The article explores how males compete for fertilizing eggs. Research shows that sperm competition affects male reproductive strategies. High sperm competition leads to males having larger testes and producing more sperm. Some males adjust sperm numbers based on competition levels. Sperm size and swimming speed may increase due to competition. However, the link between these traits is unclear. Seminal fluid proteins also play a crucial role, with males able to change them in response to rival males. The study suggests that future research should focus on both sperm and seminal fluid to understand male fertility on a genetic level.