neighborhood naturalist CORVALLIS, OREGON — FALL 2017
Black-tailed Deer article and illustrations by Don Boucher photography by Lisa Millbank
D
eer move with a kinetic poetry, and it’s a pleasure to watch them. John Muir wrote about the Black-tailed Deer in Yosemite, “...climbing with graceful ease and reserve of strength that cannot fail to arouse admiration.” Deer are ambassadors of nature, and a reminder to us all that we can encounter large wild animals ourselves, not just by merely reading a textbook or watching a wildlife documentary. Everybody agrees that deer are pretty and graceful. Unfortunately, they are often regarded as simple herbivores, and it seems the only people who pay close attention to them are hunters and wildlife managers. In truth, deer are intelligent, resourceful creatures with amazing senses and complex social lives. Even if you don’t see deer often, there are more out there than you might guess. And if deer are commonplace to you, there are fascinating hidden aspects of their lives. As the only large wild mammal that’s relatively easy to see, deer allow us the opportunity to gain a nuanced and deeper understanding of nature. We have three species of deer in western Oregon: Columbian Black-tailed Deer, Roosevelt Elk and Columbian White-tailed Deer. The ubiquitous Columbian Black-tailed Deer (Odocoileus hemionus columbianus) is found from the western Cascades to the coast in Oregon and Washington and in parts of California and British Columbia. It’s the same species as the Mule Deer (Odocoileus hemionus hemionus), which lives from the Cascade crest eastward. The Roosevelt Elk is scattered in the Coast Range, Cascades and a few pockets of relatively wild
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The blacktail’s winter coat is thick and brownish-gray, and has a tidy appearance.
In summer, blacktails appear comparatively scrawny. The gingerbread-colored coat is thin with loose hairs.
areas in the Willamette Valley, and is only distantly related to our other deer species. The rare Columbian White-tailed Deer inhabits two isolated areas, one along the lower Columbia River and another in Douglas County, around Roseburg. All modern reports of White-tailed Deer in the mid-Willamette Valley are almost certainly in error.
The Black-tailed Deer is relatively small and dark, and is characterized by a dark patch on the top of the head. However, the overall color is highly variable between individuals.
Despite their names, White-tailed, Black-tailed and Mule Deer all have white under the tail. The Mule Deer is the only species to have white on the upper side of the tail, the Blacktailed Deer has a dark upper tail and the White-tailed Deer has a longer, fluffier tail, with a tan or brown upper side. When alarmed, they all display the white underside of the tail and a white area on the rump, signaling danger to other deer. The flash of white probably also communicates to a predator that the deer have noticed it, and the element of surprise is lost.
This blue-eyed blacktail doe from southwest Corvallis has a blonde coat, a rare variation. She lacks dark facial, ear and tail markings.
Perhaps you can imagine their dark figures meandering through a large tract of primeval conifer forest, but not many deer are found there. Instead, they roam the edges of the forest, meadows and clearings at dawn, dusk, or during the night. During the day, they find hidden, shady places to sleep. In stormy weather, they seek shelter, often among a few large conifers. Throughout western Oregon, the Cougar is the blacktail’s main natural predator. There are also significant fatalities caused by humans through hunting and traffic accidents. Other predators like Coyotes, Bobcats and American Black Bears play a lesser role. Blacktails living in close proximity to people have
The blonde doe was accompanied by her two fawns, one blue-eyed and fairly pale, and one with more typical coloration.
