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Posts tagged “Odocoileus virginianus

Velvet-covered Antlers Growing

Male White-tailed Deer grow a new pair of antlers every year starting when they are one year old.  The size of the antlers depends on the age of the deer, genetics, and diet. Before antlers actually appear, structures called pedicles that connect the antlers to the skull develop.  Growth of the actual antlers begins in March or April and as more nutritious food becomes more available during May and June antlers grow more rapidly.

Antlers are one of the fastest growing bones that exist; growth is regulated by hormones which are controlled by the photoperiod, or length of day . Yearling antlers can grow about 1/8-inch a day during the summer, and adults as much as 1/4th of an inch.  While they are growing, antlers are covered with a layer of tissue called “velvet” which is dense with blood vessels that carry nutrients to the antlers. In August the supply of blood to the velvet diminishes and the antlers begin to harden. By September the velvet has dried and is falling off.  Antlers are used as weapons during rut, or the mating season, after which they fall to the ground, providing a valuable source of calcium and phosphorus for rodents. (Photo by Erin Donahue)

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White-tailed Bucks Shedding Antlers

White-tailed Deer bucks grow and shed a pair of antlers annually.  The main purpose of these bony growths is to serve as weapons against rival bucks during rut, or mating season.  During this time in the fall, prior to their 24-hour receptive period, does release chemicals to signal their readiness to bucks.  These chemicals keep the bucks’ testosterone level high, which in turn keeps antlers firmly attached to their heads.  Once rut is over, does stop emitting these chemicals, and as a consequence, the bucks’ testosterone level drops significantly.

When a buck’s testosterone level drops, it triggers cells called osteoclasts to become more active in the buck’s pedicles, the permanent bony bases which anchor the antlers to the buck’s skull. As a result, calcium is extracted from the pedicles which weakens the antlers’ connection to the buck’s skull, and eventually the antlers drop off.

It is rare that both antlers drop at the same time – usually there are four to eight days between the loss of the first and the second antler. I assumed that bucks needed to knock their antlers against something hard, such as the trunk of a tree, in order to get them to fall off.  However, years ago I witnessed a buck shedding an antler simply by dropping his head and then quickly flicking it upwards, sending an antler flying through the air. (Note pedicle where antler used to be attached. Photo by Alfred Balch)

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Some White-tailed Deer Fawns Still Nursing

White-tailed Deer are ruminants.  The process of rumination (gathering a lot of food at once and then digesting it later by chewing one’s cud) is fully developed by the age of about two months, or roughly by the end of July.  Fawns can be completely weaned and survive without milk at this time, but does often don’t wean them until 3 to 4 months. It’s not unheard of to see a fawn born in May or June still nursing, or attempting to, in October. It stands to reason that it’s hard to give up this valuable source of nutrition, for deer milk is richer in fat, protein and energy than cow’s milk. (Photo taken by Erin Donahue on September 2nd.)

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White-tailed Deer Giving Birth

deer and fawn alert _H6A8525 copy (002)White-tailed does give birth at the end of May and the beginning of June. A doe giving birth for the first time usually has one fawn; in subsequent years, two or three fawns are common. For the first three or four days after it is born, a fawn is odorless and is well camouflaged thanks to its spotted coat.

During this time the mother leaves her offspring (who remain motionless during her absence) and goes off to feed. (It can be three weeks or so before the fawns follow their mother when she feeds.) The doe stays away as much as possible from her fawns during these first days and weeks to prevent her own body scent from giving away their location. She returns to nurse her young eight to ten times in a twenty-four-hour period.

People discovering what looks to them like an abandoned fawn should know that although the doe may not be in sight, she most likely is within hearing distance and is probably watching them. The fawn has not been abandoned and should not be disturbed. (Thanks to Erin Donahue, who took this photograph.)

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White-tailed Deer Scent-Marking

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Scent-marking plays an important communication role in the animal world. A variety of species use glandular secretions to convey (for some distance) messages. From beavers spreading castoreum on scent mounds to fishers leaving their scent every time their hind feet touch the ground, the woods are alive with messages often undetected by most humans. Some of these are left by White-tailed Deer, which have two primary scent-marking behaviors: antler rubbing and scrapes.

