Fascinating facts about sharks

Are sharks fish or mammals? 

Sharks are fish, not mammals. Sometimes, sharks are mistaken for mammals because they share certain physical traits with dolphins and whales. But like other fish, sharks are cold-blooded, breathe through gills instead of lungs, and have bodies covered in denticles (tooth-like scales). Sharks are also missing several key mammalian traits—they don’t grow hair, produce milk, or have a neocortex (the part of the brain involved in perception and thought, among other things). 

Sharks are members of the group Selachimorpha, which is within the group Neoselachii. In Neoselachii, alongside sharks, are rays, skates, and sawfish, so these are sharks closest relatives. 

Marine mammals, on the other hand, are more closely related to hippos, giraffes, buffalo, and deer than they are to sharks. They evolved millions of years ago from land mammals. 

Where do sharks live? 

Sharks can be found off the coasts of every continent in the world. Some stick to the coastal and shallow waters, while others prefer the deeper waters in the middle of the ocean. 

Great white sharks are found all around the world, with large populations around South Africa, Australia and New Zealand, the North Atlantic, and the Northeastern Pacific. 

Hammerhead sharks can be found in tropical and subtropical waters around the world, with a preference for coastlines and continental shelves. They are most often seen around the Galapagos Islands and the Great Barrier Reef. 

How many types of sharks are there? 

There are more than 500 species of sharks swimming in the ocean today. They are split across eight orders: 

• Carcharhiniformes 

These are the ground sharks, the largest group of sharks. This order includes tiger sharks, hammerhead sharks, and blue sharks. 

• Hederodotiformes 

This order only contains one living genus, the bullhead sharks. 

• Hexanchiformes 

There are only seven living members of this order, which includes the frilled sharks and the cow sharks. 

• Lamniformes 

These are the mackerel sharks, which includes some of the most well-known shark species. In this order are the thresher sharks, basking sharks, great white sharks, mako sharks, sand sharks, and megamouth sharks. 

• Orectolobiformes 

This order is known commonly as the carpet sharks, which got their name because they feed on the seabed, picking up small prey like molluscs and crustaceans. Whale sharks are one member of this order. 

• Pristiophoriformes 

These are the saw sharks, which are known for their long, pointed snouts lined with sharp teeth, resembling a saw. 

• Squaliformes 

This order contains the gulper sharks, kitefin sharks, bramble sharks, lantern sharks, rough sharks, sleeper sharks, and dogfish sharks. 

• Squatiniformes 

This order contains only one living genus, the angelsharks. 

What do sharks eat? 

Almost all sharks are carnivores that feed on other animals. Most sharks have molluscs, fish, and crustaceans on the menu, and they typically swallow their food whole. Larger shark species consume bigger fish and marine mammals like dolphins and sea lions, which they don’t swallow whole but eat in bites using their sharp teeth. Filter feeders, such as whale sharks, gulp large mouthfuls of water and sift out plankton, shrimp, and small fish using modified gills. 

How many teeth do sharks have? 

There’s a huge range in the number of teeth sharks have. Whale sharks hold the record for the sharks with the most teeth—their mouths are brimming with 3,000 tiny, sharp teeth. Great white sharks, known for their fearsome bite, only have around 50 teeth. Sharks continuously shed and replace their teeth throughout their lives. 

Do sharks have bones? 

Sharks do not have bones. Instead, they have a skeleton made of soft cartilage. Because cartilage is more flexible and lighter than bone, it helps sharks maneuver in the water and minimises the energy they need to expend while swimming. 

How fast do sharks swim? 

Most sharks cruise around the ocean at a leisurely pace of one to three kilometres per hour (0.5 to two miles per hour), which is similar to the average human swimming speeds. However, there are several super-speedy species. The fastest known shark species is the shortfin mako shark. It has been clocked swimming at a whopping 74 kilometres per hour (45 miles per hour) in short bursts. Great white sharks are also fast, capable of swimming up to 50 kilometres per hour (35 miles per hour). 

How long do sharks live? 

Most sharks live for 20 to 30 years in the wild, but some species can live far longer lives. At the extreme end of the longevity scale are Greenland sharks, which can live for at least 272 years, making them the longest-living vertebrates (backboned animals) in existence. To learn more about Greenland sharks and other animals with lengthy lives, check out our blog on the animals with the longest lifespans in the world. 

How do sharks sleep? 

