White-tailed deer and their vigorous appetite: An empirical study of monetary losses in soybeans

Background/Question/Methods

White-tailed deer (Odocoileus virginianus) population growth in North America during the late 20th century has led to extensive agricultural losses. This empirical study quantifies damage and yield losses to a soybean crop due to deer herbivory throughout one growing season (May to October 2010) in Southwestern Ohio. Four 2 X 2.4 X 1.2 m experimental plots were centered along each of the four edges of twelve 0.5 ha fields. They were completely fenced with chicken wire to exclude deer browsing. Each plot was classified as high, medium, or low exposure to deer based on its proximity to a wooded edge. Soy plants were sampled in July and August to measure height, width, and percent damage. Yield and plant biomass of all plants was assessed during harvest. Data were analyzed using a factorial design with repeated measures.

Results/Conclusions

Measurements of plant height, width, and percent damage indicated unprotected plants with medium exposure were the most affected by browsing. Damage was most prevalent in July (50% greater than in high exposures, and 3 times greater than in low exposures). Overall, there was 12 times less damage in fenced compared to unfenced plots. Medium exposures were also heavily browsed in August with medium exposures having 170 times more damage in unfenced compared to fenced plots. Biomass of plants in fenced plots was 25% greater than those in unfenced plots; there was no difference between biomass at any of the exposure levels. Fenced plants yielded 50% more seed than unfenced plants, and high exposure plots yielded 50% less than those in the low exposures. Medium exposures yielded 33% more seed than those at the high exposure levels. Extrapolation of harvest data to a planting density of 100,000 plants per 0.4 ha at $10.55 per bushel amounts to a loss of $200 per 0.4 ha to deer. This translates to a $37,200 loss over the course of one growing season for a typical 75 ha Ohio farm. Thus, deer management policies should be re-evaluated to help reduce costs to farmers.