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A bonnethead shark, with is distinctive flat, protruding head shape, cruises through Caribbean Reef.

Bonnethead Shark

The smallest species in the hammerhead family, bonnetheads have a flattened, crescent-shaped head, more like a rounded shovel than a hammer.

Like metal detectors, but for electricity

Like other hammerheads, bonnetheads have eyes and nostrils on either side of their wide heads, giving them a panoramic field of sight and smell. But the stretched-out head also provides plenty of real estate for other sensory organs, most notably the ampullae of Lorenzini. Sharks, rays and a few other "primitive" fish groups have these electroreceptors, which are visible as dark spots or pores on the face. As they swim, bonnetheads sweep their heads from side to side, scanning, like using a metal detector. But instead of locating coins or jewelry, the ampullae of Lorenzini detect tiny fluctuations in the electrical fields—from muscle contractions, like heartbeats—of their prey on the seafloor.

A bonnethead shark glides effortlessly above the corals in Caribbean Reef at Shedd Aquarium

Sharks that chew their food

With their shovel-like faces, bonnetheads burrow into mud, sand, even under coral heads, to get crustaceans, shrimp, mussels, snails, octopuses and small fishes. Blue crabs are a favorite. Bonnetheads grab prey with their small, sharp front teeth, then crunch hard shells with their flat back teeth. Strong digestive chemicals do the rest! Unlike the big hammerheads, which have a reputation for ferocity, bonnetheads are timid and harmless to people.

Baby bonnethead

Bonnetheads are among the sharks that give birth to live young, and after an eight-month gestation period, a female pup was born at Shedd in January 2019. While not the first of her species born at the aquarium, she is the first second-generation bonnethead here: Her mother was born at another Association of Zoos and Aquariums-accredited facility. With the healthy pup's birth, Shedd is supporting a self-sustaining population of these fascinating small hammerheads in human care.

A baby bonnethead shark swims through the clear waters of a quarantine holding space, by all appearances a small --perhaps a bit skinnier-- version of an adult.

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