Beth Tinney, age 13, of Weston, W. Virginia, for her question:
Are squirrels really members of the rat family?
The answer may be yes or no, depending on how precise you wish to be. In everyday language, we can include the rats, squirrels and all their toothy relatives in the rat family. We also may refer to all the catty creatures as members of the cat tribe. But these families and tribes are not scientific categories. This precise classification places the rats and squirrels in different families. However, it does class them all in the larger order of rodents.
Rats and squirrels are distantly related because they share the same type of gnawing teeth. For this reason, they are classed in the animal order Rodentia. This largest group of mammals also includes the beavers and guinea pigs, the gophers and gerbils, the lemmings and porcupines and about 6,000 other rodents.
A rodent's distinguishing feature is his gnawing equipment. He has a pair of long chisel shaped incisors in front of each upper and lower jaw. As the tips are worn down by gnawing, they continue to grow from the roots. There are no sharp canine teeth, which leaves gaps between the unusual incisors and the cheek teeth in the back of the jaws. Rodents often gnaw hard wood and other inedible substances. Then they draw flaps of hairy lip through these gaps to keep this material out of their mouths. All rodents also have special skulls, jaw bones plus sturdy muscles to add extra strength to their gnawing talents.
Squirrels and rats share these same rodent features. But this is not enough to rate them as first cousins of the same family. The huge order of rodents is subdivided into several suborders, more than 20 families and about eight subfamilies. The animals in these smaller groups have more features in common and are more closely related.
The typical squirrels are classed in the suborder 5ciuromorpha and separated into the family Sciuridae. There are three other families in this suborder for the pocket gophers, the beavers and the slightly different mountain beavers. The somewhat different scaly tailed flying squirrels of the tropics belong in the suborder Myomorpha. Their family name is Anomaluridae.
In the same suborder Myomorpha, we find the large family Muridae, where the rats and mice belong. There are two subfamilies for rats and mice of the Old World and the New World. In this suborder we also find separate families and subfamilies for the jerboas and the gerbils, the lemmings and doormice.
As you see, the small family class is only distantly related to other families of the same order. Each family is subdivided into smaller genera. Each genus of close cousins includes a number of individual species. The scientific name for each animal includes his genus, with a capital letter, followed by his species, with a small letter. The pretty red squirrel is Sciurus vulgaris, the big brown city rat is Rattus norvegicus.