There is an expression — you two are fighting like cats and dogs!

Dogs and cats have gained this reputation as antagonists.

The most common reason is that the cat or dog was not properly socialized to the other species early in life. If they did not learn about each other when their brains were most impressionable (before 8 weeks of age for kittens, and 12 weeks of age for puppies), there is a tendency to see this different species with fear-of-the-unknown distrust.

Another reason for inter-species discord is found in the genetic code of each. In the wild, cats would be natural prey for coyotes and wolves. Selective breeding has retained the "chase instinct," but bred out most predatory behavior in dogs. Therefore, if a cat runs, the thrill of the chase is on!

In dogs that have retained some predatory aggression, the dog may try to capture, kill and even eat the cat. However in most cases, if the cat stops running, the chase is over. However, if cat-chasing is allowed, dogs may continuously seek this fun. This creates a fearful or aggressive rather than a dog-friendly feline personality.

Like everything in life, prevention is easier than correction. To avoid canine-feline wars, prevent household dog-chasing-cat games . Keep a newly adopted cat isolated in one room for a couple days with food, water, toys, bed, and litterbox. Then introduce your existing dog by allowing both to sniff each other under a door until some of the mystery is gone. Praise good behavior during any sniffing and interrupt barking or lunging from the dog. When the dog seems to lose interest or accepts the cat by exhibiting relaxed body postures, you may try allowing the cat to be on high surfaces with you indoors while keeping the dog on leash under supervision.

Allow the dog to see you petting the cat to make it clear that you accept the cat.

If war has broken out, here are tips on how to facilitate the canine-feline peace process: