Crocodiles Have Strongest Bite Ever Measured, Hands-on Tests Show
"Extraordinary" study hints crocs are "force-generating machines" rivaling T. rex.
Greg Erickson gauges the bite of an American alligator during tests of all living crocodilian species.Brian Handwerk
for National Geographic News
Published March 15, 2012
Crocodiles may be the world's champion chompers, killing with the greatest bite force ever directly measured for living animals, a new study says. In fact, their bite forces may rival that of mighty T. rex.
Paleobiologist Gregory M. Erickson and colleagues put all 23 living crocodilian species through an unprecedented bite test. The "winners"—saltwater crocodiles—slammed their jaws shut with 3,700 pounds per square inch (psi), or 16,460 newtons, of bite force.
By contrast, you might tear into a steak with 150 to 200 psi (890 newtons). Hyenas, lions, and tigers generate around 1,000 psi (4,450 newtons).
And while a 2008 computer model estimated that a 21-foot (6.5-meter) great white shark would produce nearly 4,000 psi (17,790 newtons) of bite force, that figure hasn't been directly measured.
Erickson and colleagues did physically measure the bites of several 17-foot (5.2-meter) saltwater crocs—as well as Nile crocodiles, alligators, caimans, gharials, and other crocs, some for the first time ever.
The team spent countless hours wrestling with the reptiles at Florida's St. Augustine Alligator Farm Zoological Park and getting them to bite a force transducer—a "very expensive, very durable, waterproof bathroom scale that's padded with leather."
"The testing is like dragon slaying by committee, often involving ten or more people to test a single animal," said Erickson, of Florida State University.
For every croc species, the transducer registered impressive power, suggesting that a big bite is at the heart of what it means to be a crocodilian, according to Erickson.
"That's why I think they've been so successful," he said. "They seized on a remarkable design for producing bite force and pressure to occupy ecological niches on the water's edge for 85 million years, and no one else evolved that could wrest those niches from them."
Bite From the Start
Surprisingly, at least to Erickson, variations in the bite forces of croc species turn out to be largely based on body size. In many animal groups this variation is tied to differing jaw shapes and tooth forms, but those features didn't much affect the croc chomps in the team's tests.
This suggests crocs were big biters from the dawn of their evolutionary line, said Erickson, a grantee of the National Geographic Society's Committee for Research and Exploration.
"I think the most primitive development of the crocs was basically as a force-generating machine," Erickson said. Variations in snouts and teeth arose later, fine-tuning that powerful bite for prey ranging from fish and snakes to birds, mammals, and even insects.
"Think of a Weed Eater with a big engine that has different attachments, like a grass cutter or a tree trimmer. During evolution [crocs] basically played around with those sorts of attachments," said Erickson, who led the new study, published Wednesday in the journal PLoS ONE.
In a typical croc environment, "big game comes to the water's edge, mollusks grow there, birds land—and anything that's around that water, they can eat it."
Paleobiologist Laura Porro, who wasn't involved in the new research, added, "People have been talking about how differences in snout shape and tooth shape and diet may impact crocodilian biomechanics, but no one has been able to collect all these data. It's extraordinary."
Mind-Boggling Bites of Crocs Past
In addition to shedding light on living crocs, the new data could illuminate the extinct animals at the roots of the croc family tree, said Porro, of the University of Chicago, who studies live alligators but also models biomechanics of extinct reptiles.
"This kind of work with living animals can help us try to validate our models," she said. "And I think you could definitely extend this model to the fossil crocs, even the giant ones, that look relatively similar to modern crocs."
Erickson and team have already done some such scaling—producing an image of a truly ferocious ancient croc.
"We tested several 17-foot [5-meter] saltwater crocs," he said. "If you scale the results up to 20-footers, you get estimates of 7,700 pounds [34,250 newtons], which is the low end of T. rex bite-force estimates.
"So if you want to see what T. Rex bite force looks like, go look at one of these crocs."
Furthermore, by Erickson's calculations, the extinct, limousine-size Deinosuchus, or "terrible crocodile," had an estimated bite force as high as 23,100 psi (102,750 newtons)—greater even than new estimates that put T. rex's bite at 12,814 psi (57,000 newtons).
"It's mind-boggling to think about that one," he said.
The University of Chicago's Porro noted that no Tyrannosaurus rex muscle survives, so estimates for the dinosaur's bite force are based on its body size, wide skull and short snout.
Those T. rex bones look capable of a stronger bite than any croc's, Porro said. "But then again, if you dissect a croc's head, it's amazing just how much muscle mass they have. They have huge jowls ... all jaw-closing muscle, so who knows?" she said. "Maybe it's a matter of crocs just having more muscle."
We may never know for sure whether a croc or a tyrannosaur was the world's all-time champion chomper (and in any case, a giant prehistoric shark likely has both beat).
"There is always going to be some uncertainty," Porro said.
