Bite Size Determines Bite Force
February 13, 2013

The Bigger The Bite Size, The Less The Bite Force

Brett Smith for —  Your Universe Online

Bite force allows animals to properly ingest food, making jaw mechanics very important -- especially for predators.

A new study in the journal Biology Letters from biologists at Brown University has found an animal´s bite force depends upon the size of the thing the animal is eating.

“Everybody measures bite force as one value,” said study co-author Nicholas Gidmark, a postdoctoral researcher at Brown. “There´s a lot more nuance to it than that.”

The nuance comes in the form of jaw mechanics and just how far the jaw muscles are stretched before taking a bite.

To study how bite size is related to bite force, the research team focused their study on carp, which typically eat snails.

“You have to break a snail in order to eat it,” Gidmark said. “If you don´t have enough bite force to break that snail, you get nothing from it.”

In the study, the scientists began by training different sizes of carp to eat food-stuffed ceramic tubes. Various sizes of tubes were coated with differing amounts of polyurethane to create a variety of strengths for each tube diameter.

The team also inserted tiny metal balls into the carps´ jaws to act as markers that would show up in an X-ray monitor. The fish were then fed tubes with different diameters and strengths. The scientists tracked the fish jaw movements using X-ray videos, noting which tubes the fish could crush and which they could not.

Finally, they created a 3D animation based on the movement and positions of the tiny metal markers.

“What the animation lets us do is actually reconstruct the positions of the whole bone relative to the whole skull,” Gidmark said. “What that shows us is the whole surface of muscle attachment on the jaw and the whole surface of muscle attachment on the skull and how those move relative to each other.”

The results of the experiments showed bite force not only depended heavily on tube size, they also showed an optimal amount of muscle stretch would result in maximum force. They found a variation of either about 85 percent or 115 percent of the optimal value led to a sizeable reduction in bite force.

“There is variable bite-force with gape,” he said. “The implications of that are all over the place. This really sets the ground for a lot of cool ecology and predator-prey interaction studies.”

Gidmark said the study could have profound implications for understanding the predator-prey relationship. For example, if a carp´s local ecosystem began growing larger or smaller, that carp could gain or lose the ability to eat them.

“Depending on how prey is defending itself, whether it is getting big or strong or both, it will have an important impact on those relationships between predators and prey,” Gidmark said.

The study´s findings are likely true for humans and other animals that have a similar jaw structure, Gidmark said. He added he is eager to see how the findings might translate to other species and their ecology.