The shark takes its scientific name, Sphyrna tiburo, from there sharp of its head. Sphyrna comes from the Greek word for “hammer.” They are the smallest of the species of the hammerhead shark.


Appearance 

The shark can be recognized by its broad, shovel-shaped head. The body is grey-brown on top and lighter on the underside, a characteristic common to large marine creatures known as countershading. Sometimes, darker spots are present on the sides of their bodies. The shark grows to around 3 feet in length. Although larger specimens, up to 4.9 feet, have also been recorded. 

Bonnethead shark swimming
Bonnethead shark swimming

Interestingly, the shark species is the only known example to display sexual dimorphism in the shape of the head. This means that the adult females have rounded heads, and the males’ heads are shaped differently. They have a distinct bulge along the anterior margin of the cephalofoil. It occurs at the onset of sexual maturity. 

Habitat 

Most bonnethead sharks live on the sides of the American coast, in the Atlantic and Pacific oceans. They prefer regions of the worlds’ oceans that are warmer, around 70 degrees F or 20 degrees C. They can be found from New England all the way down to Brazil in the Atlantic Ocean. Along the Pacific, they can be found from southern California to northern Peru. The shark spends most of its life in shallow estuaries and bays. 

The sharks travel in small groups of between five to fifteen members. But, as with dolphins, groups of thousands have been recorded. The sharks tend to move with changes in ocean temperate, and, like all shark species, the bonnethead has to keep moving, or it will sink. It is one of the most negatively buoyant of all marine species. 

Bonnethead shark underside
Bonnethead shark underside


Diet 

Amazingly, the bonnethead shark is the only known species of omnivorous shark. It feeds on blue crabs and other crustaceans, as well as small fish, mollusks, and shrimp. 

While hunting, it moves its head along the seafloor in an arch-like pattern, seeking out the smallest disturbances. When the sharks catch a crab, they use their teeth to grind it, and then suction allows the shark to swallow. The sharks have small, sharp teeth in the front of their mouths and flatter molars in the back. It’s the latter that they use for crushing their prey, such as the shells of crabs. 

Bonnethead shark lower teeth
Bonnethead shark lower teeth

Bonnetheads, as noted above, also eat plants. They ingest a large amount of seagrass, more than half of their total diet. It’s unclear exactly why the sharks eat seagrass but scientists have speculated that the grass protects the shark’s stomach against the sharp edges of the blue crab shells. 

Reproduction 

These sharks reproduce viviparously. This means that the embryo becomes fully developed inside the mother’s body. This contrasts with some other shark species that use oviparity (the female lays developing eggs that hatch externally). 

The female sharks are around thirty-two inches or eighty-one centimeters when they reach sexual maturity. In contrast, males are around twenty-four inches or sixty-one centimeters. They have a gestation period that is one of the shortest among shark species, lasting between 4.5 to 5 months. In one amazing recorded instance, a female bonnethead shark reproduced via parthenogenesis at a zoo in Nebraska, which means that the specimen used asexual reproduction without fertilization by a male member of the species. 

Bonnethead shark dorsal view
Bonnethead shark dorsal view


Threats 

At the moment, the bonnethead shark is classified as “least concern” by the IUCN. This is despite the fact that it has been heavily targeted by commercial fisheries throughout its life. In the Atlantic Ocean, along the coast of the Bahamas and Mexico, it is still a very common shark species. But, there have been significant declines in the Pacific along the coast of South America, where the shark has been labeled as “endangered.”

Facts about the Bonnethead Sharks 

  • Bonnethead sharks live to be between sixteen and eighteen years old. 
  • They have four to sixteen pups at one time. 
  • They eat blue carbs and sea grass. 
  • They are the only omnivorous species of shark. 
  • They are the only known shark species to show sexual dimorphism in the shape of their heads.
  • Bonnethead sharks can be recognized by their broad, shovel-shaped heads.


FAQs 

Are bonnethead sharks related to hammerhead sharks? 

Yes, bonnethead sharks are a small species of hammerhead sharks. They are similar in their coloration, but they have smaller heads that are more shovel-shaped than hammer-shaped.

Can you keep a bonnethead shark?

There are some zoos and aquariums around the world that house bonnethead sharks. But, they are not suitable for individuals to own in their homes. The sharks have been known to grow up to nearly 5 feet in length and need a remarkable amount of space to live successfully and happily.

Where do you find bonnethead sharks?

Sharks can be found along both coasts of the Americas. In the Atlantic, they range from New England down to Brazil and in the Pacific from Southern California down to northern Peru. But, they are far more common in the Atlantic today.

What shark is the most overfished?

Of the hammerhead shark species, the Atlantic scalloped hammerhead shark is considered to be the most overfished by the National Marine Fisheries Service. Studies have shown that the population has declined by around 80%. 

How big does a bonnethead shark get?

On average, bonnethead sharks grow to be around 3 feet in length. But, there have been studies in which larger specimens, up to 4.9 feet, have been measured.