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• Taste (gustatory) repellents repel by an offensive taste.  They often are used during the dormant season when plants do not grow beyond the repellent.
• Odor (olfactory) repellents often are used during the dormant and growing season and in enclosed areas.

Repellents often are sprayed or brushed on vegetation.  A latex sticker often is applied with the repellent to reduce the effects of rainfall.  Some odor repellents are placed in a container (such as a stocking) and hung in the problem area (such as an attic).

 Motivation (hunger) of the animals we want to deter

 Habituation of the animals that we want to repel

 Variation among species in responses to repellents

 Concentration of the repellent required for effectiveness

 Palatability of food we want to protect

 Effects of weather (rain) on the repellent

 Duration and number of applications

In general, repellents are less effective when animals are hungry, when repellents are placed on highly palatable foods, when some repellents are applied in lower concentrations, and when animals become habituated to the repellents.

Birds and mammals apparently have large differences in tolerances to various repellents.  Whereas capsaicin (ingredient of habanero, cayenne, and other peppers) has effectively repelled deer and elk, capsaicin concentrations as high as 2% are readily accepted by parrots, pigeons, and red-winged blackbirds.  Birds have been repelled by methyl anthranilate (MA) and dimethyl anthranilate (DMA), but these chemicals are used as a flavorant in grape soda and generally do not repel mammals.  Olfactory repellents generally are ineffective on birds in outdoor areas.

Repellents are used primarily to deter deer and elk from browsing on trees and shrubs.  The cost of some repellents can limit their use to fairly small areas.  Repellents appear most suitable for use on small plantings, in areas where fencing is too costly or aesthetically unpleasing, and where deer and elk pressure is low to moderate.  Rainfall slightly reduced the effectiveness of chicken eggs, Deer Away, and coyote urine.

• Tallow-based bars of soaps have been more effective than non-tallow bars of soap.

• Thiram, Hinder®, Hot Sauce®, tobacco dust, and Ziram (Rabbit Scat) are registered to repel rabbits.
• Predator odors such as the urine from red foxes and coyotes also may be effective rabbit repellents.  These odors are not commercially manufactured, but fox and coyote urines can be purchased from some trapper supply houses.
• A 20% solution of fresh chicken eggs in water has been effective in reducing deer and elk browsing and thus may reduce damage by rabbits.

• Thiram and Hot Sauce® are registered for voles.  In one study, thiram reduced damage to apple stems by 78%.
• Predator odors have repelled voles.  A 20% solution of fresh chicken eggs in water may also repel voles.

• Only Ro.pel® is registered as a beaver repellent.  Because Ro.pel® was not effective on deer and elk, it also may not be effective on beaver.
• Magic Circle Deer Repellent® (98% bone tar oil) was not effective in repelling beavers when placed on rags and hung above dams that were broken.

• Napthalene (moth balls) used at a rate of 5 pounds per 2,000 cubic feet of air space may temporarily discourage squirrels from entering attics and other enclosed spaces.  However, the smell of moth balls also can irritate humans.
• Polybutenes such as 4 The Squirrel^tm are sticky materials that can be applied to buildings, railings, downspouts, and other areas to prevent squirrels from climbing.

• Mole Med®, a repellent containing castor oil has been reported successful in repelling moles from lawns.  Moles are only found in extreme northeast Colorado.

• Bat repellents, primarily moth balls (paradichlorobenzene or napthalene) usually are used to encourage bats to disperse from attics and other enclosed areas.  Moth balls usually are applied at a rate of 5 pounds per 2,000 cubic feet of area.  The odor dissipates quickly and thus has to be replaced occasionally.  Place mothballs in bags so that they can be removed if the odor drifts into areas of human habitation.

