Cats and dogs often dislike each other at first meeting because they come from fundamentally different evolutionary backgrounds and communicate in nearly opposite ways. Cats are solitary hunters with strong territorial instincts, while dogs are pack animals that approach new situations with social curiosity and high energy [1]. When a dog bounds forward with a wagging tail and direct approach, the cat interprets these signals as threatening rather than friendly, because in feline body language, a high moving tail signals agitation and a direct approach reads as a challenge or predatory behavior [1].

The species' non-verbal cues are almost polar opposites, creating mutual misunderstanding. A dog's rolling on its back signals submission and trust, while a cat on its back is preparing for defensive combat. A dog's growl warns of aggression, but a cat's purr usually means contentment—yet a cat's hiss is a clear back-off signal that a dog may not immediately recognize [1]. This communication mismatch means the first meeting is typically defined by fear and defensive reactions rather than genuine hostility.

Additional factors amplify the initial conflict. Cats are cautious and territorial, so a new dog entering their space feels like an invasion [1]. Dogs are also larger, louder, and move unpredictably, which can trigger a cat's fear response [1]. Past experience matters significantly: cats that have been chased or startled by dogs before will react defensively immediately, even if the current dog means no harm [1]. However, with slow, calm introductions and proper supervision, many cats and dogs can eventually learn to tolerate or even befriend each other [1].