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Gnawing, Biting, Teeth as Tools
Brown rats use their teeth for a number of purposes. The molars are specifically designed for chewing while the incisors take on many different roles. These roles include: a) Gnawing through nuts, seeds, wood, and other hard substances. b) Biting to inflict an injury during a fight or against a predator. c) Holding an object in the same manner as canine teeth firmly hold food. d) Grooming for cleaning self and others as part of hygiene and social bonding. e) Grinding incisors against each other to sharpen them, display anger or stress, or display contentment and relaxation. f) Pulling, pushing, carrying and gnawing objects with the objective of not necessarily eating them but placing and opening them.
As these different roles display, a brown rat's incisors are as multi purpose as a Swiss army knife. Observing a brown rat using incisors for more gentle actions is delightful. I am always intrigued how a pet rat will passively groom the surface of its owner's skin with a lick of its tongue and careful and controlled nibble with its incisors. This grooming action serves well in rat colonies for reconciliation after a heavy play session or fight, reinforcing social structure, and developing new relationships. It's also fun to watch a pet rat use its teeth for holding, carrying, pushing, and pulling. A pet rat playing out on its own can take a single morsel of food from its owner with such grace and manner that you can barely feel the exchange. Add another pet rat to the equation and competition for food can make your pet rat display a snatching behaviour that will see it rapidly grab its food and scamper away to a private area. If you paper wrap food into small packets a pet rat can unwrap the paper without biting through it to gain access. Place an object in front of a goal and the pet rat can pull or push the object using a combination of teeth and paws. I've seen my pet rat quite comfortably remove a garment of clothing from in front of the edge of a wooden door with her teeth. She then followed up by sinking her teeth into the wooden door. When brown rats play they will gently nip or push the back of another rat's neck with their teeth or nose. If the play gets heavy the nips may turn into bites and the agitated rat will often grind its incisors together to display its dissatisfaction. In contrast, this action can soon subside and the nips turn to gentle grooming of each other's fur while the grinding of incisors displays relaxation. Brown rat behaviour can get very complicated and confusing sometimes and the whole preventing conflict process is no exception. Unless a pet rat is ill, very afraid, or particularly aggressive, bites to owners are rare. In the decades I've kept rats I've only had blood drawn once and I believe that was a case of mistaken identity. Pet rats will place your finger between their incisors but soon release once it realises its not for digesting. The gerbils and guinea pigs I've kept...now that's another story.
In addition to the above, Rat Behavior and Biology (Anne's rat page), is well worth a look for a more comprehensive and detailed examination of Wild Brown Rat teeth and gnawing behaviour. |
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The brown rat is a member of the
beasties that fall into the order of Rodentia (rodents). Rodents include
mammals such as mice, capybaras, squirrels, mole rats, gophers, porcupines...the list is vast at over 2000 species. The word
Rodentia
originates from the Latin verb rodere (to gnaw) and if you've kept rats
you'll know exactly what that means. One thing that rodents have in common
is their gnawing. In fact, the most diagnostic feature to determine a
rodent is its pair of chisel like upper and lower incisors that never stop
growing. Describing a brown rat's front teeth to chisels is an apt
comparison and one you'll find in a multitude of material related to rats. If you brush your finger across the surface of a
brown rat's incisor teeth it
feels similar to the edge of a freshly sharpened kitchen knife and
certainly has the potential to do as much if not more 'chiseling' and
'sculpturing'.
Brown
rats have sixteen teeth in
total. There are the four chisel like incisors at the front (two up and
two down) that are well designed for gnawing and twelve molars at the back
(six up and six down) that act as chewers to break down food into
swallow sized pieces. Unlike the incisors at the front, the molars are
never be replaced. A brown rat's incisors are longer at the bottom than
the top and range in colour from a light shade of yellow to
a deeper orange. The top incisors are a deeper colour than the bottom
pair. A brown rat's natural behaviour is to gnaw, gnaw, gnaw, and the
constant growth of the incisors ensures they are never worn away. When the
brown rat is cutting into something its top incisors hold the object while
the lower incisors begin their chiseling action.
When a brown rat is gnawing at an
item it will frequently move its head into an optimum chiseling position.
Brown rats' incisors curve slightly inwards which makes vertical planes
difficult to get their teeth stuck into. A pet rat will typically begin
gnawing at the corner of an object which makes wooden doors and side
boards likely targets.