Why some animals or birds aggressive towards other animals or birds?

The reason animals are aggresive is because they are defending there self. Its not really fair, for animals because humans hunt and kill these animals. If you were that animal and a hunter were about to hurt or shoot you, would you stand there and let them. No! Of course not, you are going to defen yourself. Today, humans are selfish and greedy! They kill animals in so many! Just for things that we could do with out, or even change something that wont hurt the animals!

These are just a few things that people do to kill/hurt animals because there selfish...

Logging

oil fields

Hunting

oil being spilled in lakes

trapping

litter

This isn't even a dent with what ppl do today! Animals have to defend themselves somehow.