An animal repellent does what it suggests: It repels unwanted animals from an area. The repellent uses an animal's instinctual aversion to another animal or something that it has learned to avoid or fear in its natural habitat, such as a particular smell or taste of something. Some animals, such as deer, may avoid an area that contains coyote urine. Therefore, using a repellent that mimics coyote urine may keep deer from grazing in a home garden or an agricultural crop.
Deer and rabbits are just some of the animals that pose a threat to your landscape. Though you may enjoy their presence on your property, they mostly come around for food. Building a fence works to keep some animals out but not others, such as moles and rabbits, which can tunnel under the fence and reach the other side.
Animal repellents, both chemical and nonchemical, have their place on the market. A homeowner doesn't want to lose a lettuce patch to rabbits, and farmers don't want deer damaging their crops. You can create natural repellents at home using ingredients like garlic oil and decaying eggs, but most chemical repellents on the market have some form of natural ingredients in the list.
Repellents that contain ingredients like cinnamon and pepper irritate an animal's nasal passages or mouth. The repellents' scent and flavor create a natural response in the animal and cause it to flee or avoid the area in the future. For wildlife like birds, using a repellent that contains a sticky substance may work better in places where you don't want them to nest.
Some repellents don't use taste or smell to deter animals. Motion-activated sprinklers and decoys provide visual and auditory scares, repelling animals without the need for chemical solutions. However, these products don't always work as some animals learn the difference between predators and decoys.