Rodents… some people love them and keep them as pets, some people disdain them as troublesome pests, and still others are terrified of them. There are thousands of different rodent species, from agoutis to zokors. Even taking into account only the populations of the more widespread species, there are billions of individuals worldwide—so it’s probably wise to learn a little about our small fuzzy neighbors, even if you don’t consider yourself a rodent lover.
Take this quiz to expand your rodent horizons!
Question #1: What is the characteristic defining feature of rodents (order Rodentia)?
A. Their very long tails
B. Their ability to climb
C. Their continuously-growing teeth
D. Their small, rounded ears
Answer: C. Their continuously-growing teeth.
Rodents’ teeth are specialized for gnawing; in fact, the word “rodent” has its origin in the Latin word rodere, meaning “to gnaw.” They have two pairs of incisors, one on the upper jaw and one on the lower; these teeth grow continuously throughout their life, and must be kept short and sharp through gnawing.
(Of course, there are exceptions to every rule: there is one species of earthworm-eating shrew-rat that does not gnaw, and has only two teeth in total. Rabbits and other lagomorphs also have continuously growing teeth, but unlike rodents, they have four incisors in the upper jaw, not two.)
Question #2: What percent of all mammal species are rodents?
Answer: D. 40%.
A whopping 40% of mammal species are rodents: there are approximately 2,277 different species of rodents, out of 5,702 known mammal species.
Question #3: What is the largest living species of rodent in the world?
Answer: A. Capybara.
Capybaras (Hydrochoerus hydrochaeris) live in South America, in gregarious groups of about 10-20 individuals. They are about 3.51 to 4.40 ft. (107 to 134 cm.) long, they stand a towering 20 to 25 in. (50 to 64 cm.) tall, and they weigh an average of 114 lb. (51 kg.). They prefer to live near bodies of water, as they are excellent swimmers who can stay submerged for up to five minutes. Aren’t they wonderful?
Beavers are the second-largest living species of rodent. The largest species of rodent that ever lived is the now-extinct Josephoartigasia monesi, which may have weighed as much as 5,700 lb. (2,586 kg.) in larger individuals!
Question #4: About how many households in the U.S. live with pet rats or mice?
D. 1 million
Answer: C. 500,000.
According to the Rat Assistance & Teaching Society, roughly half a million households have pet rats or mice. (Estimates for other rodent pets like gerbils and hamsters are less precise.) Mice are often curious and social companions, while rats can be very sweet, personable, and intelligent.
Question #5: Which of the following diseases can be directly transmitted by rodents? (Choose 1-4 answers.)
C. Bubonic plague
D. Rat-bite fever
Answer: A. Hantavirus, B. Rabies, and D. Rat-bite fever.
- Hantavirus is spread through contact with rodent waste products; recently, there has been a surprising outbreak of this dangerous disease in California’s Yosemite National Park.
- Rabies is more often spread by bites from rabid animals like dogs, raccoons, or skunks; however, it can be spread by infected groundhogs (which are rodents). However, smaller rodents like squirrels, rats, and mice are rarely infected and are not known to transmit rabies to humans in the U.S.
- Rat-bite fever is a rare bacterial disease, most common in Japan, that is spread by an infected rodent’s bite, urine, or mucous secretions.
- Bubonic plague is often attributed to rats, but it is actually caused by infected fleas. These fleas live on mice, rats, and sometimes other mammals; when there is an outbreak of plague within the rodent population, the fleas catch the infection but are unharmed by it. After their original rodent host dies, they move on to other rodents or to humans, thus spreading the disease.
(This doesn’t mean that you should assume that a wild rodent is disease-carrying; however, give them a respectful distance!)
Question #6: Which of these animals is not a type of rodent?
Answer: B. Shrew.
Beavers, porcupines, and squirrels are all types of rodents. Although they appear similar to rodents, shrews are not, because their teeth are short and spiky, and do not continuously grow throughout their lives.
(There is a type of rodent called a shrew-rat, because of their resemblance to shrews, but they are not true shrews.)
Question #7: True or False: Rodents live on every continent in the world except Antarctica.
They can be found on every continent except Antarctica, as well as on many islands. See the map of their distribution above. Pretty impressive, isn’t it?
Question #8: Rats can do which of the following?:
A. Fall 50 feet (5 stories or 15 meters) without injury
B. Survive being flushed down a toilet
C. Fit through openings the diameter of a quarter
D. Gnaw through concrete and steel
E. All of the above
Answer: E. All of the above
As if that’s not enough, they can also survive without water for longer than a camel can, they can swim half a mile in open water, and they can even survive large doses of radiation. They’re also very intelligent.
Question #9: True or False: Because of their fast breeding cycles and adaptability, there are no endangered rodents.
While rodents are often very good at survival, there are still many species of rodents that are threatened by human activity and invasive species. The IUCN Red List lists 65 species of rodent that are Critically Endangered (their highest risk category), including the Long-tailed Chinchilla (Chinchilla lanigera, above), Social Tuco-tuco (Ctenomys sociabilis), Lesser Stick-nest Rat (Leporillus apicalis), and Little Earth Hutia (Mesocapromys sanfelipensis).