For primates, males’ fancier ornaments are linked with smaller testes, according to a new comparative study.

Members of species with shells they must hold onto for survival have larger sexual tubes than those with less precious private property.

The exaggerated horns and elongated forelegs of male flower beetles, which use these appendages as weapons in combat for females, do not slow down the insects in a race.

The male proboscis monkey’s large nose probably evolved in response to female preference and competition between males.

The lizards may be signaling one another using fluorescent cues that we can’t see.

Andean highlander genomes possess cardiovascular-related variants, while populations from other regions evolved different solutions to manage the lack of oxygen.

A protective coating on ocellated wrasse eggs helps female fish select sperm from nest-building males.

A study reveals why some male fruit flies produce sex cells that are 20 times the length of their bodies.

Sex assignment in bearded dragons can flip from one based on chromosomes to one driven by temperature, researchers report.