by Joe Hutto
Making Sense of Scents
Scent and olfactory reception are among the most ancient and highly evolved biological systems, as molecular information is transferred from one individual directly into the central nervous system of another. Scent is an important component of mule deer social life, and it could be considered another means of communication involving a complex vocabulary, as vital information is conveyed and received throughout the herd. Both bucks and does have similar external scent glands that are used to express individuality and social status, as well as physical well-being, sexual prowess, and reproductive status. Of the mule deer’s many glands, the most conspicuous are the tarsal glands located on the inside of the hocks and the metatarsal glands that run longitudinally outside and below the tarsal gland over the rear cannon bones. Both tarsal and metatarsal glands are covered with hairs that trap pheromones and convey information from one individual to the next. Although conspicuous, the longitudinal metatarsal gland may be largely vestigial but retains the specialized hair. In both sexes, the tarsal gland is “urine-rubbed,” meaning that the deer crouches and urinates on the hocks, which undoubtedly serves a significant role in mule deer sexuality. However, the tarsal gland also serves to express information throughout the entire year, even among fawns, so the significance appears to be much more complex than for mere reproduction. Glands are also located between the toes, known as “interdigital,” and may serve to mark certain geographical pathways and perhaps even the individuals who have used those pathways. Small, gender-specific glands located along the base of a buck’s antlers are useful in disseminating information, as the whitetail delicately leaves his mark above his “scrape” on an overhanging twig the diameter of a toothpick, or the mule deer may leave his mark on a well-rubbed trunk of a small tree or shrub. I have often noticed that freshly shed whitetail antlers have a distinct musky odor around the rosette—the burr or base—where it intersected the hairline, and this scent lingers for about twenty-four hours after shedding. Having retrieved hundreds of freshly shed mule deer antlers, some within seconds of falling, I have never been able to detect any noticeable scent.
The various external glands of mule deer may be expressed individually or in concert. The tarsal gland in particular can be quite pungent and strong, even to the human nose, especially during the rut when bucks are making their most overt olfactory displays. However, females also emit strong tarsal gland scents at other times and in other social settings that have no apparent reproductive significance. It even appears that, on occasion, these scents can be mysteriously expressed in an instant, and then in another instant the scent disappears, almost as if an aerosol had been emitted that was not captured in the specialized hair surrounding the glands. Although all deer are fastidious and constantly lick the tarsal gland clean, mature bucks in rut allow urine to remain on their tarsal glands and therefore can retain a more pungent scent for the duration of the breeding season. Fawns are inclined to urine-rub their tarsal glands, and does are careful to constantly groom the fawns’ hocks to reduce scent. Young bucks also keep their tarsal glands spotless. Though their scents can be quite musky and distinctive at certain times, they’re not as strong as those of a buck in rut. Most of the time mule deer emit no detectable scent to the human nose. And if the unlikely opportunity arises to bury your face between the ears of a friendly mule deer, you will discover that, like most healthy wild animals, the deer has a very pleasing, clean, warm scent, bearing no similarity or relationship to the musky scent glands.
A buck urine rubbing his tarsal glands during the rut.
