by Joe Hutto
The mule deer is a formidable animal, with males commonly achieving a weight of 250 to 300 pounds, and with occasional individuals attaining 400. The largest whitetails may average 200 pounds, with some individuals weighing much more in some of the particularly robust populations, but most populations would average closer to 150 to 175 pounds for a fully mature, healthy buck. Most deer are characterized by distinct sexual dimorphism, with females of the majority of species considerably smaller than males.
Having spent no small part of my life living with both species, it would be tempting to describe the mule deer as a superior creature in many ways. But it is at least unfair and probably inaccurate to ever compare one species qualitatively to another. Every species, by virtue of its mere existence, has achieved some level of perfection and has in essence found its own perfect means of adaptation and survival. So, in some sense, every species has proven itself incomparable.
The whitetail is supremely adaptable, and the infallible crucible of time has proven this species to be capable of extraordinary resilience. The mule deer could be considered an evolutionary work in progress and a species that has not withstood the ten-million-year gauntlet that forged the apparently irrepressible white-tailed deer. However, much of the ten million years of evolutionary fine-tuning that defines the white-tailed deer still exists within the genome of the complex mule deer. Whereas the whitetail has been described as an opportunistic “weed species,” dispersing into every conceivable habitat in the western hemisphere—from the lush boreal and hardwood forest of eastern Canada to the jungles of South America—the mule deer has confined itself to a more rigidly defined set of environmental parameters. Although the mule deer is also a hardy ecological opportunist, it is more vulnerable to various ecological changes or perturbations. This is a creature who may still be biologically constrained by a certain evolutionary specificity.
Perhaps the most telling of the many differences between the two species is the “stocking” and relocation phenomenon. Classically, the adult whitetail can be transported and introduced to almost any new and exotic ecology—desert, mountain, farmland, or prairie—and it can be expected to not only survive but thrive. When the wildlife manager hears the landowner ask, “How do I increase my whitetail deer population?” the answer is always the same—“Just put a padlock on the gate!”
But when a mule deer is relocated from its original ecology into an apparently identical habitat, the mule deer in contrast may halter, become unthrifty, and possibly die. Survivors characteristically have low birth rates and are slow to establish a foothold in a new location. Attempts to reestablish mule deer into ranges where they have been eliminated, or introduce these deer into new but apparently suitable ecologies where none exist, have largely met with failure. Mule deer have adapted to a wide variety of Western landscapes, but once that adaptation is fixed, they appear to be somewhat obligated in a very particular way to a very particular habitat. Even though many mule deer are seasonally migratory—in some cases traveling one hundred miles or more between winter and summer ranges—these often narrow corridors are ancient, and every migrant has been initiated by the previous generation to the various changes in habitat and the specific locations of ideal forage availability along the way. It could be suggested that unlike some bird and insect species that are “hardwired” toward specific migratory behavior, those specific inclinations and destinations of mule deer migration are passed on through successive generations by the example of social affiliates, constituting learned behavior and knowledge that is passed on from one mule deer to the next, perhaps over hundreds or even thousands of years. Learning and transmitting knowledge from one generation to the next is a fundamental tenet of culture and is distinguished from those social systems that are defined by the instinctive obligations of genetically defined social behavior.
The antlers of white-tailed deer are normally smaller than those of mule deer and are structured as individual tines ascending upward from a single main beam. Mule deer antlers are larger and heavier and tend toward bifurcation as each tine ascends from the main beam. The first branch from the main beam on many deer occurs just above the forehead and is often referred to as the brow tine. Whitetails can have very tall and well-developed brow tines, whereas mule deer typically have more diminutive brow tines, and in many cases brow tines are absent entirely.
Another distinct phenotypic or conspicuous visual difference between whitetails and mule deer is the shape and size of their ears. The white-tailed deer has relatively small ears set slightly higher on the head, and are not densely haired. By comparison, the defining ears of mule deer are very large, are filled with hair, and are carried more out to the side. It is impossible to know whether the mule deer’s ear represents a larger sound-gathering device, but it would stand to reason that where the ecology is wide open and sound is unobstructed—often traveling great distances—a larger ear may be beneficial. A larger ear may gather low frequencies more efficiently. Mule deer are also creatures adapted to the constant presence of strong winds. A larger ear that is filled with dense, soft, curly hair may serve as a filtering device that may quell or even discriminate past the specific frequency of the continuous high wind passing across the ear—much like the large, furry wind screen devices that cover microphones on windy locations.
Mule and white-tailed deer are generally adapted to different habitats, although the whitetail has proven itself capable of readily occupying almost any former mule deer range, including now the high mountain basins in this area of Wyoming. Whitetails are more commonly identified with the flatter lowlands and river valleys where water is abundant and Mule Deer versus White-Tailed Deer thus dense cover and trees normally define the ecology. Mule deer in our area are more likely to be found on the dry, rolling sagebrush steppe, the rocky canyons and draws, and the many higher drainages issuing from the mountains. In summer these same deer may migrate up into the higher country and may even be observed browsing along the timberline and occasionally venturing onto the high tundra, momentarily sharing the range with bighorn sheep. While studying bighorn sheep in the northern Wind River Mountains of Wyoming, I briefly observed mule deer near my twelve-thousand-foot elevation campsite on multiple occasions. However, mule deer are more often identified with an ecology that offers rugged and steep terrain, with dense heavy sagebrush, a maze of rocky outcrops, steep draws, and cliff faces. In reality, mule deer and whitetails can survive on the same browse, but both are first and foremost “prey species,” so the differences in habitat preference may be defined more by the availability of suitable terrain in which to employ vastly differing escape strategies.
