A cat repeller is a device or substance used to discourage cats from entering an area, or to encourage them to leave if they do enter. Such deterrents are most commonly used by gardeners, in order to prevent damage to their gardens, to avoid cat feces, or to protect birds. Some repellants could be: * Lemon juice or scent * Water sprayed around the yard * A scent cats do not like * A harmless spray cats do not like * Litter that cats do not favor