At over 20 feet long and weighing over 3,000 pounds, you would know if you met niuhi the great white shark. The first one I saw while scuba diving came right at me while I was spearfishing, and turned away at the last moment, looking me right in the eye. It all seemed to happen in slow motion, and I could see some of its huge teeth that lined a very big smile. It was a peaceful-but-very- thrilling event.
Only when the big shark circled back three times looking to steal the big fish I had just speared did I start to get a little worried, as I was out diving by myself in 60 feet deep of water. When the great white got too close I gently poked it in the nose with my spear. Not hard enough to hurt it in any way, but just enough to say “back off a bit.” It worked, and the monster shark left on its own and I brought my fish in for dinner. After the dive I wrote my first article I have ever written about sharks, “Face To Face with a Great White Shark.”
Since that time I have written dozens of shark articles and shot many movies, including for National Geographic Sharkfest on “Go Wild,” and I have been around the world studying shark behavior. On one occasion I was in the water surrounded by five 15-to-20-foot great whites at the same time. We have learned a lot about shark behavior over the past 10 years, and we now know they are not the “killing machines” that they were portrayed in the “Jaws” movie years ago. In fact, these giants of the sea all have different personalities, feeding habits and travel patterns, and are usually quite friendly to humans in the water.
Hawaii has very-large, 20-foot-plus great white sharks that come to visit the islands once a year, usually in the fall and early winter. These large sharks all tend to be females, and it was once thought that they do not feed when they are in Hawaiian waters. Only recently, several giant females were observed feeding on a dead whale here in Hawai‘i, and we think we now know why. Many of these large sharks have GPS tracking units attached to their dorsal fins, and they travel once a year all the way to Hawai‘i from the West Coast of the U.S. and Mexico. They stop for a while to feed in a spot in the middle of the Pacific Ocean called “the shark cafe.”
We now know that the large great whites are warm-blooded, and they need a lot of animal fat in their diet to stay warm in the cold waters they live in most of the year. In order to produce enough energy to hunt and keep their body temperatures up, they have to feed on high-fat animals like seals and large tuna. The sharks have good eyesight, and they have electromagnetic sensors on their snout where they can tell the difference between a seal and a human from over 100 yards away. The sharks also have an excellent ability to feel pressure waves in the water created by an animal swimming, including us humans. By using pressure waves they can tell the fat content in the animal they are following at a distance.
We believe that the great white sharks do not eat people because we do not have enough fat content and are too bony. The shark would have to use more energy catching and eating a human than it would get back in energy from the meal. From time to time a great white may accidentally bite a human, mistaking it for a seal, but rarely if ever does the shark actually eat the human.
This explains why us shark researchers can usually dive safely up close to these very large sharks, and I have done so many times and have never been bothered by them.
Only the very large female great whites come to Hawai‘i, and we think that they may be doing so to feed on baby humpback whales that have an extremely-high fat content. This would explain why they only seem to show up when the humpbacks are here to give birth.
I will be done with my new movie soon, “The Truth About Hawaiian Sharks,” and it will be up on the underwater web page at underwater2web.com. You can also watch my shark segments on TV in the National Geographic “Go Wild” show during Sharkfest.
Terry Lilley is a marine biologist living in Hanalei and a co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate, see reefguardianhawaii.org.