One used to associate an antler rub with the act of a buck removing drying velvet from its antlers. However, it turns out that very few rubs are made by deer removing antler velvet, a process that’s normally completed within 24 hours. Instead, most rubs are made by relatively few dominant bucks to signal their readiness to breed and to mark their territory.

All White-tailed Deer possess specialized forehead glands that become increasingly active in autumn, particularly in adult males. All bucks spread their scent by rubbing their foreheads (which contain specialized scent glands) against trees and shrubs that have smooth bark, few, if any, lower limbs and are ½” to 4” in diameter. (Older bucks also will rub trees six or more inches in diameter.) In the Northeast, Trembling Aspen, Staghorn Sumac, Red Maple, and willows are often used for this purpose.

Mature, socially high-ranking bucks exude greater amounts of the glandular secretion than do younger males or females. They begin marking their territory soon after losing velvet and continue marking until they cast their antlers in December or January. The chemical signals left at a rub site tend to suppress the aggressiveness and sex drive of young males. However, those same signals stimulate females. The amount of rubbing an individual buck does depends on the level of testosterone in his blood, which in turn is largely determined by the animal’s age and dominance status.

We may not be able to detect the chemicals on a rub, but it’s hard to miss the sight of the light-colored blazes that magically appear in the woods at this time of year. (Photo: White-tailed Deer rub on Staghorn Sumac. Thanks to Chiho Kaneko and Jeffrey Hamelman for photo op.)

 


Three-month-old Fawns Soon To Lose Spots

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By the end of August, White-tailed Deer fawns are about three months old. Their mother weans them between two and four months of age and during this time they molt, losing their white spots. A new gray-brown winter coat replaces the coat they were born with.

 


Coyotes and White-tailed Deer

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Coyotes will eat just about anything they come across – rodents, rabbits and hares, beavers, muskrats, birds, even garbage. Whatever is available and whatever they can catch they will consume. Very often you find white-tailed deer hair in their scat (see photo), and while a majority of the time it comes from deer carcasses that they have come across, there are two times of year when they are known to hunt deer. One is in the spring, when fawns are vulnerable, and the other is during the winter, when one of two conditions are present that favor coyotes: when the snow is deep and deer have to struggle to move faster than coyotes, and when there are crusty conditions, when coyotes are held up on top of the crust, but deer break through, often cutting and exhausting themselves.

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White-tailed Bucks Shedding Antlers

1-2-16-antler-049a2440Antlers, the fastest growing mammal tissue on earth, are grown by male White-tailed Deer (and very occasionally females) every year and shed every year. They begin growing in the spring, usually April, and complete their growth in August or September. During this period they are covered with “velvet,” a soft skin containing blood vessels and nervous tissue that supply oxygen and nutrients to the antler. Once growth ceases, the velvet dries up and falls off or is inadvertently rubbed off. The mating season of White-tailed Deer, or rut, during which time their antlers are instrumental in establishing hierarchy and securing a mate, peaks in mid-November. Once mating is over, the disadvantages of antlers (cumbersome shape for traveling through woods, and the energy required to carry them) promote the shedding of these bony structures. Specialized cells (osteoclasts) destroy the bone tissue between the antlers and the skull and antlers are shed sometime between the end of December and the beginning of February.

Most sources state that antlers just fall off or that the buck knocks them off by striking them against a tree. My personal observation of a buck in captivity clarified the way antlers are dropped, at least in this one instance. The buck put his head down, quickly jerked it up and to one side, and the antler went flying.

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White-tailed Deer Winter Diet

1-4-16-fungus-eaten-by-deerimg_0948The diet of White-tailed Deer varies with the seasons, but in general deer require a high-quality diet and tend to choose the most nutritious options available. In addition to mast (fruit, acorns, beechnuts) and browse, herbaceous plants and fungi make up the greatest portion of their food. However, their foraging choices are extensive. White-tailed Deer have been known to consume the washed-up carcasses of alewives after they (the alewives) have spawned as well as insects, mice and the nestlings of ground-nesting songbirds.

