If you've ever seen a beaver smile, you will have noticed that their teeth are orange, at least the teeth you were able to see. The orange color does not result from poor dental hygiene, but rather from iron in the tooth enamel that makes them extra strong.
Behind that hardened layer, the tooth is softer and wears away, creating a chisel-sharp biting surface. These teeth, in combination with very muscular jaws, make it possible for beavers to cut down trees.
Unlike most teeth, these incisors (and the incisors of similar herbivores) will continue to grow throughout a beaver's lifetime. These incisors aren't the beavers' only toothy wonders. Their molars have ridged grinding surfaces that allow them to chew up the very woody plants that make up much of their diet.
These rough foods keep their teeth clean. It also helps that their diet is low in sugar.
Teeth tell us a lot about how an animal lives. They can serve as a springboard to propel your kids into thinking about animal adaptations. Let's start with human teeth.
The teeth in the front of our mouths, the incisors, are sharp — not as sharp as a beaver's, but then we don't have to cut down trees with them. The pointier, wedge-shaped teeth around to the side are canines.
In the back are our grinding teeth, the molars. Have your kids can examine their teeth in a mirror and identify the different kinds.
How are these different types of teeth used? Have a “Test your Teeth” Tea Party! Along with your tea, serve tidbits that will demonstrate the roles of different teeth. Offer something large and crisp, like carrots, celery and pretzels. Did your kids use their sharp incisors to nip off a piece?
Canine teeth tear tough foods. Try something chewy like fruit leather or crusty bread to demonstrate the usefulness of such fangs.
Molars do the chewing work to prepare food to be swallowed. To show their purpose, include something small and crunchy on the snack plate, like goldfish crackers or trail mix.
Now we're ready to think about the teeth of the wild animals around us. Different types of teeth allow animals to eat different kinds of food.
Meat eaters, or carnivores, have large canine teeth for catching prey and tearing very tough food — raw meat. Their molars are also modified and have become self-sharpening shears. Wild carnivores that live near us include the weasel, mink, bobcat, fox and coyote.
Chisel teeth are the main feature that makes a rodent a rodent. All rodents have paired self-sharpening incisors. Who are the rodents? Beavers, porcupines, woodchucks, squirrels, chipmunks, voles and mice.
If you compare the skull of the tiny mouse to that of the beaver, you will find the same arrangement of teeth. These teeth enable rodents to chew through nutshells, snip off twigs and browse on bark. Rabbits have a similar diet, and therefore similar teeth, but they are not rodents.
Some people assume that all tiny mammals are rodents, but look at the teeth on a shrew skull. Is it an herbivore? No!
The pointy little teeth of a shrew, the smallest animal that lives in Vermont (there are several different shrew species), are used to eat mostly insects, but also prey upon amphibians and other small mammals. The most abundant shrew species, the short-tailed shrew, has venomous saliva that paralyzes its prey.
There is another group of plant-eaters that don't have chisel incisors: moose and deer. In fact, these animals don't have ANY front teeth on the top. They have no trouble tearing up tender plants in the summer.
In the winter, their set of lower teeth act as a sharp scraper that lets them peel strips of bark from young trees, an abundant though not a very nourishing source of winter food. Their broad pointy molars are needed to chew up tough bark.
Omnivores can eat whatever food is available. Our omnivorous neighbors include black bears, raccoons and opossums. Most have sharp canines and wide molars.
In some cases, their long canine teeth are mostly for show. When an opossum is frightened, it opens its mouth to show its pointy canines — a terrifying sight!
Why don't people have long, pointy canines? We have two things that these other omnivores don't: fire to cook food, which makes it easier to chew, and hands that can hold tools, like knives for cutting up our meals. Our canines became smaller early in our evolution when such fangs were no longer useful.
Things to look for and think about on your winter walks:
- What might you eat in the woods if you had (describe a set of teeth)?
- Look for seeds, insects, tasty twigs. What kind of teeth would you need to eat these things?
- Visit a beaver pond and look for places where they have cut down trees.
- Do deer winter nearby? Can you find places where they have scraped off bark to eat?
Second Nature is submitted by the naturalists at Bonnyvale Environmental Education Center in West Brattleboro. Join us for Winter Vacation Camp Feb. 17 to 21 and save the date for Nature Days March 3 and 4 on no school days for students in Kindergarten through grade 5. Information and registration can be found at BEEC.org or call 802-257-5785.