What kind of shark is the bonnethead shark?

The bonnethead shark is a type of hammerhead shark, and as its name suggests, its head is laterally expanded, resembling a 'hammerhead.'

However, if you look closely, you'll see that they have four eyes, two on each end of their head. This laterally expanded head is called a 'cephalofoil,' and its shape resembles a 'hammer' or a 'shovel.' In English, they are called 'bonnethead sharks.' A 'bonnet' is a type of women's hat, and their head shape resembles a bonnet, which is how they got their name.

What is the secret behind the bonnethead shark's head shape?

The bonnethead shark's unique head shape is thought to serve several purposes.

・Wide field of vision: Their eyes are located on the cephalofoil, giving them a wider field of vision than other sharks. This helps them find prey and avoid predators.

・Enhanced sense of smell: The cephalofoil also acts as an olfactory organ. By swinging their cephalofoil from side to side, they can detect the scent of prey from a wider area.

・Electroreceptors: The cephalofoil contains a high concentration of electroreceptors called 'ampullae of Lorenzini.' These organs can detect weak electrical fields generated by other organisms. They use these organs to locate prey hidden in the sand and to detect the presence of predators.

・Lift: The cephalofoil also acts like an airplane wing, generating lift. This allows them to move through the water with less energy.

The shape of the bonnethead shark's head is a remarkable adaptation that helps them survive in the ocean!

What do bonnethead sharks eat?

Bonnethead sharks are carnivores, primarily feeding on crustaceans, especially blue crabs and shrimp. They use their cephalofoil to probe the seafloor in shallow waters to find prey.

They also eat small fish, squid, and octopus. Sometimes, they eat seagrass.

[Quiz!] What is different about the bonnethead shark compared to other hammerhead sharks?

The bonnethead shark is the smallest of all hammerhead shark species. Also, their cephalofoil is more rounded compared to other hammerhead sharks.

That's why they are called 'bonnethead sharks' in English. A 'bonnet' is a type of women's hat, and their head shape resembles a bonnet.

[Quiz!] Is it true that female bonnethead sharks can give birth without mating with males?

Yes, it's true! Female bonnethead sharks can reproduce through a process called 'parthenogenesis.'

Parthenogenesis is a fascinating form of reproduction where females can produce offspring from unfertilized eggs. In 2001, a female bonnethead shark in a US zoo gave birth despite not having mated with a male. This was the first confirmed case of parthenogenesis in sharks, causing a global sensation.

[Quiz!] Are bonnethead sharks endangered?

Unfortunately, the bonnethead shark is listed as Endangered on the IUCN (International Union for Conservation of Nature) Red List. Their numbers are declining due to overfishing and habitat degradation.

Bycatch from shrimp fisheries is a major problem, particularly along the American coasts. Pollution and climate change are also threats to their survival. To protect bonnethead sharks, we need to implement various measures, including fishing regulations, habitat conservation, and environmental education.