The ability to make excuses is uniquely human. If my son has a scrap with a playmate, he can plead like a lawyer to convince me that he is entirely on the side of justice.
Animals can get into scraps too.
Some dogs I am acquainted with will bark ferociously if I come within half a block of their homes. They would probably bite me if they could get past the fences. But they would not try to justify their behavior. When I spend a whole day getting almost nothing done, I start telling myself, and sometimes other people, all the reasons why I didn't get anything done. If you watch your pet fish all day, you will probably notice that it does not get much done either, but at least it does not make excuses.