by Ela Schwartz
From tiny arthropods, we travel up the food chain to the large, marine mammals known as pinnipeds, which include the seals and sea lions studied by Heather Liwanag, Ph.D., assistant professor of biology.
Unlike smaller animals, such as the geckos Dr. Liwanag also studies, these long-lived mammals “are not going to adapt or evolve as rapidly, and a lot of them are in trouble. So we need to figure out how to keep them with us, and not just in zoos,” she says.
Dr. Liwanag is active in what she calls the “upand- coming” field of conservation physiology, which looks at how animals physiologically respond to environmental changes. “The common thread in my research is critical temperature,” she says, meaning the maximum and minimum temperatures organisms can tolerate before having to adjust their physiology.
Another question she seeks to answer is: “How fast does a seal’s fur grow back?” Why? Because researchers glue data tags to the seal’s fur, then cut the seal’s fur to remove the tag. “No one has looked at how the loss of fur may compromise the seal’s ability to insulate itself, including when it dives for food into higher pressures,” she says. Dr. Liwanag raised the funds to purchase a small hyperbaric chamber that re-creates the higher pressures that occur underwater so that she and her students can insert pelts and measure the amount of water that can penetrate the fur under pressure.
Dr. Liwanag is also collaborating with Linnea Pearson, a Ph.D. candidate at the University of Alaska Anchorage, to study insulation in harp seals from birth to adult and how this relates to environmental temperature changes. She explains that baby seals are born on the Arctic sea ice and nurse for only 12 days before they are abandoned by their mothers. They fast on the ice for another four to six weeks. “When they are first born, they have very little blubber and instead rely on thick, fluffy fur to keep warm,” Dr. Liwanag explains. “As the blubber develops, their fur changes from the thick pelage they had at birth to a thin, more streamlined…pelt like the adults have.” If there isn’t enough ice for these seals to sit on while they develop, they’ll be forced to venture into the water before they’re physiologically ready to withstand the icy temperatures.
In addition, if the waters seals inhabit become warmer and the sea ice continues to recede, these creatures may need to maintain their body temperatures by raising their metabolism, which requires them to increase food intake. If food sources are no longer plentiful, they must expend energy to forage. “So it’s a downward spiral,” she says.
In the future, Dr. Liwanag hopes to apply her research on critical temperatures to polar bears. “The ice is receding at rates not predicted in even the most liberal of climate models,” she says. “Polar bears are spending more time swimming, and we have no idea what their thermal capabilities are in water. I’m hoping to work with captive polar bears in zoos to look at lower critical temperatures in water and acquire data that will help us understand how [climate] changes are going to affect them.”
This piece appeared in the Erudition 2013 edition.