Located at the inside corner of the mule deer’s eye, where the lachrymal gland would be located on a human, there exists a small slit that runs down from the eye toward the muzzle and forms the opening to the pre-orbital gland. Common to cervids and other artiodactyls, this gland is found on both sexes of mule deer and may be opened or “expressed” in an array of contexts, including various states of excitation involving curiosity, fear, aggression, and perhaps even pleasure. Although clearly related to a broad spectrum of important emotional states and social functions that have been explored by many observers, the true significance of this organ remains poorly understood, if not altogether misinterpreted. With the provocation of some stimulus, an almost invisible line at the interior edge of the eye opens into a roughly oval, pinkish orifice an inch in diameter that can correspond with fright and caution, or, on another occasion, may precede and accompany a bout of violent, aggressive hostility. When in the company of dominant bucks, especially during the rut, I always keep an eye on the pre-orbital glands of nearby individuals to assess the mood of a possibly agitated deer. When competing bucks engage in serious fighting, the pre-orbital glands of both combatants may be seen widely flared, and it could be inferred that these “glands” probably have some profound visual significance and act as signaling devices in addition to any transmission or reception of olfactory information. Unlike the glands of bighorn sheep, the pre-orbital glands of healthy mule deer do not seem to produce a scented discharge. In fact, by rubbing my finger down the hairline covering the opening to the pre-orbital gland, I can detect no significant scent on my finger, either before, during, or immediately after the gland is open. And, by the way, never attempt the same experiment on the tarsal or metatarsal gland, as a mule deer may “cow-kick” you in the face with tooth-shattering force if your touch comes as a surprise! The pre-orbital glands in bighorn sheep clearly serve as true secretory glands that produce or express a readily discernible waxy, scented discharge that is used for marking. However, this gland on wild sheep is entirely superficial, confined to the thick hide, with little or no apparent involvement with the bone below—not even a small vascular foramen. In stark contrast, the underlying skeletal structure in the nasal bone and maxilla directly beneath the pre-orbital gland of mule deer provides a large, almost gaping access to an extremely complex sinus labyrinth connecting directly to the sensitive membranes surrounding the convoluted nasal turbinates, as well as direct pathways to the olfactory bulbs of the brain. These glands must be important, considering the extraordinary risk of severe cranial injury and infection that this opening presents on the face of an animal that fights with penetrating weapons on its head. Indeed, on numerous occasions I have observed bull elk and buck mule deer suffering persistent necrotic infections of a pre-orbital gland after a foreign body or pathogen had been introduced during combat. Once established, these infections may persist for years or even throughout the life of the animal.
It appears that the pre-orbital glands in deer may serve as more of an information receptor than a true secretory gland of expression, implying that they are not true glands at all. It should also be noted that both does and bucks may flare their pre-orbital glands when experiencing pleasure, as, for example, when an otherwise inaccessible itch is being scratched. Rather than facilitating mere primitive responses to stimuli, these functions may pertain more to abstract communication and expression, involving those subtle elements of emotion, including fear, aggression, insecurity, pleasure, or the recognition of individuality. Because of the difficulty in studying this type of elaborate animal communication, it may be impossible to quantify the more conscious experience of a species. We humans are often left only guessing.
Dogs literally “see” the world through their noses and gather a similar degree of complex information about their surroundings. But dogs not only smell in the same three dimensions that we enjoy with human vision; they can probably also smell with great temporal accuracy into the past and simultaneously explore a fourth dimension of time. We can only clearly see that a deer track is not fresh, whereas a dog probably knows without question whether a particular track is two hours or two days old. Perhaps in imagining the significance of scent in the lives of other creatures, we would be better informed by looking toward the science of linguistics for encouragement and understanding.
Deer Speak
Many people are surprised to hear a mule deer’s voice,
but in fact these deer are quite loquacious. In any ordinary mule deer herd, you may hear frequent vocalization. However, these voices are ordinarily quite subtle and can only be heard from a few meters away. Mule deer have an interesting repertoire of vocalizations, and it could be safely said that they in fact have a vocabulary of sorts.
Most mule deer vocalizations are variations of a simple nasal-sounding “wheh” that may vary greatly from one individual to the next. Some voices in does may be a deeper “uhhh,” and, although seemingly of a modest volume, they send a fawn running to its mother’s side from a great distance. Or, the same sound might be from a frustrated but optimistic buck repeatedly pleading to some despondent doe for attention. Mule deer have hearing that clearly borders on the supernatural, but often these calls are emitted at what seems to me to be a relatively low volume, yet the fawn may respond from a distance of a quarter-mile. Often the simple “wheh” is an expression denoting the need for acknowledgment and perhaps a solicitation toward some need that is not being met. It could also represent some mild level of frustration. If I am known to have a deer wafer in my pocket, which is often the case, and I fail to acknowledge or return eye contact to an individual who would like some recognition, either fawn, mature doe, or buck may suddenly make a frustrated plea of “wheh,” accompanied often by a brisk upward nod of the head—as if to imply, “Hey—can you not clearly see me?” If this fails to gain my attention, I might get a gentle hoof to my backside or a good nudge and rubbing from a fuzzy head on my hip.
