What deer eat and why: A look at white-tailed deer nutrition. Mike Miller Technical Guidance Biologist Wildlife Division - District 3

Transcription

1 What deer eat and why: A look at white-tailed deer nutrition Mike Miller Technical Guidance Biologist Wildlife Division - District 3

2 Dietary strategy Nutritional requirements Food habits Influences on forage availability Nutrition is a fundamental aspect of white-tailed deer management

3 Dietary strategy White-tailed deer are concentrate selective feeders. Forage and seek cover. Cannot eat enough low quality forage to meet nutritional needs.

4 Digestive anatomy Photo by David Hewitt

5 Plants they're what s for dinner Browse tender growth & leaves of woody plants. Forbs broad-leaved weeds Grasses Mast fruit of woody plants

6 What is a nutrient? Protein Energy Minerals Vitamins Water

7 True or False? Protein is the most limiting nutrient in Llano County. False

8 Energy More limiting than protein Ability to do work Cost = BMR + activity Maintenance at 2.17 kcal/g. Drought 2 kcal/g. DE Good conditions ~ 3 kcal/g. DE Carbs = 4.5 kcal/g. GE Fats = 9 kcal/g. GE Multiple of BMR

9 Are the deer getting adequate DE? Body condition, fat, field-dressed weight

10 What can I do? Manage for diversity of plants Lower energy expenditure: Reduce travel distance Maintain proper cover Supplement

11 True or False? Forages need to provide a minimum of 18% protein, year-round to maintain deer herds in Central Texas. False

12 Protein Muscles, hair, hooves, bones, antlers (45%) Plant protein - microbial protein 8.5 Protein Needs % CP needed for maintenance Select diets w/ 13-16% CP

13 What are the implications of a low protein diet? Nitrogen recycling for body maintenance Small, weak fawns Smaller antlers

14 Minerals 14 mineral requirements Can be difficult to understand Macro: Ca, P Will utilize antler and bone 2:1 ratio optimum Seasonal osteoporosis Micro: Cu, Zn, I, Se Support multiple enzyme systems that maintain health Scarce forbs = mineral deficiencies Mat euphorbia

15 Vitamins Required in small amounts Support enzyme systems Fat Soluble: A, D, E, K Stored in fat and in the liver Water Soluble: 10 vitamins Dietary sources & microbe synthesis Vitamin E is linked to immune function and fawn survival Vitamin A deficiencies may slow antler growth Both vitamins are provided by green, leafy vegetation

16 Water Daily requirement: 3-6 quarts Water restriction can decrease food intake (63% in one study). Drinking, preformed and metabolic Browse 45-65% water Forbs 70-90% water 90 F vs. 40 F

17 Nutrient requirements highest in summer and early autumn. Ca and P needs triple in the spring and summer. 16% CP essential for lactation. Photo by Dana Wright

18 Obtains nutrients from mother s milk during summer. Otherwise, nutrient requirements highest in the fall and remain fairly high until yearling status reached.

19 Nutrient requirements highest in summer. 8-10% CP required the rest of the year. Feb-Mar critical as bucks recover from rut. Photo by Dave Carter

20 True or False? Browse is the most important forage class for white-tailed deer. True

21 Deer Food Habits Cross Timbers and Prairies, White-tailed deer food habits Forage Crops 7% Feed 5% Grass 12% Mast 20% Forbs 20% Browse 36%

22 What impacts forage availability? Precipitation Mast 10% Supplemental/ Crop 3% Sedge 1% Grass 19% Forb 38% Browse 29% Rolling Plains above avg. rainfall filaree

23 What impacts forage availability? Precipitation Rolling Plains drought conditions

24 What impacts forage availability? Season 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Forage Use, Cross Timbers Food Habits Study, (abundant rainfall) 0% spring summer fall winter unknown crops/feed mast grass forbs browse

25 What impacts forage availability? Habitat type

26 What impacts forage availability? Competition

27 True or False? Goats compete with white-tailed deer for food resources. True

28

29

30 Kerr WMA 100% White-tailed Deer Food Habits (No Grazing) 100% White-tailed Deer Food Habits (Heavy Grazing) 80% Forbs 80% Forbs 60% 40% Browse 60% 40% Browse 20% 20% Grass 0% Spring Summer Fall Winter Grass 0% Spring Summer Fall Winter

31