North America's Strongest Biter

Which North American mammal has the strongest bite relative to body size?

  • NWF Staff
  • Jan 19, 2010
It’s Not a Polar Bear . . . 
. . . and it’s not a wolf or a mountain lion, either. Recent research by Australian and Canadian biologists tells us that a tiny killer of mice and other rodents—the least weasel—ounce for ounce has the most powerful jaws of any predator in North America. In a study of 151 living meat-eaters, as well as a few extinct hunting species, the biologists used a computer model that allowed them to calculate an animal’s bite power, adjusted for the animal’s size. Then the biologists assigned scores to the animals they tested. A score of more than 100 meant the animal had a bite force greater than expected. Among living predators, the African lion scored nicely at 124, the tiger at 130, the giant panda at 151.



But What About the Least Weasel?
Oh, yes. The least weasel’s score was an impressive 164, second only to the Tasmanian devil, which scored 181—but then the Tasmanian devil is designed for crushing and eating bones, so what do you expect?

“For its size, the least weasel definitely has the strongest bite of any North American carnivore in our data set, which included most of them,” says Stephen Wroe of the School of Biological Sciences at Australia’s University of Sydney.

Why Least Weasels Bite So Hard 
The research by Wroe and his colleagues suggests that in wild dogs, cats and weasels, the bigger the prey, the stronger the killer’s bite has to be. The least weasel’s small size—the animal weighs only about 2.5 ounces—makes its tiny prey huge by comparison. Consequently, like gray wolves (bite score: 127) killing bison, or African lions taking down Cape buffalo, a least weasel attacking a relatively massive, 4-ounce chipmunk needs powerful jaws for delivering a crushing bite to the windpipe or to the back of the skull.

Strongest Biter Among Extinct Species 
The top scorer among the extinct species tested, as well as the top scorer of all, was the marsupial lion, which, being a marsupial (a type of mammal that usually gives birth to almost embryonic young that then mature in a pouch on the mother’s belly), was in fact not really a lion or even a cat. This stocky creature averaged about 250 pounds and was the only marsupial armed with retractable claws, like those of cats. It also bore on each front foot a thumb that was semi-opposable, meaning the animal could actually grab hold of its prey. It may at times have stood upright on its hind legs and tail, like a kangaroo. Its jaws bristled with sharp, heavy dentition with which it could deliver a bite of 380 pounds, for a bite score of 194—a substantial 13 points greater than that of the Tasmanian devil. The marsupial lion went extinct more than 40,000 years ago.

Adapted from "My, What a Big Bite You Have," by Roger Di Silvestro, National Wildlife , December/January 2009

Get Involved

Where We Work

More than one-third of U.S. fish and wildlife species are at risk of extinction in the coming decades. We're on the ground in seven regions across the country, collaborating with 52 state and territory affiliates to reverse the crisis and ensure wildlife thrive.

Learn More
Regional Centers and Affiliates