If you ever visit Sarasota, Florida (USA) you must stop by the Mote Marine Laboratory and Aquarium! Here, you’ll see one of Sarasota Bay’s most common sharks: the bonnethead shark, Sphyrna tiburo. (Fun fact: TFUI founder Melissa first wanted her undergraduate thesis to be about bonnetheads and how they utilize habitat in an aquarium.) The bonnethead is often known as the “shovelhead shark,” a moniker it owes to its rounder “hammer” of a head. It 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 tend to be larger than males.
This shark is a gray to dark brown color, with a white underbelly. #Finfact: 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). 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).
Like most sharks, they are hunters as well as prey. Large sharks, such as tiger and lemon sharks, prey on these smaller critters. 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. #Finfact: These sharks can also excrete a unique cerebrospinal fluid (Cl-excess) that is believed to let other bonnetheads know, “Yo! I’m here!” 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.
Bonnethead sharks engage in some fascinating mating behavior. #Finfact: Female bonnethead sharks can store sperm for a while! Females will migrate to shallow bays and estuaries for the pupping season, and males will move elsewhere. After a gestation period of six months (the shortest of all sharks), females can deliver 4-14 pups, which tend to live up to 12 years of age. But bonnethead sharks are under pressure of overfishing, both as targeted animals and as bycatch. The IUCN has assessed these sharks as Least Concern (LC). Want to see some in real life? You can see then in a number of aquariums!
did you know about the bonnethead shark?
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TFUI Founder Melissa C. Marquez is author of all animal bios and "Behind the Fins" segments.
SEE MELISSA'S TEDx TALK HERE:
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