A very small number of wild animals experience menstrual cramps, but it is rare. Only certain primates, specific bat species, the elephant shrew, and the spiny mouse menstruate by shedding the uterine lining. Most mammals have an estrous cycle, reabsorbing the uterine lining instead.
Key Findings on Animal Menstruation and Cramps
- Animals that menstruate: Chimpanzees, gorillas, orangutans, rhesus monkeys, baboons, and a few bat species show similar menstrual bleeding to humans.
- Presence of cramps: While research is scarce on wild free-ranging animals, species with menstruation likely experience similar cramping to humans, due to the contraction of the uterus to expel the lining.
- Why only some species: The evolutionary reason is likely due to having a highly invasive placenta, which requires a thicker uterine lining that must be shed if pregnancy does not occur.
- Other mammals: Dogs, cats, and most other mammals do not menstruate — they have ‘heat’ cycles and do not experience this type of cramping.
Menstruation in animals is generally considered an anomaly. With most mammals having an estrous cycle, menstruation does not involve visible, bloody bleeding.
Conclusion
True menstruation (shedding the uterine lining) and thus the potential for menstrual-like cramps are rare in the animal kingdom, confined mainly to some primates and a few other species. In most mammals, the estrous cycle involves reabsorption, not bleeding, so cramps in the human sense are not the norm.
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