Deer Anatomy and Physiology:
In order to understand and humanly harvest our quarry it is in the bowhunter's best interest to spend some time learning this subject. The Whitetail Deer is physically well suited to not just survive but to thrive in the habitat in which it resides. This has been pointedly demonstrated by its phenomenal expansion in North America.
Life Span: Although most bucks are killed before they even reach their prime at five years of age, many does live to be much older. Deer have a usual life span of eight to eleven years. There is one authenticated record of a deer kept in captivity that lived to be nineteen years old. Does begin to decrease in fertility after they are nine years old, although most does bear at least one fawn a year till they die.
Pennsylvania's Game Research Division has found
from records of antlered deer killed that the age of bucks breaks down
The most common way of determining a deer's age is to check the
amount of wear on the premolars and the molars. At birth, the fawn
has eight incisors. Four premolars develop in about a week and the
last pair is in place in a month. At three months of age, the first
set of molars erupt, the second set of molars at six months, and in nine
months the third set of molars completes the dentition. At seventeen
months of age the three cusped cap of the rear premolar drops off and is
replaced by the permanent two cusped cap. From this time on, the
age of the deer can only be estimated by wear on the teeth. Many
factors affect this wear, but it is still the best field method of telling
a deer's age. A more accurate method, counting annual rings inside
a deer's tooth, requires laboratory equipment.
Outward Appearance: The whitetail differs from the mule or blacktail deer mainly in the shape of its antlers. The whitetail's antlers consist of two main beams that grow out and backward from their bases and then sweep forward. Single tines, or points, grow upward off these main beams, and there is a small tine above the brow. The mule and blacktail deer have antlers that branch into forks, with each fork branching again into two tines. There is also a brow tine near the base of each antler, but it is smaller than the whitetail's.
The most common misconception about the whitetail is its size. Almost everyone, including experienced hunters who should know better, usually holds his hand shoulder-high when indicating the size of this deer. He would do better to hold his hand a little above his belt, for the average whitetail stands between 36 and 40 inches high at the top of the shoulder. Especially big bucks may be 42 inches high. They have a total length of between 60 to 75 inches and an average weight of about 150 pounds. The Florida Key deer seldom weigh more than 80 pounds, while the largest whitetail deer on record is 511 pounds.
As previously mentioned, deer vary in color shadings from area to area. They also vary with the season. All whitetails shed twice a year. In the spring, they get a new coat that is a bright reddish-brown, the hair solid and thin. As cold weather approaches in the fall this hair is replaced by the winter coat, which shades from bluish to a grayish-brown. The winter hair is long, kinky, and filled with air pockets providing excellent insulation. I have often seen deer whose bodies lost so little heat that snow and sleet did not melt on their backs but remained encrusted on the hair.
Despite regional differences, deer are colored basically alike. They have a jet-black nose with two white bands behind it. The face is brown, the eyes circled with white. The insides of the ears, beneath the chin and the large throat patch are pure white. The body is darkest down the middle of the back, shading lighter till it abruptly reaches the white stomach. The upper portion of the legs on the outside are brown and the insides are white. The top side of the tail is brown with some having various amounts of black at the tip. The underside of the tail and rear portion of the deer is a sparkling white. Like the pronghorn antelope, the whitetail can erect and flare its rump hairs when alarmed. However, bucks do not flaunt their tails as commonly as do the does. It is thought that does do this to guide their young as they flee from danger through the dark night or deep forest. When the deer clasps its tail down tightly and keeps the rump hairs bent inwardly, it is almost impossible to see any of the telltale white.
Albinism, which appears in most forms of life, is a genetic change that prevents pigments from forming in the body. Without pigment, the hair is white, the eyes are pink (due to visible blood vessels), and the hooves are gray. While some true albinos occur in deer, most of the so-called "white" deer are only partial albinos and have patches of white hair on a normally brown coat. It has been observed that these "white" deer usually have a hearing deficiency and that the normal deer avoid them.
Deer's metatarsal gland, halfway between the toes and the heel of the foot, on the outside of the hind leg, gives off musk, but its purpose is not well understood.
Halfway between the toes and the heel of the foot on the outside of the hind leg, the deer has a metatarsal gland. Of the three deer found in the United States, the whitetail has the smallest metatarsal gland. The size of this gland is often used as a means of identification if only the legs are available. Supposedly this gland also gives off a musk; its purpose is not well understood. At the deer's hock on the inside of the leg is the tarsal gland. This gland plays a very important sexual role. In addition to giving off a strong musk, which is attractive to other deer, both bucks and does bend their legs together and Curve their bodies so that they urinate on the hair tufts covering the glands.
Tarsal gland, at the hock on the inside of the hind leg, gives off musk which attracts opposite sex during breeding time.
