Creature Feature: Bonnethead

Photo by Serena Epstein

Photo by Serena Epstein

Today we will discuss a shark related to the hammerhead. The Bonnethead (Spyrna tiburo) Shark gets its name by the shape of its head, which looks like a bonnet or a fattened shovel. The Bonnethead is one of the smallest in the hammerhead genus with a max length of 59 inches. The habitat range spans the Northern Hemisphere, from New England to Gulf of Mexico and Brazil in the Atlantic Ocean. In the Pacific Ocean, you will find them from southern California to Ecuador. This species migrates closer to the equator when the temperature of the water drops in the winter.

Sharks have an amazing sensory adaptation known as ampullae of Lorenzini. These are organs are known as electroreceptors, (jelly-filled pores that sense electricity) located around the underside of the snout and mouth. The Bonnethead has a very keen and highly evolved sensory system which makes them very adept predators. Using the ampullae of Lorenzini, along with vision, hearing, and high level lateral line sensitivity, they are especially efficient at locating prey.

Photo by Heather Hosely

Photo by Heather Hosely

Their prey consists of mostly crustaceans that they can find during the day. Picture this scene: a blue crab walks along the ocean floor, unsuspecting and unaware. From a considerable distance above, a Bonnethead senses the crab and slowly moves closer. Once in range, the Bonnethead darts quickly forward. SNAP. End scene. Against the Bonnethead’s powers of prey detection and stealth, the blue crab never stood a chance.  It will be devoured in the sharp toothed mouth of the Bonnethead Shark. Bonnetheads possess a variety of different types of teeth in their many rows. Their front teeth lack serration and are quite sharp. The teeth at the back of the mouth begin to flatten into molars.  This allows this species to crush the harder outer layer of their prey.

Join us next week as we look at one of the smallest sharks.

References: 
Edited by KC O’Shea
Photography: Serena Epstein and Heather Hosely 
http://www.aqua.org/explore/animals/bonnethead-shark
http://www.flmnh.ufl.edu/fish/gallery/descript/bonnethead/bonnethead.html
http://www.aquariumofpacific.org/onlinelearningcenter/species/bonnethead_shark
http://www.iucnredlist.org/details/39387/0

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