The mule deer is a classic high-stepper.
By Jay W. Sharp
"A mule deer escaping from a predator poses an enigma," wrote Valerius Geist in Deer of the World: Their Evolution, Behavior and Ecology. "Instead of using its speedy gallop [more than 30 miles per hour], it bounds off in long, high bounds — the 'stott.'... When stotting, the deer departs in high, pogo stick-like bounds.
Mule deer jumping fence, into path of oncoming car. Fortunately, the driver was moving slowly, so he did not strike the deer.
(Photo by Jay W. Sharp)
"The mule deer throws obstacles in the way of pursuing predators. The obstacles may be gravity, hurdles 1 to 1.4 meters [about 3 to 4.5 feet] in height, or gaps up to 8 meters [about 26 feet] wide. It can twist its body in flight through narrow spaces between poles and branches. It can vary its jumps to match the irregularities of the terrain."
Since the mule deer can easily clear objects more than six feet in height, it must be ranked, like famed dancer Fred Astaire, well up the list of the classic high steppers.
The mule deer (Odocoileus hemionus) — usually somewhat larger than its relative, the whitetail deer (Odocoileus virginianus) — stands three to three and a half feet at the shoulder and measures some four to seven feet from the tip of its nose to the tip of its tail. Typically, the buck weighs in around 200 to some 250 pounds; the doe, around 100 to 150 pounds. In our region, according to Desert Exposure outdoors columnist Larry Lightner, a mature buck ranges somewhat smaller. It typically weighs 150 to 200 pounds. The mule deer, says the US Geological Survey (USGS), has a stocky body with "long, slim but sturdy legs."
Although colors and patterns may vary somewhat among individuals, the deer's upper coat, generally, takes on a reddish tan hue in the summer and a grayish tone in the winter. Its lower parts — including its throat and rump patches and its belly as well as the insides of its legs — trend toward light tan or cream-colored.
The head of a "muley" features two large, mule-like ears that the animal moves continually and independently, like antennae, scanning for sounds of potential danger. It has wide-set eyes, which give the animal a broad view of its surroundings. Between its eyes, it has a dark, ragged-shaped patch, which tends to be more defined on the buck. Like a dog, it has a moist nose, which soaks up odor particles from the surrounding air.
It comes well equipped for detecting predators. Its hearing is highly sensitive. Its eyes have more light-detecting cells than humans' eyes. Its nose can pick up the slightest of smells. The muley can often sense a predator — especially if the threat is moving — several hundred yards away, even in the dim light of dawn or twilight.
Each year, the mature mule deer buck (and rarely, the female) produces a rack of antlers, which it will shed after the breeding season. The main beam of each antler forks into two branches that may fork yet again, into two roughly equal-length tines. Under favorable conditions, a buck in his prime may have a rack with a spread of three feet or more. By comparison, a mature whitetail buck also produces a rack each year, but with the main beam of each antler forking not into main branches but only into several tines. Generally, a whitetail's rack spans a foot and a half to two feet.
Locally, says Lightner, our smaller muley's typical antler spread is 22-28 inches with four to five points on a side. A yearling may sport thin spikes or may have as many as three points per side depending on genetics and diet.
The mule deer's tail, white underneath and reddish tan or gray on top, has a black tip. In flight, the muley keeps its tail tucked against its rump. The whitetail, by comparison, has a tail with a brown topside, a white underside and no black tip. In flight, a whitetail holds its tail up — using the white underside and its white rump patch as a flag of alarm should a predator threaten.
Distribution, Habitat and Diet
The mule deer ranges across most of western North America, from as far north as the Great Slave Lake in Canada to as far south as the Central Highlands of Mexico. The animal is "remarkably adaptable," says authority Michael Misuraca, writing for the University of Michigan Museum of Zoology. "Of at least 60 types of natural vegetation west of the 100th meridian in the United States, all but two or three are or once were occupied by O. hemionus."
Two subspecies that occur in New Mexico include the Rocky Mountain mule deer, in the northern two-thirds of the state, and the desert mule deer, in the southern third, according to the New Mexico Department of Game and Fish's "Mule Deer of New Mexico." The desert mule deer is the most common in the southwestern quarter of New Mexico.
Bucks crossing a road. (Photo by John Catsis)
The desert mule deer ranges from the ponderosa pine forest margins of our higher mountain slopes, down through the piñon and juniper woodlands of the mountain flanks and into the shrublands of the desert basins and the riverine environments of the river and stream drainages. It may move from habitat to habitat, elevation to elevation, depending on the season, the weather and the forage.
Often the animal appears to seek moderate cover on a rocky hillside near a water source as a favored habitat. There, the mule deer can find sufficient protective shelter during the heat of summer days and the cold of winter storms. Utilizing its keen senses, it can spot predators through the relative openness. Utilizing its stotting ability, it can capitalize on rugged landscape to elude predatory attacks. Usually, it can find at least some browse.
Since the mule deer is a relatively "small ruminant [a hoofed, cud-chewing mammal with a compartmentalized stomach] with limited ability to digest highly fibrous roughage [such as many of the grasses]," according to Misuraca, the animal must seek out "highly digestible, succulent forage." In New Mexico, according to the Department of Game and Fish, the mule deer — an opportunistic "browser" — feeds on a variety of leaves, woody stems and buds as well as some grasses. By comparison, grazers — ruminants with a greater ability to digest fibrous roughage — tend to feed primarily on the more uniformly dispersed grasses.
Locally, says Lightner, mule deer typically eat oak leaves and acorns as their primary food, but will readily eat juniper branches also.
Behavior and Life Cycle
A mule-deer population may number from perhaps a dozen to more than 100 per square mile, depending on the quality of habitat, according to the USGS. Individual animals tend to occupy distinct summer and winter territories, with the buck laying claim to a somewhat larger range than that of the doe. Both the buck and the doe may wander from their usual home range during rutting season.
The buck may choose a solitary life, or he may join a small group of unrelated bucks. The doe, says Misuraca, remains with a clan of maternally related females. Both groups maintain stability through a dominance hierarchy established and enforced by posturing, forefoot flailing and chasing — usually by the largest and most powerful member. Both groups may join to form herds in the winter. In southern New Mexico's Organ Mountains, for example, I have seen herds of more than 30 mule deer in the winter.
During the breeding season, or rut, which lasts from autumn into the winter, a dominant male — his neck swollen in anticipation — courts and tends a receptive female for several days. He may have to fight another buck, sometimes in a long and determined battle, for the privilege. After breeding, the buck abandons the doe to find another female or resume a solitary life or rejoin a bachelor herd. He will soon lose his antlers and begin growing a new rack. The doe, meanwhile, will carry complete responsibility for bearing and raising the young.