Climate change is taking its toll on a majority of Earth's species — from habitat and to even their diet. Scientists from U.S. Geological Survey (USGS) studied the effects of climate change on polar bear's diet to assess the extent of adaptation and its effects on the overall health of bears.
Zoo curator Amy Cutting acknowledged that climate change is indeed happening at an alarming rate. Understanding the bear's response to environmental changes will help them in making decisions that would protect the animals in the wild.
Researchers from USGS used Oregon Zoo polar bears, Conrad and Tasul, to collect baseline information before studying bears in the Arctic regions.
"Scientists and wildlife managers need to understand how polar bears are responding as sea ice retreats," said Cutting. "But polar bears are notoriously difficult to study in the wild. Direct behavioral observations are nearly impossible."
The shift in the Arctic ice has significantly altered the diets of polar bears. Instead of consuming ringed seals, polar bears in East Greenland are now eating hooded seals.
Does diet have health implications on polar bears?
To understand how polar bears process their food, the USGS researchers used stable isotopes that are present in the animal's tissues and serves as their dietary signature. These chemical markers can reveal what and where the food was eaten.
USGS wildlife biologist and study lead Dr. Karyn Rode said that the use of stable isotopes has allowed them to use blood and hair samples to see whether the polar bears changed its diet since the 1980s and the effect of the meal diversity in their health.
To assist in data collection, Conrad and Tasul switched their diet between terrestrial and marine foods, dubbed by zoo staff the "surf-and-turf experiment." The researchers then compared new samples from their USGS archived samples from 25 years ago.
Rode said the comparison includes how the bears processed the food.
"It's not just that a 50 percent salmon diet shows up as 50 percent salmon in the body," Rode explained. "Some gets routed toward body fat, some gets stored and some is transformed directly to energy. I need to understand how the bear body processes food before I can understand how different diets may affect them."
The study is not only helpful in understanding the diet of polar bears but also invaluable in terms of preserving their population. The International Union for Conservation of Nature (IUCN) stressed the gravity of threat to the polar bears existence. With only about 26,000 left, the IUCN included it in the 2015 Red List of Threatened Species.
Since they depend on sea ice when they eat, IUCN said that melting ice forces the polar bears to starve longer as they hunt for food and starvation significantly affects the animal's reproductive abilities.
The study was published in Physiological and Biochemical Zoology.
Photo: Jodie Wilson | Flickr