Wild white-tailed deer choose to respond to a perceived danger by running in an unimpeded straight line, at high speeds for long distances on flat terrain, without ever looking back. Indeed, it has been my observation that whitetails even have an instinctive behavioral “trigger” device, whereby a perceived pursuit by another animal will suddenly warrant an involuntary flight response that cannot be switched off until the deer has run for perhaps more than a mile. Whitetails that have been impounded by captivity or circumstance often meet with disaster if this behavior should be elicited for any reason. In mindless panic they may run into any obstacle and will attempt to jump the highest fence. Often the seeming terror doesn’t subside until the hapless deer is exhausted and bloody or even badly injured. Eliminating the source that triggered the response will not curtail the desperate behavior.
The study of mule deer escape strategy suggests many things about their complex adaptive behavior and even their extraordinary intelligence. When a mule deer observes an obvious or perceived danger, and in particular if that perception is in the form of a sudden stimulus, the response may be reactive and explosive, much like the whitetail. However, unlike its not-so-distant relative, the mule deer displays a diametrically different response. Although capable of tremendous speed when galloping across open ground, the frightened mule deer does not choose to gallop, but rather tu
rns and bounds uphill into steep, rocky terrain that may be often overgrown in a maze of thick brush. And rather than attempting to gallop through this impenetrable maze of obstacles, the mule deer employs the four-legged bounding gate known as the stot. Springing high into the air, and often with erratic moves to this side and that, the deer expends incredible energy but puts near-impossible obstacles between itself and a confused predator. But, then, after about one or two hundred yards, and if no predator is fast on their heels, mule deer do a fascinating thing—they stop to evaluate and assess the possible danger. They appear to be asking the fundamental questions: Have they in fact reacted to a legitimate danger? If the danger is a predator, is this particular predator actively hunting? If it is on the hunt, is it actually interested in this particular deer? The mule deer appears to employ reason and understanding to dangerous situations rather than blind obligatory instinct. Of course this often constitutes a fatal response when a human hunter is carrying a weapon that can call in an air strike at six hundred yards. Interestingly, the mule deer has become specifically responsive to a human, and, in particular, inordinately suspicious of even the smallest object in a human hand. But throughout their development as a species, the peculiar human predator was the one in mere possession of a bow and arrow, an atlatl, or simply a sharp stick. It is only recently in their development that they have come to fear the mysterious missile that comes at them in silence from one half-mile away. Since their evolutionary genesis during the end of the Pleistocene, the mule deer may have always known and identified the human species as one of their many possible predators. Like the mountain lion, the bear, and the wolf, humans are clearly hardwired into the racial memory of this creature, and we have probably always been at least a marginally predictable feature on their evolutionary landscape. And, therefore, the mule deer, unlike more ancient species, may have always been directly and indirectly associated with humanity. But our relationship may also be unique in that we represent an evolutionary paradox. Perhaps like the grizzly, we are alternately the most deadly of predators and then that creature who may also peacefully share the landscape eating roots, crickets, and berries or perhaps even herding or shepherding other species. As humans we have probably always represented a conundrum of schizophrenic proportions. We are that strange creature who will pull you as a helpless fawn from the frozen water or cut you free from a tangled mass of barbed wire and then tomorrow kill your mother standing at your side and leave her gut pile in the sage brush for you to ponder. So, like their response to any other potential predator, mule deer also ask those confusing fundamental subjective questions: Is this creature human? Is this human in predatory mode? Is this human a direct threat to me today? The mule deer is gradually adapting to the high-powered rifle, and those individuals who survive one hunting season tend to learn that there is no safe proximity to a human, and will quickly abandon the area at a fast, gliding trot without another look back. In dealing with certain other predators, the mule deer will often respond with extreme caution, but may only maintain a safe distance, wanting only to keep an eye on the possible danger rather than making a blind and often unnecessary retreat.
Surprisingly, mule deer will commonly react to a possible predator with coordinated group aggression. Even though coyotes are known to prey heavily on mule deer, which are vulnerable to organized packs, I have often watched individual coyotes as they are relentlessly persecuted and chased by a storming and angry herd of deer with dominant females who I recognize, out ahead and leading the charge. Confused fawns and yearlings cautiously bring up the rear. In circumstances where a perceived danger cannot be fully identified, many mule deer feel a strong urge to cautiously approach and investigate the origin of their concern—overriding fear with curiosity. With heads held high, with ears canted forward, and with slow-prancing, deliberate steps, they cautiously approach a strange object or unidentified animal. It is an obvious display of a well-earned self-confidence, and it is strong evidence that a seminal and definitive adaptive strategy of the mule deer involves the powerful suggestion—for this animal there is no survival advantage in ignorance.
