Research released in this month's Journal of Mammalogy suggests that, if polar bears adapt their summer diets, they may be able to survive through longer periods without sea ice. The study evaluated whether alternative foods that polar bears have been documented eating opportunistically during summer months could provide the energy the bears need to survive and reproduce. Researchers Markus Dyck and Ermias Kebreab suggest that these foods could sustain polar bears if the bears would change behavior and adapt to eating those foods as primary sources, reports the Wildlife Management Institute.

Polar bears depend on sea ice that they use as a platform to hunt their primary foods?ringed and bearded seals. Seal blubber has substantial energy value and allows the bears to survive through the summer on land when the ice retreats. With sea ice melting earlier each spring due to climate change, polar bears are spending far more time on land, leading to declining physical condition when stored body fat is not sufficient to survive extended fasting. The reduced condition is particularly problematic for pregnant females because it jeopardizes success.

During summer months, polar bears have been seen hunting caribou, ringed seals and Arctic char as well as eating berries. However, these foods traditionally are eaten on an opportunistic basis and have played only a minimal role in the bears' diets.

Dyck and Kebreab sought to evaluate whether the foods could provide enough energy for the bears to survive longer periods on land. They analyzed existing data regarding the energetic contributions of the food sources and mathematically evaluated if each could contribute sufficient energy to offset the bears' daily loss of body mass. According to their calculations, the researchers found that it is possible for polar bears to maintain their body mass while onshore by feeding on Arctic char and seal blubber and that smaller bears?up to 280 kilograms?(617 pounds) could gain sufficient energy from blueberries. All of these alternative food sources are found in abundance where polar bears range during summer months.

The research could not evaluate how many bears within a population would be able to acquire the skills necessary to hunt seals and char from land. "It should be recognized that the methods presented in this paper only elaborate on theoretical, mathematical concepts, and that the outcome (i.e., bears consuming alternative food sources) is contingent on the behavior of polar bears. The food sources containing the energy are readily available," Dyck and Kebreab explained. ?"However, in order to examine the true digestional energy value of the diets used in this study, feeding trials with captive polar bears should be conducted. Moreover, behavioral and physiological studies that record whether summer feeding occurs, either via direct observations or by other means, are encouraged." (jas)