This summer at the WSU Bear Research, Education, and Conservation Center, energy use is the order of the day.
From cardiac monitors to special collars to foraging experiments, WSU researchers are trying to figure how bears gather energy and then spend it.
“Bears in the wild have a very short time window to make their living,” said Tony Carnahan, a WSU Ph.D. student studying bear energy usage. “They have to make sure they have enough fat stores in their body to make it through winter. We want to figure out where and how they determine what to spend their energy on.”
To figure that out on wild bears, they’re first starting with our bears to get a baseline understanding.
The collars, worn by 9 of the 11 bears at the center, have accelerometers that measure acceleration data in three directions. The collars allow the researchers to tell when a bear is walking, running, grazing, or basically any movement the bears make. They collect 30 data samples each second, and it’s stored in a box on each collar. Every two weeks, the box is swapped out for a new one and the data is downloaded.
“It’s a lot of information to go through,” Carnahan said. “But we’ll combine it with other data and hope to figure out just how much energy the bears are using.”
Another wrinkle that’s new this year is allowing bears to primarily get energy from foraging in the exercise yard. For two weeks, two bears will have 24-hour access to the yard. One bear will be randomly selected to receive supplemental food with approximately twice the calories of a maintenance diet. The other bear will receive a supplement below a maintenance diet.
The hypothesis is that the bear on the minimal diet will spend a greater proportion of their time grazing and resting than the bear on the high calorie diet, Carnahan said.
The bears will also receive water that contains markers that can measure energy usage, a method that’s been proven for decades on a variety of animals.
In addition to the collars, nine bears at the center have an implanted cardiac monitor that feeds data to researchers regularly. So over the course of the two weeks that a bear is out in the yard, they’ll know the average heart rate for each bear and how closely heart rate correlates to energy expenditure.
Combine that with the collar data and researchers will have an excellent overview of what each bear did at any given moment, and how much energy they used altogether, Carnahan said.
The overall goal is to use the energetic values from the water to validate the cardiac monitors and accelerometers to predict energy expenditure in wild bears. Then they hope to move on and do similar work on wild bears.
Energy collection is important to learn because bears’ environments are changing rapidly. If they’re no longer able to collect energy at the same rate, or at the same time of year, that could impact their long-term survival.
“It’s all about energy collection, from the bears’ point of view,” Carnahan said. “We want to make sure they can continue doing everything they need to make it through the winters.”