National Museum of Natural Science

Male stag beetles will fight each other over territory and females using their mandibles. Among males of the same species, the one with larger body size and larger mandibles is usually the victor, and may even be considered the winner by default, without having to fight. However, if there is a battle between males of different species, the larger male does not necessarily win. Usually the fighting stops once one of the males retreats or falls off the tree. There are rarely fights to the death. 

Image is of male Lucanus cervus (Linnaeus). 

Photographer: Alwyn Ladell.

Stag beetle conflicts