Deborah McArthur

Nature Connection

A friend called my 7-year-old daughter "spaghetti teeth." Her two front teeth are out. Gaps between her tiny milk teeth show the window of opportunity for slurping up individual spaghetti strands. Before the tooth fairy exchanged teeth for treasure, we compared our human teeth to our local wildlife. How are our teeth similar and different?

Humans and most mammals have two sets of teeth during our lives -- we're called diphyodonts (from Greek "di" -- two, "phyo" -- to produce, "dont" -- tooth). We start with 20 primary teeth, replaced eventually by 32 permanent teeth. Like the leaves of non-evergreen trees that shed their leaves in the fall, the first set of teeth are called our deciduous teeth. Do you ever think about dogs and cats loosing baby teeth? Well, they do. Kittens and pups often swallow their milk teeth at 3-6 months old, mostly unnoticed.

Non-mammal vertebrates -- reptiles, fish, and amphibians -- have serial replacement; they can grow a new tooth to replace one that falls out. Sharks are the extreme example of this in the animal world -- with a conveyor belt of teeth they can replace weekly to monthly.

Mammals have different teeth shapes -- incisors, canines, bicuspids and molars -- that serve different purposes. These four kinds of teeth are standard throughout the class of mammals in different combinations. Reptiles, amphibians and fish do not have these distinct tooth shapes.

We lose our eight incisors first, from 6-8 years of age. These are the sharp cutting teeth we use to bite into an apple. The four pointy canines and the four bicuspids (or premolars) we use for ripping, gripping and tearing fall out starting at 9 years old. And the final "baby teeth" -- the four molars we use for grinding -- fall out by the time we are 12.

Teeth are a great way to identify animal skulls you find on the trail. Count how many total teeth there are and the kinds (incisors, canines, premolars, molars) on the upper and lower jaws. Opossums have a whooping 50 teeth. Canines (coyotes and foxes) have 42. Raccoons, 40. Deer 32. Mountain lions, 30 and bobcats, 28.

Look at the shape of the molars. If these large teeth are flat for grinding plants, you're looking at an herbivore (and these animals often lack canines). If the molars are serrated for cutting, it's a carnivore. Omnivores have a full set of all four shapes of teeth -- a combination of both herbivore and carnivore structures.

Check out: -- a great online resource for identifying skulls with teeth -- for more tooth truth.

Deborah McArthur is an environmental and outdoor educator. Contact her at