Zebra shark

 

Common Name:
Zebra Shark
Scientific Name:
Stegostoma tigrinum
Type:
Fish
Diet:
Carnivore
Size:
7 to 9 feet long
IUCN Red List Status:
Endangered

What is a zebra shark?

Zebra sharks are a docile, nocturnal species best known for their characteristic stripes and spots—in juveniles and adults respectively. For this reason, they’re also called leopard sharks in Australia and the United Kingdom—but are not to be confused with another species, Triakis semifasciata, that's called a leopard shark in the United States.

Found in shallow Indo-Pacific reefs, these slow-swimming sharks are harmless to humans but perfectly adapted to squeezing into narrow spaces to pounce on their preferred prey: crustaceans. They’re also notable for their ability to have virgin births.

Appearance 

Zebra sharks don’t look like the ferocious hunters most people expect of a shark. They have rounded, sandy-colored bodies with five ridges, small mouths, whisker-like organs called barbels in front of their snout, and powerful tails that can be nearly as long as the rest of their bodies.

Adults usually grow up to nine feet long—around the same length as a Bengal tiger—but have been reported to reach 12 feet.

(Learn more about other shark species.)

Juveniles are born with dark-brown-and-white stripes resembling the patterns of a zebra. These stripes fade over time and turn into the leopard-like spots they keep into adulthood. Adults look so different from juveniles that until 1823, scientists believed they were two separate species.

In the ocean, a zebra-striped pattern is an important defense mechanism for the small, vulnerable pups. Because their stripes mimic those of a venomous sea snake, other species keep away in case the pattern indicates danger.

Habitat and behavior

This nocturnal species can be found in shallow coral reefs in the Indo-Pacific, often resting on the sandy seabed. They hunt at night and rest on the bottom during the day while pumping water over their gills. Unlike some other species of shark, zebra sharks don’t have to keep swimming to breathe.

Diet

A zebra shark’s diet is mainly made up of mollusks and crustaceans, though they are also known to eat small fish. They are well adapted for finding and eating this type of prey.

Their flexible bodies allow them to squeeze into tight crevices to seek out small invertebrates to eat. After using their whisker-like barbels to detect prey in the dark, they use their small mouths and powerful gill muscles to suck their meal from its shell. They can also crunch through tough shells with their strong, flat teeth.

Reproduction 

Zebra sharks are oviparous, which means they lay eggs. After mating, a female will use special fibers to attach between one and four egg casings securely to the seafloor. Pups develop inside the casing for around six and a half months before emerging as 10-inch baby sharks. Pups are born fully independent and can swim and hunt on their own.

(Learn how some animals have ‘virgin births.’)

In 2011, scientists were excited to document parthenogenesis in zebra sharks—a phenomenon that’s essentially a virgin birth, in which unfertilized eggs develop into genetically unique embryos without any male involvement. While over 80 vertebrate species are known to reproduce using parthenogenesis, it’s rare in complex vertebrates such as sharks. In zebra sharks, these virgin births have been documented both in females that had never mated and those that had previously reproduced with a male.

Threats to survival

Zebra sharks are endangered, according to the International Union for Conservation of Nature. Although they do sometimes fall prey to larger predatory sharks, their main threat is from humans. Populations around the world are decreasing due to overfishing, bycatch, and the shark fin trade.

(Learn about the perils of overfishing.)

Their preferred shallow water habitat is also easily destroyed by human activities such as coastal development and bottom trawling—a destructive fishing method which involves dragging large, weighted nets across the seafloor.

Because these sharks have a slow reproductive rate, it takes even longer for the species to recover from these threats.

Conservation efforts—including tagging to better understand individuals’ movements, and repopulation attempts through releasing eggs laid in captivity—are underway around the world to help protect this endangered species.

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