Stag beetle battle behavior and its associated anatomical adaptations
Faculty of Sciences. Biology
Faculty of Sciences. Physics
New York, N.Y.
Journal of insect behavior. - New York, N.Y.
, p. 227-244
University of Antwerp
Male stag beetles battle for females with their impressive, oversized mandibles. We describe their fighting behavior, which is essential to understand the evolution and morphology of their weaponry. Our behavioral analysis reveals several anatomical structures that are important for fighting, and our morphological investigations show how these may be adapted for their functions. Stag beetle fights are much more variable than other armed beetles battles. They spend considerable time and effort in dislodging their opponent, that clings to the substrate with its tarsal claws. These tarsal claws are also indispensable to maintain balance in the most spectacular battles, when they lift a rival high in the air. The male claws are highly curved and have an increased height for this purpose. The prothoracic muscles are hypertrophied to support the lifting movement. The largest beetle wins in 85 % of the fights and the smaller the difference in mandible length is between the rivals, the longer the battles can last. The long mandibles enable males to reach the opponents legs in order to dislodge it. For this purpose, they bite with all parts of their mandibles, even though the distal part is more vulnerable for failure and transfers less bite force. Blindfolded experiments prove that visual information is not a requisite for a successful battle.