10 Surprising Hamster Facts

Hamsters are cute, furry mammals with oversized cheek pouches and short tails. These small rodents live in the wild, and some species are popular as house pets. There are about 20 hamster species found in a variety of habitats, from deserts and plains to dunes and agricultural fields across Europe, Asia, and Northern Africa. One species, the European hamster, is critically endangered.

From their elaborate burrows to their continuously growing incisors, there’s much to learn about these little fluff balls. Here are a few things you may not know about hamsters.

1. There Are About 20 Species of Hamsters

Hamsters belong to the family Cricetidae, which includes voles and lemmings as well as rats and mice. The 20 or more species of hamsters are quite varied. Some are ratlike, like the seven members of the Cricetulus genus, while the lone member of the Cricetus genus, the European or common hamster, has unique black fur on its belly.

The most popular species for pets are the golden or Syrian hamster (Mesocricetus auratus), and three different members of dwarf hamsters: the winter white dwarf hamster (Phodopus sungorus), Campbell's dwarf hamster (Phodopus campbelli), and the Roborovski hamster (Phodopus roborovskii), the smallest of all hamster species.

2. They Are Nocturnal Creatures

Being prey for so many animals, it’s no wonder that most hamsters are nocturnal. They spend their days hiding from snakes, eagles, foxes, badgers, and other carnivores. In the wild, hamsters dig burrows with deep tunnels and multiple entrances for protection and to sleep during bouts of torpor. They are solitary animals, spending most of their time in their burrows alone. They are also fiercely territorial and will attack invading hamsters that dare venture near.

3. They Are Promiscuous

Male and female hamsters are polygynandrous—meaning they have multiple mates. During breeding season, males travel from burrow to burrow and mate with any female, provided that the female hasn't already mated. Once she has mated, a copulatory plug forms on the female to prevent any further insemination. Hamsters are territorial, and females frequently kick the male out after mating.

Females normally birth two to four litters a year—their gestation period is only 15 to 22 days—and litter sizes can range from one to 13 young, though the average is around five to seven.

4. Hamsters Are Banned in Hawaii

Given their high reproductive rate and that Hawaii’s climate is similar to the hamsters' native habitat, these critters are illegal in Hawaii. Hamsters could quickly establish large colonies in the state if they ever escaped into the wild, posing a problem for agriculture and other native species.

Hawaii’s list of banned animals also includes hummingbirds, snakes, gerbils, hermit crabs, and salamanders.

5. Their Teeth Never Stop Growing

Like all rodents, hamsters’ incisor teeth have no roots and never stop growing. By gnawing, they keep their teeth nice and sharp while preventing them from becoming too overgrown.

Researchers studying rodents’ teeth have discovered that their incisor teeth contain active stem cells. This factor, coupled with rodents’ trait of constantly regrowing their teeth, gives scientists hope of one day replicating the tooth regeneration process in humans.

6. They Hoard Food

Hamsters are built for food storage. Their cheeks are like tiny totes they can fill with fruit, grains, roots, and leaves—up to an amount equivalent to their body weight. When they find an abundant source of food, they fill those cheek pouches and return to their burrows where they have prepared food chambers for storage. In fact, their name comes from the German word "hamstern", which means to forage.

But their cheeks also have a secondary purpose: They fill up with air so hamsters can float in water.

7. They Are Prone to Bacteria and Viruses

Hamsters carry salmonella and, while rare, they are also prone to Lymphocytic choriomeningitis, a virus that can result in flulike symptoms. The primary methods of zoonotic disease transfer from hamsters and other rodents to humans is through bites, direct contact with the animal, and indirect contact with contaminated objects. Young children and pregnant adults are particularly at risk of contracting it.

8. Some Hibernate (Sort of)

While most hamsters do not hibernate during cold weather, one species called the golden hamster (aka the Syrian hamster, commonly kept as a pet) stays in its burrow, blocks the entrance with soil, and sleeps in a grass-lined nest, waking once per week to eat food it has stashed. While hibernating, its heart drops from the usual 400 beats per minute to just four, and it only takes two breaths per minute.

9. They Have Poor Eyesight

Most hamsters are nearly blind in bright light. It does much better at seeing in dim light, which is why it's a nocturnal animal. Even so, it can't see much past the tip of its nose. Because of this, a hamster relies on other senses to navigate during the daytime, such as its super-sensitive whiskers and scent glands on its back that leave traces to guide it back home.

10. European Hamsters Are Critically Endangered

Once widespread throughout Europe, the black-bellied, European, or common hamster is critically endangered. The only member of the Cricetus genus, this hamster's range and population have declined significantly throughout western, central, and eastern Europe, no longer inhabiting an estimated 75% of its native range. Changes in agricultural practices, commercial and residential development, pollution, and climate change are the biggest threats to these small animals.

While conservation, monitoring, and reintroduction measures in parts of the hamsters’ range have been successful, European hamsters’ decline has occurred rapidly. Plans to conserve throughout all countries where they occur are needed to prevent extinction.