Galápagos tortoise
Most terrestrial species are sexually dimorphic, with males larger than females; fighting between males often establishes a dominance hierarchy for access to mates, including in the Galápagos tortoise. For most semi-aquatic and bottom-walking aquatic species, combat occurs less often; males of these species instead often use their size advantage to mate forcibly. In fully aquatic species, males are often smaller than females, and rely on courtship displays to gain mating access to females.