Why Repellents Fail

Understand the strengths and weaknesses of repellents before you buy. Repellents for wildlife

One of the most common questions we receive goes like this,

“I am having a problem with such and such and animal doing xyz. I don’t want to hurt him, I just want him to go away. Is there anything I can spray that will keep him away from my property?”

Unfortunately, the short answer is no.  Repellents rarely work the way we want them to.

1. Just walk on by. The first problem with repellents is that free-roaming mammals can simply walk past a smell that disturbs them. Think of all the times you have smelled bad and repulsive odors. Did it stop you from going where you needed to go? Probably not. Now consider it from an animal’s point of view. The animal has a choice. Continue to eat and smell a bad smell or not smell a bad smell and starve. Which path do you think the animal will take?

2. I’m used to it. The second problem lies with familiarity. Say you find a repellent that does drive the animals from your property. We would call this a perimeter repellent. Chances are it would work on the principle of fear of a predator. For example, if you used coyote urine you may reduce woodchuck damage because coyotes eat woodchucks. The problem, however, is that over time the woodchuck will realize that it smells coyotes but doesn’t see them. Or if there are actually coyotes around, then the woodchuck has to choose between getting eaten or starving.

3. Mistaken Cause. A third problem with repellents is how often people attribute effectiveness to them when the repellent really didn’t work at all. Too many people believe that if they do X and Y happens, then they assume that X caused Y. For example, assume you have a skunk under your deck. Someone tells you to throw mothballs at the entrance. You do. Two days later the skunk is gone. You assume that the mothballs drove the skunk away. Maybe what really happened is that the skunk was hit by a car two streets away from your house. The mothballs may  have had nothing to do with its removal.

4. Who follows directions? In fairness to the repellent manufacturers, sometimes repellents fail because the user doesn’t follow the instructions. Repellents frequently have to be reapplied after a rain or to cover new plant growth. An effective taste or tactile repellent can only continue to be effective if it is still on the plant.

5. I have no choice. Under dire circumstances animals, have no choice but hold their noses and eat food that tastes or smells bad. If they don’t, they will starve. No repellent can drive away an animal that only has death as an alternative.

People Continue to Believe in Repellents

One reason people continue to think that repellents will solve their animal damage problems lies in their faith in the chemical industry. Chemistry has solved a number of problems in the U.S., and since animals use their noses a lot, why couldn’t a smell keep animals away? Well, repellents rarely work the way people think they work. Most repellents are used in production agriculture where farmers have hundreds of acres of crops. If they can reduce crop damage by 10% through the use of a repellent, they can save a large amount of money. The problem is that town and city dwellers want the damage stop completely. So even when a repellent has been shown to work, it only works in an agricultural setting where the standard of success is substantially less than 100%.

Another problem with repellents lies in the restrictions surrounding their use. For example, you shouldn’t use a taste repellent on plants you are planning to eat. You can use them on plants that you don’t eat to stop/reduce animal browsing, but if you spray them on food you plan to eat, be careful. If you notice that your mouth is getting hot, for example then you know you sprayed the wrong plants with pepper spray (capsaicin). Read the label carefully to ensure you are using the repellent properly and for the right purpose.

Still another difficulty with repellents is that they wash off in the rain. While some residue may still be left on the plant, it may not be enough to stop an animal from browsing.  You will need to continue to reapply repellents after a rainfall. This is a task that many property owners don’t wish to do. In addition, any new growth will be free of repellent, so you will need to reapply to the plant for complete coverage. This is one of the reasons why people don’t get desired results with deer repellents on their shrubs. They forget to keep adding the repellent after the shrub grows.  While repellents have a place in animal damage control, one needs to use these chemicals in certain specific situations. They are not a cure-all.