a range of physiological features including samples of breath

They concluded that in the summer seasons, the bears didn't slow down, they simply starved when food was short.

"Their metabolism is very much like a typical food limited mammal rather than a hibernating bear," said John Whiteman from the University of Wyoming, the paper's lead author.

"If you or I were to be food-limited for weeks on end we would look like the bears' data."

While the bears may not be able to change their behaviour when it comes to food, they do seem to have a significant adaption that helps them to cope with swimming in cold water.

"They have this ability to temporarily allow the outermost portion of the core of the body to cool off substantially and this protects the innermost vital organs - there was not an expectation of that, it was very surprising," said Whiteman.

The researchers detailed the extraordinary swimming ability of the bears in their study, with one female surviving a nine day, 400 mile swim from shore to ice.

When she was re-captured some seven weeks later, the bear had lost 22% of her body mass, as well as her cub.

The scientists say that despite this strong performance in cold water, it doesn't compensate for the lack of food and the inability of the bears to slow down their metabolism in response.

"We've uncovered what seems to be a fascinating adaptation for swimming in cold arctic waters, but I don't think that is going to play as big a role in determining their fate as the loss of hunting opportunities will," said Whiteman.

"We think this data also points towards their eventual decline."

The costs of the study were steep, requiring around 200 people, and the hiring of an icebreaker and helicopters. The researchers believe that the endeavour is unlikely ever to be repeated,

"The cost was extremely high for such a study but our results are indisputable so I doubt anyone will feel the need to repeat this," said Prof Merav Ben-David, from the University of Wyoming, another author.

The paper has been published in the journal Science.

From BBC News Science/ Environment

Fifty sharks spotted swimming in West Sussex, England

Up to fifty sharks have been spotted swimming in waters near Selsey in West Sussex.

In June, a few sharks had been spotted at Medmerry, and half a dozen were also spotted in nearby PSRB Pagnam Harbour, but the huge number was unprecedented.

Mr Hughes told the Chichester Observer: "We do not know if the spectacle is going to repeat itself.

“Those wanting to look for the sharks can view from the new footpaths around the perimeter of Medmerry.

“Anyone new to the area should pick up a trail map and get advice from the RSPB Pagham Harbour visitor centre at Sidlesham.” ( From The Mirror)

The sharks were identified as smooth hound sharks, which can grow to around 1.5 metres in length.

The RSPB's Peter Hughes, who filmed the event on Thursday, said: "It was astonishing. There were just these huge fish everywhere in knee-deep water.

"We knew in time that Medmerry was going to be a great place for wildlife, but I don’'t think anyone expected this. We assume they were coming in to feed on the crabs and other marine life that have made their home at Medmerry."

Footage courtesy of RSPB warden Peter Hughes

From CBBC Newsround

Great white shark rescued from beach

A great white shark has been rescued after it was stranded on a beach at Chatham, Massachusetts in the US.

Witnesses say the seven-foot male shark got stuck as the tide went out.

Members of the public kept the shark alive and wet by splashing it with buckets of water until officials arrived.

The harbour master then attached a line to his rear caudal fin and pulled it back into open waters to release it safely back into the sea. ( From CBBC Newsround)

Witnesses said the two-metre male was stranded by a receding tide. ( From The Guardian)

Local harbour master Stuart Smith was able to attach a rope to the shark and, with the help of colleagues, dragged it back into the sea ending the rescue at around 5pm.

“Twenty, 25 years ago, they wouldn’t be exactly helping the shark. They’d be harming the shark. But now every single person on that beach was trying to assist it,” Mr Smith told the Boston Globe. “The people on the beach made the difference.”

Greg Skomal, a biologist from the state’s Division of Marine Fisheries, was also on hand to help, attaching an acoustic tag to the animal to enable researchers to track its movements along the Cape Cod coast.

He also praised the actions of the crowd, noting that when the great white eventually started swimming roughly a mile out to sea spectators “started clapping on the shoreline”.

Although the video does not appear to show the shark swimming, it has been reported that the fish survived – despite appearing close to death in much of the video. ( From The Independent)

Climate 'vice' constricts bumblebees' natural ranges

Climate change is threatening the survival of bumblebees, significantly reducing the habitats in which they can survive, researchers say.

Across Europe and North America bumblebees have lost ground to climate change

They say the natural ranges of these key pollinators are being compressed in both Europe and North America.

The analysis indicates that warming is having a greater impact than pesticides or land use change.

To ensure bees survive, humans may have to help move them to cooler areas, the European and American researchers add.

Century of data

Many creatures, including butterflies, have responded to a warming climate by moving towards the poles or towards higher ground.

Bumblebees have dealt with the increasing heat by disappearing in large numbers from portions of their southern ranges, but the insects seem to have baulked at moving north.

Climate change can significantly reduce the habitats in which bees can survive

The study was carried out by a team of scientists from Europe, the US and Canada.

They examined more than 420,000 historical and current records of bumblebee observations between 1901 and 2010 relating to 67 different species.

Taking the period between 1901 and 1974 as their baseline, the researchers found that in recent decades when temperatures have increased, the bees started to die off in the southern part of their ranges in both Europe and North America, at the same time.

"These species are at serious and immediate risk, from rapid human induced climate change," said lead author Prof Jeremy Kerr from the University of Ottawa.

'Impacts large'

"The impacts are large and they are under way - they are not just something to worry about at some vague future time."

The researchers say the losses amount to a retreat of around 300km or around 9km a year from the bumblebees' traditional southern limits in Europe and North America.

"This is a surprise," said Dr Leif Richardson, one of the authors, from the University of Vermont.

"The bees are losing range on their southern margin and failing to pick up territory at the northern margin - so their habitat range is shrinking."

Researchers say that temperatures are having a greater impact than pesticides or land changes

The researchers argue that the bees are "hitting a wall" on their northern ranges. They believe the insects are struggling to go further towards the pole because the lack the capacity to rapidly grow a new population when they move.

"This population growth rate limitation we suspect may be implicated as the key limitation on their capacity to track shifting climate conditions northward and into colder areas," said Prof Kerr.

• Bumblebees are seen as critically important for pollinating not just food crops but many wild plants and flowers as well.

• Pollination by insects is a key to the production of around one third of the food and drinks that humans consume.

• The larger bodies of bumblebees allow them to generate more heat so they can fly earlier and later in the day and in colder weather than most bee species, including honeybees.

• Many species have been in decline in recent years, with two - Cullem's bumblebee and the Short-haired bumblebee - going extinct in the UK this century.

The authors believe that the squeeze has not been caused by two other significant threats to the bees' survival: pesticides and land use changes.

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