Too close for comfort with a hammerhead shark

June 24, 2021
By Marcy Shortuse

BY MARCY SHORTUSE – Recently a Boca Grande hammerhead made the news in our area for creating a scene on a local beach. Yes, we said “on” the beach, not “near” the beach. That’s because this particular shark, looking to be about 10 feet long, came so close to the beach he was laying on the sand at several points … much to the curiosity of numerous human beachgoers.

The North Port woman who filmed the shark, Wendy Donnelly, told local news channels that they were all relaxing on the beach when people around them started running. Wendy grabbed her phone and ran down to where the action was. That’s when she found a crowd gathered around the hammerhead, who was wiggling vigorously to move through half sand, half water at the edge of the shore.

After a brief time, the shark went back into deeper water of its own accord. But what made the shark act like that in the first place? According to science, there are several reasons it could happen.

First, it is not a common practice for any shark to beach themselves, unlike dolphins or whales, so you don’t have to worry about being eaten by a shark on land unless you catch it and bring it to shore yourself.

Sometimes a shark will find its way to shore so as not to become a victim of the food chain. If they receive a serious injury, or are ill, or just ate a big meal, they will move away from deeper water where other predators could feed on them while they are vulnerable. This particular hammerhead seemed relatively fit, though, and he was moving quickly as if having had a big meal was not his issue.

Sometimes sharks run very close to the shore – sometimes a little too close – when they are chasing a meal, but because of their muscle structure they can almost always find their way back into the water. Some sharks have been observed chasing turtles or dolphins out of the water, onto shore. White sharks commonly swim partially out of the water to grab prey off the rocks along the shore, and the smooth-hound shark, a species that feeds on terrestrial crabs, will go onto a muddy shore or bank to retrieve their favorite food.

Another reason a shark might come that close to shore is a bit more scientific, as it has to do with geomagnetic fields. In 1993 a researcher was using sonic telemetry to study the movement patterns of tagged scalloped hammerheads in the Sea of Cortez. He found that while the sharks didn’t care much about the temperature of the water, currents or underwater topography, they did seem to move along the ridges and valleys underwater that corresponded with the local geomagnetic field. In short, it means that the shark’s internal compass and sense of direction could possibly be thrown off, which would be a deviation from the normal movement that occurs with species of animals that move along geomagnetic fields.

In his research he found that these sharks were schooling during the day but feeding separately at night. He then concluded that the hammerheads were locating “seamounts” (an underwater mountain formed by volcanic activity) using geomagnetic cues, using magnetic highways. If a shark were to misread the geomagnetic map, so to speak, while hunting they could very well end up too close to shore. It rarely happens with sharks, though, like it does with whales and other species.

It is not as likely that this is the situation with the hammerhead on the beach last week; a simpler explanation is usually the correct one. Hammerheads feed on fish like tarpon and stingrays, and stingrays have the ability to move very close to shore because of their body configuration. If a shark were to overreach while chasing one, he could end up partially beached.

As an added bit of information, is not recommended that you try to save a shark if you find one beached on the shore. Sharks are very unpredictable and very flexible, and they might turn around and bite the hand … or leg … of someone who is trying to help them. If you have people around to help you, and you can pull the shark back in the water by the tail, it’s possible you could be successful. The key is to make sure the shark needs help before you put your hands on it, and in the case of this particular shark on a Boca Grande beach it seemed to have no problem making its way back into the water by itself.

If you are at the beach and you do see one or more sharks in the water, and they are moving erratically and coming very close to shore, exit the water. You should also exit the water if you see schools of tarpon in the area. Don’t swim at night when a shark can’t see you well enough in the water to distinguish you from food. Hammerheads in particular have a large blind spot in their front vision (as their eyes are on the sides of their hammer head, hence the name), so swimming at night in our waters is most definitely not recommended. The placement of a hammerhead’s eyes allow them a full 360-degree view, so they can see above and below easily … just not directly in front of their face.

Also, do not swim where people are fishing, do not wear shiny jewelry in the water, and brightly colored bathing suits can also attract sharks.

Another interesting fact about hammerheads is that they often live between 25 and 35 years. Hammerheads also have the ability to tan, as they cruise in shallow water or on the surface for long periods of time. Lastly, sharks like the hammerhead have electro receptors, called the ampullae of Lorenzini, which allow them to pick up the very small electrical pulses that all living things emit. They are so acute, a shark can sense the beating heart of a human from several miles away.

Enjoy your time at the beach, and don’t worry about a shark creeping up on you on land.