Nutritional Ecology of White-Tailed Deer: Assessment of an Index to Diet Quality and a Repellent

Concentration of fecal nitrogen has been used widely as an indicator of forage quality for free-ranging ruminants. Differences in digestive function between species of dimorphic ungulates render interspecific comparisons of fecal nitrogen unreliable; however, it is unknown whether sexual differences in digestive function also may bias this nutritional index. My objective was to compare sex-specific variation in the concentration of fecal nitrogen using male, non-lactating female, and lactating female white-tailed deer (Odocoileus virginianus) on control and restricted diets. During weekly trials, I monitored intake rates, collected feces twice daily, and used Micro Kjeldahl procedures to determine percent fecal nitrogen. I also determined nitrogen content of feces following a neutral detergent fiber (NDF) rinse during pre-, peak-, and postlactation. Fecal nitrogen reflected general differences in dietary quality between diets; however, fecal nitrogen of lactating females in both dietary groups was lower (P < 0.05) than for males or non-lactating females throughout the lactation period. In addition, nitrogen concentration following a neutral detergent fiber rinse was lower for lactating females during peak lactation. I hypothesize that the remodeling of the digestive tract by lactating females enhances their ability to extract nitrogen from their forage; therefore, fecal nitrogen is influenced by reproductive status of females. Agricultural producers lose millions of dollars annually to depredation caused by ungulates; although multiple repellents exist for deer, most are ineffective. Tannins are a plant defensive compound that have an astringent taste, reduce digestibility, reduce protein availability, and are toxic to rumen microbes, resulting in the reduction in feeding by large herbivores. I hypothesized that chemical application of tannins to soybeans and other forages would provide a non-lethal method to reduce crop depredation in areas susceptible to deer damage. I designed an experiment to test the effectiveness of tannins at deterring feeding by captive white-tailed deer (Odocoileus virginianus) on soybeans and other forages in 2010-2011. First, using a cafeteria trial, I monitored weekly intake rates of captive deer (n=10) offered a highly-preferred feed treated with varying concentrations of quebracho tannins (control, 3%, 5%, 10%, and 20%). Second, I manipulated food plots (n=3) by treating 3 separate blocks with different concentrations (0% [control], 10%, and 20%) of tannins. I monitored feeding preference relative to tannin treatments within food plots three times per week, during mid- (May – July) and late-summer (August – September) using scan sampling. During cafeteria trials, intake rate of control feed was at least three times greater (all P < 0.05) than all other tannin treated feeds. Similarly, in manipulated food plots, application of 10% and 20% tannins resulted in a 72% and 89% reduction in probability of feeding during the summer; this pattern of preference was intensified when trials occurred on consecutive days (P<0.001). Strategic application of tannins to agricultural crops may provide a natural deterrent to deer depredation. In a free-ranging assessment, I designed an experiment to test the effectiveness of tannins to deter feeding by white-tailed deer on corn and soybeans in areas of high white-tailed deer density in 2010-2011. I monitored depredation in strategically placed plots (n = 25) in agricultural fields in eastern South Dakota. Each plot consisted of three treatments; control, 10% tannins, and 20% tannins. I counted number of plants browsed on a weekly basis to assess total amount of depredation. In 2011, I added an adjuvant to the tannin concentration to increase retention on the plants. Corn and soybean plots without the adjuvant deterred feeding 7% to 36%, whereas corn and soybeans with the adjuvant deterred feeding by 0% to 20%. Strategic application of tannins to agricultural crops may provide a natural deterrent to deer depredation.

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis - University Access Only

Discipline thesis:degree_discipline

Natural Resource Management

Year

2012

Author dc:creator

• Monteith, Kyle Bradley

Contributors dc:contributor

• Jonathan A. Jenks

• Natural Resources and Conservation

Statement dc:rights

• Copyright © 2012 Kyle Bradley Monteith. All rights reserved.

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/550

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-1550