White-Tailed Deer and How they survive in winter BY: Lindsey Keiser and Kimberly Berger
OVERVIEW • Body & Behavioral Adaptations to Winter Climate • Deer Yards • Winter Food • Threats to Survival • Conclusion
Body & Behavioral Adaptations to Winter Climate • Their coat changes from their summer coat of a reddish color to their winter coat that is a darker brown • This process is called Photoperiodism • This starts to occur in late August early September • Once their winter coat is fully grown they must constantly shake to rid themselves of the water that has soaked in.
Coats WINTER SUMMER
Preparations for Winter • Most deer go into winter with some fat on their bodies. • Amount is determined by the quality and quantity of food available. • They build up the fat reserves in September and October. • The way that they achieve this is by searching out food with the most nutrition. • Examples are apple orchards, hay, and cornfields.
Metabolism Rate • Basic Metabolism- measure of energy requirements. • Heat production must equal heat loss. • Deer to not respond to cold in this manner. • Their metabolic rate drops instead of speeding up when the temperature gets below freezing. • This rate requires a minimum calorie count of 1,140 cal. Per 100 lbs. of body weight. • With this low metabolism rate, deer will lose 12-15 % of their body weight.
Endocrine System • The parts of the endocrine system that are effected are: • Adrenals, pituitary, and the thyroid glands. • They are at there smallest and inactive during Jan. and Feb., the period of the coldest weather. • If the Temp. drop is slow and steady, the deer can adjust to the slowing down of their endocrine system more easily. • If the temp. drop is fast and severe they may go into shock and die.
Bedding down for Winter • During winter deer scrape away the snow to lie on the leaves underneath, creating a bed, this is counter productive. • They burn more cal. Scraping the snow away, when the snow would be more effective if it enveloped the body like a blanket, creating heat. • They spend 90% of their time in winter bedded down, and do little to no activities to conserve energy • Deer use these beds over and over again , and will even become territorial about their beds. • During a heavy snow fall they will lie down & not move unless disturbed. • Literally they are buried in snow
Deer Yards • Deer Yards- are usually in dense evergreen swamps, draws, gulleys, or along brushy waterways. • White tails travel no more than 2-3 miles to yard up • The max. distance they will travel is 15 miles. • Main Objective-to get out of the wind. • Also in deer yards the snow depth is less because the snow gets caught on trees. • Also these spots are warmer then the outside climate due to the fact the trees holding the snow act as a insulator. • Not only is there a food shortage & physical stress, the deer yards have a tendency to become over crowded. • Whitetails are not herd animals by nature, they gather into herds only when forced to.
Deer Yards- aggression & Dominance • Aggression is very common among deer in the yards. • Examples of aggression are the bucks turning on the does and the does turning on the fawns. • They turn on each other because of food shortage. • Dominance is always in a state of flux. • This is due to it always having to be reestablished at every contact because of the need for food. • Bucks are usually dominate because they are bigger and stronger then does • Because Bucks lose their antlers prior or during winter, they fight by kicking out at each other.
Winter Food • The growth of summer vegetation gives false impression that their food is plentiful. • It is important but the critical vegetation is that which is available during winter • Most deer revert almost entirely to brows because they are forced to. • Most herbaceous food is not available. • They mostly search out small, nutritious twigs • The protein level of the plants drops as the plants begin to dry up. • Can drop as much as 25-40% • Their digestibility also lessens • In spring they can digest 70% of plants consumed, in winter it drops as low as 12%
Winter Food cont. • Deer are selective feeders. • They instinctively look for the food with the highest protein. • Deer need a mixture of forage types. • The very best food will only sustain them for 2 wks. • White tailed deer love to eat acorns, oak leaves, whatever corn that has been lost to the picker, and rye grass. • Deer also get nutrition from the bark that they eat & not from the cellulose of the wood.
Threats to Survival • Two main threats to the survival of deer: • Starvation & Snow depth’s effect on their movement. • Starvation is a major cause of white tail deaths during the winter season. • When easily reached food is gone, deer will stand on their hind legs to reach food on upper branches. • A 7-mon. fawn can reach about 5 ft., an adult doe can reach 6 ft., while an adult buck can reach 7 ft. • Naturally, this causes the fawn to get less food. • The 7-ft height is called the “brows line”. • When food is gone from here it really means starvation
Deer prefer brows no thicker then a wooden matchstick. • When hunger is severe they will eat brows up to the size of a wooden pencil. • When the deer eat the browse of a larger diameter, it is a losing battle. • The older bark of the larger twigs has less protein, and is less digestible. • Also larger twigs have less bark in proportion to their volume. • This means that when they eat the larger twigs they are getting less than half of the nutrients . • There is one last problem, and this sometimes pushes the deer over the edge of starvation. • When they eat brows in winter, it must produce extra body heat to thaw out the frozen twigs in its paunch before they can be utilized.
A deer can lose 30% of it body weight and survive. • The critical point lies between 30-33% • A loss of a full third is always fatal • As temp. drops this is when the fat deposits are used. • The fat surrounding the back and hams is first to go, and then that of the abdominal cavity. • Then the fat in the bone marrow will be used . • A deer in good condition contains 95% fat. • As starvation cont. the liver is also effected. • Ordinarily the liver produces glycogen from glucose and proteins and stores it to be released to the muscles as energy. • Without glucose, the deer develops hyperglycemia. • Hyperglycemia-low level of blood sugar.
Snow depth and its effects • The legs of a average deer are 18-22 inches long. • Fawn legs are 16-18 inches • Deer can walk around in 15 inches of snow but can’t in 24 inches. • In deep snow deer must bound instead of walking. • This is very hard for fawns, and this leads to a high number of fawn deaths in winter.
Conclusion • In this presentation we covered • Body & Behavioral Adaptations to Winter Climate • Deer Yards • Winter Food • Threats to Survival