On the other side of winter

Animal activity during hunting season, summertime and just as animals prepare for the winter is often discussed. Bears and ungulates, hoofed mammals, and for this article’s purpose, elk, deer and antelope, may be less active in deep winter months, but their focus is keen.

Early fall and winter

Bears prepare for hibernation as fall begins. Before snow accumulates, natural food sources like juniper berries and white bark pine are easily accessible. Much research has gone into understanding what exactly triggers bears to enter their dens for hibernation. “We do know that food and lack of snow can impact the timing of when they do go in and when they emerge,” Kris Inman, with the Wildlife Conservation Society, said.

Inman recalled a season in Virginia when male bears never entered their dens due to an abundance of acorns of the ground. Males are last to den if food is available, and in the Virginia case, sometimes never den at all. Females will always make their way to the den at some point during hibernation season.

Ungulates put high priority on putting on body weight before winter, much like bears. While conserving energy becomes important as the winter draws on, this time period enables them to use energy to stock up on productive food sources. Conditions going into the winter, such as early storms or quantity of food sources, affect how ex- treme energy loss for ungulates may be.

Physiological changes

Physiological changes affect how bears survive hibernation. Body temperature drops, oxygen rates decline, heart rate goes down and urination and defecation cease. Bears do not lose bone or body mass or suffer brain injury while oxygen levels are low.

“The state of torpor that they go through is really interesting and still a mys- tery,” Inman said. National Aeronautics and Space Administration (NASA) scientists studied blood samples from collared bears to try and understand these phenomena to no concrete conclusions.

Hormone changes trigger physiological responses in ungulates, along with the varying amount of daylight. “Generally,
elk, deer and moose, their whole objective through this late winter period is to conserve energy,” Dean Waltee, wildlife biologist with Montana Fish Wildlife & Parks (FWP), said. Ungulates spend much time bedded and out of the wind to conserve energy.

Any time ungulates are up and moving, they are burning energy and are unable to replace it with food available during winter months. They try to soak up as much sun as possible to counter the ‘negative energy balance.’ “When it gets cold enough, it just naturally increases their metabolic rate, so they have to burn more calories just to maintain temperature,” Waltee explained.

Human interaction

If habituated to human food sources, bears may come in and out of their dens during hibernation. They have incredibly acute memories and can recall where they received a food reward with great ease. This explains why even when trash is secured, a bear may return to the site to look for food they remember finding before.

“We typically say you don’t want to have attractants around starting by mid-February,” Inman said. In low-snow years, bears may emerge from their dens earlier. Inman recommends getting into the routine of securing trash year-round so it becomes habit.

Avoiding predators is a big energy using source for ungulates. The stress of interacting with a predator combined with the energy necessary to stay away is detrimental in the winter. Human recreational activity ends up being a cause of unnecessary ungulate movement.

Wildlife biologists advocate to the public how important it is to minimize disturbances during in the winter, Waltee explained. FWP maintains recreational closure on elk winter ranges administered by the organization to support animals’ needs.

Onset of spring

Coming out of hibernation, bears regain physiological processes that were paused while denning. Heart rate and metabolism increase, and urination and defecation begin again. Finding food is on top of the to-do list and therefore it is crucially important to secure trash by March.

As the first patches of green grass appear on hillsides, ungulates congregate around this early food source. They come out of starvation and are looking for proper nutrition to rebuild energy. Foliage becomes available and easier to access, as it is not buried under deep snow and does not require additional energy to access.

FWP begins population trend surveys following hunting season and the winter to assess ungulate populations’ resiliency in the winter months. “Their ability to survive is quite incredible, through extended periods, through very, very difficult conditions,” Waltee said.