Courtship behavior is very similar in many Xiphophorus species. The maculatus/variatus hifin male on the left is persistant in his efforts to inseminate the female. He is not distracted by the large numbers of immature fish in the tank. However, if other mature males are present, the dominant male will often leave the female temporarily to aggressively chase them away.
A similar mating behavior is shown on the right. The X. birchmanni hifin hybrid male swims in front of the female, and extends his body and dorsal fin in a mating display. For the mating to be successful, the female must allow the male to move close enough so that his gonopodium can hook onto the female's genital opening and deliver the sperm packets.
As Xiphophorus species males mature they display aggressive behavior against other males in their territory. This ritualistic behavior serves to establish a dominance hierarchy for courting and mating with receptive females. The yellow Birchmanni hybrid males on the left are vying for dominance in a relatively peaceful manner. In contrast, the Birchmanni hifin hybrid and the marigold wag swordtail males on the right are considerably more aggressive. They extend their fins and their bodies contort as they make contact. This aggressive behavior can often result in torn fins. Also note that these two males are focused exclusively on each other despite the presence of many other fish in the tank.
The lyretail maculatus males on the right are also very aggressive as they "fight" for dominance. Even though lyretail males can't inseminate females naturally due to their elongated and misshapen gonopodia, they can exhibit normal Xiphophorus behaviors in preparation for courting a female and mating.
Courting the Female
Females, especially female swordtails, can also exhibit aggressive behavior. They can often become the dominant fish in a tank, chasing away courting males and other females.