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adapted well, but predators like Cougars, Gray Wolves and bears generally have not. Hunting isn’t allowed around human settlements, and the minimal predation results in higher deer populations than in wilderness areas. If not for traffic fatalities, populations could be even higher. Blacktails are attracted to some suburban areas due in part to the lack of natural predators and the abundant food options. These areas also resemble their natural habitat because they are a mosaic of open areas, parks, landscaped lawns, forested creeks and river corridors. Unfortunately, this leads to humanhabituated deer that can be a nuisance when they nibble cultivated plants and vegetable gardens. Popular picnic areas and campgrounds also have populations of semi-tame blacktails. Nevertheless, these deer give us a chance to observe the subtleties of their behavior at close range. Even though they seem tame, they still act like wild animals, especially if they encounter you where they don’t expect to see people. The same deer who will browse a few yards away from people on a back porch may flee if they see people in a seldom-visited woodlot or creekside forest. Less-habituated deer are challenging to observe. Superb noses, ears and eyesight, combined with quick reflexes, give them a thorough threat-detection and avoidance system to thwart humans and predatory animals. Their noses are their foremost tool to avoid danger, and are crucial for their social communication. A Black-tailed Deer’s olfactory sensitivity is hundreds of times greater than a human’s, and deer reflexively pay attention to wind direction. Even if you do your best to be free of scents, they can smell your breath and body odor up to a half-mile away—even if your scent isn’t detectable by nearby humans. Therefore, approaching them from downwind is essential. Black-tailed Deer use various scent glands and urine to send signals to each other. The tarsal glands, dark tufts of hair on the inside of the back legs, are the most important for olfactory signalling. When blacktails greet, they sniff and lick each others’ tarsal glands. The glands secrete pheromones, but more importantly, deer regularly sprinkle that area of their back legs with urine. The mixture of urine and pheromone odors is enhanced by the metabolic byproducts of bacteria that live on the tarsal gland hair tuft. The complex scent conveys information about the sex, age, health and mood of the individual. The interdigital glands lie in the cleft of each hoof, on the top side of each foot and are hidden by hair. These glands leave a scent trail as a deer walks, which helps deer locate and identify one another. When mothers need to locate their fawns, or when bucks follow does during the breeding season, they may use interdigital scent trails. Do predators take advantage of these scent trails? Yes, but predators like Gray Wolves, Coyotes and Cougars have other ways to scent-track their prey, even without these interdigital scent trails. For deer, the benefits of the these scent trails outweigh the risks from predators.
Tarsal gland Metatarsal gland
The tarsal glands on the back legs are important to blacktail social communication. The role of the metatarsal glands is not well understood.
Forehead glands
Forehead glands on a doe
This buck is gently rubbing his forehead on the back leg of a smaller buck, near his tarsal gland. Summertime bucks have a friendly relationship, but this may be a casual show of dominance. Perhaps the dominant buck was depositing scent from his forehead glands on the other buck’s leg.
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The preorbital glands are near the tear ducts, and blacktails carefully rub secretions from these glands on twigs, and sometimes on their forelegs. Their forehead glands are rubbed on objects and sometimes on other deer. Lastly, they also have metatarsal glands, located low on the outside of each leg, midway from the hoof to the ankle joint, and their purpose is not well understood. Both Black-tailed and Mule Deer have large ears, supposedly resembling the prominent ears of a mule. They’re always listening, even when feeding, and to some degree when asleep, rotating each ear independently to focus on sounds. In addition to excellent directional hearing, they can hear much higher frequencies than humans can. For blacktails, what they listen to is as important as how well they can hear. They’re instinctively tuned in to the sounds of wildlife around them. Even a quiet hiker’s quick and steady footsteps are distinctive and may alarm wildlife. Waves of alarm calls from birds and squirrels radiate in all directions from the hiker, or similarly, from a predatory animal. Up ahead on the trail, deer notice changes in the sounds of wildlife around them and can move away from the source of alarm without needing to observe it directly. Deer probably learn through experience which types of alarm calls may signify a serious threat, and which they can ignore. A deer’s visual experience is also quite different from ours. Compared to humans, deer have more light-sensitive rods in their retina. They also have a layer of tissue behind the retina, called a tapetum lucidum, that acts as a light amplifier. When light passes through the retina, the tapetum lucidum reflects the light back into the retina a second time. This is why deer and other wildlife show eyeshine when you shine a bright light at them at night. They are acutely sensitive to movement and detect danger from nearly any direction. While they don’t have great binocular vision like humans and many predators, the position of a deer’s eyes on the sides of its head give it a visual field of about 260°. Their depth perception is more limited than a human’s, and they
When alarmed, a blacktail raises its tail, revealing a large white area.
