The iconic polar bear is facing extreme difficulty as disappearing sea ice makes it almost impossible for them to eat enough food to raise healthy cubs, a study found.
Polar bears rely on sea ice to hunt seals, mate and give birth to their cubs.
But this crucial sea ice is vanishing at an alarming rate due to climate change and it has been proved that it is causing the animals significant problems.
They are being forced to spend more time fasting on land — as the sea ice vanishes earlier and reappears later in the year — which is affecting their weight.
Dwindling fat levels makes it harder for females to raise their young and they are now producing smaller litters.
Experts predict litters will continue to shrink over the next three generations if sea ice carries on vanishing at its current rate.
As an apex predator at the top of the food chain, the impact of climate change is amplified and it acts as a prophecy for all other species, indicating many more species will suffer similar fates.
‘Polar bears are a harbinger for the future,’ said Kristin Laidre, an Arctic ecologist at the University of Washington.
‘The changes we document here are going to affect everyone around the globe.’
They have long lives, long gestation periods and need to eat vast amounts of food to survive. As a result, they are less flexible to change over generations.
And rapid alterations to the environment is causing mayhem for the carnivores.
In a new study published in Ecological Applications, Dr Laidre monitored 43 adult females from 1991-1997 and 38 adult females from 2009-2015.
Bears were either assessed from the air or tranquillised and assessed to determine their fat levels and overall health.
‘Climate-induced changes in the Arctic are affecting polar bears,’ said Dr Laidre, who was the main author of the study.
‘They are an icon of climate change, but they’re also an early indicator of climate change because they are so dependent on sea ice.’
The research revealed the bears are spending 30 more days on land now than they did in the 1990s as sea ice vanishes.
Satellite data gathered by NASA shows a population of polar bears is arriving and leaving their home on Baffin Island at different times than they have done historically.
Sea ice has been breaking up earlier in the spring and is forming later in the autumn.
‘That’s important because when the bears are on land, they do not hunt seals,’ said Dr Laidre.
‘They have the ability to fast, but if they don’t eat for longer periods, they get thinner. This can affect their overall health and reproductive success.’
The team quantified the condition of bears by assessing their level of fatness on a scale of 1 to 5.
It proved their healthiness was directly linked to how much sea ice was available in the current year and the one beforehand.
As a result of this diminished state, mothers then have smaller litters.
Larger litter sizes were found when mothers were in a good body condition and when spring breakup occurred later in the year, meaning bears had more time on the sea ice in spring to find food.
Mathematical computer models were then employed by the scientists to predict the impact on future generations.
It found the normal cub litter size of two cubs is unlikely to be sustained in the next three polar bear generations (37 years).
The prime reason for which is the loss of sea ice.