Documents: Special Interest: Wildlife Gardening:

Deer Repellents
by Havahart®
May 29, 2011

Deer Repellents

The idea of deer walking in the fields and rabbits munching on grass paints a beautiful picture. What isn't beautiful is the damage these animals can do to your landscape or garden. Hungry deer and rabbits can wreak havoc on your yard, destroying plants, and undoing the hard work you put into your property. You can prevent deer from damaging your landscaping by using deer repellents.

How Deer Repellents Work

Generally, deer repellents work by conditioning deer to stay away by through the use of avoidance in one of four ways: fear, discomfort, or a revolting taste and/or smell.

Fear-inducing repellents contain compounds that emit sulfurous odors, such as meat proteins or garlic. We interpret the avoidance of these odors as a fear response, suggesting herbivores perceive sulfurous odors as indicators of predator activity. Other fear-inducing repellents work by releasing bursts of water when a sensor detects an animal nearby.

Discomfort occurs when the ingestion of a food is paired with nausea or gastrointestinal distress. Animals generally stop eating food when it's associated with illness. Another way discomfort is used in deer repellents is by causing a harmless shock when the deer comes in contact with an electronic repellent. This will condition them to stay away from your yard.

Because deer have an acute sense of smell and taste, there are deer repellents that target both of these senses. Typically, putrescent egg is used to mimic the smell of a dead animal, alerting the deer that a predator is nearby. Taste is targeted with capsaicin, which causes immediate irritation, stopping and then dissuading deer from eating your plants.

Motion Activated Water Repellents

An alternative to liquid deer repellent is a motion-activated sprinkler. This repellent device has a sprinkler, which produces a sudden jet of water to frighten the deer. This high-tech system includes an infrared sensor to detect when deer are in close proximity.

This automated deer repellent requires little user intervention and some can cover a 1,000 square-foot area. Newer water repellents are also eco-friendly since they only use 2-3 cups of water per spray. (Havahart Spray Away - Motion Activated Water Repellent)

Electronic Deer Repellents

Electronic deer repellents are another alternative and work like an electric fence, but don't require the cost or hassle of installing a fence. These repellents use a lure to attract deer, and then emit a harmless, electrical shock when they are in proximity. This trains the deer not to return to the location by taking advantage of their instinctual behavior.

These electric shock repellents are easy to install and cover about a 1200 square-foot area. Also, one set of batteries lasts over a year. (Havahart Electronic Deer Repellent)

How Liquid Deer Repellents are Applied

Liquid deer repellents may be incorporated into the plant (systemic delivery), spread throughout an area (area delivery), or applied to the plant (contact delivery).

Systemic repellents are compounds absorbed and translocated by the plant, rendering the foliage less desirable. With systemic delivery, the repellents are contained within the plant. They cannot be washed off, and the aversive agents are moved to new foliage as it grows. Few, if any, products have effectively incorporated repellents into a plant at concentrations that did not harm the plant.

Area repellents are products that create a chemical barrier animals will not cross, or products that permeate an area with an odor that cause animals to avoid the area. Little evidence suggests animals will abandon areas treated with area repellents except when highly palatable alternative foods are readily available elsewhere.

Contact repellents are products that are topically applied or attached directly to a plant. If the goal is to reduce consumption of plants, available evidence suggests that liquid repellents are most effective when they are applied directly to the plants. (Trent, Nolte and Wagner)

Environmental Factors Influencing a Repellent's Effectiveness

  • Additional food sources: If there are better food sources readily available, the deer are more likely to move on to these when they come in contact with a treated area.
  • Experience: As deer become familiar with the food and the surrounding area, they will be conditioned to avoid treated areas.
  • Population: The density of the surrounding deer population can dictate how effective a repellent will be. A larger population may require more frequent applications.
  • Weather: Rain decreases a repellent's effectiveness and requires more frequent application.
  • Palatability: Depending on how palatable a treated plant is to the deer, a hungry deer may be more determined to eat it.
  • Location: Deer that are downwind from a repellent are more likely to avoid the area.

    The Most Effective Deer Repellent

The most effective repellent is one that targets both the deer's sense of taste and smell. Deer have a highly developed sense of smell, which is one of their most effective ways to detect danger. Similar to dogs, deer can pick up the faintest of odors. Moisture inside a deer's nose causes odor particles to stick, and the scents are drawn to olfactory organs, which can detect approaching danger from several hundred yards away.

Deer enjoy a variety of plant buds, shoots, fruits, and vegetables. Even supposedly deer-resistant plants are on the menu when deer become hungry and other food sources are scarce. This is why it's important that the deer repellent makes the plant almost impossible for deer to eat. Look for a repellent with capsaicin, the component that gives chili peppers their "heat." Deer find this taste repulsive and will quickly learn to stay away from treated plants and shrubs.

By choosing a repellent that targets both senses, you'll have more success in keeping deer away. If for some reason the deer get past the odor, they will experience an immediate irritation if they taste the treated area, stopping them from continuing to eat and destroy your plants.

Works Cited

Parizeau, Nicole. "Repelling Bambi." Whole Earth 2001: 47.

Swift, C.E. and M.K. Gross. Preventing Deer Damage. April 2008. 23 April 2010 .

Trent, Andy, Dale Nolte and Kimberly Wagner. "Comparison of Commercial Deer Repellents." USDA National Wildlife Research Center - Staff Publications July 2001.

Havahart Electronic Deer Repellent. 1 6 2010 .
Havahart Spray Away - Motion Activated Water Repellent. 1 6 2010 .

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