Anatomy of a Whitetail Deer

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Buck Silhouette
The Whitetail Deer is the one of the hardest animals to hunt. Their bodies are built like fine tuned stealth jets, able to pick up the slightest scent, or the most minuscule abnormality in their surroundings. And the older they get, the smarter they are.

Deer are hoofed animals and can grow about six feet long and 3 to 4 feet high. They are reddish or grayish in color; depending on the season. Although weight varies, the larger bucks may be over 400 pounds. The natural life span of a whitetail is 11 to 12 years of age, (17 to 20 yrs. in captivity). However, many live for less time, since they are either hunted or killed by predators. It is believed that whitetails that are hunted live for only about 1.5 years.

A deer's anatomy allows it to be a very clever and versatile animal. Mother Nature has blessed the deer with ultra, keen senses, which allow it to survive in a forest filled with predators. For example, deer possess a sense of smell which is unfathomable to humans. Unlike us, deer rely on their sense of smell for almost everything; from choosing a suitable mate to detecting an approaching predator.

Deer also possess many interesting physical characteristics, such as a deer's antlers and a deer's glands on the outside of their body. Evolution has given deer the ability to transfer important information about themselves through urine and gland secretions. These are truly amazing and appreciable features which aren't known to the average deer enthusiast.

Deer Digestive System

Deer are ruminants, meaning they are equipped with a four-chambered stomach. An interesting characteristic about a ruminant's stomach is that it allows the animal to gather a lot of food at once and then chew and digest it later. The four chambered stomach is needed to process the large quantities of low nutrient food that deer eat.

Depending on food type and abundance, deer can fill its stomach in about one or two hours. When a deer eats, food is moved by the tongue to the back of the mouth, where it is chewed just enough to swallow. The food then passes down the gullet into the stomach.

The four sections of a deer's stomach are the rumen, the reticulum, the omasum, and the abomasum. First the food goes into the rumen which stores 8 to 9 quarts of un-chewed food and acts as a fermentation vat. Most of the digestion occurs in this area of the stomach. Deer depend on billions of microorganisms that live in its stomach to break down the fibers, cellulose, and other basic plant components, and convert them into materials that can be used by the deer's digestive system. The lining of the rumen has small spaghetti-like fringes called papillae, which vary in length from 3/8 to 1/2 inch. Over 40 percent of a deer's energy is derived from the acids absorbed through the papillae and the walls of the rumen.

Big Buck in Woods
The most unique and highly sought feature of a buck is his antlers. Contrary to popular belief, antlers are live tissue, composed of bone.

After the deer has filled its paunch, it will lie down in a secluded place to chew its cud. After chewing its cud for some time, the deer re-swallows the food, which then passes to the second portion of the stomach, the reticulum. The reticulum has a lining that looks like a honeycomb. The reticulum holds the food in a clump, which can grow to the size of a softball. The main function of the reticulum is to filter out any foreign material.

After about sixteen hours, the food passes to the third chamber, the omasum, where intensive digestion and absorption take place. The omasum's lining has forty flaps of varying heights, which absorb most of the water from the food.

The last compartment, the abomasum, has a very smooth, slippery lining with about a dozen elongated folds. The abomasum produces acid to break down the food pieces for easier absorption of nutrients. The food eventually passes through 67 feet of intestines, where most of the liquid is absorbed, leaving an impacted mass of undigested particles. These particles are passed out as excrement. A deer will defecate an average of 13 times every 24 hours. Usually 65 percent of the food will be used by the animal, and 5 percent is lost as methane gas, 5 percent as urine and 25 percent as feces.

Whitetail Deer Antlers

The most unique and highly sought feature of a buck is his antlers. Contrary to popular belief, antlers are live tissue, composed of bone. Antlers are the fastest growing tissue in the animal kingdom; growing at an average of 1 to 2 inches per week. During this growth period, antlers have a constant blood and nerve supply. Researchers agree that antlers have evolved as a weapon to gain dominance over other bucks during breeding season. Fawns are born without antlers, and the first sign of antler growth typically appears after the first year of life. While they are growing, the antlers have a thin layer of velvet, which will be rubbed off after the antlers are fully grown.

