Quantcast
Environmental News for a Healthier Planet and Life

Help Support EcoWatch

Shark Week Looms, but Don’t Panic

Insights + Opinion
Shark Week Looms, but Don’t Panic
It's OK, I'm a filter feeder: Whale shark off Indonesia. Marcel Ekkel, /Flickr / CC BY

By Gavin Naylor

Sharks elicit outsized fear, even though the risk of a shark bite is infinitesimally small. As a marine biologist and director of the Florida Program for Shark Research, I oversee the International Shark Attack File — a global record of reported shark bites that has been maintained continuously since 1958.


We are careful to emphasize how rare shark bites are: You are 30 times more likely to be struck by lightning than be bitten by a shark. You are more likely to die while taking a selfie, or be bitten by a New Yorker. In anticipation of the anxiety that's typically generated by the Discovery Channel's Shark Week programming, here are a few things about sharks that are often overlooked.

A Big, Diverse Family

Not all sharks are the same. Only a dozen or so of the roughly 520 shark species pose any risk to people. Even the three species that account for almost all shark bite fatalities — the white shark (Carcharodon carcharias), tiger shark (Galeocerdo cuvier) and bull shark (Carcharhinus leucas) — are behaviorally and evolutionarily very different from one another.

The tiger shark and bull shark are genetically as different from each other as a dog is from a rabbit. And both of these species are about as different from a white shark as a dog is from a kangaroo. The evolutionary lineages leading to the two groups split 170 million years ago, during the age of dinosaurs and before the origin of birds, and 110 million years before the origin of primates.

Yet many people assume all sharks are alike and equally likely to bite humans. Consider the term "shark attack," which is scientifically equivalent to "mammal attack." Nobody would equate dog bites with hamster bites, but this is exactly what we do when it comes to sharks.

So, when a reporter calls me about a fatality caused by a white shark off Cape Cod and asks my advice for beachgoers in North Carolina, it's essentially like asking, "A man was killed by a dog on Cape Cod. What precautions should people take when dealing with kangaroos in North Carolina?"

Know Your Species

Understanding local species' behavior and life habits is one of the best ways to stay safe. For example, almost all shark bites that occur off Cape Cod are by white sharks, which are a large, primarily cold-water species that spend most of their time in isolation feeding on fishes. But they also aggregate near seal colonies that provide a reliable food source at certain times of the year.

Shark bites in the Carolinas are by warm-water species like bull sharks, tiger sharks and blacktips (Carcharhinus limbatus). Each species is associated with particular habitats and dietary preferences.

Blacktips, which we suspect are responsible for most relatively minor bites on humans in the southeastern U.S., feed on schooling bait fishes like menhaden. In contrast, bull sharks are equally at home in fresh water and salt water, and are often found near estuaries. Their bites are more severe than those of blacktips, as they are larger, more powerful, bolder and more tenacious. Several fatalities have been ascribed to bull sharks.

Tiger sharks are also large, and are responsible for a significant fraction of fatalities, particularly off the coast of volcanic islands like Hawaii and Reunion. They are tropical animals that often venture into shallow water frequented by swimmers and surfers.

Humans Are Not Targets

Sharks do not "hunt" humans. Data from the International Shark Attack File compiled over the past 60 years show a tight association between shark bites and the number of people in the water. In other words, shark bites are a simple function of the probability of encountering a shark.

This underscores the fact that shark bites are almost always cases of mistaken identity. If sharks actively hunted people, there would be many more bites, since humans make very easy targets when they swim in sharks' natural habitats.

Local conditions can also affect the risk of an attack. Encounters are more likely when sharks venture closer to shore, into areas where people are swimming. They may do this because they are following bait fishes or seals upon which they prey.

This means we can use environmental variables such as temperature, tide or weather conditions to better predict movement of bait fish toward the shoreline, which in turn will predict the presence of sharks. Over the next few years, the Florida Program for Shark Research will work with colleagues at other universities to monitor onshore and offshore movements of tagged sharks and their association with environmental variables so that we can improve our understanding of what conditions bring sharks close to shore.