have to bob and sway their heads to get a 3D view of something that looks suspicious to them. In good light, the human retina can detect much more detail than the deer retina. On the brain side of vision, humans have better pattern and shape recognition than deer. Even if you are in plain sight of a deer, you may go unnoticed if they are otherwise unaware of your presence. You can easily be concealed from a deer if you hide motionless behind a few branches, while such a ruse may not work on another human. It’s not entirely true that deer are colorblind. Deer can see colors on the blue and green end of the spectrum. Colors like red, orange and yellow are probably perceived as shades of gray. That’s why hunters wear that bright safety orange. In the end, the colors you wear may not matter much to deer. Many people treat camouflage clothing as a primary way to conceal the wearer from deer and other wildlife. In truth, neutral, earthy colors are typically good enough. Given that deer will smell you, hear you, or react the alarm calls of other wildlife before they can see you, camouflage clothing makes little difference unless all other factors have been meticulously addressed. When a deer is curious about a disturbance or potential oncoming threat, it freezes, sometimes for minutes on end. Once it’s convinced that it has detected a threat, the deer will sometimes stomp a front foot on the ground. This sends an audible signal to other deer nearby who are out of sight. When highly alarmed, blacktails blow air forcefully through their nostrils to produce a loud snorting or barking sound. They quickly flee with their tails flashing white.
Not all blacktails have black tails; many are shades of brown.
Black-tailed and Mule Deer have an escape strategy, unique among North American deer, called stotting or pronking, where they jump along with all four feet simultaneously. African wildlife documentaries often feature the exaggerated stotting display of the Springbok antelope. While it’s not as fast as galloping, stotting is effective when climbing steep terrain and while leaping over shrubs, logs and other obstacles that will
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hinder the advance of their predators. Perhaps like Springboks, stotting may also signal to predators that a deer is too vigorous to chase. While on open ground, or if stotting isn’t fast enough for escape, blacktails and Mule Deer will gallop swiftly, as Elk and White-tailed Deer do. It’s not always easy to approach and observe deer, but it’s usually possible to find evidence of where they’ve been. Look for tracks along silty riverbanks, on muddy trails in winter, or in fine dust during the dry season. Our occasional light snowfalls offer superb tracking opportunities. Where tracking is poor, scat can give clues about deer. Blacktails usually leave scat in the form of oval pellets, roughly ½–1” in length, and often in loose piles. When they eat soft, moist food like fresh leaves and grass in the spring, or apples in the fall, they will leave scat of flattened pellets clumped together. In winter or during the dry season, the pellets are smaller, rounder and uniform in size. Elk pellets are flatter and about twice the size, about the diameter of a penny, but elk calves leave pellets that are comparable in size to blacktail pellets. Rabbit pellets will approach the size of small deer pellets, but rabbit pellets are nearly spherical, dry and left singly. As browsers, deer eat a little bit of vegetation in one spot, and then move on to another area to eat something else. Grazers, like cattle, bison, sheep and horses eat mostly grass and spend a lot of time feeding heavily in one productive area. Unlike these grazers, deer can’t get much nutrition from eating dry grass or hay. Deer eat whatever foods are seasonally available. In the spring, deer eat shoots, fresh grass and other emerging vegetation, while in summer they eat more leaves from trees and shrubs. In the fall, they’ll take advantage of acorns, nuts and fruits, but their diet shifts to twigs, buds, conifer needles and lichens in the winter.
A curious deer will wait motionless to carefully observe.
Like cattle, sheep, goats and antelopes, deer are ruminants and have four-chambered stomachs. They need to limit the time they spend foraging because, when their attention is focused on looking for food, they aren’t as alert to predators. When foraging, a deer collects a large amount of food quickly and stores it in the first stomach chamber, called the rumen. The deer then finds a safe place to rest, and begins regurgitating and chewing its cud. It repeats this process until the food particles are the optimal size for fermentation. Specialized bacteria break down the cellulose fibers of the food within the rumen. In the other stomach chambers, there’s a complex process where some bits are returned to the rumen for further fermentation, and then farther down the line, enzymes break down the by-products of the rumen. Like other ruminants, deer have no upper incisors. They pinch vegetation between their lower incisors and a hard plate on the upper mandible, and then rip it off. In contrast to the roughly torn stems where deer have been feeding, rabbits and rodents clip vegetation neatly with their sharp pairs of incisors. Another sign is left where deer bed down repeatedly, leaving an oval-shaped depression of compressed vegetation or forest duff. The front leg joints sometimes leave divots in soft ground when the deer stands up, and there may also be scat in the bed or nearby.