Bucks in Velvet

Velvet covers the buck's antlers during the antler's entire growth period. Velvet is a fur which contains a network of blood vessels and nerve endings, supplying the antlers with much needed nutrients during growth. Velvet is also very fragile and bruises easily. Out of fear of damaging their velvet, and thus their antlers, bucks usually remain more docile during the months that the velvet covers their antlers.

When velvet antlers reach peak growth, the velvet covering will die and dry up. The bucks soon become irritated by this dead tissue and attempt to remove it by rubbing their antlers against trees and other protruding objects until the velvet comes completely of; what deer hunters refer to as a buck rub. The buck will then either leave the velvet alone, or eat it. Once the velvet is off, the antlers stop growing and the buck is ready to challenge other bucks for breeding rights.

There is a distinct change in behavior during the periods where the velvet covers the antlers and the subsequent rub-off. During the summer, bucks are very passive, and often attack with their four legs, no doubt to protect their antlers. However, with velvet gone and hard horns exposed, bucks are ready to do battle with each other as testosterone levels increase.

Deer Eyes

Buck Harvest
Some deer hunters wait their entire lives to get an 8 point buck. That is why harvesting a 10, 12, or even a 14 point buck is such an extreme accomplishment. Hunter shown wearing Lost Camo.

Because their eyes are located on the side of their head, deer are able to view a wide range of area at once. This location of the eyes allow a deer to see 310 degrees around itself, which means it is totally aware of the surroundings, even when it appears to stare straight ahead.

Deer see best at night, which is just one of the reasons they are most active at night. Deer have more light-detecting cells in their eyes than humans, which aids their nocturnal vision. Like most nocturnal animals, their eyes exhibit a shine when exposed to harsh light at night. This is due to a reflection off a special membrane in the eye, called the tapetum.

Although their vision is not as acute in the daytime, it is still very keen. Under strong light, such as that present during the daytime, the deer's pupil contract into a narrow band, which allows the deer to focus across the entire horizon. Thus the deer can clearly detect oncoming danger from the horizon while grazing. It is also believed that deer can see in the ultraviolet light range, which is abundant during the earlier AM, late afternoon hours, as well as overcast days.

Although it possesses excellent vision, the deer does not have many of the additional features which most humans take for granted. For example, since the deer's eyes are on the side of its head, the deer cannot focus on one location with both eyes. This results in very poor depth perception. Deer also see at a much lower resolution than humans, and are believed to be color blind. Some research has shown that only in very harsh light can they see color. However, all these additional features are not important to a deer; all that is necessary is the ability to detect danger, which a deer's vision does very well. Despite all these limits, the deer's vision, combined with its other senses, make it a very clever animal.

Deer Ears

The whitetail's ears are crucial to helping it avoid danger. They can easily detect the faintest sound, and in a split second they have the ability decide whether danger is involved or not. Their ears contain many complex muscles which allow it to move freely and with incredible control. Like dogs, deer can hear sounds at higher frequencies than humans, although their frequency range is not as high as that of a dog. The deer's ear can rotate in any direction, which is helpful in determining the direction of a sound. A deer's hearing is so acute that it can also detect the time it takes for a sound to reach one ear relative to the other; this allows the deer to establish how far away a sound is. Once a sound is made, both ears instantly focus on that noise and carefully try to decipher its source. The deer will stop moving and wait for the sound to reappear. If a group of deer are together, their ears become a way of communicating; with a simple flick of an ear they can warn each other about approaching danger.

Deer Coat

Molting Deer
Molting is the transition period between Winter and Summer coats, it makes deer look scraggly but is perfectly normal.

The main purpose for a deer's coat is to provide camouflage and thermoregulation. Years of evolution have turned the deer's coat into a brownish color which blends well with its natural environment. In order to regulate the deer's body temperature, deer will grow different coats during the beginning of the winter and summer months; this process is called molting. Molting is triggered by hormonal changes brought about by the change of the seasons.

However, no matter what the season, all whitetails have a patch of white on their throats, a white belly and a white side of each leg. They also have a 12 to 15 inch long white tail (hence the name). The tail of the doe is more commonly waived in the air than that of the buck. Perhaps this is to help young fawns see their mother and follow her away from danger. It is because of this behavior that whitetails are often referred to as the fantail or flag tail.

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