What is a periodic condition in male elephants characterized by highly aggressive behavior called?

Musth or must is a periodic condition in bull (male) elephants characterized by highly aggressive behavior and accompanied by a large rise in reproductive hormones.

Testosterone levels in an elephant in musth can be on average 60 times greater than in the same elephant at other times. However, whether this hormonal surge is the sole cause of musth, or merely a contributing factor, is unknown.

Although it has often been speculated by zoo visitors that musth is linked to rut, it is unlikely there is a biological connection because the female elephant's estrus cycle is not seasonally-linked, whereas musth most often takes place in winter. Furthermore, bulls in musth have often been known to attack female elephants, regardless of whether or not the females are in heat.

A musth elephant, wild or domesticated, is extremely dangerous to both humans and other elephants. In zoos, bull elephants in musth have killed numerous keepers when normally friendly animals have become uncontrollably enraged. In contrast to normal dominance behavior, bulls in musth will even attack and kill members of their own family, including their own calves.

"Shooting an Elephant" is an autobiographical account by George Orwell (English novelist, 25 June 1903 – 21 January 1950) in which he describes how an elephant in Burma had an attack of musth and killed an Indian, which in turn, caused the death of the elephant.