The variable size and shape of these deer pellets is due in part to a diet of fresh spring vegetation. When deer eat drier foods, the pellets are smaller and more uniform in size.
Blacktail bucks make antler rubs on saplings, and while they aren’t widespread, they’re very obvious signs. You can only find fresh ones in late fall or early winter, around rut season. Look for a small tree that has been stripped of bark and small branches, from ½–3” in diameter, and 10–45” off the ground. Elk bulls also create rubs, but the size of the trees they use is proportionally larger and the rub marks can be much higher.
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Antler rubs have random long, shallow grooves. This looks different from where herbivores strip off bark with their teeth, or when some predators gouge trees with their claws. In both situations, this leaves deep and evenly spaced grooves. Rabbit or rodent
Deer
You can tell where deer have been browsing by the signs of torn vegetation. Rodents and rabbits clip off vegetation neatly with their sharp upper and lower incisors.
Antler rubs only occur during the rut, after their velvet is shed. Bucks have been observed using vegetation to scrape off velvet, but this is not the same as the aggressive rubbing that removes tree bark. While making an antler rub, they spread scent from the forehead and preorbital glands onto the tree, and then rub their scent from the tree onto their bodies. The scent left on the tree acts as a signal to other deer. Some bucks return to the same areas year after year, and you may see the healed scars on nearby small trees. A combination of increased hormones and exercise from antler rubbing leads to bucks having thickened necks during the rut. A buck’s neck thickness may be enhanced by his neck hairs raising when he’s excited. Deer antlers are different from horns because they are shed and regrown each year, whereas horns are permanent. The size of the antler rack is determined by a combination of body size, health, diet and genetics. On average, bucks reach their maximum body size, and antler growth potential, at 4½ years of age. The oldest bucks may not grow the largest antlers as their health begins to decline.
Streamside silt is an excellent place to view tracks.
Blacktail and Mule Deer tend to have a repeatedly forking antler structure. Whitetails, on the other hand, have a curving main beam with a set of unbranched tines. This isn’t a reliable way to determine species because exceptions to the trend are common. Also, young bucks of both species have similar-looking single spikes or forked antlers. Antlers are usually shed sometime in late winter. Finding shed antlers can be a challenge in western Oregon because of the thick vegetation, and they also resemble fallen tree branches. Rodents, raccoons and other animals (including other deer) nibble on shed antlers as a source of minerals, and an antler may be eaten up within a couple of years. Tracks, scat, antler rubs and feeding signs are all connected by another important deer sign—trails. To some degree, deer use human-made hiking trails, or even roads, but more often they use narrow, crude trails made by deer and other wildlife. Knowing where these trails go, and which ones are most heavily used, helps in understanding the movements of a local deer population.
This Douglas-Fir sapling is the victim of a blacktail buck’s rubbing.
Each blacktail will habitually follow certain trails and visit its favorite places on its daily routine. A deer has a home range of about one to two acres, but they don’t keep well-defined territories. The size varies with the quality of habitat, the local deer population, natural and man-made boundaries and other factors. Home ranges overlap, there can be seasonal shifts, and a deer may also leave its home range if there is an abundant food source nearby. Bucks may leave their home ranges during the rut to follow does.
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Blacktail Tracks Blacktail tracks adult walking
Blacktail track running, leaping, or stotting
Elk track
Front hoof 2¼” – 3¾” long
Blacktail tracks are wedge-shaped with cloven hooves, and they don’t closely resemble any other wild animal tracks in our area. Elk tracks are more oval and about twice as long. Deer hooves spread when they run, accelerate, climb, or when they walk on soft substrates. In these situations, the dewclaws may also leave impressions. When running, stotting, or jumping, the front edges of the tracks have prominent ridges and/or flecks of debris in front of each track from the impact of the hooves. Stotting The tracks made by stotting often register dewclaws.
