National Wildlife Research Center Repellents Conference 1995

Repellent Trials to Reduce Reforestation Damage by Pocket Gophers, Deer, and Elk

Gary W. Witmer et al. — Tue, 13 Feb 2007 13:17:37 PST

We tested selected, potential repellents in pen and field trials to determine their ability to reduce consumption of palatable foods by pocket gophers (Thomomys talpoides), deer (Odocoileus spp.), and elk (Cervus elaphus). Only sulfur-based compounds (predator urines and Deer Away®) deterred feeding by captive gophers. Chemically hot, bitter, and noxious compounds and plants did not deter gopher feeding. Rapid reinvasion of available habitat by pocket gophers in a field trial occurred despite the presence of encapsulated, sulfur-based semiochemicals of stoat (Mustela erminea) on trial plots. Coyote urine and Deer Away deterred browsing by captive deer for the 3-day period of pen trials. A bitter compound, garlic oil, and encapsulated, sulfur-based semiochemicals of stoat did not deter feeding by captive deer. In a winter field trial with these test materials and Deer Away, hungry deer and elk were deterred only by Deer Away. We recommend further trials with encapsulated volatile compounds of predator urines.

Effectiveness of Varpel Rope@ on Norway Rats and House Mice in Laboratory and Field Conditions

J.D. Wilhide et al. — Tue, 13 Feb 2007 13:11:44 PST

This study is based on observations made during the efficacy testing for EPA product approval of Varpel Rope®, a temporary repellent for Norway rats (Rattus norvegicus) and the house mouse (Mus musculus). Animals were tested under both laboratory and field conditions. Laboratory testing was conducted at Arkansas State University, Jonesboro, AR, and resulted in 75-97% repellency. Field testing that resulted in repellency rates from 50 to 100%, was conducted in Newport, AR. Over 140 hr of videotape were recorded during the 1,800 individual laboratory and field trials. Testing was conducted from June 1989 through May 1992.

The Role of Sensory Cues and Feeding Context in the Mediation of Pine-Needle Oil's Repellency in Prairie Voles

Shirley A. Wager-Page et al. — Tue, 13 Feb 2007 13:06:14 PST

Pine-needle oil inhibits feeding in vertebrate species through sensory cues. Prairie voles (Microtus ochrogaster) significantly decreased their ingestion of raw apple pieces when pineneedle oil (10% vol/vol) was applied as a repellent coating. During single-choice tests, voles selected similar amounts of sunflower seeds from pine-needle oil-scented jars and vegetable oil-treated jars. However, when jars containing both stimuli were presented simultaneously, voles retrieved significantly more food from the vegetable oil-treated jars than the pine-needle oil-treated jars. Neonatal administration of capsaicin chronically depletes neurotransmitters in C- and A-a fibers greatly diminishing or abolishing pain transmission in the affected neurons (i.e., trigeminal nerve). Capsaicin-desensitized prairie voles decreased their ingestion of pine-needle oil-treated apples to the same extent as the sham-injected control group of animals, suggesting that pineneedle oil's repellency was not mediated by activation of pain fibers. In settings where alternative foods are available, and where minimal sampling of the product does not represent a hazard, Siberian pine-needle oil may be useful as a rodent repellent.

Repellency of Mongoose Feces and Urine to Rats (Rattus spp.)

