Complex sentence: Even though he is a rat, he is offended by being called one however he can easily be identified as a rat since he has four fingers and a thumb on each hand while all the other mice have three fingers.
Split into simpler sentences: Even though he is a rat, he is offended by being called one. However, he can easily be identified as a rat since he has four fingers and a thumb on each hand while all the other mice have three fingers.