1. “We show that males invest more in sperm size and number in species where sperm from multiple males compete to fertilize eggs compared to monogamous species,” Fitzpatrick explained.
2. They also found that the size of the female influences whether it is better for a male to produce longer or more sperm.
3. In larger females, with bigger reproductive tracts, sperm can be lost or diluted on its journey to the egg. Therefore, in larger species males produce a lot of tiny sperm.
4. In contrast, in small species where sperm have an easier time finding the egg, males produce comparatively longer sperm.
5. “This demonstrates that the location where sperm compete – inside the female’s reproductive tract in mammals – determines when it pays a male to produce longer or more sperm,” the researchers said.
The study was published in the Proceedings of the Royal Society of London.
