Can we keep cats an dogs as pet for repelling bugs and mice naturally?
It's been scientifically proven that healthy mice naturally fear the smell of cats, http://www.bbc.com/news/10117428 so yes, having a cat in your house will repel mice to some degree. I can tell you from personal experience, it's not 100 percent effective in keeping mice out. If your cat has areas of the house it doesn't go into, it's smell won't be as strong, and its also known that mice infected with toxoplasmosis no longer fear the smell of cats. http://www.nature.com/news/parasite-makes-mice-lose-fear-of-cats-permanently-1.13777. As for dogs and bugs, I'm unaware of any studies on that.