system
Given the following post, respond as if you're commenting on Reddit:
human
Do all mammals have a menstrual cycles? Are there any species where the males have cyclical fertility?
gpt
There is some disagreement in definitions between sources, menstruation is generally considered to be limited to primates. Females of other species of placental mammal undergo estrous cycles, in which the endometrium (lining of the uterus) is completely reabsorbed by the animal at the end of its reproductive cycle. To answer your second question, there aren't any male mammals with a "reproductive cycle" but there are males that carry offspring and birth them rather than the female i.e Seahorse.