San Diego Zoo Wildlife Alliance Stories

Polar bears are one of the most mobile quadrupeds on the planet—often walking vast distances on the Arctic sea ice in search of food. Previous research in the 1970s and 1980s suggested that these bears were inefficient walkers that use two times more energy to travel than other mammals. Now, newly released information from an ongoing polar bear energy study indicates that the costs of walking in these large Arctic bears may not be so expensive as once thought. The results, published this month in the Journal of Experimental Biology, show that when researchers measured the energy expended by polar bears while walking, the bears consumed the same amount of energy as other large animals, such as grizzly bears. This new information will provide important insights for better understanding of this species as researchers continue to quantify the energetic requirements of polar bears that are being impacted by drastic changes to their native habitats. The energy study was a collaborative effort led by the U.S. Geological Survey (USGS) and the University of California, Santa Cruz, with contributions by San Diego Zoo Global, the Oregon Zoo, Washington State University, SeaWorld and Busch Gardens Conservation Fund, and Polar Bears International. For decades, scientists have had the challenging task of studying polar bears in extreme Arctic environments to collect detailed data. In an effort to gain a vital understanding of the species’ energy output, USGS initiated a groundbreaking project to obtain the metabolic rates of polar bears while at rest and while they are walking. They did this by reaching out to scientists at both San Diego Zoo Global and the Oregon Zoo. The combined team then gathered data from a collar-mounted accelerometer—which works something like a Fitbit for polar bears—to measure activity while the large animals rested and while they walked on treadmills, and simultaneously measured how much energy the bears were expending. Scientists said the study will give them valuable insights into the bears' daily behavior, movements and energy demands. “This study will allow us to quantify the impacts of increases in polar bear movement patterns, in response to sea ice declines, on overall energy expenditure—and the implications for polar bear survival,” said Anthony Pagano, a research wildlife biologist with the U.S. Geological Survey. “Training polar bears to voluntarily walk on a treadmill was a hugely ambitious project, and it wouldn't have been possible without the creativity and patience of everyone involved at the San Diego and Oregon zoos.” Polar bears are listed as Vulnerable on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, and they are listed as threatened under the U.S. Endangered Species Act. If Arctic sea ice continues to decrease at the current rate, the world’s polar bear population is projected to decline by at least 30 percent in the next 30 years. For more than a decade, San Diego Zoo Global’s researchers and its U.S. and Canadian partners have focused on contributing to science-based conservation strategies to preserve and understand wild populations of polar bears. Today, it is estimated that there are approximately 23,000 polar bears living throughout the Arctic. However, human-induced climate change reductions in sea ice have caused declines in the number of bears, with young polar bears having a higher mortality rate than adults. Scientists said the next step is to examine the implications of declines in Arctic sea ice on overall energy demands. “We'll be linking the data collected in this study to data from accelerometer collars on wild polar bears in the Beaufort Sea,” said Pagano. “This will help us quantify the seasonal energy expenditure of polar bears in the wild.”