The buck Stumpy greeting the author with a nod.
Many vocalizations have to do with various levels of discord that often arise in the group. Trespassing on one’s space is cause for some level of censure, which may involve a few brisk whacks to the backside, accompanied by a few staccato grunts that help reinforce the gravity of the perceived trespass. When individuals stand and face one another on hind legs with violently striking hooves, their voices can be exceedingly loud and seem to correspond in volume and intensity to the level of anger and violence. These events, whether between bucks or does, always remind me that this level of viciousness could be devastating if directed toward a human. Often bucks in territorial conflict will emit similar huffing barks like the does, but the larger, resonating bodies and the degree of anger can make the vocalizations much more impressive, but these sounds should not be confused with the territorial rut roar. The bellowing, roaring voices and the savage aggression of an all-out confrontation between two dominant, warring bucks, with mud, snow, and fur flying and with the ear-splitting crack and clatter of massive antlers, make for a spectacle of truly monumental proportions. These mercifully rare fights are testimony to the true power of this animal. I am always inspired to just stand back and move away slowly.
The fawns are the most predictably vocal of all the deer and often may be heard calling to their mothers when they suddenly feel vulnerable or abandoned. They will vocalize repeatedly with one of the most heart-wrenching sounds in all of nature. With an almost irresistible, high-pitched, pleading “mew” that would soften the most hardened heart, they plaintively and repeatedly call until mother returns with her “come-to-me” call, and the pitiful little waif runs to its mothers side with tail raised high and wagging. One of the most heartbreaking experiences of my life has been listening to the inconsolable calls of a fawn or pair of fawns as they cry for days and nights for a mother who has been killed. It is most horrible when the fawns are still young and spotted, but fawns often continue nursing and remain completely attached to their mother for many months after spots have disappeared. Even these older fawns in fall and winter will wander for days calling and searching for their lost mothers. Furthermore, a fawn in mortal distress, whether somehow trapped or captured by a predator, will discharge a bloodcurdling, shrill cry that can be easily heard for half a mile. When I hear that sound, I always instinctively grab a rifle and go on the run, and there is no room for negotiation.
Elvin, always a sick fawn, seen here vocalizing with the author.
As a human observer who has in essence made himself a member of this group and interacts in close—even hands-on—proximity, I am constantly, and by design, pushing the possible boundaries of human and wild mule deer interaction. The deer let me know when I have gone past their obligatory boundaries, and I quickly correct my inappropriate behavior—so far with no apparent cause for resentment in any individual. In previous relationships with other species, I have made a concerted effort to avoid ever using my human voice, but not so with mule deer. I do find that they have the capacity to comfortably relate to my voice in fascinating ways. For example, I have always found it interesting that mule deer clearly learn and know their names.
As soon as we named the first deer, Rayme, she recognized it and responded. We soon realized that others had the same predisposition. They clearly had some capacity for this form of individual recognition and identification. So, I began to demonstrate over and over again that within a browsing group of thirty deer, I could call, “Rag Tag!” or some other deer’s name, and, in almost every instance, Rag Tag or the other individual in question would look up inquisitively and amble over to my side, at which time I might offer her a little grooming or perhaps a cookie. In a few minutes she might lose her fascination with my company and begin browsing at my feet. Another strangely interesting and mysterious observation that occurs without fail is the response to my voice in times of fear. If one deer suddenly startles for any reason, all the other deer will respond with some level of panic, and the deer may all run and scatter. This response is rarely from the stimulus of a charging mountain lion, for example—but that is always a possibility—so the level of response is obligatory and completely appropriate as an important survival strategy. No deer stands around questioning why another deer is so upset. But, more often, it is merely a reaction to someone—deer or human—accidentally slipping on the ice or some other clumsiness that created an involuntary stir. If I perceive that the source of the fright was not caused by a real danger, I can actually quell their fear and stop their flight with a few words. A simple “it’s OK, girls” will often conclude the drama, and everyone will immediately reassemble and relax, as they clearly recognize that their reaction was not based on a real threat. And not uncommonly, of course, I was the sole source of the clumsy or awkward thing that created the turmoil in the first place. Similarly, if I approach a particularly shy deer who has always been uncomfortable with my proximity, and this individual is clearly starting to become disturbed and bordering on panic, I can simply say something like, “It’s all right, girl, it’s just me,” gain her eye, and then look away—and immediately it has a calming, reassuring effect. In almost every case, the deer will turn and face me, and the eyes will soften. Then, to show that she is convinced, she also will look away. Of course, deer do not understand human language, but, without a doubt, they tend to derive some meaning from the context and tone of my words. These deer are clearly consoled by my voice, but, more important, they are attentive to any possible meaning and appear to make associations with specific words. In our interaction with dogs, for example, we find nothing extraordinary about associations and responses to the human voice. However, dogs have been bred for thousands of years to pay attention in this way. Accounting for these traits in a wild mule deer is an intriguing mystery as I question the origins or advantages of this obvious ability.