More to Know

There still is much to learn about sharks, especially the 500 or so species that have never been implicated in a bite on humans. One example is the tiny deep sea pocket shark, which has a strange pouch behind its pectoral fins.

Only two specimens of this type of shark have ever been caught — one off the coast of Chile 30 years ago, and another more recently in the Gulf of Mexico. We're not sure about the function of the pouch, but suspect it stores luminous fluid that is released to distract would-be predators — much as its close relative, the tail light shark, releases luminous fluid from a gland on its underside near its vent.

Sharks range in form from the bizarre goblin shark (Mitsukurina owstoni), most commonly encountered in Japan, to the gentle filter-feeding whale shark (Rhincodon typus). Although whale sharks are the largest fishes in the world, we have yet to locate their nursery grounds, which are likely teeming with thousands of foot-long pups. Some deepwater sharks are primarily known from submersibles, such as the giant sixgill shark, which feeds mainly on carrion but probably also preys on other animals in the deep sea.

Sharks seem familiar to almost all of us, but we know precious little about them. Our current understanding of their biology barely scratches the surface. The little we do know suggests they are profoundly different from other vertebrate animals. They've had 400 million years of independent evolution to adapt to their environments, and it's reasonable to expect they may be hiding more than a few tricks up their gills.

Gavin Naylor is the director of the Florida Program for Shark Research at the University of Florida.
Disclosure statement: Gavin Naylor receives funding from the National Science Foundation and the Lenfest Ocean Program.

Reposted with permission from our media associate The Conversation.

EcoWatch Daily Newsletter

Methane flares at a fracking site near a home in Colorado on Oct. 25, 2014. WildEarth Guardians / Flickr

In the coming days, the U.S. Environmental Protection Agency (EPA) is expected to use its power to roll back yet another Obama-era environmental protection meant to curb air pollution and slow the climate crisis.

Read More Show Less
Researchers on the ICESCAPE mission, funded by NASA, examine melt ponds and their surrounding ice in 2011 to see how changing conditions in the Arctic affect the biological and chemical makeup of the ocean. NASA / Flickr

By Alex Kirby

The temperature of the Arctic matters to the entire world: it helps to keep the global climate fairly cool. Scientists now say that by 2035 there could be an end to Arctic sea ice.

Read More Show Less
President Vladimir Putin is seen enjoying the Opening Ceremony of the Sochi 2014 Winter Olympics in Sochi, Russia. Pascal Le Segretain / Getty Images

Russia's Health Ministry has given regulatory approval for the world's first COVID-19 vaccine after less than two months of human testing, President Vladimir Putin said on Tuesday.

Read More Show Less
A John Deere agricultural tractor sits under a collapsed building following a derecho storm on Aug. 10, 2020 near Franklin Grove, Illinois. Daniel Acker / Getty Images

A powerful series of thunderstorms roared across the Midwest on Monday, downing trees, damaging structures and knocking out power to more than a million people.

Read More Show Less
A scenic view of West Papua. Reza Fakhrudin / Pexels

By Arkilaus Kladit

My name is Arkilaus Kladit. I'm from the Knasaimos-Tehit tribe in South Sorong Regency, West Papua Province, Indonesia. For decades my tribe has been fighting to protect our forests from outsiders who want to log it or clear it for palm oil. For my people, the forest is our mother and our best friend. Everything we need to survive comes from the forest: food, medicines, building materials, and there are many sacred sites in the forest.

Read More Show Less
Everyone overthinks their lives or options every once in a while. Some people, however, can't stop the wheels and halt their train of thoughts. Peter Griffith / Getty Images

By Farah Aqel

Overthinkers are people who are buried in their own obsessive thoughts. Imagine being in a large maze where each turn leads into an even deeper and knottier tangle of catastrophic, distressing events — that is what it feels like to them when they think about the issues that confront them.

Read More Show Less

Trending

A newly developed catalyst would transform carbon dioxide from power plants and other sources into ethanol. DWalker44 / E+ / Getty Images

Researchers at the Department of Energy's Argonne National Laboratory have discovered a cheap, efficient way to convert carbon dioxide into liquid fuel, potentially reducing the amount of new carbon dioxide pumped into the atmosphere.

Read More Show Less