Mule deer

The mule deer (Odocoileus hemionus) is a deer that lives in western North America. It is called the mule deer because it has large ears, like those of a mule. There are two types, or subspecies, of mule deer, and they are sometimes grouped together with the black-tailed deer.

Mule deer are only found in certain places, such as the western Great Plains, the Rocky Mountains, the southwest United States, and the west coast of North America. Their home area is much smaller than that of the related white-tailed deer, which live in most of North America east of the Rocky Mountains and in valleys within the Rocky Mountains from Idaho to Wyoming and further north. Mule deer have also been brought to live in Argentina and Kauai, Hawaii.

Taxonomy

Mule deer can be divided into two main groups: the mule deer and the black-tailed deer. The mule deer group includes most subspecies, while the black-tailed deer group includes two special types: the Columbian black-tailed deer and the Sitka black-tailed deer. Even though some people thought they were different species, most experts today say they are the same species because they can have babies together.

There are ten recognized subspecies of mule deer. Some live in places like California, Nevada, and Mexico, while others are found in areas such as the Rocky Mountains and the Pacific Northwest. Each subspecies lives in specific habitats, from deserts to forests, showing how adaptable these animals are to different environments.

Description

Mule deer have some easy-to-see differences from white-tailed deer. Their ears are bigger, their tail ends in black, and their antlers grow in a special way, splitting into two points instead of branching out from one main beam.

Each year, male mule deer, called bucks, lose their old antlers in mid-February and grow new ones almost right away in the spring.

Even though mule deer can run fast, they often do a fun hop called stotting, where all four legs go up together.

Mule deer are usually bigger than white-tailed deer. They stand about 80 to 106 cm tall at the shoulders and measure between 1.2 and 2.1 meters from nose to tail. Male bucks weigh between 55 and 150 kg on average, while females, called does, are smaller, weighing between 43 and 90 kg.

Seasonal behaviors

Mule deer change their behavior with the seasons, especially during breeding time. The mating season, called the rut, starts in the fall. During this time, males become more aggressive as they compete for mates. Females may mate with more than one male and can try again to have a baby if the first attempt doesn’t work. After about 190 to 200 days, female deer give birth to babies called fawns in the spring. About half of these fawns survive. Fawns stay with their mothers through the summer and are ready to eat solid food by the fall.

Male deer lose their antlers in the winter, but they grow back before the next mating season. The size of deer groups also changes with the seasons. There are usually fewer deer together during the spring when fawns are born and more deer together in the winter.

Besides people, the main animals that hunt mule deer are coyotes, wolves, and cougars. Other animals like bobcats, Canada lynx, wolverines, American black bears, and grizzly bears might also try to hunt deer, but they usually only go after baby deer or very weak ones. Bears and smaller hunters often look for food wherever they can but don’t usually threaten healthy adult deer.

Diet and foraging behaviors

Mule deer eat many different kinds of plants, and what they eat changes with the seasons and where they live. They mostly eat leaves and small plants, but they also munch on grass, fruits, and nuts when they can find them. In some places, like Yellowstone, scientists found that mule deer are very flexible eaters, trying many different plants.

In places where people have planted crops or gardens, mule deer will eat those plants too. For example, in the Sierra Nevada mountains, they rely on a special kind of lichen called Bryoria fremontii during the winter when food is scarce.

Some of the most common plants mule deer eat include big sagebrush, mountain mahogany, quaking aspen, and Gambel oak. They also enjoy eating yarrow, lupine, and many kinds of grasses. In the right conditions, they’ll even eat wild mushrooms, which are especially helpful in late summer and fall.

People sometimes try to help mule deer by giving them extra food during very cold winters. However, experts advise against this because it can spread diseases among the deer, disrupt their natural movements, and damage the plants they depend on. If extra feeding is done, it needs to start early in the winter and continue until natural food becomes available again.

Mule deer are often seen alone or in small groups, with most groups having about three to five deer. The largest groups usually have around seven deer.

Nutrition

Mule deer are ruminants, which means they ferment plant material before digesting it. When they eat food high in fiber and low in starch, they need less food and spend more time chewing to get the most nutrients.

Their bodies change with the seasons. They store the most fat in October and use it through the winter, reaching their lowest fat levels by March. Hormones in their bodies also change to help them adjust to these seasonal differences.

Migration

Mule deer travel from lower areas where they spend the winter to higher areas for the summer. Not every mule deer migrates, but some travel very far—up to 150 miles! They move in the fall to avoid cold, snowy weather that hides their food, and in the spring they follow new plant growth northward.

During their journeys, mule deer face dangers such as changing weather patterns and human activities like building roads and cities. These can block their paths and make it hard for them to find food and safe routes. Protecting these travel paths is very important for their survival.

Risks

Mule deer face many challenges while migrating, including changes in climate and disturbances from humans. Climate change can alter the growth of plants, making old migration routes less useful. Human activities such as building roads, cities, and natural resource projects can also harm mule deer by destroying their habitats and blocking their paths. For example, roads can danger mule deer and also stop them from crossing safely. Fences and urban development can change their behavior and force them to take different routes, sometimes leading to fewer deer in certain areas.

Management

Protecting migration corridors

Keeping migration paths safe is crucial for healthy mule deer populations. Everyone can help by using cleaner energy and reducing waste. Managers can study these risks and take steps to reduce their impact on mule deer and other wildlife.

Highways

To help mule deer cross roads safely, managers have built special fences with escape routes and created natural overpasses and underpasses. These allow deer to move across highways without being hit by vehicles.

Natural resource extraction

To lessen the impact of drilling and mining, rules can limit when these activities happen and where they are placed. Careful planning and barriers can also reduce noise and protect deer habitats.

Urban development

As cities grow, they can disrupt mule deer migrations and their ability to mix with other deer groups. One way to help is to avoid building in important deer habitats. Property owners can also plant plants that deer don’t eat, use noise-makers to scare deer away, and avoid feeding them. This can help protect deer populations and their migration routes.

Disease

Wildlife officials in Utah found that in late 2021, some mule deer had been infected with a virus that also affects people. One female deer in Morgan County had a type of this virus called the Delta variant. White-tailed deer, another kind of deer that can mix with mule deer, have moved into areas where mule deer live since the early 2000s.

Chronic wasting disease

Main article: Chronic wasting disease

Chronic wasting disease is an illness that has been spreading among deer and elk. It was first found in captive deer in Colorado in 1967 and has since affected many wild mule deer across North America.