1) In many species, members of the species exhibit aggressive behavior toward one another, often with a focus on territoriality, the fight for exclusive control of a particular area. The level of violence in territorial aggression varies widely from species to species, though few species fight other members of the species to death and instead rely on non-lethal contests for control of territory that involves noise-making maneuvers such as roaring or hissing or aggressive posturing or gestures.

2) Most bird species are known to be territorial to some degree, though the territorial behaviors exhibited by most species are limited to singing contests, which can go on for days, or threatening postures with wings lifted or extended. The swan, on the other hand, is quite unlike other birds in this respects. The swan may seem particularly elegant and sereno as it glides across the surface of a lake; however, male swans are, in reality, quite territorial and will fight other male swans for the exclusive use of a lake no matter how large the lake is. Males will engage in ferocious contests, with their necks entwined as they attempt to cause mortal injury to each other.