Microorganisms inside a deer’s four-chambered stomach enable cellulose in the plant material consumed to be digested. In winter, the microorganisms within the deer stomach are different from the microorganisms in spring, summer, and fall. This change allows deer to digest a diet of woody browse during winter months and turn the high-fiber diet into proteins through intricate physiological processes. Offering food items during this period other than woody browse (such as hay) is detrimental to deer, as it requires different microorganisms in the stomach in order to be digested. Thus, even though a deer’s stomach might be full (of hay, for instance), it may starve due to the inability to digest it.   (Photo: shelf fungus eaten by White-tailed Deer, showing lower jaw incisor grooves)

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White-tailed Deer Diet In Transition

10-25-16-deer-scat-20161017_5319Even if you didn’t know that a white-tailed deer’s diet changes in the fall, their scat would be a dead giveaway. Its texture and formation are excellent indicators of what a deer has been eating. During the summer, individual pellets are often lumped together due to the moisture content of their summer diet (grasses, clover, alfalfa, apples and other herbaceous food). As winter approaches, deer transition to a diet of twigs, leaves and acorns which results in the formation of individual, dry pellets. At this time of year, it is possible to find both forms of deer scat.

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White-tailed Deer’s Diet Changing With The Season

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Being ruminants, white-tailed deer have a four-chambered stomach which allows them to digest a wide variety of food, including leaves, twigs, fruits and nuts, grass, corn, alfalfa, and even lichens and fungi.  Their stomach hosts a complex set of microbes – organisms such as bacteria, which are too small to be seen with the naked eye – that change as the deer’s diet changes through the seasons.

In general, the green leaves of growing plants are consumed in the spring and summer, while fruits and seeds are eaten as they become available. Hard mast foods, such as hickory nuts and acorns, are an extremely important component of fall and early winter diets when deer need to establish fat reserves. The buds and twigs of woody plants are a mainstay of their diet in winter.

At this time of year it is not unusual to see deer grazing in fields that are just starting to have a touch of green. Grass is a welcome change from their winter woody diet, but it only comprises a very small (less than 8%) of a deer’s overall diet, due to its low crude protein and digestibility. Because their rumen (the stomach chamber where most microbial fermentation takes place) is small relative to their body size, a white-tailed deer’s diet must be high in nutritive value and capable of being rapidly degraded in the rumen.  Therefore, white-tailed deer rely primarily on alfalfa, clover, beans and other legumes, additional herbaceous flowering plants, and browse, all of which have more protein and are more easily digested than grasses.

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White-tailed Deer Scraping Bark

3-3-15  deer scraping2IMG_0490During the winter, white-tailed deer browse on the twigs, buds and bark of trees. Deer have incisors in the front of their bottom jaw, but none in the front of their top jaw, just a hard palate. They grip the bark with their bottom front incisors and scrape their jaw upwards, leaving behind grooves the width of their bottom incisors. Often there are frayed ends of bark at the top end of the groove, due to the deer having to use its hard palate and incisors, rather than two sets of incisors, to separate the bark from the tree. Favorite trees include red and striped maples, oaks, poplar, pines, hemlock, arborvitae and balsam fir.

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White-tailed Deer Breeding Season Winding Down

12-10-14  antler rub 195 The breeding season of White-tailed Deer extends from late October to mid-December. Fresh buck rubs, where bucks literally rub the velvet off of their antlers as well as communicate with other deer via their scent, can be found throughout this period of time.

Mature bucks make two distinct types of visual and olfactory signposts —early-season and breeding rubs. The early-season scraping of antlers builds up neck and shoulder muscles, designates a buck’s territory (both visually and by scent deposited from forehead glands) and releases aggression caused by rising testosterone levels. Later in the season, once the rut begins, bucks move out of their home ranges into doe territory, where they make breeding rubs. These rubs announce the bucks’ presence to does, and are thought to hormonally suppress small bucks to the point where their testosterone levels stay so low that they do not attempt to mate.

When a deer or moose strips bark off a tree to eat it, the de-barked area is torn only at one end — the deer grabs one end of the strip of bark and tears it off of the tree. The rubbing of an antler leaves ragged bits of bark at both the top and bottom of the rub. Staghorn Sumac, as pictured, is a favorite rubbing substrate.

