Unwinding in a bath after a long day isn’t just limited to humans – in fact, large bodied mammals in the wild have been observed doing the exact same thing.
In collaboration with Washington State University, University of Wisconsin-Madison and the U.S. Geological Survey, researchers at the University of Idaho set out to find answers about why bears appear to enjoy taking a dip, especially during hot months.
In the study, led by Associate Professor of Wildlife Sciences Ryan Long and UI graduate student Savannah Rogers, researchers found that grizzly bears in Yellowstone National Park take baths in cool water to help prevent overheating.
Because the body temperature of mammals rises during lactation, female grizzly bears may fully submerge in natural depressions containing water deeper than the wallows used by ungulates such as elk. The “bathtubs” help facilitate increased milk production and ensure offspring survival.
“Back in 2016, National Geographic published a series of camera trap photos and videos of grizzly bears using these pools to immerse themselves on a regular basis, and at the time everybody thought it was a novel behavior,” Long said. “There’s a couple previous studies in other parts of the world but people have largely not pursued this question of how important heat is as a determinant of bear behavior.”
Long’s study focused on behaviors in female bears and the limitations that come with being a large animal in hot weather. Mammals generate heat internally and body functions are limited to how much energy it spends by its ability to cool back down again, Rogers said.
Bears don’t have the ability to sweat and cool down by laying on cool ground or in water. Their findings highlight the importance of bear behaviors, but especially for female bears who are lactating and producing additional internal heat.
There has been a great deal of focus on bears in the Yellowstone area studying external factors that influences their behavior. This includes food related factors, human disturbance and the environment, according to Long. Instead of traveling to the park, researchers were able to make a stimulating model and analyze bear behavior through technology.
The model creates a digital world. Data was taken from bears at the WSU Bear Center and translated into the model along with collared bears from Yellowstone. Anesthetizing the bears at WSU, they measured how dense they were and included their dimensions, according to Long.
Researchers set up a treadmill and were able to record the bear’s metabolic rates and walking speeds. All of the information was transferred to a computer, where they were able to run different scenarios that bears in Yellowstone may experience.
“Since my project was largely analytical, I didn’t have as many field-work challenges as many researchers do, but I did run across some hiccups,” Rogers said. “Simulation-based studies need to be meticulously checked and rechecked to be sure our predictions are realistic.”
Along with finding out why female bears take baths, researchers were able to explain the physiology behind their behavior. Hearing anecdotes about bears playing in water, it’s interesting to know the reasons why, Rogers said.
“The study highlighted the challenges that large bodied animals are up against as the climate continues to warm,” Long said. “They also highlight the sort of behavioral flexibility that animals like bears have and finding ways to overcome those constraints.”
In the future, Long and Rogers will collaborate on more wildlife projects, including a study of how large and small African antelope regulate internal temperatures in their environments. Recently starting her PhD at the University of St. Andrews, Rogers looks forward to developing new methods of estimating dolphin population abundance and survival rates.
Emily Pearce can be reached at [email protected] or on Twitter @Emily_A_Pearce