4/14/2017 6:46:39 AM
The Smelly Search for a Seal Supper: How Wind Helps Polar Bears Locate Their Seal Prey
Polar bears make their living on the sea ice by searching for and eating their main prey, seals. But how exactly polar bears search for their prey has remained unknown, until recently. Our research team examined adult female polar bears in Hudson Bay, merging their movements with wind patterns to explore how they find their meals in this harsh environment.
Polar bears have a couple options when it comes to hunting: They can lie in wait for seals to come to them (still hunting) or engage in active hunting where they move to locate their next meal. Sea ice is a complex habitat with ridges and piles, so it can be hard for polar bears to locate seals by sight when active hunting; they often must use their sense of smell.
Many predators search for prey using smells in the air; once they smell something good, they will travel up-wind to the source. Detecting these smells successfully can depend on how the predator moves in relation to the wind. If a predator travels up-wind or down-wind, it remains in the same stream of air and will be exposed to fewer prey smells. However, a predator that travels cross-wind will receive a steady supply of new air-streams, maximizing the area that it picks up through smell.
Our research used GPS satellite-linked tracking collars on 123 polar bears spanning 11 years, along with wind data, to look at whether polar bears use the cross-wind strategy for hunting seals. We found that polar bears do use the cross-wind strategy. They rely on the technique most frequently when winds are slow (fast winds make it hard to pinpoint prey), during winter (when polar bears hunt seals, in contrast to summer when bears are on land), at night (when vision is less effective), and when the bears are on the move (active hunting in contrast to still hunting).
These findings broaden our understanding of polar bear foraging and raise questions about the implications of climate change. Wind speeds in the Arctic are projected to increase in a warming world; it will be important to understand how this might affect polar bear hunting success. Further, as development in the north expands, understanding polar bear movements relative to winds may assist in forecasting the impacts of an oil spill.
The more we know about polar bears, the better we can manage and conserve them, especially when it comes to understanding how they search for seals on the sea ice.
Graphic courtesy of Ron Togunov, University of Alberta.