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The Silent Communication of White-tailed Bucks

9-23-14  antler rub IMG_7310Rising levels of testosterone circulating in a buck’s blood toward the end of summer results in the maturation of antlers and the drying up of the velvet that was providing nutrients to them. It used to be thought that bucks engaged in rubbing their antlers against saplings at this time of year in order to remove the velvet, but research has shown there is much more behind this behavior. Rubs are visual and olfactory sign posts that transmit important information to other bucks and does in the area prior to and during rut, such as individual buck identification, breeding readiness, age and hierarchy.

The positioning of the antlers against a tree is not random — a buck generally rubs the base of his antlers and his forehead skin against the tree. The skin between antlers contains a multitude of scent-producing skin glands called apocrine glands (humans have them and utilize them during emotional sweating). These glands typically are inactive during the summer months, but in response to rising testosterone levels, they become increasingly active in the fall. The most active glands are found in mature dominant bucks.

Thanks to recent studies we know that more rubs are made in years of good acorn production than in poor mast years. Young bucks appear to make fewer rubs than mature bucks, and they tend to start rubbing much later in the fall (so rubs you find now were most likely made by mature bucks). Research suggests that older bucks may be making more than 1200 rubs during the roughly 90-day rubbing period, which comes to about 15 rubs per day.

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Opportunistic White-tailed Deer

white-tailed deer and nip twigs 008One of the most obvious signs associated with porcupines is the presence of “nip twigs” on the ground – severed tips of Eastern Hemlock branches dropped from above after porcupines have eaten the buds off of them. It usually doesn’t take long for White-tailed Deer in the area to detect this easily-accessible source of food. Tender tips that would be out of reach without the assistance of porcupines are quickly consumed by White-tailed Deer. Look for deer tracks and scat beneath trees in which porcupines are feeding. (Note wide porcupine path on left leading to den tree. All other trails were made by deer.)

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White-tailed Deer Pheromone Glands

11-15-13 white-tailed deer glands 582Animals communicate with their own species through strongly scented chemicals known as pheromones. Many mammals have glands that generate pheromones. The messages the scents convey vary according to the pheromone that is used – they can indicate alarm, territorial boundaries, the age of an animal and/or its sex, hierarchy and the receptiveness of an animal during the breeding season, among other things. White-tailed deer have scent glands where you might not expect them – their heads, legs and feet. Their primary glands and their functions are: forehead (scent left on antler rubs and overhanging branches), preorbital (near eye, doe uses it to communicate with fawns), interdigital (between the two toes of each hoof, foul-smelling yellow substance left on the ground with every step a deer takes), nasal (inside nose, may produce a scent, or may just lubricate the nose), preputial (on inside of buck’s penal sheath, function unknown), tarsal (inside of hind legs near middle joint, urinated on to spread scent, used intensely by bucks during rut) and metatarsal (outside of hind legs between ankle and hoof, function, if any, unknown).

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White-tailed Deer Bed Positions

2-26-13 deer bedsIMG_5183If you walk in many of New England’s woods, it is likely that you will come upon deer tracks. If the snow isn’t deep enough to keep the deer confined to one area, or “yard,” such as this year, then tracks can often be found throughout the woods. Where there are tracks, there are also beds – spots, often on higher ground, where deer bed down for the night. By looking at the edges of the indentation left when a deer lies down, you can usually determine which direction the deer was facing. (It’s back leaves a fairly symmetrical curve in the snow, and its knees often make impressions.) Deer frequently travel in herds and bed down together. Because they are prey for numerous animals, it should come as no surprise that their actions, even ones as simple as in which direction to lie down, are intentional. If you look at an area where several deer bedded down, you will usually find that each deer is facing a different direction. This is so that, together, they have as much of a 360 degree view as possible, in order to spot an approaching predator. The deer that occupied the closest bed in this photograph was facing right, while the further deer was facing left.


