Nurse Shark

“Nurse sharks have smoother skin than most sharks. It feels like sandpaper.”

Sometimes called the couch potatoes of the sea, nurse sharks are large, peaceful fish that slowly drift along the bottom of the ocean in shallow water, sucking up food as they go. They hunt alone at night but return to the same comfortable resting place during the day where they enjoy dozing in piles. Although their habitat is alongside humans, these fish are rarely harmful; they will only bite if startled or provoked. These gentle sharks are quite comfortable in zoo aquariums and can live up to 25 years in captivity.

5 Nurse Shark facts

• Unlike many other shark species that must swim at all times to breathe, the nurse shark uses the buccal pumping method to breathe. They use their oral muscles to pull water into their mouths to oxygenate their gills, allowing them to stay still and even sleep.
  
• These sharks don’t pose any threat to humans unless they are disturbed. In fact, many people swim right by these sharks without ever knowing they were there.
  
• When a school of nurse sharks finds a comfortable resting place, they return there each day after hunting rather than migrating like many other fish species.
  
• They use their pectoral fin to “walk” across the ocean floor, and females will sometimes bury their pectoral fins in the sand to avoid the mating advances of males.
  
• Rather than chasing their prey and catching it in a flurry of chomping teeth like other sharks, this species swims just above the ocean floor and sucks up their food like a vacuum cleaner. After sucking their food into their mouths, they use rows of serrated teeth to crush up their food before swallowing.

Read more incredible Nurse shark facts here.

Scientific name

The nurse shark is in the Ginglymostomatidae family and the Chondrichthyes class. Its scientific name, Ginglymostoma cirratum, is a mix of Greek and Latin and means “curled, hinged mouth.” This name is rather fitting because this shark always looks like he’s puckering up. Since this species of shark prefers to stay close to the ocean floor, many scientists believe its name came from the Old English word “hurse,” which means sea-floor shark.

Evolution Of The Species

It is believed that all sharks evolved from the Acanthodian, a group of spiny fish that were first around over 400 million years ago, during the Palaeozoic era. This group of fish then diverted into the two main groups of fish that we now have today – cartilaginous fish (Chondrichthyes), of which sharks are part of, and bony fish (Osteichthyes), which includes salmon.

Types Of

Besides the Atlantic nurse shark, this species of shark includes two others, and should not be confused with the grey nurse shark which is a different species of shark (Carcharias taurus). The nurse sharks consist of the following:

• Tawny nurse shark (Nebrius ferrugineus)
• Shorttail nurse shark (Pseudoginglymostoma brevicaudatum)

Appearance

The nurse shark has a wide body and a short snout with a small, rectangular mouth. They have two sensory organs called barbels that grow down from their upper lip. These barbels help them find small fish and crabs hiding in the sand.

This species of shark looks a bit different than many of its more dangerous cousins. Their thick skin is smoother than most other sharks, and their dorsal fin is rounded rather than the customary sharp dorsal fin that is commonly associated with other species. Their color sets them apart from the others as well — they are tawny brown rather than grey.

These sharks grow to about 7.5 to 9 feet long and weigh between 150 and 300 pounds. The largest nurse shark on record to date is 14 feet long, which is more than two times longer than the average man is tall. Unlike more dangerous shark species, their dorsal fins are rounded rather than sharp. They also have long tails, which can make up about a quarter of their total length.

Behavior

The nurse shark is a solitary, nocturnal hunter, but if you see one during the day, it will probably be resting in a pile of other similarly sized sharks. These sharks don’t migrate; when they finish hunting for the night, they will return to their favorite cave or coral reef to rest.

Habitat

Nurse sharks like warm, shallow water and can be found all across the eastern part of the Pacific Ocean and the western part of the Atlantic Ocean. They live in close proximity to human activity and, while they are not usually aggressive, can bite in self-defense if humans encroach on their territory.

Population

The abundance of nurse shark populations worldwide was estimated using an analysis of distance sampling and it is believed that their current numbers range from 3,858 to 14,375, though their numbers have been reduced in certain areas due to previous overfishing for their skin and oil. Since humans no longer routinely hunt these sharks, the species as a whole is thriving, and depending on the location, their numbers may be listed as either vulnerable or of least concern.

Diet

A nurse shark’s mouth possesses rows of tiny, serrated teeth that are designed to crush hard-shelled crustaceans and snails. Small fish, shellfish, shrimp, and squid are some of the nurse shark’s favorite foods, though they will also eat algae and coral from time to time. Since they hunt at night, it is believed that they eat fish that are resting, making those fish slow enough to be easy prey.

For a complete list of nurse shark prey, see our ‘What do Nurse Sharks Eat‘ article that goes in-depth on their diets.

Predators And Threats

The nurse shark isn’t hunted regularly by any specific predators, but it can make an easy meal for larger fish such as tiger sharks or lemon sharks. This species of shark is not a threatened or endangered species.

Reproduction, Babies, And Lifespan

When a nurse shark wants to mate, the male will bite the female’s pectoral fin to hold her in place for the mating process. Studies have shown that this species is unique in its reproductive process compared to other sharks because more than one male can fertilize the same litter.

This species of shark is ovoviviparous, meaning that the female carries the fertilized eggs inside her to incubate. When the 6-month incubation period comes to an end, she gives birth to a litter of about 25 live pups. These pups are roughly 8-12 inches in length when they are born. After giving birth, it takes the female 18 months to produce eggs and go through the reproductive cycle again.

In Zoos

Nurse sharks do well in captivity, possibly because they are less active than other shark species. Since they don’t need to stay swimming to breathe, they are less bothered by smaller living spaces than their more active cousins. The average lifespan for a nurse shark in captivity is up to 25 years.

You can find them at Point Defiance Zoo & Aquarium in Tacoma, Washington; Omaha’s Henry Doorly’s Zoo & Aquarium in Omaha, Nebraska; and the National Aquarium in Baltimore, Maryland to name just a few.