Distinguishing the Differences Between Rabbits and Rodents: Why Rabbits are Not Rodents
Photo: Wiki Commons
It's All In The Teeth...Well, Actually There's More.....
The iconic image of spring is that of rabbits and bunnies, and for those with a chocolate penchant the Cadbury bunny and his chocolate eggs. In honor of Spring I decided it's time for a post on the confusion I commonly find, when leading programs, about why rabbits are not rodents. First, there's a wide range of rodents living in the world, in fact it's the largest class of mammals. They're everywhere and on nearly every continent. Rodents can range in size from .25 oz (the African pygmy mouse) to the capybara which can weigh from 150-200 lbs!
The order Rodentia, from which rodents get their name, derives from the Latin meaning "to gnaw or chew." This is what makes them unique, their teeth. Dentition is a commonly used feature for biologists to sort animals into families and orders. Rodents are specialized gnawers. They all have one set of upper and lower incisors (front teeth) and varying numbers of molars and per-molars (flat teeth in the back of the mouth) with a gap in-between called the diastema. Rodents lack canine teeth. The outer surface of rodent incisors is covered with enamel which ranges from orange to orangish-yellow in coloring (If you find a skull with these colors on the incisors it's always a rodent). It's thought that this coloring is due to strengthening by the addition of iron and minerals. The front of the tooth is very hard compared to the back of the tooth which is covered in dentin, a soft pulpy material. Unlike humans, whose teeth stop growing when they reach a certain stage, a rodent's incisors erupt/grow continually. This is called indeterminate growth. The tooth can continually grow because the base of a rodent's incisors is rootless and open so the tooth keeps growing. Human teeth have roots and are mostly closed off because the teeth do not need to grow anymore.