2001 United States Department of Agriculture Study
A study was completed by the United United States Department of Agriculture, Animal Health Inspection Service, Wildlife Services and National Wildlife Research Centers. They tested many different repellents available on the market today. The results were published in the Wildlife Society Bulletin 2001 stated:
"...products using fear as a mode of action were more effective than products using other modes of action..." [a]
Colorado State University's Study termed: "Chemical Visual and Auditory repellents for reducing urban wildlife problems"
This CSU study looked at the effects of many different repellents including: Hot Sauce of differing strengths, Chicken Eggs and water, Coyote Urine (Fox Urine), Hinder, Thiram, Hot Peppers, Tabasco Sauce, Soap Bars, Human Hair and Other Commercial Repellents.
The study found that "Predator odors such as the urine from red foxes and coyotes also may be effective rabbit repellents" [b]. In fact, Coyote Urine was the only repellent found to be rated "HIGH" on their Effectiveness Scale for both Deer and Elk. [c]
In a similar study, Colorado State University found predator urine to work against Voles:
"Predator odors, such as the urine from red foxes and coyotes, also may be effective vole repellents"
Cornell's Department of Natural Resources Study
Cornell's Department of Natural Resources also did a study on Wildlife Damage Management. Their "Cayuga Heights Deer Project" and white papers on various animals.
Their study included these thoughts: "There are no products currently registered with the EPA for use as woodchuck repellents." However, when looking at those repellents that were not requiring registration the study stated that; "Predator odors may be a useful repellent for woodchucks." [d]
Penn State University Department of Horticulture's Longevity of Repellents Study
Penn State University Department of Horticulture carried out a study on the longevity of repellents used on edible plants. In their studies, they compared the results of different types of commercial products readily available.
They broke the products down into main ingredients; Salts and Fatty Acids, Garlic Oil, Capsaicin, Odor (Coyote Urine and Fox Urine) and Odor Taste. In their Table 1 - Repellents for Use on edible plants, predator urine saw the best longevity (30 days plus or minus) than all the others. [e]
Incidentally, in this same issue and report there contained an article titled "Facts About Deer Repellents". This article mentioned that: generally, odor-based repellent products usually out-perform taste-based products. [f]
The University of Minnesota Horticultural Science Division Studies
The University of Minnesota Horticultural Science Division also did studies of many types of repellents. In their study they took a look at which repellents were most effective in a Minnesota reforestation project.
In this study UM documented the effects of a Sulphur based repellent (Urine Smell), Ammonium Soaps of Higher Fatty Acids (Hinder), Thiram, Feather Meal, Meat Meal, Hot Sauce, and a Control Group. The Urine Smell (sulphur) based repellent performed the best of the group by 25% over the second placed repellent and DOUBLE the performance of the rest of the group! [g]
[a] United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Society Bulletin
[b] Managing Conflicts with Wildlife, CHEMICAL, VISUAL AND AUDITORY REPELLENTS FOR REDUCING URBAN WILDLIFE PROBLEMS, Cooperative Extension, 1 Administration Building, Colorado State University, Fort Collins, CO 80523-4040
[c] Relative effectiveness of repellents tested on hungry, captive mule deer and elk in Colorado during 1989, 1991 and 1992. (Compiled by W.F. Andelt et al.)
[d] Wildlife Damage Management Fact Sheet Series, WOODCHUCKS, Paul D. Curtis and Kristi L. Sullivan, Cornell Cooperative Extension, Wildlife Damage Management Program
[e] Ornamental Horticulture Monthly Newsletter Volume 3 No. 2, April 2000, Cost of IPM scouting: A case study with Poinsettia, Alan H. Michael, Roland Freund, Judy Smith, Robert D. Berghage
[g] University of Minnesota Horticulture Science, Odocoileus verginianus as a Stressor in Forest Restoration, Christine Vatovec.