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Today on Animal Fact Files we’re discussing bonnethead sharks. These fish are part of the hammerhead shark family. They’re the easiest of the ten living hammerhead species to identify because of their uniquely shovel-shaped head. This lends to their other common name: the shovel shark. Bonnetheads are the smallest living hammerhead sharks averaging three feet (91cm) in length compared to the great hammerhead’s twenty foot (6m) length. Like the great hammerhead, female shovel sharks are larger than males. Male and female bonnetheads can also be told apart by the claspers present in reproductive aged males that are absent in females as well as their head shape. Adult female bonnetheads have a more round head shape compared to the male’s slightly more pointed head shape. This is thought to occur at maturation, similar to how the male pelican eel’s nose gets bigger.

Bonnethead sharks live in warm, coastal waters along the Atlantic and Pacific coasts of North, Central, and South America, as shown here. They prefer water approximately 70 degrees Fahrenheit (21 degrees Celsius). When it’s cold, they migrate to warmer waters. Bonnetheads live in bays, estuaries, reefs along insular and continental shelves. These areas are typically no deeper than 50 feet (15m) and are frequented by humans. This puts bonnetheads at higher risk of human contact and human related death. They’re frequently caught as by catch and their habitats may be destroyed for development. At this point, bonnethead sharks are listed as endangered to extinction.

Natural predators to bonnetheads include larger shark species like white sharks. Bonnetheads themselves eat crustaceans and even have molars for crushing these shelled animals. They’ll also eat mollusks, small fish, cephalopods, and even seagrass making them some of the only known plant-eating sharks! It’s unknown if seagrass is eaten accidentally, as it’s more often found in the stomachs of juveniles who may still be learning hunting techniques. It may also be eaten to help with digestion. We discussed this in our general hammerhead shark episode, as well!

Bonnethead sharks are also unique for their gestation which is the shortest of all known living sharks. Female bonnetheads can store sperm for up to four months to ensure their babies are born at an optimal time for food availability. It only takes four to five months for the shark pups, of which there can be up to fourteen per litter, to develop inside the mother’s body. After this, they’re born live in shallow, warm water estuaries with few predators. Around the time they’re preparing to give birth, mother bonnetheads lose their appetite. This is a preventative measure which ensures the mothers don’t eat their babies. Male bonnetheads just stay away from the pupping grounds altogether. The pups will stay here for their first two to three years of life at which point they'll reach reproductive maturity and venture further from their birthplace.

Bonnetheads travel in schools of up to fifteen unrelated individuals during the year but may form large gatherings numbering up to thousands during peak breeding times in spring and fall. In the wild, bonnethead sharks typically do not live more than ten years. They’re considered harmless to humans, and Kylie, the other narrator of Animal Fact Files has actually swam with them! They’re some really neat sharks!

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