Even though mule deer and whitetails are fully capable of interbreeding, the hybrid offspring inherits specific traits from each parent that are behaviorally incompatible, making survival in much of typical mule deer habitat virtually impossible. Ironically, the hapless fawn inherits the predisposition to elude predators by running uphill into rocks and heavy brush, but is mechanically or behaviorally incapable of employing the stot to pass safely over these impediments.
Another significant difference between whitetails and mule deer is the differing patterns of daily activities. White-tailed deer tend to be creatures of habit and if undisturbed can predictably be found in certain locations at certain times, seeming to conform to a daily schedule of activities. If a whitetail buck visits a scrape or rub today at 4:00 p.m., he is very likely to be there tomorrow at about the same time. If he goes to water or visits a hay field at first light, you can predict with some certainty that he’ll be there again at the same time the following day.
In contrast, the mule deer is a circuitous creature, and even though he may be compelled by necessity to revisit certain sites over and over for food or water, he is much more inclined to be in a different place every day at a different time. Mule deer will find different routes to take from one area to the next, and if these deer have moved through a specific area in a specific direction this afternoon, you can predict with a degree of certainty that they will not be moving the same way, in the same direction, tomorrow. Clearly all predators make note of the presence of a possible food source and are particularly alert to the habitual movements of their various prey. It is around the predictable habits of their prey that efficient predators plan their hunting and attack strategies. Mule deer often stay one step ahead of their predatory adversaries by employing a strategy of unpredictability. However, if you think you can depend on this deer to be predictably unpredictable, be prepared to be disappointed, for even the absence of a habit can become a habit, and they apparently know better.
Sadly, wildlife management agencies all over the West have demonstrated many times that once mule deer are in danger of starvation during a difficult winter, they are likely to continue to decline, starve, and die—even after nutritious supplemental food has been provided. This is due in part to a sensitive and complex digestive system that may have already shut down and cannot be restarted, but it is also clear that a hungry mule deer will simply refuse to eat any food with which they are unaccustomed. Indeed, I have introduced palatable, nutritious, and normally desirable food to mule deer under various circumstances and in different seasons, observing their immediate disinterest or even revulsion to a strange food. Often it will take at least weeks if not months to habituate a mule deer to a new but otherwise desirable food source. Apples are a classic example. Initiated mule deer relish the taste of apples—as every apple-growing rancher is all too aware. I personally know mule deer who will mug you if they suspect you have an apple in your pocket! But the deer who has never been exposed to the apple orchard will almost always find the exotic fruit at least uninteresting and, in many cases, will react to the strange smell of an opened apple with apparent disdain, shock, or even fear. Suffice it to say that the mule deer, although robust, resilient, and intelligent, is, nevertheless, a sensitive creature. I personally have always had my doubts about the advantages of sensitivity.
Over time and by various means, however, mule deer almost always eventually become displaced by whitetails. The reasons for displacement are complex and controversial, possibly involving human augmentation to the landscape of which whitetails are more tolerant. Crossbreeding of whitetail bucks to mule deer does is known to be a factor in some populations—accounting for 30 percent of fawns in these populations, which, of course, don’t survive. But in many cases, whitetails may simply occupy former mule deer ranges from which the mule deer have mysteriously disappeared. Thirty-five years of observat
ion in this area of Wyoming has lent me an insight into this dramatic and disturbing phenomenon. I have seen complete displacement of mule deer occur in areas where no whitetail existed three decades ago. The whitetail diasporas began in Montana decades ago, and now much of the state’s intermountain habitat is entirely dominated by this aggressive relative of the mule deer. In areas such as Swan Valley, the Bob Marshall Wilderness, and even northward, including Glacier National Park, much of Montana’s former mule deer habitat has now been entirely replaced with white-tailed deer.
Typical whitetail buck antler configuration. Photo by Marcia Murdock.
Note tendency in this large buck toward extreme bifurcation in antler form.
C H A P T E R T W E L V E
The Essential Mule Deer
All individuals within any species share common physical traits, so the phenotype or outward appearance immediately distinguishes them from any other animals. White-tailed deer and mule deer display very little similarity in their outward appearance, except that they share the same phenotypic traits that define their genus, Odocoileus, or the traits that define the appearance of all deer family members known collectively as Cervidae—or “the cervids.” The same silly lack of distinctions that humans often apply to other races within their own species is the same lack of discrimination that we tend to apply to other species. It’s not that the physical stereotype is inaccurate; it just implies a failure to look past the obvious—a failure to pay attention to the details. We may look at a herd of Angus cattle and see one hundred black animals that appear to have been dropped out of a large cookie cutter. But any working cowboy worth his salt gets to know his herd of one thousand mother cows as surely as you can recognize each of your three Labrador retrievers a quarter-mile away. In this way it could be said that every mule deer looks very much like any other mule deer, but with closer examination and a little familiarity, every deer is entirely individual and unique.