The bonnethead is often known as the “shovelhead shark,” a moniker it owes to its rounder “hammer” of a head. It also differs from its cousin in that its nostrils are located closer to its eyes. The bonnethead is one of the smallest members of the Sphyrna family, averaging 10.8 kg (24 lbs). The maximum length recorded for this shark has been 1.5 m (5 ft); they usually measure 0.7-1.2 m (2.5-4 ft). Like most sharks, females are larger than males.
This shark is a gray to dark brown color, with a white-ish underbelly. They can be seen in the tropical/subtropical waters of North America, and have been observed in southern Brazil, southern California and Ecuador. Primarily inhabiting estuaries, shallow bays, and coral reefs, here they feed on crustaceans, clams, small fish and octopus. They can also be found on continental shelves up to 80 m (260 ft) deep, but more commonly seen at 10-25 m (31-82 ft).
Bonnethead sharks engage in some fascinating mating behavior; females can store sperm for four months! Females will migrate to shallow bays and estuaries for the pupping season, and males will move elsewhere—this probably prevents the males from munching on newborn pups. No shark snacks for you! After a gestation period of six months (the shortest of all sharks), female bonnetheads can deliver 4-14 pups, and they tend to live up to 12 years of age.
Since bonnethead sharks are a hardy species to keep in captivity, scientists have been able to study their behavior at length. This includes: threatening postures towards others (a hunched back), biting of smaller males and females, patrolling, head-shaking, jaw-snapping, etc. These behaviors are most likely a display for dominance in the group. These sharks tend to school (5-15 sharks) in a mixed group of males and females, with numbers rising anywhere from 100 to 1,000.
Bonus fun fact #2: Bonnethead sharks are the only sharks that show sexual dimorphism (males and females look different). Adult females have a broad, rounded head while males have a bulge along the anterior margin (front) of the cephalofoil (basically, its head).
These are one of our favorite sharks! What about you?