• Anise oil, methyl nonyl ketone, Ro.pel®, and thymol are registered to repel dogs and cats but there is little objective evidence indicating that these chemicals are effective.
• Methyl nonyl ketone and cinnamic aldehyde sprayed on bags containing food reduced feeding by dogs and cats in the lab by 69 to 100% but it was not effective in the field.
• Capsaicin spray, sold commercially as Halt® or Dog Shield®, is used by mailmen to repel dogs.  Capsaicin spray, when sprayed in the eyes of black bears, has deterred their approaches to humans and the bears did not display aggressive behaviors.

Mothballs have not been successful for repelling starlings from nest boxes.

Methiocarb has effectively reduced starling, robin, and cedar waxwing damage to cherries and grapes, but it is no longer allowed because of unacceptable residue levels.

D-Pulegone, a mint flavor used in food additives, methyl anthranilate and dimethyl anthranilate have reduced consumption of food by starlings, but additional research is needed before these chemicals can be registered for use on starlings.

• Avitrol®, a chemical frightening agent, is available as a whole corn bait for pigeon control.  It is a Restricted-Use Pesticide.  Birds that consume sufficient amounts of the treated bait will die but they first display distress symptoms which frighten other members of the flock away.  In urban areas, this chemical only should be used cautiously because high mortality can cause adverse public reactions.
• Napthalene applied at 5 pounds per 2,000 cubic feet may repel pigeons from enclosed areas.
• Various sticky substances such as Roost-No-More and Bird Tanglefoot® can be placed on ledges to temporarily discourage pigeons.

ReJeX-iT^tm (methyl anthranilate) and Bird Shield, recently has been registered for repelling birds such as Canada Geese from golf courses and turf areas.  This  product has repelled geese for relatively short periods (about 4 days) and it is relatively expensive.

• Dr. T's Snake-A-Way® (7% napthalene and 28% sulfur), a commercial snake repellent, has not been successful in repelling golpher snakes, rattlesnakes, and plains garter snakes.  Several home remedies including gourd vines, moth balls, sulfur, cedar oil, a tacky bird repellent, lime, cayenne pepper spray, sisal rope, coal tar and creosote, liquid smoke, artificial skunk scent, and musk from a king snake (they eat other snakes) were not successful in repelling black rat snakes.

• Various frightening techniques can reduce conflicts with urban mammals.  These repellents usually are most applicable to carnivores, ungulates, and birds; but they usually are not very applicable to rodents.  They are less permanent than exclusion or habitat alteration.
• Essential ingredients of successful frightening programs include:

• Timing - Employ as soon as the damaging animals arrive.  They are harder to frighten away once they have been using the area regularly.  Employ techniques for 3 hours starting 1 ½ hours before dark and for at least 3 nights to disperse bird roosts.
• Organization - Urban bird roost dispersal programs should be planned with adjacent neighbors, police, and the community.
•  Diversity - Use several frightening techniques concurrently.  Usually, no single frightening technique should be depended upon.  Moving the frightening devices to various locations reduces habituation.

Propane exploders

• Produce large explosions (similar to rifle or shotgun blasts) that temporarily frighten animals.  These devices are not applicable to urban areas because they create loud noise.
• Gas exploders have deterred coyotes from killing sheep for an average of about 31 days but they have only temporarily (2-4 weeks) frightened deer, elk, and pronghorn from damage sites.
• One exploder per 50 acres has been recommended to frighten waterfowl and 1 exploder per 10 acres to frighten blackbirds from corn, sorghum, and sunflower fields.
• Habituation by animals to gas exploders can be delayed by moving the device to various locations, by changing the firing rate, or by using rotating guns called Double Johns.

• These devices consist of an electric timer wired to a strobe light, a warbling-type siren, and a 12-volt battery, and have been designed to deter coyotes from preying on domestic sheep.

PYROTECHNICS

Shell crackers

• Shell crackers are exploding shells fired from a 12 gauge open-bore shotgun.  The projectiles travel about 100 yards before exploding.  They have been used to effectively frighten several species.  Effectiveness is dependent upon persistent use of these devices.