Sharks don’t sleep in the same way humans do, but they do have periods of activity and rest. Until very recently, it was assumed that sharks never sleep because they have to constantly swim to pass water over their gills and extract oxygen. But not all shark species use this method of breathing. Some instead use the muscles in their mouths to pump water over their gills, which allows them to breathe even when they’re resting. Recent research has confirmed that New Zealand’s draughtsboard sharks—a mouth-breathing species—do in fact fall asleep during their resting periods, sometimes with their eyes open! 

How do sharks mate and reproduce? 

Unlike some fish, sharks are internal fertilisers, meaning the egg and sperm come together inside the female shark’s body. Some sharks lay their fertilised eggs on the ocean floor, and others give birth to live young (called pups). 

Though sexual reproduction is the most common method among sharks, some species are capable of a process of asexual reproduction known as parthenogenesis, which is uncommon among complex vertebrates. One species with this ability is the zebra shark. 

How many sharks are killed each year? 

Humans kill an estimated 100 million sharks every year. That’s an average of almost 274,000 sharks every day, over 11,000 sharks every hour, and around three sharks every second. 

One way people kill sharks is through shark finning. This involves catching sharks, removing their fins, and discarding them back into the ocean, where they often die slow, painful deaths. Shark fins are in demand due to their monetary and cultural value. An estimated 23 to 73 million sharks are finned each year. 

Bycatch is another way sharks are killed by humans. This is the unintentional catching of sharks in fishing nets. 

Sharks are also hunted for their meat, internal organs, and skin to make food, leather, and other products. Shark meat has been shown to carry toxic amounts of substances like mercury and ciguatoxin. 

How many people do sharks kill each year? 

In contrast to the staggering number of human-induced shark deaths, fewer than 10 people worldwide are killed each year by shark attacks. For comparison, every year, about 24 people die after being hit by flying champagne corks, about 700 people die from toasters, and about 2,000 people are struck and killed by lightning. 

Experts believe shark attacks on humans are usually unintentional. They are most likely cases of confused sharks mistaking kicking feet for small fish. 

What threats do sharks face? 

More than one third of shark species are currently threatened with extinction. Populations of sharks in the open ocean have declined by 71% over the past 50 years. 

Much of these declines are due to global demand for shark meat and fins, which is pushing some shark species to the brink of extinction. Commercial fishing also impacts sharks through bycatch, when they are accidentally caught in fishing nets. 

Meanwhile, sharks are also rapidly losing their homes. Shark habitats—particularly in coastal waters—are being destroyed by residential and commercial development, including through the cutting down of mangrove forests and pollution. 

Sharks are particularly vulnerable to all these threats because they take a long time to reach sexual maturity, and most sharks only have a few pups at a time. Many sharks get killed before they have a chance to reproduce, making it difficult for their populations to rebound. 

How do sharks help their ecosystems? 

As the relationships between species are interconnected, every animal is a critical part of its ecosystem—sharks included. Sharks help keep the ocean healthy and even play a role in mitigating climate change. 

Because many sharks are apex predators, they are important for regulating the populations of animals lower on the food chain. When sharks are overfished, this can have ripple effects on the entire ocean ecosystem. If the larger fish sharks eat become overpopulated, they consume too many of the smaller, algae-eating animals, leading to an overabundance of algae. In turn, algae overpopulate coral reefs and kill these crucial marine habitats. 

Sitting at the top of the food chain, sharks help ensure biodiversity in the ocean, which is a critical piece of making our planet more resilient to the effects of climate change. This is why protecting sharks is so important. 

What is IFAW doing to help sharks? 

IFAW works to reduce the number of sharks killed and protect them from overfishing by advocating for limits on the trade and catch that drives shark population declines. 

For over a decade, we have partnered with member countries of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) to achieve limitations on the trade of shark species. We have successfully achieved Appendix II protections for nearly 100 species of sharks, ensuring that any continued trade is legally and sustainably managed. 

Trade in species listed in Appendix II of CITES is regulated and monitored by governments around the world to ensure it is sustainable. Effective enforcement of CITES shark listings helps prevent illegal trade in shark products and drives better fisheries management. 

In addition to advocating for sharks, IFAW provides support to those fighting on the frontlines against wildlife crime, including trainings on enforcing shark protections and identifying shark products in trade. We also help develop technical tools for governments looking to implement CITES protections. 

We hope that protection for sharks under CITES will ultimately prevent the trade in shark products from driving these animals to extinction. Learn more about how you can help us take action for animals.