Of Space and Species
Most social animals possess a clearly defined sense of space, and even though instinct often demands that these organisms remain in close proximity, that proximity may be rigidly defined, and each animal is expected to respect the individual space of the other. When any deer’s space is violated, she becomes noticeably uncomfortable, then, often with a raised chin, perhaps with ears pinned back, she warns the offender. If this gentle reminder is insufficient, a lurch forward with a raised front leg will often send the offending deer back into its rightful space. Any deer’s butt in your face is deemed unacc
eptable and regardless of status is cause for a brisk whack across the offending derriere. And, in almost every such instance, regardless of rank, the offending doe, buck, or fawn always politely and with a sudden leap surrenders that space without a resentful glance back. Clearly, it is an innocent mistake and not a deliberate affront. Young, unsocialized fawns are constantly reprimanded with a stern hoof across the backside or between the ears as the herd passes the rules of mule deer etiquette from one generation to the next. However, when two deer of similar rank seem to find their proximity in dispute, and often when a desirable food is in contention, hostilities may escalate into a frontal assault resolved with only a couple of well-placed hooves to the head or shoulder. If this confrontation is complicated, perhaps by hostilities involving previously unreconciled disputes, both deer may rear up on hind legs, with ears pinned, and with loud, staccato, grunting vocalizations, hammer each other violently. Usually in short order, one deer submits, and then may be pursued with one or two more obligatory and humiliating blows to the backside. These rare disputes can be violent and frightening, as sharp hooves send surprisingly powerful blows resonating through a body cavity, sounding more like the blow from a baseball bat than from the hoof of a deer. And, once in a great while, one will be slammed violently to the ground, becoming vulnerable to injuries more serious than mere bruised dignity. Fortunately, these fights rarely escalate to such viciousness, and mule deer society remains, in large part, one of apparent harmony and accord.
The Touch Factor
The deer love to be scratched and groomed. It’s an essential aspect of our interaction. One day, while standing among twenty deer and interacting more directly with a deer that I had known for several years, she became resentful of a nearby deer. This is a predictable occurrence with many deer, and I cautiously suggest that it appears to be some sort of jealous behavior. As she pinned her ears and began to charge the intruding deer, I wanted to forestall some unnecessary rancor and thoughtlessly grabbed the 150-pound deer with considerable force, using one arm across her chest and holding her tight with another arm over her back. She was suddenly stopped and completely restrained! To my great surprise, rather than being instinctively resistant or even terrified by her confinement, she simply relaxed in my arms and gave up on her attack, but continued to focus her attention on the retreating doe—and not her apparent captor. I released her, and we resumed our interaction. I have repeated this intervention many times with particularly familiar deer to prevent hostilities, especially when the hostilities are directed toward a smaller yearling or fawn. And, so far, we have never had any misunderstandings, resentments, or fear—so, I ask: How can a wild deer calmly accept physical restraint from a human? Why would it have the capacity to allow restraint by an alien species, when the only restraint a deer can possibly know is on the occasion of being seized by a large predator? Who can account for such unexpected behavior in these extraordinary creatures? Of course, I would never be so foolish as to intervene with two mature bucks expressing hostilities. In these cases, I am strongly inclined to move in the opposite direction.