As the ocean's top predators, sharks are known for their hunting abilities, whether it's stealth ambushes by Greenlandic sharks or whip-like tails in thresher sharks. Still, experts don't know the animals' characteristics, such as their maximum speed and bite force.
Most of the scientific knowledge about bite force comes from experiments or computer modeling of captive sharks. Not surprisingly, working with "wild-living, large, charismatic sharks has big logistical limitations," said Dan Huber, a shark biologist at the University of Tampa.
But underwater photographer Brock Maxi, who helps run South Africa's diving company, Shark Explorer, wanted to take on the challenge. In one experiment, Maxi managed to document the bite force of a wild, free-swimming tiger shark and a large hammerhead shark (the world's two largest predatory sharks), a challenge never before.
Brock Maxi recorded the bite force of a large female tiger shark using a custom bite force meter at Tiger Beach in the Bahamas
Studying bite force helps scientists understand how sharks have evolved hunting strategies over the past 400 million years to become such efficient predators, said Huber, who was not involved in the new experiment.
It's also important data for conservation efforts, he said:
Huber explained that knowing what these declining species eat is crucial, given that the International Union for Conservation of Nature lists tiger sharks as near threatened and the sledgehammerhead shark as critically endangered. If a species has evolved to specifically hunt specific prey, such as endangered sea turtles, there are serious implications if that food is no longer provided.
Lemon sharks gather on the surface of the water, and Maxi tries to record their bite force
Dumpsters for the sea
In the experiment, Maxi commissioned a custom meter to measure shark bite force. He designed it to be sensitive enough for accurate readings, but strong enough to withstand a powerful jaw. Then, in the Bahamas, he used bait to encourage sharks to bite the meter.
Maxi and his team took 505 pounds of readings from an 11-foot hammerhead shark and 864 pounds from a nine-foot tiger shark. Despite being two feet smaller than a hammerhead shark, tiger sharks have a bite force of 70% higher.
Huber says that's the data he got based on his mathematical model.
Hammerhead sharks swim under the sunlit water
Tiger sharks are sometimes referred to as the dumpster of the ocean because it is not only more aggressive but also known for eating almost anything, including turtles. They wrap their prey with large mouths and even the hard shells of turtles. Hammerhead sharks require less strength and can grab food, including stingrays and squid, with a quick bite.
While sharks can have tremendous bite force, that's usually "with their huge size," Huber said. When considering body size, their bite force is relatively low compared to other animals, such as hippos (1,827 pounds) and saltwater crocodiles – their 3,748 pounds bite force is the strongest in the animal kingdom.
Because their mouths are "full of steak knives," he said, large sharks don't need to bite strongly against each other to get food.
How fast can mackerel swim?
In another debut of the new documentary, wildlife filmmaker Andy Casagrande tries to catch a mako shark speed record, one of the fastest sharks in the world.
The shark, called Makos, is sometimes called a deep-sea cheetah, and it's "shaped like a torpedo," says Marianne Porter, a biologist at Florida Atlantic University who studies shark biomechanics. They are "smooth and streamlined," she says, down to the "perfect dot" of the nose, perfect for penetrating water. They are also propelled by their powerful crescent-shaped tails.
While there are anecdotal reports of Marcos swimming at 43 miles per hour, Casa Grande hopes to be the first to definitively record his top speed.
In a new experiment near San Diego, Casa Grande had a mako shark chase fish-shaped bait and then followed the shark in an ultra-fast, GPS-equipped drone. The shark took two seconds to swim 72 feet (0.01 miles), measured by a floating ruler, at a speed of 24.54 miles per hour. The experiment validated Casa Grande's method, but it is unlikely that the speed was the fastest of Marcos.
Despite the disappointment, Casa Grande understood why no one had yet recorded Marcos' final top speed. "It's almost impossible." He said.
Difficulties in studying sharks
Both Huber and Porter cautioned that it would be difficult to determine the maximum speed or bite force of any animal.
For example, Huber said, the voluntary bite force of wild sharks may be "grossly underestimated" because providing them with bait "is not a realistic predatory scenario."
"Yes, sharks bite, but there's no reason to need to perform at your highest level."
He said we humans can empathize.
As with bite force, shark speeds can vary greatly depending on the situation, said Porter, who was not involved in speed experiments. "We don't know if the shark followed this bait out of curiosity, or if it was legitimately trying to catch food, as if its life depended on it."
Confirming the maximum speed of animals would require a long period of "a lot of data," she added, but Casa Grande's small-scale experiment could inspire further experiments.
She was also pleasantly surprised to find that using drone video, scientists could see why sharks move so fast, as never before.