Why Do Different Species of Animals Have Territories That Are

Why do different species of animals have territories that are different sizes?

A) Different species need different sized territories depending on their food source
B) They must be able to travel the entire territory in one day to defend it
C) They only need to maintain a territory that is large enough for the male and one mate
D) They must be able to sing loudly enough to be heard throughout the territory
E) They must be able to mark the entire territory every day so others of their species will not invade it