Hammerhead sharks inhabit tropical and temperate ocean waters both close to shore and farther out. They feed mainly on stingrays, but their diet also includes fish, crustaceans and cephalopods. They live to be between 20 and 30 years old in their natural habitat.
- Scientific & Common Names
- Present Status
Scientific & Common Names
There are nine species of hammerhead sharks. These include Sphyrna corona (scalloped bonnethead, crown shark, mallethead shark), Sphyrna lewini (scalloped hammerhead), Sphyrna media (scoophead shark), Sphyrna mokarran (squat-headed hammerhead shark, great hammerhead), Sphyrna tiburo (bonnethead shark), Sphyrna tudes (smalleye hammerhead shark, curry shark), Sphyrna zygaena (smooth hammerhead), Sphyrna couardi (whitefin hammerhead) and Eusphyra blochii (winghead shark, slender hammerhead).
Hammerhead sharks have heads that are shaped like mallets and eyes that are set wide apart, which helps them find prey. They vary in color, depending on species, but are usually a shade of grayish-brown or green. They also have white bellies, mouths full of serrated teeth and prominent dorsal fins. Adults weigh between 500 and 1,000 pounds and measure between 13 and 20 feet long. The great hammerhead is the biggest species.
Female hammerhead sharks have a gestation period that lasts roughly 10 to 11 months or longer, depending on species, after which they give birth to live pups. The number of pups in a litter can range from 6 to 55. Females usually reproduce every two years. After the pups are born, they do not receive any parental care and must find food on their own.
Most hammerhead shark species are usually not aggressive, with the exception of great hammerheads. They gather in groups, called schools, at times, although they usually hunt alone. When hammerhead sharks find stingrays, they pin their fins down with their elongated heads. They communicate with other members of their species by pointing their fins down, shaking their heads or ramming them with their snouts.
Hammerhead sharks have been targeted by the shark fin trade, which has reduced their numbers in recent years. In 2013, they were added to international legislation that enforces stricter regulations on the shark fin trade.
The squat-headed hammerhead shark and the scalloped hammerhead shark are listed as endangered, while the smooth hammerhead shark and smalleye hammerhead shark are listed as vulnerable. The scalloped bonnethead is listed as near threatened. The main threats to hammerhead sharks are the shark fin trade and incidental capture by fisheries. Conservation efforts include shark fin trade regulations and modifications to the equipment used by fisheries to prevent incidental capture.
- <a href="http://animals.nationalgeographic.com/animals/fish/hammerhead-shark/" target="_blank">http://animals.nationalgeographic.com/animals/fish/hammerhead-shark/</a>
- <a href="http://www.nmfs.noaa.gov/pr/species/fish/greathammerheadshark.htm" target="_blank">http://www.nmfs.noaa.gov/pr/species/fish/greathammerheadshark.htm</a>
- <a href="http://animaldiversity.ummz.umich.edu/accounts/Sphyrna_lewini/" target="_blank">http://animaldiversity.ummz.umich.edu/accounts/Sphyrna_lewini/</a>
- <a href="http://www.iucnredlist.org/details/full/39385/0" target="_blank">http://www.iucnredlist.org/details/full/39385/0</a>