Modern crocs are remarkably similar to prehistoric ones, which in some ways makes things easy for ancient-croc researchers, she noted. But "we have nothing today that looks very much like a T. rex."
news.nationalgeographic.com/news/2012/03/120315-crocodiles-bite-force-erickson-science-plos-one-strongest/www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0031781-----------
Australian Saltwater Crocodiles Are World’s Most Powerful BitersScienceDaily (Mar. 16, 2012) — In Greg Erickson's lab at Florida State University, crocodiles and alligators rule. Skeletal snouts and toothy grins adorn window ledges and tables -- all donated specimens that are scrutinized by researchers and students alike.
Lately, Erickson, a Florida State biology professor, and his colleagues have been pondering a particularly painful-sounding question: How hard do alligators and crocodiles bite?
The answer is a bite force value of 3,700 pounds for a 17-foot saltwater crocodile (as well as tooth pressures of 350,000 pounds per square inch). That's the highest bite force ever recorded -- beating a 2,980-pound value for a 13-foot wild American alligator Erickson's lab measured in 2005. They estimate that the largest extinct crocodilians, 35- to 40-foot animals, bit at forces as high as 23,100 pounds.
Erickson, along with several colleagues, including Florida State biology professors Scott Steppan and Brian Inouye, and graduate student Paul Gignac, reported their findings in the journal PLoS One.
Funded by the National Geographic Society and the FSU College of Arts and Sciences, their study looks at the bite force and tooth pressure of every single species of crocodilian. It took more than a decade to complete and required a wily team of croc handlers and statisticians, as well as an army of undergraduate and graduate students. Erickson describes crocodilian bite-force testing as being a bit like dragon slaying by committee.
"Our work required a team effort," he said.
As a result of the study, Erickson and his team have a new understanding on how these animals became so successful and a better understanding about the remarkable biology of living crocodiles and alligators. They've also developed new methods for testing bite forces.
The data contributes to analyzing performance in animals from the past and provides unprecedented insights on evolution and statistically informed models about other reptiles such as dinosaurs.
The study's findings are so unique that Erickson's team has been contacted by editors at the "Guinness Book of World Records" inquiring about the data.
Over the 11 years that his current study took place in both the United States and Australia, Erickson and his team roped 83 adult alligators and crocodiles, strapped them down, placed a bite-force device between their back teeth and recorded the bite force. An engineering calculation was then used to estimate the force generated simultaneously by the teeth nearest the front of the jaws. The team molded the teeth with dentist's dental putty, made casts and figured out the contact areas.
Talk about dangerous work.
As Erickson describes it: "I have to admit, the first time I placed our meter into the maw of an adult crocodile, I was nervous. It was all over in the blink of an eye. When it struck, it nearly wrested my grip from the handle. The noise of the jaws coming together was like a gunshot. The power of the animal was astounding, and the violence of the event frightening."
Overall, the researchers looked at crocodilians both mundane and exotic, from American alligators to 17-foot Australian saltwater crocodiles and the Indian gharial. Among the world's most successful predatory reptiles, these creatures have been "guardians of the water-land interface for over 85 million years," Erickson said.
But just how they were able to occupy and dominate ecological niches for so long is a mystery.
Erickson and his team knew that the reptiles evolved into different sizes, from 3-footers to 40-footers, and they showed concurrent major changes in their jaw shape and tooth form, while their body form remained largely unchanged.
"We set out to answer how this anatomical variance related to their ability to generate bite force and pressures for feeding in the different forms and thus how they have been so successful," Erickson said. "The bite force over the contact area is the pressure, which is more pertinent to feeding performance than bite force. Ultimately, it tells us just what they were doing with those prodigious bite forces."
And, he added, gators and crocs have comparable maximal bite-force capacity when measured pound for pound. They basically all have the same musculoskeletal design, just different snouts and teeth.
"It is analogous to putting different attachments on a weed eater -- grass cutter, brush cutter, tree trimmer, they all have the same type of engine," Erickson said. "There are bigger and smaller engines, with higher and lower horsepower, but they have the same attachments."
His research team is already using the study's data to explore bite-force and tooth-pressure performance in fossil forms. The team is building the world's most sophisticated models for extinct crocodiles and dinosaurs based on the findings, as well as continuing to study the significance of croc snout form.
As for modern-day crocs and gators, well, there's little doubt that they are truly the world's bone-crushing champions. Just remember that old Floridian maxim: Always maintain a healthy distance between yourself and the nearest gator.
"If you can bench-press a pickup truck, then you can escape a croc's jaws," Erickson warned. "It is a one-way street between the teeth and stomach of a large croc."
All crocodilians have essentially the same musculoskeletal design, Erickson explains, just different snouts and teeth.Gregory M. Erickson, Paul M. Gignac, Scott J. Steppan, A. Kristopher Lappin, Kent A. Vliet, John D. Brueggen, Brian D. Inouye, David Kledzik, Grahame J. W. Webb. Insights into the Ecology and Evolutionary Success of Crocodilians Revealed through Bite-Force and Tooth-Pressure Experimentation. PLoS ONE, 2012; 7 (3): e31781 DOI: 10.1371/journal.pone.0031781
