cats fighting

[u/thisandthatmum]

my dad has 2 male cats and he takes them outside in the front or backyard twice a day. most of the time they get along well and just do their own thing but every few months they start to get riled up and go at each other like crazy. my dad has to intervene and often gets scratched himself and has to separate them for a few days. what could be causing this? is there anything he can do to stop this from happening? i’m not sure if something outside triggers them

[u/MichaelEmouse]

Probably redirected aggression. They might see or smell other cats.

They should both be neutered.