• Noise bombs are also referred to as whistle bombs, bird bombs, and racket bombs.  They are fired from a 15 or 17 mm pistol.  They have a shorter range than shellcrackers.  The exploding type of noise bombs may be more effective than the whistling types.
• Screamer shells were used to successfully frightened Canada geese from urban areas in Fort Collins, Colorado.  They also were used to successfully frighten black-crowned night-herons and great blue herons from a fish rearing facility near Bellvue, Colorado.

• Firecrackers have been inserted in 5/16 to 3/8 inch cotton rope that is lighted to frighten primarily birds and secondarily ungulates.

• Scarecrows have been recommended for frightening birds, raccoons, and bears from problem areas.  Human-like scarecrows placed on high knobs and ridges, accompanied by harassment, appeared to reduce eagle predation on domestic lambs.  Scarecrows also reduced the use of fields by geese.

• This device consists of a plastic human effigy that inflates with air, a siren, and a light.  Two devices reduced black-crowned night-heron numbers 87% during the first 4 nights of operation but reduced their numbers only 33% by the 18th night of use at a fish rearing facility near Bellvue, Colorado.

• Model owls have been used in an attempt to frighten various birds.  Effectiveness usually is only temporary.

• One 7 1/2 inch diameter shaving/cosmetic mirror that enlarges the image has been placed on each side of a home to frighten woodpeckers.

• Silhouettes of hawks have been suspended from windows to frighten woodpeckers from homes.

• Tin foil and plastic has been cut into 1 1/2 inch wide by 3 foot long strips and suspended from the side of homes to frighten woodpecker.

• Pie tins have been used to frighten raccoons from gardens and woodpeckers from the side of homes.  Their effectiveness may only be temporary.

• Two foot diameter balloons have been filled with helium and suspended with 50-75 pound monofilament line above fields to frighten waterfowl.

• Helium filled balloons with the image of a hawk painted on the bottom were more successful than propane exploders, and avitrol for frightening blackbirds from corn fields.  One hawk-kite was suspended above 0.3 to 8 ha fields.

• Black and also white plastic cut into 2 by 3 or 2.5 by 5 foot rectangles and attached to 4 foot tall laths so that they move in a breeze can repel waterfowl from fields.  One flag per acre is recommended where waterfowl have been damaging fields and 1 flag per 5 acres is recommended where waterfowl have not yet arrived.

• Alarm and distress calls of birds are often tape recorded and played in an area where birds are a problem.  The calls work fairly well for frightening a variety of species.  Electronically produced sounds may not be as effective as real calls.
• Crow distress calls frightened American crows from urban roosts in California.
• Goose alarm calls did not frighten Canada geese from urban areas in Fort Collins, Colorado and black crowned night heron and great blue heron distress calls only temporarily frightened herons from a fish rearing facility near Bellvue, Colorado.
• Av-Alarms reduced use of fields by geese.

• Bright and/or flashing lights have been reported to frighten badgers, bears, foxes, mountain lions, raccoons, and other carnivores from areas where they cause problems.
• Bright flashing lights reduced great blue heron and black-crowned night-heron numbers about 30% but did not prevent foraging on fish at a fish rearing facility near Bellvue, Colorado.
• Lights can help to repel bats from the attics of homes.

• Radios and blaring music have been recommended to frighten coyotes, bears, mountain lions, and raccoons from problem areas.

• Barking dogs have been recommended for frightening bears, raccoon, deer, and other animals.

• Bird scaring reflective (Mylar) tape has been stretched across millet, sweet corn, and sunflower fields to reduce damage by blackbirds.  It successfully reduced damage when spaced at 3 to 7 m intervals but failed at 16 m intervals.  They are costly and vulnerable to high winds.
• Mylar tape reduced the use of fields by geese.

• Ultrasonic sound is greater than 20,000 cycles/second.  It does not work on birds because their hearing range is similar to that of humans which is below 20,000 cycles per second.  These devices have not been effective in repelling mice and cockroaches.

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