Many hunters advise cutting off the tarsal glands as soon as you kill a buck, before they taint the meat. These glands do not taint the meat while the deer is alive and cannot do so when the deer is dead. If a hunter is sloppy and handles the glands and then handles the meat, he can transfer the odor. One method is to leave the glands intact until you are ready to skin and butcher the deer, then cut off the entire leg about 2 inches above the gland.
In front of the deer's eye is the lachrymal or preorbital gland. it is used to mark bushes.
Evolutionists believe the ancestors of the deer originally had five toes on each of their feet. Through evolution, the first toe corresponding to our thumb disappeared entirely. The second and fifth toes diminished in size and moved to the rear where they now function as dewclaws. The third and fourth toes became enlarged and form the main hooves as we know them today. Actually, the deer walks on its toenails instead of its toes. This type of foot is very efficient for fast movement over well-packed earth. Between the center hooves is the interdigital gland, which gives off a yellow, waxy substance that marks the ground as the deer walks. This enables the animals to track one another, particularly the doe to follow a straying fawn. Of course, it also enables predators to track the deer.
Buck deer have antlers for the main purpose of fighting other bucks during the breeding season. Recent research shows that the antlers may also be an erotic stimulant. Most bucks lose their antlers during the months of December or January. They have nothing but the antler bases, called pedicels, on their heads until April. During this month, these bases start to swell with the growth of new cells. Horns that are not shed, such as those on mountain sheep, have a center core filled with blood cells which foster growth. Antlers of the deer are solid and nourished externally by a network of blood vessels called "velvet."
Between January and April, after the antlers of the previous year have fallen off, a buck has only pedicels on his head, the bases on which the new antlers will grow.
Musculature System: Muscle and Meat Content: The water content of fresh deer meat was found to be 77.8 percent, and protein content varied from 21-24.3 percent. The glycogen level was found to be relatively high--0.491 percent. Also, muscle fibers are finer than those of any livestock.
Fat Deposits: Fat levels in deer depend on nutritional and social conditions, and sex, age, and season. Fat is stored first in the bone marrow, then deposited around the kidneys intestines, and stomach cavity, in that order. Mobilization of fat reserves should follow in reverse order. Fat that infiltrates bone marrow changes the color and texture of the marrow, making it possible visually to estimate the grade of fat present. Femur marrow generally is used for fat analyses. According to the study of Stockle et al. (1978), measurement of bone marrow fat can be improved using the ''Hobart Percentage Fat Indicator." Marrow fat itself was not found to be a reliable indicator of physical condition in deer.
Heart. Whitetail Deer, like most
mammals, have a four chamber heart which circulates blood through the circulatory
system. It transfers oxygen and nutriants throughout the body and
carries away carbon monoxide and waste materials for disposal.
Digestive System: Members of the deer family, unlike most mammals, do not have any teeth in the front of the upper jawbone. Replacing the teeth is a resilient pad that makes contact with the lower incisors. Deer have 32 teeth: 8 incisors, 12 premolars, and 12 molars. They usually do not have any canine teeth.
The members of the deer family are ruminants, having a four-compartmented stomach, which allows the deer to feed very rapidly, chewing its food just enough to swallow it. This partially chewed food goes into the storage section of the stomach known as the rumen. A feeding deer is at a disadvantage because while feeding it cannot be alert to danger. Not having to masticate its food thoroughly, the deer can fill its paunch rapidly and then retire to a safe place to do the job properly. When the deer is ready, it regurgitates a ball of partially chewed food about the size of an orange and rechews it. it then reswallows the food, which now enters the second section of the stomach, the reticulum. From there, it goes into the omasurn, then through the abomasum into the intestines where digestion is completed.
Deer do not have a gall bladder on their livers. This allows them to eat vegetation that would kill domestic animals.
Deer are ruminants, meaning they are equipped with a four-chambered stomach. An interesting characteristic about the ruminant's stomach is that it allows the animal to gather a lot of food at once, then chew, and digest it later. The four chambered stomach is needed to process the large quantities of low nutrient food the deer eat.
Depending on the type and abundance of food, the 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 unchewed 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. These microorganisms 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.
After the deer has filled its paunch, it lies down in a secluded place to chew its cud. After chewing its cud for awhile, 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 goes to the bathroom"
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.
In following articles we will cover Species Behavior & Habits, Species
Habitat Requirements & Preferences with special attention to Diet,
and finally, Hunting Tips & Techniques particular to the Species, all
in the quest of better preparing ourselves in harvesting this wily creature,
the Whitetail Deer......
In the next article of this series we review the Species Behavior & Habits of the Whitetail Deer in Whitetail #3.
Until Then Good Luck and God Bless.......Stu Keck