Mark E. Tobin et al. — Tue, 13 Feb 2007 13:03:45 PST

Chemical repellents derived from predators might offer more effective and longer lasting protection from vertebrate depredations than current damage control measures. Thus, we conducted laboratory and field studies to evaluate the repellency of mongoose feces and urine to black rats (Rattus rattus) and Polynesian rats (R. exulans ) . We exposed captive wild rats to water, butyric acid, mongoose (Herpestes auropunctatus) feces, or mongoose urine in a 150- x 60- x 120-cm partitioned arena and recorded their behavior with a video camera. None of the test substances had any apparent effect (P> 0.05) on behavior or the percentage of observations spent (1) in the transfer cage, (2) in tunnels, (3) on the side of the arena with the treatment, (4) in, on, or near the tunnel with the treatment, or (5) in the tunnel with the treatment. Nor did we observe any effect on latency until rats emerged from the transfer cage or entered the treated tunnel or time spent in the treated tunnel during their first visit. During the field test, we set and monitored 50 pairs of live traps along each of 12 transects in forested areas and along the perimeter of recently harvested sugarcane fields. Mongoose feces or urine was applied to one trap in each pair. We captured 49.2 rats (R. rattus and R. exulans) per transect during 4 nights of trapping. We captured fewer (P< 0.05) rats in traps soiled with mongoose feces than traps soiled with mongoose urine or unsoiled traps. The gender of the mongoose that was the source of the feces or urine had no effect (P>0.05) on capture success. The discrepancy between the laboratory and field studies indicates that researchers should incorporate relevant factors in the natural environment into their test paradigm and interpret the results of tests with captive animals cautiously. Additional research is warranted to determine the active compound(s) in mongoose feces that repel rats and to explore the use of such compounds to reduce rat damage to agricultural crops.

Tue, 13 Feb 2007 12:58:26 PST

Repellents in Wildlife Management Symposium
Table of Contents

Repellency of Predator Urine to Woodchucks and Meadow Voles

Robert K. Swihart et al. — Tue, 13 Feb 2007 12:57:03 PST

Woodchucks (Marmota monax) and meadow voles (Microtus pennsylvanicus) can be serious pests in orchards where they damage young fruit trees by gnawing on main stems. Previous work indicated that topical application of bobcat (Lynx rufus) urine to apple trees could reduce woodchuck damage by an average of 98%. Here, we report on field trials designed to determine whether various fractions of bobcat urine could achieve comparable reductions in gnawing activity. Trials with smooth sumac (Rhus glabra) resulted in an average reduction in gnawing over a 4-week period, relative to controls, of 86% for undiluted urine, 56% for a methanol extract of urine, and 25% for a solution of 5 nitrogen-containing compounds (indole, phenylacetamide, 1-methylhydantoin, 2,6-dimethylpyrazine, 6-valerolactam) in the approximate concentrations they were found in urine. Trials with apple seedlings and cuttings resulted in an average reduction in gnawing over a period of 2-3 weeks, relative to controls, of 90% for undiluted urine, 49% for a methylene chloride extract of urine, 34% for a solution containing a single sulfur-containing compound extracted from urine (3-mercapto-3-methy l-butanol) , and 30 % when this compound was mixed with three additional sulfur volatiles from urine. Reductions due to the nitrogen- and sulfur-containing fractions were not significant. We also conducted laboratory trials in which we recorded the amount of time meadow voles spent in treated versus untreated halves of an arena. Preliminary trials indicated strong aversions (P<0.01) to areas containing bobcat, red fox (Vulpes vulpes), or coyote (Canis latrans) urine, and no aversion (P = 0.56) to woodchuck urine. In subsequent trials, we tested various fractions of bobcat urine and found that the methylene chloride extract and solutions containing either 3-mercapto-3-methyl-butanol, P-mercaptoethanol, or thiophenol caused significant aversions, but the mixture of five nitrogen-containing compounds did not. Woodchucks and meadow voles respond aversively to predator urine, but we were unable to identify fractions of bobcat urine capable of eliciting aversions comparable in magnitude to those achieved with undiluted urine.

