Male-male combat of Otton frogs II

Male-male combat of Otton frogs

Major cheliped use in intruder male during male-male contest of hermit crab

Male-male competition of Japanese scorpionfly

Male-male agonistic behavior of Carrhotus xanthogramma

Male-male fighting of northern elephant seals

Major cheliped use in owner male during male-male contest of hermit crab

Male-male agonistic behavior of Sitticus penicillatus (2)

Male-male agonistic behavior of Sitticus penicillatus (3)

Male-male agonistic behavior of Sitticus penicillatus (1)

Male-male fighting of Harbor seals 1

Male-male fighting of Harbor seals 2

Male-male competition in Uca arcuata

Male-male fighting in a butterfly

male presenting to male

Male-male fighting behavior of the seed bug, Togo hemipterus

Male-male sexual behavior in Cobitis magnostriata

Suffering of a small male

The re-invasion behavior of Japanese scorpionfly males that lost the male-male competition

Flight of a Morpho amathonte male

Female fighting of Dorcus rectus rectus

Male competition of the field cricket

Territorial defense of male three-spined stickleback Gasterosteus aculeatus

Egg care of male three-spined stickleback Gasterosteus aculeatus

Interruption of copulation by an intruding male