The muskrat is a rodent, with the teeth to prove it. Rodents have upper and lower incisors that can munch through hard things all day and keep on growing. Unlike landlubber rodents such as rats and porcupines, muskrats live a large part of their lives in water, like beavers and nutria.
Color Me Toothy
Muskrats, beavers and nutria have colored incisors. The beaver's are brown, the nutria's bright orange and the muskrat's light orange to yellow. This coloring is due to a special layer of enamel on the front of the teeth. Muskrat and nutria teeth are more noticeable than beaver teeth -- they're lighter and brighter, so they stand out against the brown fur all three sport.
Muskrat teeth -- the front ones, that is -- look too big for the size of the critter, and they're even bigger than you can see. Half the length of each incisor is hidden inside the tooth socket in the skull, waiting to move down as the leading edge of the tooth wears away. The muskrat uses these teeth to cut his food, including tree branches, cattails and other woody plants. He's officially called an herbivore, or plant-eater, and he has the flat back teeth necessary for grinding. The muskrat will also go for snails, crawfish and baby birds.
Tooth as Tool
The muskrat's front teeth are actually outside his mouth. The furry lips close water-tight behind the big choppers so that he can harvest plants underwater and carry them to his feeding platform without getting water in his throat or lungs. He does a lot of harvesting, because he builds his house out of sticks and reeds out in the water, piling them about 3 feet high and then gnawing out a chamber above the waterline from underneath. Here he's safe when ice closes the waterway to his bank-side den. In this refuge he can haul out, breathe and dry off -- and he has food, even if he's literally eating away his home.
Toothed and Dangerous
The muskrat's orange incisors are his principal defense. Harder on the front than they are on the back, they wear down to the shape of a wood chisel with a knife edge. He can use them like a knife, too. If you get a muskrat bite, or your dog does, be aware that muskrats can carry nasty diseases, including rabies, tularemia or rabbit fever, leptospirosis and giardiasis. See your doctor or your dog's as soon as possible.