4/28/2016 11:00:00 AM
To Swim or Not to Swim?
The question of to swim or not to swim, at least for polar bears, can only be answered in light of sea ice conditions. I discovered this after working with a team of scientists from the University of Alberta and Environment and Climate Change Canada-led by Dr. Nicholas Pilfold-to better understand swimming behavior in polar bears in the Beaufort Sea and Hudson Bay populations.
In results published in Ecography, our team found that more frequent long-distance swims (> 50 kilometers) by polar bears are directly related to sea ice melting faster and retreating farther from shore in the summer.
The data we studied from collared polar bears (2007-2012) showed an increase in swimming behavior related to changes in the amount and location of summer sea ice. Long-distance swims occurred more frequently in the Beaufort Sea than in Hudson Bay. This pattern of long-distance swimming by polar bears in the Beaufort Sea showed the influence of climate change. In 2012, 69% of the tracked adult females in the Beaufort Sea swam more than 50 kilometers at least once, the same year in which Arctic sea ice hit a record low. This is important information for polar bear management, especially in light of Arctic sea ice reaching a new record low in the winter of 2016.
Previous research showed that swimming may be energetically costly to polar bears. Due to the continued trend of sea ice loss, scientists are concerned that the need to undertake more frequent long swims may have serious implications for populations of polar bears living around the Arctic Basin.
Our team found that climate change was not the only factor in long swims. Swimming frequency and distance varied between individual bears and showed differences depending on age, sex, body size, and the geographic features of the region. Females with young cubs tended to swim less-probably to avoid submerging their vulnerable cubs in cold waters-while solitary subadults swam as frequently as solitary adults. The longest recorded swim in the study was by a subadult female who traveled over 400 kilometers in nine days!
The degree to which sea ice changes have an impact on long swims likely varies within and between populations. This is not an unexpected result as scientists know that climate change impacts polar bears in different ways and rates across the Arctic. Even so, this work drives home the fact that in order to protect polar bears and their way of life for future generations, we need to protect their sea ice home throughout their range-and soon!
Alysa McCall is PBI's director of conservation outreach and staff scientist.