Yes
Certainly they can. Without any external stimulation from their own kind the roosters natural display tendencies will be lessened.
Yes. As cockerels (As Male Chickens Younger than a year are referred to) grow into Roosters they begin to become sexually mature. Roosters, if not seperated when they are fully grown will begin to fight. The reason the Roosters fight is because they want to become top of the pecking order (you can research this more if you wish) but mainly want to become the leader of the flock so they have all rights to the hens. Any other Male is considered an 'intruder' wanting to battle over the rights of owning the flock. If two Roosters are placed together they will fight and often to the death. This is why you must separate Male Chickens to ensure they don't fight and become aggressive.
He didn't become aggressive, it was the fear that he would at some point become that way and possibly hurt one of the children. He went to live with his trainer around the time Blanket was born.
Normally one will dominate over the other when the flock is together but not respected when ranging and around corners, roosters will often challenge each other from time to time or if caught. Challenges become much more frequent when the roosters are older and develop spurs.
== == He is protecting his hens and his property. He is also showing you he is the man - sort of like he would react around another rooster. He feels threatened. Roosters are complex creatures--not unlike human men. I have one rooster that never attacks me or the other roosters but who likes to give me "love bites" when I first pick him up each morning. I have another that is incredibly aggressive to the other roosters and will peck at me initially but who loves--demands it, in fact--being held, even turned on his back and having his feet rubbed. The third rooster is the only one who actually "attacks," and he's the biggest pussy cat of all. So, the shorter answer is that it takes time (a lot) to deal with roosters, but they are well worth the trouble. At least that's my opinion.
Yes it can but it is not nesscialary aggressive it mostly fear.
Cockatiels do not become aggressive unless they are treated badly.
They are aggressive at hatching and stay that way for their whole lives. They are VERY AGGRESSIVE when they are breeding.
it is mostly dominence your cat thinks that what it has been around belongs just to him and sharing it would be a loss of pride
Possibly
I've heard that sharks, for some reason, become very aggressive during July-August or sometime around then
It could be multiple issues. If there is a female, even if she is not in heat, they could get protective over her, or if they feel threatened by this other male dog they will become aggressive.