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Whitetail Deer Anatomy
The whitetail deer (Odocoileus virginianus) is perhaps the most common big-game mammal found in North America. Native to Canada, Mexico, portions of South and Central America as well as to the United States. In the U.S. alone, whitetails (as they are more commonly referred as) exist in all but 5 states (although close relatives, the mule deer and black-tailed deer can be found there.) Those states include Nevada, Utah, California, Hawaii, and Alaska.
Throughout the spring and summer the deer’s coat is a reddish-brown color. As the fall approaches (and throughout winter) their coat turns to a grey-brown. The underside of a deer is often white and continues through to its tail, which when shown becomes a signal to other deer of possible danger. The deer does this by raising its tail during escape. This is where its name originates from.
Male whitetails (also known as a buck) typically weigh from 130 to 300 pounds (although several bucks in excess of 375 pounds have been documented). Female (does) usually weigh in at 90 to 200 pounds. The length of a whitetail will vary from 62 to 87 inches, including the tail, with a shoulder height of 32 to 40 inches.
Easy to recognize, bucks grow and re-grow antlers on their head every year. However, about 1 in 10,000 female deer can also have antlers. Antlers begin to grow each spring of the buck’s life, progressively getting larger as the deer ages. During the spring and summer the antlers are covered with a highly vascular tissue more commonly referred to as velvet. These velvet antlers grow at a rapid pace, sometimes extending more than an inch a day. As the breeding season for the deer approaches in late summer, bucks shed their velvet by rubbing small bushes and saplings. Bucks have also been known to eat their own shed velvet. Bucks eventually shed these hardened antlers after the breeding season has ended (from December through March) and begin the cycle all over again in spring.
Female deer enter into estrus typically in the fall. This period of the year is often referred to as the rut, and is usually triggered by the photoperiod (declining daylight). During this time males compete for the opportunity of a breeding female through the sparring of their antlers. Bucks will attempt to breed as many females as possible during the rut, often neglecting their own need to rest or eat. Because of this, bucks can become highly susceptible to injury or death when the winter sets in, particularly in northern climates where snowfall is greatest.
Females will typically give birth to 1-3 fawns sometime in late spring (May or June) or about 200 days after they have been bred. Fawns are first born without scent and with many white spots to help camouflage them into their environment. This is easily the most vulnerable time in a whitetail’s life as many fawns will fall victim to area predators like the coyote or wolf. Fawns will lose these spots before winter when they typically weigh from 44 to 80 pounds.
Whitetails communicate in a wide variety of ways including, scent, sounds, body language, and tail-positioning. The sounds an individual deer can create are unique to each animal. For instance fawns can produce a very high-pitched squeal referred to as a bleat, to call out to their mothers. Adult does can also bleat. All deer can produce a grunt, a low guttural sound that is most commonly heard in the deer woods. As a buck matures his personal grunt will get lower. Both bucks and does often snort through their nose, a sound that often signals danger by clearing out the scent particles to get a better whiff of that danger. Bucks also can produce a grunt-snort-wheeze pattern that often shows aggression towards another buck. This sound is most commonly heard during the rutting phases.
All whitetail possess many glands throughout their bodies which allow them to communicate without ever seeing each other. Most of these scents are undetectable to the human nose, but some however are so stringent they can be easily detected.
Whitetail have four major glands, they are the pre-orbital, forehead, tarsal, and metatarsal glands. The pre-orbital gland is located in front of the eye; recent research suggests it may be used when it is rubbed on the over-hanging branches (called licking branches) located above scrapes or just as a territorial scent but further research is needed. The forehead gland is located on the head between the antlers and eyes and is often used when a buck rubs along a tree to strengthen his neck before the rut, or by either gender upon the overhead branches that usually accompany a scrape. The tarsal gland is found on the upper inside or middle joint on each deer’s hind leg. An area commonly referred as the hock. Scent from this gland is left on the ground and vegetation below as the deer walk. Last, the metatarsal gland is located on the outside of each hind leg, between the ankle and hooves. Most biologists believe this gland may be used as an alarm scent, only opening when a deer feels it is in danger.
Whitetail Deer Digestive System
Unlike most mammals, deer do not have teeth in the front of the upper jawbone. A resilient bony pad eventually makes contact with the lower incisors as the animal feeds. This pad makes it hard for a deer to break some plants but provides protection from the rough edges of certain foods. Deer have about 32 teeth, which include 8 incisors, 12 pre-molars, and 12 molars. It is rare for a deer to have canine teeth. Deer biologists commonly estimate the animal’s age by the wear on its teeth.
Whitetail deer are ruminants, which mean that they have a four-chambered stomach. However, deer do not have a gall bladder attached to their liver, a function that allows deer to eat vegetation that might otherwise kill another ruminant. Each of the four chambers has a specific function; allowing the deer to eat many different foods quickly and then digest them at a later time in a safer area of cover. Deer must browse quickly since they cannot be at full alert while feeding.
Deer can fill their stomach in about one or two hours, depending on vegetation or mast it eats. They will quickly feed, chewing only enough to swallow. The partially chewed food will then go into the first chamber of the stomach (the storage area) called the rumen. The rumen houses small spaghetti-like fringes called papillae, which vary in length anywhere from 3/8 to 1/2 inch. Over 40 percent of a deer's energy results from the acids absorbed through these papillae and the walls of the rumen.
When the deer reaches security it will regurgitate a ball of partially chewed food and re-chew it properly. This regurgitated food is known as cud. Once re-chewed, this food will now enter the second chamber of the stomach called the reticulum. The reticulum has a lining that looks like a series of honeycombs and its main function is to filter out any foreign material(s). About sixteen hours after the food visits the reticulum it then passes into the third chamber, the omasum, where the most intensive digestion and absorption will take place. The omasum's lining absorb most of the water from the food. The last compartment, the abomasum, has a very smooth lining that produces acid to break down the food pieces for easier absorption of nutrients before they enter the intestines.
Once the food enters into the intestines it will have to pass through about 67 feet of it, where most of the rest-over liquid will be absorbed, leaving an impacted mass of undigested particles to be left behind as urine or feces. The average deer will “go to the bathroom” about 13 times every 24 hours. Roughly 65 percent of the food will be utilized by the animal.
Whitetail Deer Circulatory System
Whitetail deer, like most mammals, have a heart made up of four chambers which circulate oxygen carrying blood throughout the body. In addition, the heart also carries away carbon dioxide and other waste materials away for eventual disposal.
There are approximately ten vital circulatory channels in a whitetail deer. In the middle of the upper section of the neck is the oblique cervical. While the jugular vein lies in the middle of the lower neck. Below the jugular vein lies the carotid artery. Near the heart lies both the aortic arch and exterior pectoral. Just above the legs is the interior pectoral. The dorsal aorta lies in the middle of the upper back. Leading to the heart from the intestines is the posterior vena cava. In the back hip lies the femoral artery. Along with the heart these circulatory channels push about 8 pints of blood through an average 150 pound deer.
The lungs of a deer complete the same basic function as it does in all mammals, carrying oxygen into and carbon dioxide out of the circulated blood. An average sized 150 pound deer will have two lungs, each about the size of a dinner plate.
The spleen of a deer is a very important producer of certain blood cells known as lymphocytes and stores erythrocytes. Lymphocytes help protect the deer from illness, while erythrocytes are red-blood cells. The storage of these red-blood cells is what can make a whitetail so resilient to blood loss.
In autumn, the blood of a deer carries high levels of both Vitamin K1 and K2. These vitamins act as an anti-hemorrhaging agent and help promote clotting.