Moose and White-tailed Deer Track Comparison

1-29-13 deer & moose track IMG_2286Even with the knowledge that the moose is the largest member of the deer family, the discrepancy between the size of its hoof and that of a white-tailed deer’s is impressive. A moose’s front foot track is somewhere between 4 ¼ ” and 7” long, whereas a deer’s front track is between 1 ¼ “ and 4” long. Both have hooves that are heart shaped, and point in the direction of travel. Deer are more hindered by snow than moose, so finding a deer taking advantage of a moose’s trail by stepping directly in the moose’s tracks (see photo) makes perfect sense. (The moose’s foot was dragging as it stepped into the snow, thus causing the groove that leads to the track.)


White-tailed Deer Population Estimation

12-14-12 deer scat IMG_6670White-tailed deer are known to eat over 600 species of plants in North America. They consume, on average, about 5 to 8 pounds of food for every 100 pounds of body weight, per day. As a result, a deer, on average, defecates about 13 times a day. A crude but somewhat accurate way to estimate how many white-tailed deer are in your area is to count the number of scat piles you find in a square mile within 24 hours, and divide this number by 13. A little snow on the ground would make this particular method of population estimation a lot easier!


White-tailed Deer Carcass

12-11-12 Deer Carcass IMG_5851Long before the beetles and flies move in to get their share of a dead carcass many meat eaters have usually taken advantage of the easy meal. A motion camera on a dead white-tailed deer recently captured the images of 12 scavengers over a six day period. They included an opossum, several coyotes, a raccoon, red fox, striped skunk, American crow, raven, turkey vulture, red-tailed hawk and bald eagle. By the end of this time, there wasn’t much left except for bare bones, which, as winter progresses, will eventually be eaten as well. Not a shred is wasted – nature knows how to recycle and has been doing it for eons.


White-tailed Deer Diet & Digestion

11-30-12 deer eating IMG_6035A white-tailed deer’s diet consists of a wide variety of herbaceous and woody plants, the ratio of one to the other being determined by the season. Fungi, fruits and herbaceous plants form much of the summer diet. Dried leaves and grasses, acorns, beechnuts and woody browse are important autumn and early winter food. After snowfall, the winter diet consists mostly of woody browse (twigs, leaves, shoots and buds) from many different trees (maples, birches and cedars among them). Come spring, deer eat buds, twigs and emerging leaves. Deer are ruminants (as are cattle, goats, sheep and moose). They have a four-chambered stomach, which is necessary in order to digest the cellulose in the vegetation they consume. Food goes first to the rumen, the first of the four chambers, which contains bacteria and other microorganisms that help digest the cellulose. Food is circulated from the rumen back to the deer’s mouth by the second chamber, or reticulum, and the deer ruminates (“chews its cud”). The third chamber, or omasum, functions as a pump, sending the food to the final chamber, the abomasum, where the digestion process is completed.


White-tailed Does Still Nursing

A doe giving birth for the first time usually has one fawn.  The following year, and until she is quite old, twins are the norm.  Triplets are fairly common, quadruplets are known, and there are at least two records of quintuplets.  Fawns nurse for eight to ten weeks before being weaned.  It’s apparent from this doe’s udder that her young are still nursing in late July.


White-tailed Deer Carcass on Ice

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Often when a deer goes down on ice, it is unable to get back up on its legs. Because of how a deer’s hip and shoulder joints work, one fall can tear connective tissues in a way that keep it down. Its legs splay outward as it falls and it can’t get up.  It is then destined to freeze, starve or be found by predators.  Whether it slips on its own, or is chased out onto the ice by a coyote or some other predator, a fall can be a death sentence for deer. However, its carcass does not go to waste.  It doesn’t take long for predators and scavengers to become aware of this bountiful supply of food.  For years, in Massachusetts on Quabbin Reservoir, bald eagles have relied on ice-stranded deer for their winter survival.  The deer in the accompanying photographs was consumed in a few days by a wide variety of predators, including bald eagles, coyotes, red foxes and a great many ravens, judging from tracks found nearby.  Not a morsel did they waste – the hide was thoroughly cleaned, and the organs, flesh and many of the bones were eaten.  The only portion of the deer that hadn’t been touched was the contents of its intestines – everything else had been picked clean as a whistle.