At this time of year, mule deer are migrating and breeding in Central Oregon. Your best chances of seeing this nighttime-feeding deer are in the early hours of the morning or in the late evening. On a chilly November morning, High Desert Museum Curator of Wildlife, Jon Nelson, led a group of people eager to learn more about mule deer.

Mule Deer in the West

The mule deer is uniquely adapted to the environment of the American West. In the spring and summer they browse on plants in mountainous areas. As winter approaches, mule deer pack on the calories and move to lower elevations. Deer in the Cascades migrate eastwards and have to navigate their way past Highway 97. Underpasses help large numbers of deer make that journey. As the deer continue eastwards, hundreds can be seen in the area between Silver Lake and Fort Rock during fall and winter months.

In Central Oregon, deer feed mainly on bitterbrush, Idaho fescue grass, and sagebrush. They are not as dependent on the availability of water since they get much of what they need from their diet. On the field trip, Sand Spring was one of the few water sources we saw. It’s fenced to keep cattle out but the deer, as you probably know, can easily clear most fences if they want to get a drink.

Should you feed deer in your yard? No. If deer eat food provided by humans, it can have devastating effects. Their gut has evolved to process certain foods. If they eat other foods, it can kill the good bacteria in their stomachs. This can cause illness or even death. Certain diseases are spread to other deer via their saliva so you may not want to give them salt licks either.

Mule deer can often be found in ecotones, edge habitats between two plant communities. They can also find their preferred food plants in areas that are becoming re-established, including those affected by fires and clear-cutting. Deer seek out certain areas using behavioral thermal regulation. For example, they bed down on south and east facing slopes where it tends to be warmer.

Mule deer are adapted to living in areas with high snowfall. However, depths deeper than 20” for extended periods of time, like we had last winter, can cause many deer to die. Scavengers benefit by feeding on winter-kill deer. On this trip, we found a dead buck and bald eagles and ravens were congregating nearby to feed on it. It appeared that coyotes had been there as well.

Factors Affecting Mule Deer Population Levels

When you see numerous mule deer around Central Oregon you may assume they are doing well. That, unfortunately, is not the case. The number of mule deer in Oregon is steeply declining. In the 1960’s, there were more than 300,000 mule deer in the state; now the number is estimated to be around 200,000. On this trip, we drove south on the China Hat Road, east of the Museum. Several years ago it would have been common to see lots of deer in this area. We didn’t see many deer until we were many miles away from Bend.

There are several factors contributing to declining numbers. Fences affect deer populations by excluding them from some areas and also entangling them, which can lead to injury or death. Other factors include disturbance due to more people living in and visiting the area. Activities such as OHVing, mountain biking, and hiking with off-leash dogs, disturb deer. The many roads of Deschutes National Forest (more than any other National Forest in the U.S.) help in firefighting but also bring more people into the backcountry.

Poaching is a big problem in Oregon. More deer are taken illegally than legally. Due to budget constraints, the few officers responsible for enforcing the laws must cover huge geographic areas. On January 1, 2017, fines for poaching increased. The fine for poaching a deer with four or more points on at least one antler is now $7,500. While that is a lot, some people are still willing to break the law to bag a deer.

The mule deer’s iconic antlers can affect their population levels. Some hunters prefer bucks with large antlers but another type of hunter is out looking for antlers. Shed hunters look for antlers that have been shed where deer tend to congregate in the late winter and early spring. This activity disturbs the deer at a crucial time of year. Selling the antlers, priced by the pound, is a lucrative business. Some states regulate how long shed hunters are allowed to collect antlers so that deer are not disturbed in the spring, when fawns are born.

Deer are managed through hunting throughout the U.S. Here in Oregon, seasons run from September through early December. Different types of firearms and restrictions are allowed at different times of the season. Hunters report their success and this information is used to set future seasons and manage the population.

A Bit About Mule Deer Life History

Predators also affect deer populations. Cougars are the primary predator of deer in this region. Black bears and coyotes sometimes prey on fawns. Wolves have moved into the state over the last few years and they too prey on deer. One of the ways mule deer ensure more of their young survive is through a behavior known as swamping. All of the does become pregnant at about the same time. There are so many young fawns at once that predators can’t possibly get them all.

In the fall, breeding season starts for mule deer. The hormone levels in the bucks skyrockets. Their antlers grow at the amazing rate of up to an inch per day. The bucks shed the velvet on their antlers by rubbing on trees – or unlucky signposts. Big antlers attract mates and deter other males. The slim necks mule deer have in summer, become muscular and massive. Their eyes turn red and they sometimes drool. The rutting bucks are  ready to fight any male that gets too close to their harem of does. Harems can contain 15-20 does. The does choose which bucks they want to breed with. Fawns are born in late May through June after a 212 day gestation. Once they are more than a year old, does often have twins.

Diseases That Affect Mule Deer

Mule deer have a lifespan of about ten years in the wild but their life may be shortened by disease. Two diseases affecting deer were mentioned on this field trip. Adenovirus Hemorrhagic Disease (AHD) is passed  through direct contact, bodily fluids, and airborne routes. Symptoms may include a blue-colored tongue, mouth ulcers, severe weight loss, and weakness. AHD affects mule deer, white-tailed deer, elk, moose, and pronghorn and is often fatal. Chronic Wasting Disease (CWD) is a disease with symptoms similar to mad cow disease. It occurs in deer, elk, moose, and reindeer and is always fatal.

You may have heard a story in the news recently about a local person cited for possessing a deer bagged in Montana. Oregon is CWD free and does not allow certain parts of deer and elk to be imported into the state from Montana, 24 other states, and one Canadian province that have the disease . Once it was determined that this particular deer had CWD, the deer meat was confiscated and every place it had been stored or disposed of had to be decontaminated. This highly contagious disease could be a serious problem here in the future.

So the next time you are concerned about mule deer eating your landscaping, keep in mind that their numbers are declining. Do what you can to keep them away from your most treasured plants and appreciate them for their beauty and grace.

Reprinted from High Desert Voices December 2017 newsletter. To see more issues, go here.