Electronic Rodent Repellent Devices: A Review of Efficacy Test Protocols and Regulatory Actions

Stephen A. Schumake — Tue, 13 Feb 2007 12:51:41 PST

A wide variety of sonic/ultrasonic, electromagnetic, mechanical/vibrational, and electrical barrier devices have been researched, developed, and marketed over the past 30 years. Although there are currently no Environmental Protection Agency' (EPA) registration requirements, human safety and repellent efficacy test data for these devices may be requested whenever they are commercially manufactured, marketed, and retailed. This chapter reviews research reports and data sets for devices operating at selected frequency ranges, pulse rates, duty cycles, and intensity levels. It also describes examples of laboratory and field test protocols as well as recent EPA and Federal Trade Commission (FTC) regulatory actions in relation to the compliance requirements of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and provisions of the Federal Trade Commission Act (FTCA), respectively. State regulations may be imposed on manufacturers and retailers of repellent devices when they are carried as stock items through local stores or through mail-order service companies. Controlled efficacy test protocols have indicated only marginal repellency effects with six commercial ultrasonic devices (i.e., 30-50% reduction in movement activity), and rapid habituation (i.e., no significant repellency effects beyond 3 to 7 days of exposure). An analysis follows of research and development attempts to reduce habituation effects, to incorporate and integrate ultrasonic devices into traditional rodent control methods and to improve efficacy.

An Integrated Strategy to Decrease Eared Dove Damage in Sunflower Crops

Ethel N. Rodriguez et al. — Tue, 13 Feb 2007 12:49:19 PST

Eared doves (Zenaida auriculata) damage mature sunflowers in Uruguay. Although repellents might be useful as a control method, durability and expense have discouraged their use. In the present report, we describe laboratory, aviary, and field research designed to evaluate methiocarb and calcium carbonate as durable, economical repellents. Calcium carbonate (CaCO₃) was as effective as CaCO₃ /methiocarb in combination in deterring consumption of sunflowers. Moreover, treating field borders with CaCO₃ or the CaCO₃ /methiocarb combination was as effective as treating the entire field for at least 12 days. This period is sufficiently long to deter damage to sunflower during the critical period just before harvest. We conclude that CaC0₃ can provide an economical tool to reduce bird damage to sunflower in Uruguay.

Bird Deterrent Research and Development: Marine Oil Spills

Timothy J. Reilly — Tue, 13 Feb 2007 12:44:55 PST

A wide range of techniques are available for deterring birds from coastal oil spills, including (but not limited to) pyrotechnics, aircraft, boats, flags, reflecting devices, and artificial sounds. Many of these deterrent devices have had little field testing to determine optimal deterrent strategies. The Marine Spill Response Corporation (MSRC) developed a research and development (R&D) plan which has identified critical research which would need to be conducted to determine these optimal strategies. This program was initiated through the generation of a report which described the state-of-the-art of deterring birds from marine oil spills. Following this report, MSRC hosted a workshop consisting of deterrent experts and practitioners from the private and public sectors. This panel determined priority areas of marine oil spill bird deterrent R&D. A group consisting of research personnel from government and industry are currently involved in implementing a high-priority R&D project as identified by the deterrent workshop panel. The present paper describes these research efforts.

Recent Studies on Flavor Aversion Learning in Wildlife Damage Management

Russell F. Reidinger Jr. — Tue, 13 Feb 2007 12:43:34 PST

Flavor aversion learning (FAL) occurs experimentally when a mammal is presented with a distinctive-flavored food followed by a postingestional illness. Birds may learn aversions to visual cues. Aversions follow a single pairing and may be robust. During the past decade, at least four directions were followed in evaluating FAL for managing wildlife damage: compounds already registered for use on crops such as herbicides, insecticides, or fungicides were tested for their abilities to also repel birds and small mammals from crops; naturally occurring compounds such as sucrose or charcoal were similarly evaluated; eggs were treated with different compounds in attempts to protect untreated eggs from predators; and FAL was used as a model for understanding bait shyness associated with some rodenticides. Use of registered pesticides, or naturally occurring and generally regarded as safe ones, reduces costs for registration, but also limits choices of potential repellents. No mammalian or avian repellents based on FAL are presently registered. Most research is based on a single model of FAL in which the flavor (or visual cue) is paired within 6 hours with postingestional illness, and that flavor or similar flavors (through generalization) are subsequently avoided. Other models of FAL, including those based on overshadowing and salience rather than generalization of learned aversions, might offer applications.

