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  Behavioral Education for Human, Animal,
Vegetation & Ecosystem Management

Stories of Applied Animal Behavior
Created by members of a graduate Foraging Ecology Class
     at the University of Idaho and Washington State University
     under the direction of Drs. Karen Launchbaugh and Lisa Shipley

Surviving Winter in the Face of Habitat Loss:
Biological Constraints of Elk and Deer

By Jeff Manning


Anyone who has witnessed large herds of elk and deer standing in deep snow on the outskirts of town during winter has wondered where they find food, water, and shelter. They are capable of traveling far distances and often migrate to satisfy some of their requirements, but these may not enable them to overcome rapid changes in their environments such as the loss of habitat from human development? Elk and deer have biological characteristics that constrain them from being able to adapt rapidly, and competition for resources that are all too often in short supply during winter may further constrain how they cope with habitat loss. These constraints are not only difficult to identify, their interaction with rapid changes across seasonal ranges, food availability, air temperature, and even competition makes their effects elusive.

Knowledge of some basic principles of how elk and deer learn about seasonal ranges, maintain energy and foraging requirements, and compete for resources may help us recognize some biological constraints that may hinder their ability to adapt to environmental change that we contribute to. An understanding of how they may compete for resources and how habitat loss may accentuate the effects of competition is also important in recognizing the plight of mule deer, for this species has been in decline since the 1950s.

Seasonal Ranges and Social Learning

Elk and deer live in large home ranges divided into summer and winter ranges. The winter ranges of elk and deer are typically the lowest elevations in their home ranges. Because these areas are low in elevation, they generally have shallow snow depths that enable elk and deer to travel between sheltered forests and open foraging areas. Once they arrive in a winter range, they are dependent on the food and shelter they can find there until the snow melts in spring.

Young elk and deer learn migration routes to winter ranges by following their mothers and other individuals. Consequently, these animals use the same migration routes and winter ranges year after year, and over generations. Migration routes can therefore be viewed as historical links to elk and deer herds from the past. They generally continue to follow these same paths to familiar places because they learned that they provide food, shelter, and water.

Foraging Requirements

Deer have biological characteristics that require them to specialize in eating nutritious browse like shrubs that are high in energy and easy to digest. Elk are generalists in that they are adapted to eating nutritionally deficient grasses as well as nutritious shrubs. Because elk are taller, they browse on tall shrubs that may be out of reach from deer. Studies have also shown that although smaller herbivores like deer require less food, their specialized diet requires that they spend more time selecting the more nutritious food compared to the larger species like elk that can eat large mouthfuls of grass in a short period of time. Being a generalist affords elk with the opportunity to eat grass as well as the same foods as deer, and their higher reach and their larger size enables them to outreach deer for food.

Elk and deer are always in search of food because it provides energy that helps them regulate their body temperatures. They also depend on shelter to stay warm in winter. They will travel to forested areas on south-facing slopes or river bottoms where trees provide shelter from wind and warmer temperatures.


Elk and deer often live together throughout the year, but winter brings them in close contact where they must share the same food and small area where snow is shallow. Recent research indicates that they have the potential to compete for forage about one-third of the time in spring and summer, but that it increases to over two-thirds during winter.

Elk are larger and generally more aggressive than deer, and can therefore directly interfere with deer that are eating or searching for shelter in winter. Because elk have access to more food, tolerate colder temperatures, use less energy traveling through snow, and can walk through deeper snow, they also exploit more forage and shelter areas in the winter range compared to deer. The competitive effects of elk can therefore reduce the availability of food and shelter for deer, and therefore reduce their fitness in winter ranges. Nonetheless, elk and deer have been coexisting in the same winter ranges for thousands of years.

Habitat Loss

Our homes are often built in valleys and foothills, and roads are constructed along the base of mountains. These areas are often the low-elevation areas that young elk and deer learned from their mothers to travel to each winter to find food and shelter.


So, what does an elk or deer do when it needs to find food and shelter for the winter? Their adaptations for energy balance, forage requirements, and locating seasonal ranges requires them to migrate to low elevation areas. To reach the winter areas, they travel along historical migration routes that they learned about from their parents. But, the rapid development of winter range into homes and cities reduces the availability of food and shelter, causing overcrowding, increased competition, and reduced abilities to reach an energy balance. In this scenario, the fitness of mule deer is depressed because they are the weaker competitor, and probably leads to them not surviving severe winter snows.

Management Suggestions

We need to recognize that elk and deer are in our yards and gardens because they are trying to find food, water, and shelter in the only places that remain in their home range. Providing a food crop and shelter between your home and the nearby hills may represent the most environmentally friendly way to keep them away from your home while enabling them to feed, maintain an energy balance, and continue to live through harsh winters.

Suggested Readings

The Mule Deer Foundation: a non-profit conservation organization dedicated to stopping the decline of this deer. or 888-375-DEER.

Hedrick, M. and B.L. Smith. 1995. Too many elk, too little habitat: current challenges in wildlife management. Page 12 in Proceedings of the western states and provinces 1995 joint deer and elk workshop. Idaho Department of Fish and Game, Sun Valley.

Henderson, R.E. and A. O'Herren. 1992. Winter ranges of elk and deer: victims of uncontrolled subdivisions? Western Wildlands 18:20-25.


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Learn more about the Foraging Ecology Class by visiting http://www.cnr.uidaho.edu/range556/