Male lemurs grow bigger testicles when there are other males around

Dominant male Verreaux’s sifakas always have the largest testicles in their group to make the most sperm, and they can grow their gonads to make sure of it Dominant male Verreaux’s sifakas always have the largest testicles in their group to make the most sperm, and they can grow their gonads to make sure of it  New Scientist – News