Direction of travel Rear hoof: 2” – 3¼” long
Dewclaws
About twice as long
When deer walk, the rear hoof commonly steps on the front track, leading to overlapping tracks. A single deer leaves hoofprints of two different sizes. That’s because the front hooves are larger than the rear hooves, and they also bear more of the deer’s weight.
Some blacktail populations migrate to lowlands in winter, and in summer, they go to higher elevations. Bucks typically range farther and higher in the summer than does do. During hunting season, deer may seem to disappear, but instead of leaving their home range, they will hide more often or restrict their activity to night.
Front hooves
Rear hooves
other with their front hooves. Most of the time, conflicts are avoided with scent markings and body language. The social ranking among bucks is followed a little more loosely, but escalates during breeding season from mid-October through December. Dominant bucks are very aggressive to does
When a deer sniffs the air, it’s not merely sampling the air for a potential predator, it’s assessing what other deer have passed by, and how long ago. The boundaries of their home ranges aren’t too important to deer because they instead maintain a dominance hierarchy. It’s like a pecking order, where some individuals move about more freely than others, and they may enjoy more privileges around food resources or resting areas. Does have a social order that is strictly followed, all year long. A dominant doe walks among others confidently, with her head held high. She freely approaches others to sniff their tarsal glands. A submissive doe gives others a wide berth, with her head low. During squabbles, a sign of physical aggression is a light kick with a front hoof, and a submissive deer will back away. Escalations lead to does rearing up and swiping at each
A young blacktail buck at the highest point of the stotting gait
Stotting is an escape strategy that is characteristic of Black-tailed and Mule Deer.
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Many bucks remain solitary for most of the year, while other bucks hang out together in small groups of buck-bros, typically six or fewer. Outside of the breeding season, they casually assert their dominance through scent and body language, but tend to get along quite well. Bucks also groom one another to reinforce their friendly bonds.
This blacktail buck visits a suburban neighborhood in summer. Although his antlers are still in velvet, it looks like he may have grown a rack of ten points.
and other bucks during the rut. Large bucks lock antlers in fierce combat, though most interactions are settled through posturing or chasing. At this time, younger bucks will spar with each other, but aren’t too serious about it. Even so, bucks don’t rule deer society. Dominant does have much more control over where other deer go and what they do. Bucks generally work within that social structure and have little control over it.
The does’ family group dynamics change in May or June, when pregnant does stake out hiding spots to give birth. A doe may become very aggressive about maintaining her privacy, and she may drive away the older fawns in her family group. Twins are more common than single fawns, and triplets are rare. For the first few weeks, when a fawn isn’t nursing or being groomed, it lies low, nearly odorless, in a shady hiding spot, while the mother feeds nearby. After that, the mother and her young gradually venture out together, and the new fawns encounter other deer for the first time. Fawns keep their spotted coats for three or four months, until they start to grow their winter coats. Now that the Black-tailed Deer’s breeding season is underway, there’s increased deer activity. It’s an ideal time to start paying attention to their behavior and the signs they leave if you’re out in natural areas. Maybe, with a little more knowledge and appreciation for these fascinating animals, you can improve your chances for special deer encounters. ó
Small family groups consist of a mother and her fawns, and maybe some yearlings from the previous year. The group may include the oldest doe’s grandchildren, and if they are female, they may stay within the group until they’re yearlings. Bonds are maintained by mutual grooming around the face and neck, and other cues from scent and body language. In winter, they may gather in larger numbers, especially around food sources, but within these larger groups, families tend to stay affiliated with one another. Watch a video about Black-tailed Deer at www.neighborhood-naturalist.com
Neighborhood Naturalist promotes interest about nature in mid-Willamette Valley backyards, neighborhoods and countryside.
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Velvet covers the antlers from spring through early fall. Under the dense cover of short hair is vascular tissue that nourishes the growing bone underneath.
2855 NE Lancaster St. Corvallis, OR 97330
541-753-7689 donaboucher@gmail.com www.neighborhood-naturalist.com ©2017 Don Boucher and Lisa Millbank
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