What Animals Have A Period
A-z - Animals

What Animals Have a Period: Exploring Menstruation in the Animal Kingdom

As humans, we are familiar with the concept of menstruation, but did you know that certain animals also experience a menstrual cycle? From primates to bats and even some species of whales, menstruation is not unique to humans. In this article, we will explore which animals have a period, the evolutionary significance of menstruation, and more.

But first, let’s clarify what we mean by “a period.” Menstruation is a natural process that occurs in female mammals, where the lining of the uterus sheds in preparation for a potential pregnancy. This process is characterized by the shedding of blood and tissue from the uterus, which is known as a period.

Now that we understand what a period is, let’s dive into the fascinating world of menstruation in the animal kingdom.

Definition of Menstruation

Red pandas are one of the few animals that experience menstruation
Red pandas are one of the few animals that experience menstruation

What is Menstruation?

Menstruation is the process by which a female mammal sheds the lining of its uterus, including blood and tissue. This process usually occurs once a month and is a sign that the female is not pregnant.

Understanding the Menstrual Cycle

The menstrual cycle is the series of changes a female’s body goes through in preparation for pregnancy. The cycle is regulated by hormones produced in the brain and ovaries and typically lasts around 28 days. During the cycle, the uterus thickens, preparing to receive a fertilized egg. If the egg is not fertilized, the uterus will shed its lining, resulting in a period.

Although menstruation is most commonly associated with humans, many other animals also experience a menstrual cycle. In the next section, we’ll explore which animals have a period.

Animals that Menstruate

Have you ever wondered which animals have a period? Here are some of the most well-known:

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Humans are not the only primates that menstruate. In fact, all female primates, including apes, monkeys, and lemurs, experience a menstrual cycle. However, the length and frequency of their cycles can differ from humans.


Believe it or not, female bats also experience a menstrual cycle. However, their cycles are much shorter than humans, lasting only a few days.


Certain species of whales, such as humpback whales and orcas, also have a menstrual cycle. However, given their aquatic environment, their periods go largely unnoticed.

Elephant Shrews

These small, insect-eating mammals found in Africa are one of the few non-primate species that menstruate.

While these animals may have a menstrual cycle, there are some differences between their cycles and that of humans. For example, the length and frequency of their cycles can vary, and not all animals experience the same symptoms as humans. Nevertheless, the existence of menstruation in these animals highlights the evolutionary significance of this process.

Animals that Bleed but Don’t Menstruate

Explanation of animals that experience bleeding but not menstruation

While some animals do experience a menstrual cycle, there are also many that do not. These animals may experience bleeding or discharge, but it is not directly related to the shedding of the uterine lining.

In some cases, animals may experience uterine bleeding due to injury or infection. This can be seen in animals such as dogs, who may experience a bloody discharge due to pyometra (a uterine infection) or injury to the reproductive tract.

Another reason for bleeding in animals is the estrous cycle. Unlike the menstrual cycle, which occurs in primates and a few other species, the estrous cycle is a reproductive cycle that occurs in many mammals. In this cycle, the uterus does not shed its lining, but rather the animal experiences a period of fertility where it is more receptive to mating.

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Examples of animals that fit this category

One example of an animal that experiences a bleeding cycle but not menstruation is the dog. Dogs experience an estrous cycle, where they undergo a period of fertility and may experience a bloody discharge.

Other animals that do not menstruate but may experience bleeding or discharge include cats, cows, horses, and pigs. These animals all have an estrous cycle rather than a menstrual cycle.

While these animals may not experience menstruation, their reproductive cycles are still fascinating and important to understand. By studying these cycles, we can gain a greater understanding of the diversity of reproductive strategies in the animal kingdom.

Evolutionary Significance of Menstruation

Menstruation is a complex process that has evolved over time in various species, but why did it develop in the first place? Here, we’ll explore some possible explanations for the evolutionary significance of menstruation.

Menstruation and Reproduction

One of the most widely accepted theories for the evolution of menstruation is that it’s related to reproduction. Menstruation allows for the shedding of the uterine lining, which prepares the uterus for a potential pregnancy. In humans, this process occurs every month, but in other animals, it may be less frequent.

Protection Against Infection

Another theory is that menstruation may have developed as a way to protect against infection. Because menstruation involves the shedding of the uterine lining, it may help to clear out any harmful bacteria or viruses that have accumulated in the reproductive tract. This could be particularly important for animals that mate frequently or have multiple partners.

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Hormonal Changes

Finally, hormonal changes may also play a role in the evolution of menstruation. The menstrual cycle is regulated by a complex interplay of hormones, including estrogen and progesterone. These hormones are involved in a variety of physiological processes, including bone density, mood regulation, and cardiovascular health. It’s possible that the development of menstruation was related to the evolution of these hormones and their effects on the body.

While the evolutionary significance of menstruation is still not fully understood, these theories provide some insight into why this complex process has developed in certain animals.


In conclusion, the concept of menstruation is not unique to humans, and many animals also experience a menstrual cycle. From primates to bats and even some species of whales, the phenomenon of menstruation is widespread in the animal kingdom.

Understanding which animals have a period is not only fascinating but also has important implications for our understanding of evolution and reproductive biology. By studying menstruation in different species, we can gain valuable insights into how this process evolved and its significance in terms of reproductive success.

At 10 Hunting, we believe in exploring the natural world, and understanding menstruation in the animal kingdom is just one example of the many fascinating topics that we cover. Whether you’re an avid hunter or simply curious about the world around you, we hope that this article has provided you with valuable insights into what animals have a period and the evolutionary significance of menstruation.