The Chemistry of Plant/Animal Interactions

Paul B. Reichardt — Tue, 13 Feb 2007 12:42:07 PST

Chemical approaches to studying plant/animal interactions have led to an appreciation that plant chemistry strongly influences patterns of herbivory. Although this chemistry is often rather complex, two basic factors have emerged: plant chemistry influences herbivores in both positive and negative ways by determining dietary quality of plants and by providing feeding cues. Examination of the results from numerous studies addressing these issues has led to the development of three working hypotheses: (1) there is a molecular basis for chemical cues; (2) the molecular diversity of chemical signals implies specific mechanisms for plant-initiated attraction or repellence of herbivores; and (3) there are dynamic elements to many plant chemical defenses

Origins of Food Preference in Herbivores

Frederick D. Provenza — Tue, 13 Feb 2007 12:40:18 PST

Food preference is best understood as the interaction between taste and postingestive feedback, determined by an animal's physiological condition and to a food's chemical characteristics. Taste (as well as smell and sight) enables animals to discriminate among foods and provides hedonic sensations associated with eating. Postingestive feedback calibrates taste in accord with a food's homeostatic utility: preference increases when foods are adequate in nutrients; conversely, preference decreases when foods are deficient in nutrients, when they contain excesses of toxins, and when they are too high in rapidly digestible nutrients. Preference also decreases when familiar foods are eaten too frequently or in excess, which causes animals to eat varied diets. Experiences early in life affect preference. Young animals acquire dietary habits as a result of eating particular foods, and they are reluctant to eat novel foods or familiar foods whose flavors have changed. These findings suggest: (1) deterrents based merely on offensive flavors are not likely to be effective in the absence of aversive postingestive effects, (2) many repellents are ineffective because they merely change the flavors of familiar foods (i.e., novelty effects), and (3) management to deter herbivores from eating foods must provide nutritious alternatives.

A Preliminary Evaluation of Three Food Flavoring Compounds as Bird Repellents

Richard E.R. Porter — Tue, 13 Feb 2007 12:38:54 PST

There is an increasing demand in New Zealand for nonlethal bird repellents to protect food crops and prevent poisonous mammal baits being eaten by native birds. Three food flavorings, dimethyl anthranilate (DMA), methyl anthranilate (MA), and a peppermint extract (Optamint), were applied to wheat as surface coatings at different concentrations and then offered to individually caged house sparrows (Passer domesticus). The birds were given one of four levels of treated wheat (control, 0.25, 0.5, and 1 .O% by weight for DMA and MA; 0, 1, 3, and 5 % by weight for Optarnint). Only Optamint at the 5% level significantly reduced consumption of wheat. All three Optarnint-treatment levels were phytotoxic to grass.

Predator Odors as Repellents to Brushtail Possums and Rabbits

David R. Morgan et al. — Tue, 13 Feb 2007 12:36:29 PST

Repellents are being developed as an alternative to the use of poisons, traps, or firearms for controlling damage to forest and farm plantings by the introduced Australian brushtail possum (Trichosurus vulpecula) and European rabbit (Oryctolagus cuniculus). Such repellents need to protect seedlings from irreversible damage for at least 6 months after application. Seven synthetic predator odor compounds were compared with "Treepel", a moderately effective commercial repellent, by assessing relative browse on treated Pinus radiata seedlings in pen tests. Predator odors were repellent to both animals. Generally they were more repellent to possums than to rabbits, but the predator odor-based TOM (formulation confidential) was particularly repellent to rabbits. In a longer field trial at a site heavily infested with rabbits, both TOM and Treepel gave good initial protection, TOM being more effective. However, effectiveness declined after 56 days, and extensive browning was affecting foliage, particularly after treatment with TOM. The formulation of TOM therefore needs refinement to prevent phytotoxicity and to prolong effectiveness. The results support the existence of a sensory mechanism that enables herbivores to avoid predators by detecting by-products of meat-eating animals. If this mechanism is innate for all herbivores rather than interspecific for particular herbivores and predators, development of broad-spectrum herbivore repellents may be possible.

