White-Tailed Deer and How they survive in winter BY: Lindsey Keiser and Kimberly Berger

 Body & Behavioral Adaptations to Winter Climate  Deer Yards  Winter Food  Threats to Survival  Conclusion

 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.

SUMMER 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.

 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 % of their body weight.

 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.

 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- 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.

 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.

 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%

 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.

 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.

 The legs of a average deer are inches long.  Fawn legs are 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.

 In this presentation we covered  Body & Behavioral Adaptations to Winter Climate  Deer Yards  Winter Food  Threats to Survival