The Jaw Pressure of a Snapping Turtle

A turtle's mouth is made up of the lower and upper mandibles, each of which is beak-like and covered with a horny layer of keratin. All extant turtles lack teeth, though they are able to tear or cut prey with their sharp beak. Both varieties of snapping turtles have relatively large heads, which helps to generate more force thanks to the higher muscle mass in the head than similarly sized turtles. Alligator snapping turtles have a fleshy appendage in the mouth that resembles a worm, and is used to lure prey close enough to be captured.

An animal's diet can provide clues to its biting capabilities. Common snapping turtles consume a significant portion of herbivorous material in their diet, along with fish, amphibians, reptiles, birds and mammals that share the same habitat. Alligator snapping turtles have a similar diet, though less vegetation is included. Though neither species are good at catching fast fish, they can successfully catch slower fish species. The fact that both are noted to occasionally consume other turtles confirms they have strong jaws. In a 2006 study by Ruth Elsey published in "Southeastern Naturalist," almost 80 percent of the alligator snapping turtles studied had turtle shells in their digestive system.

Animals that can bite hard may use this as a defense mechanism. Both of these turtles are noted for being very defensive on land, and will readily bite perceived predators. Turtle species that are unable to fully withdraw their head into their shell, such as both snapping turtle species, will readily bite in defense. Both species are benign when encountered in the water, where they needn't fear any predators; it is only on land where they are out of their element and feel vulnerable.

The University of Antwerp, Belgium, led one of the only comprehensive surveys of turtle bite pressures, and the results were published in a 2002 issue of the "Journal of Evolutionary Biology." In the study, 28 species of turtle were tested with the same method and equipment, and the data collected was surprising. The bite of the common toad-headed turtle (Phrynops nasutus) had the hardest bite measured of 432 newtons. This was more that twice the common snapping turtle's score of 208 newtons or the alligator snapping turtle's score of 158 newtons.

Newtons are not units that are used commonly in day-to-day life, so a few comparisons are helpful. Starting with the most familiar animal, humans have been recorded to generate bite forces between approximately 200 to 600 Newtons. Shark bite pressures have been recorded at over 18,000 newtons, nearly 90 times more powerful than the common snapping turtle. With these comparisons, it becomes clear that though snapping turtles definitely have strong jaws, they are not as strong as is commonly supposed.