New research reveals that not all animals experience menstruation like humans do. Scientists have identified around 15 mammal species with menstrual cycles, including primates, bats, and spiny mice. While the exact evolutionary purpose is still unclear, experts propose various theories, such as preparing for pregnancy, detecting embryo viability, or storing sperm.

Source: https://www.livescience.com/animals/why-do-only-some-animals-have-periods