Avian Repellents: Options, Modes of Action, and Economic Considerations

J. Russell Mason et al. — Tue, 13 Feb 2007 12:33:53 PST

The present manuscript considers visual, auditory, tactile, chemosensory, and physiologic repellents currently available for use in the United States. Discussion of tactile, chemosensory, and physiologic repellents is emphasized for three reasons. First, these products are preferred by users. Second, application of these substances is regulated by state and federal agencies. Third, only four active ingredients are legally available at the present time. This lack reflects difficulties in obtaining regulatory approval and limited market size.

The Public is Attracted by the Use of Repellents

Cathy A. Liss — Tue, 13 Feb 2007 12:31:33 PST

Americans have long been in favor of humane treatment of animals. Increasingly, the public is involved in dictating acceptable wildlife management practices. The U.S. Department of Agriculture's Animal Damage Control program has been the recipient of much adverse publicity regarding its killing of target and nontarget animals. Growing opposition to various methods of lethal control such as use of steel jaw leghold traps or poisons likely will result in continuing restrictions or outright prohibitions against their use in the future. Alternative methods of wildlife control are critical.

Nonlethal techniques are key to the future of the Animal Damage Control program. Repellents represent an area of great promise. There is much research which needs to be conducted in this area including continuing isolation and identification of natural repellents. The success with methyl anthranilate (MA) as a humane method of control demonstrates the utility of this approach. Just imagine the public's response to a switch from lethal methods of control to a new arsenal of tools which includes so gentle and environmentally harmless a substance as "grape juice" (MA) to repel birds.

Review of Synthetic Predator Odor Semiochemicals as Repellents for Wildlife Management in the Pacific Northwest

Pontus M.F. Lindgren et al. — Tue, 13 Feb 2007 12:29:10 PST

The use of synthetic predator odor semiochemicals as area repellents has considerable potential for protection of forest and agricultural crops. Certain predator odors originating from feces, urine, or scent (anal) gland secretions elicit a "fear" response when detected by prey species. At least some genera (e.g., Microtus) appear to have an innate response to these odors. Synthetic constituents from the weasel family (Mustelidae) have been particularly effective in laboratory and field bioassays with a variety of mammal species. Semiochemicals from the stoat (Mustela erminea) and red fox (Vulpes vulpes) have successfully reduced feeding damage to forest seedlings by snowshoe hare (Lepus americanus). Synthetic compounds from stoat anal gland secretions have generated significant avoidance responses in voles (Microtus montanus and M. pennsylvanicus) and northern pocket gophers (Thomomys talpoides) in small-scale field trials. When applied on a larger scale (1-4 ha), some degree of population disruption has been recorded for both pocket gophers and montane voles. Field trials of semiochemicals for protection of coniferous tree seedlings from feeding by black-tailed deer (Odocoileus hemionus columbianus) have yielded inconsistent results. However, commercialization of semiochemical products (mammal management devices) is expected in the very near future.

