As a naturalist I am sometimes confused when I hear someone uses the term “rodent” to describe an undesirable person or animal. Since when was being a rodent such a bad thing?
So, let’s take a look at the rodents and find out what exactly they are and why they have such a bad reputation. And then we can decide if calling someone a rodent is a good thing or bad thing.
To start with, there are over 4,500 species of mammals in the world. In order to be a mammal you need to have some basic traits, such as being warm-blooded and have fur or hair on your body. Females must have mammary glands that secrete milk to feed their young. That is all that is needed to be in the mammal club.
There are 10 orders of mammals in North America, with rodents being the largest. The rodent order is called (Rodentia) under the Mammalia class. In fact there are nearly 3,000 species of rodents, which means that about three quarters of all the mammals in America, or the world, are a kind of rodent.
In North America, rodents range from tiny mice and shrews which may weigh a fraction of an ounce to the Beaver which can weigh up to 90 pounds. So what makes a rodent a rodent? As varied as these animals are, they all share some common traits, such as having two pairs of incisor teeth. The incisors are the sharp front teeth on the top and bottom used for gnawing. In addition to the incisors rodents don’t have any canine teeth, which leaves a gap between the incisors and the molars. Also, the incisors are enameled on the front surface. Enamel strengthens the tooth and gives it a yellowish appearance.
The incisors of a rodent grow continuously throughout the animal’s life. The action of the upper incisors working against the lowers wear away the teeth in a characteristic chisel-like beveled edge which is how these animals are able to snip right through things like wood with a single clean bite.
If the teeth fail to wear down the incisors will grow too long and a malocclusion may occur, which means the teeth fail to wear down properly. These teeth will grow out of the mouth and prevent the animal from eating, resulting in death. This also explains why rodents are constantly gnawing on hard surfaces. They are wearing down their incisors.
Also to be a rodent you need bulging eyes on the sides of the head, enabling them to see forward and behind at the same time. In addition rodents have four toes on the forefeet and five toes on the hind foot.
Most rodents are nocturnal and are active year round. Some will hibernate during winter while others become less active during the hot days of summer (estivate).
Rodents also reproduce faster than other mammals. Many rodents become sexually mature in less than 60 days of age and reproduce up to 3-4 times a year. However since just about every large predator eats these rodents they need to reproduce quickly or not survive.
So there you have it. When you call someone a rodent you are basically calling him or her a small furry animal with sharp teeth, bulging eyes and that reproduces often. Come to think of it, I have a cousin like that.