Niuhi can grow to 18-feet long and weigh 2,000 pounds and it is the most dangerous shark in Hawai‘i but also the most gentile shark! After 40 years of diving with sharks world wide from 20 foot long Great White Sharks to two foot long Horn Sharks the Hawaiian Tiger sharks are the most difficult to get a movie of because they are so shy. When we jump off a boat where a large Tiger Shark has been spotted we don’t look at the shark at first. We actually look the other way as if we don’t see it. That is because Tiger Sharks are stealth feeders and they like to surprise their prey so if you make eye contact they will just turn away from you and leave.
So why do these giant top ocean predators sometimes bite swimmers and surfers? Very simple. Mistaken identity. Humans are not on the sharks menu because we have only recently entered their habitat. Sharks have been in the sea feeding naturally for millions of years but humans have only been in the sea with them for a few hundred years. Humans also have a lot of bones and when a Tiger Shark bites its normal prey it looses a few teeth. These sharks have several rows of teeth and when they loose a few, others fall into place within a few days so the shark can continue to feed. The big sharks feed on sea creatures with a high fat content vs bone mass. Humans simply do not have enough fat to be worth eating and we have so many bones the sharks would loose way to many teeth trying to feed on us. This is good for us surfers and divers!
Big sharks have an amazing ability to know when humans are in the water because they have very specialized electromagnetic sensors that can detect the electrical field that all animals give off. These sharks do not need their eyes to “see us” as they can detect our aura in the salt water from over 50 yards away. The large sharks also have very sensitive skin that can detect the pressure waves humans create when swimming through the water and they can even detect our fat and bone content based on the pressure waves we give off.
Niuhi is the garbage collector of the sea. They eat sick and wounded animals because they are not fast enough to catch a live healthy animal. They love to feed on dead or sick whales, dolphins, turtles and even cows that may wash out to sea in the rain. They will also catch a sea turtle from time to time by coming from below and surprising a turtle feeding on the surface. This happened to me while out surfing at Hanalei Bay a few months back when a 12 foot Tiger Sharks launched a sea turtle right out of the water ten feet up in the air right in front of us catching a wave!
Sometimes surfers and swimmer look like a wounded sea turtle because we move so slowly in the sea. A large Tiger Shark will occasionally bite a surfer when it is chasing a sea turtle and the turtle goes right under the persons surfboard. Due to the power of the sharks bite the surfer could loose a limb but the shark immediately realizes the surfers is not a turtle and leaves its mistake behind.
Niuhi are usually lone predators and it is rare to see more than one at any given time where other large sharks like the Great White are quite social. On the National Geographic series I am in this summer called Sharkfest I talk about how the large Tiger Sharks are attracted to raw sewage leaks and injection wells leaking sewage out into the sea. The sharks detect sewage as something dead and they come in to clean it up but they won’t find any food and they get hungry. This can cause a hungry agitated shark to be looking for food in stinky murky water right where lots of people may be surfing and swimming and that increases the chance of an accidental bite to occur. We feel that the leaking sewage from injection wells in Maui just may be causing the spike in accidental shark bites.
You can see niuhi in action in my underwater educational series up on my web at www.underwater2web.com and also watch my segment on National Geographic When Sharks Attack which is currently on TV.
Terry Lilley is a marine biologist living in Hanalei Kauai and co-founder of Reef Guardians Hawaii, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawaii go to www.reefguardianshawaii.org.