In-Water Electroshock Techniques to Repel Aquatic Mammals and Birds

A. Lawrence Kolz et al. — Tue, 13 Feb 2007 12:24:21 PST

Nonlethal electroshocking devices have been developed at the Denver Wildlife Research Center for repelling aquatic mammals and birds from selected areas. These devices are augmented with infrared motion sensors to turn on the apparatus only when warm-blooded animals are present, thereby conserving electrical energy and allowing battery operation. Electronic safety controls are incorporated to prevent animals from being over-exposed or repeatedly exposed to the electrical fields. The technical basis for this equipment is based upon research originally reported in the electrofishing literature. Obviously, any animal immersed in water is highly susceptible to electrical shock, but permanent injury can be avoided by controlling the intensity of the electrical energy. As the intensity of the electrical field is increased, the severity of the electrical shock experienced by an animal is known to progress through several stages including mild initiation, extreme agitation, electronarcosis (an unconscious state), tetany (characterized by muscular rigidity), and death. Fortunately, with proper engineering, in-water electroshocking apparatus can be designed to limit the degree of electrical shock to the desired threshold. Additionally, controlled studies with fish provide evidence that there is a predictable relationship between the intensity of the electrical shock and the magnitude of the electrical power transferred from the water into the fish. By applying this electrical model and measuring the electrical conductivity of the water, it should be possible to predict the level of electrical power density required in the water to elicit a particular electroshock response.

The Role of Analytical Chemistry in Repellent Research

Bruce A. Kimball et al. — Tue, 13 Feb 2007 12:21:03 PST

Development of effective repellents requires in depth investigation of the interaction of animals with their chemical environment. This multidisciplinary field, chemical ecology, has received much attention in the area of plant/invertebrate herbivore interactions. At the Denver Wildlife Research Center (DWRC), we have benefited by the close collaboration of chemists and biologists when studying the interactions of vertebrates with natural products. Typically, this combines chemical assays that provide information on the characteristics of chemical cues with bioassays that generate information on the mechanisms that drive animal behavior. The chemistry role in this research can be either supportive or interactive. Two recent studies illustrate the integral role of chemistry in the study of plant/animal interactions.

Dilution and Detoxication Costs: Relevance to Avian Herbivore Food Selection

Walter J. Jakubas et al. — Tue, 13 Feb 2007 12:17:47 PST

Toxicity and digestive inhibition are commonly thought of as the primary postingestive consequences by which plant secondary metabolites (PSM's) limit herbivore food selection. However, food selection may also be modified by nutritional costs imposed by detoxication processes and nutrient dilution. Few studies have determined the magnitude of these costs for vertebrate herbivores and their ecological significance. Research clarifying the mechanisms by which PSM's repel animals may give new insights into the development of repellents for nuisance wildlife and improve our ability to predict ecological interactions involving herbivores. Using captive ruffed grouse (Bonasa umbellus), we tested whether PSM ingestion interferes with energy and nitrogen retention and whether food selection was related to costs associated with detoxication and nutrient dilution. Two feeding experiments were conducted. In one experiment, grouse (Group 1) were fed quaking aspen (Populus tremuloides) flower buds with different levels of conifeql benzoate (CB), the primary PSM in the buds. In the other experiment, birds (Group 2) were given a formulated diet treated with CB (6.5 % dry wt.). We measured energy and nitrogen utilization efficiencies and the output of detoxication products. Intake of CB was associated with decreased food utilization efficiencies in both experiments. The low energy utilization efficiency of Group 1 birds consuming high levels of CB, was mainly attributed to nutrient dilution by CB. These birds retained 24% less metabolizable energy than when feeding on buds with low CB levels (P = 0.010). Group 1 birds excreted 10 to 14% of their daily metabolizable energy intake as glucuronic acid and ornithine. Excretion of detoxication conjugates and ammonium increased with CB intake in both experiments. Nitrogen excreted in the form of ornithine and ammonium accounted for approximately 30% of the daily nitrogen intake in both experiments. During the high CB trials, the excretion of ornithine conjugates alone increased Group 1 birds' minimum daily nitrogen requirement by 90.0% over that required when consuming a diet containing no PSM's. Relative to Group 1 birds, Group 2 birds excreted a higher proportion of their daily nitrogen intake as ornithine, despite having one-forth the nitrogen intake as Group 1 birds and despite being in negative nitrogen balance. For the development of repellents to control nuisance wildlife, additional research should be conducted to determine the extent to which repellency can be increased by raising nutrient dilution costs or by manipulating detoxication pathways.