This article provides general information about Nurse Sharks. From what they eat and where they live to hunting behavior and natural enemies that hunt them.
Nurse sharks are largely sedentary creatures that spend much of their time resting on the sea floor.
They are one of the most widely studied shark species because they are robust enough to tolerate capture and handling.
As a result, we have more interesting facts about nurse sharks than almost any other species, although we’re still unsure how they got their name.
These bottom-dwelling sharks have little in common with better-known species like the great white, spending their days relaxing on the sea floor and their nights sucking up unsuspecting prey.
They rarely bother moving faster than around 2.4kph, which makes them popular among divers and snorkelers.
Although generally non-aggressive, nurse sharks are “ranked fourth in documented shark bites on humans.”
Keep reading to learn more about the nurse shark, its diet, and its hunting strategies. This information might prove handy should you find yourself face-to-face with a 10ft long nurse shark one day!
What Does a Nurse Shark Look Like?
There are four different species of nurse sharks, all of which share certain characteristics. They are mostly yellowish to dark brown, although a few appear grey.
As juveniles, they are covered in small, black spots, which gradually disappear as they mature.
Nurse sharks vary in size, with the short-tail nurse shark being the smallest at around 2.46 ft long. The largest species of nurse shark is the Ginglymostoma cirratum, which can reach up to 10ft long.
All nurse sharks have spineless dorsal fins, fleshy barbels below their mouths, and spiracles behind each eye.
The nurse shark uses these barbels to find prey hidden in the sediment on the sea floor. The spiracles are part of its respiratory system.
They act a little like straws, enabling the shark to take in water and ventilate the gills even when resting, which is something the nurse shark does a lot of.
Nurse sharks have very small eyes, so they need barbels to help them find their prey.
A nictitating membrane or third eyelid does not protect nurse sharks’ eyes, but their prey is rarely dangerous enough to require that level of protection.
Nurse shark Taxonomy
All sharks are members of the elasmobranch subclass and all other cartilaginous fish.
Beyond that, they belong to the order, Orectolobiformes, which includes all seven families of carpet sharks.
Nurse sharks belong to the family Ginglymostomatidae, which comes from the Greek words meaning “hinge” and “mouth.” The name refers to the nurse shark’s “somewhat puckered appearance.”
There are three different genera within the Ginglymostomatidae family.
The tawny use shark, or Nebrius ferrugineus, is the only surviving member of the Nebrius genus, while the short-tailed nurse shark, also known as the Pseudoginglymostoma brevicaudatum, is the last of its genus.
Quite how the nurse shark acquired its English name remains something of a mystery, although some believe it evolved from the old English word for dogfish, which was either huss, husse, or hurse.
Others suggest that the name comes from the sound the nurse shark makes when feeding at the surface, which some say “resembles a nursing animal.”
Nurse Shark Characteristics
Nurse sharks aren’t the most active shark species and have earned themselves the unflattering title of “couch potato of the shark world.”
Nurse sharks lead a largely sedentary life and can often be found resting and sleeping in large groups, like a litter of puppies.
Even when they do rouse themselves into action, they don’t travel very fast, averaging around “1.5 mph (2.4 kph).”
Unsurprisingly, the nurse shark feeds primarily on slow-moving prey, but if it has to, it can achieve bursts of speed that see it reaching a maximum velocity of “up to 25 mph (40 kph).”
The fact that nurse sharks have spiracles means they can live a largely inactive life.
Pelagic sharks, like the great white, rely on ram ventilation, which means they have to keep moving to force water over their gills.
On the other hand, Nurse sharks are benthic sharks, which means they can breathe even when stationary by using their spiracles to draw water over the gills.
Nurse Shark Life Cycle
Nurse sharks congregate in the same breeding grounds each year. Mating occurs between June and July, when both males and females will have multiple partners.
Male nurse sharks bite the females to hold themselves in place during copulation.
They also have a special adaptation, known as a siphon sac, that enables them to flush rival sperm out of the female nurse shark.
The gestation period for nurse sharks lasts between five and six months, which is considerably shorter than for most sharks.
Being ovoviviparous, the female nurse shark first lays eggs inside the uterus. The pups hatch inside the female’s body, living off a yolk sac until they’re ready to be born.
Female nurse sharks give birth to between 20 and 50 pups, each of which is around a foot long. These young nurse sharks congregate in grass flats and shallow coral reefs, utilizing these as nursery habitats.
Nurse sharks reach sexual maturity when they achieve a certain length. For male nurse sharks, this is between 6.5 and 7 feet in length, by which time they are 10 to 15 years old.
Female nurse sharks mature a little later at 15 to 20 years.
Given that nurse sharks only live for approximately 20 to 25 years, this doesn’t give them many opportunities to reproduce, especially as the females “only reproduce every other year.”
Where do Nurse Sharks Live?
Nurse sharks inhabit warm, shallow waters in the tropical and subtropical waters of the Eastern Pacific and Eastern and Western Atlantic.
You can commonly find them in: Jamaica, Aruba, Puerto Rico, Panama.
They are bottom-dwelling sharks that come close to shore, utilizing the intertidal zone for feeding purposes.
Juvenile nurse sharks stay within shallow nursery areas, where they rarely descend deeper than 13 feet below the surface. They prefer the safety offered by “shallow reefs, mangrove islands, and seagrass beds.”
Adult nurse sharks utilize a wider area and can be found at depths of up to 250 feet.
These nocturnal predators are largely sedentary during the day and can often lie on the ocean’s bottom.
They tend to congregate in large groups during the day, which scientists believe is “in response to prey availability, rather than for predator avoidance or mating purposes.”
It was believed that the nurse shark was not migratory for many years. It was observed staying in the same relatively small home range and “repeatedly returning to the same spot after hunting for food.”
More recent studies suggest that the nurse shark engages in partial migration, probably in response to prey availability or to avoid potentially harmful courtship behaviors.
Nurse Shark Behavior
Nurse sharks are nocturnal creatures that spend their days lolling around on the bottom of the ocean.
They congregate in large groups of up to 40 individuals during the day before setting off on solitary hunting expeditions at night.
As bottom-dwellers, nurse sharks search the ocean floor for their prey, using a combination of suction and powerful jaws to capture small fish and crustaceans.
Nurse sharks have large, oil-filled livers that help them maintain buoyancy at the ocean’s bottom. The grey nurse shark also gulps air and stores it in its stomach to maintain neutral buoyancy.
In addition to these adaptations, the nurse shark is one of the few species that can seemingly walk along the bottom of the ocean.
Using its muscular pectoral fins, they can “walk” along the ocean floor, conserving energy as they search for prey.
Nurse sharks are generally considered slow-moving and non-aggressive, but that hasn’t stopped them from being involved in both provoked and unprovoked attacks on humans.
One of the most serious nurse shark attacks occurred in the Bahamas in August 2022 when three nurse sharks attacked an eight-year-old boy.
Some reports say people were chumming the waters, which excited the nurse sharks. The boy, Finlay Downer from the UK, is now recovering from his injuries after undergoing a 3-hour surgery.
This isn’t the first time nurse sharks have attacked humans, but most of those occur when the shark is provoked or accidentally trodden on. None of these attacks have been fatal.
What do Nurse Sharks Eat?
The nurse shark’s diet consists primarily of small fish and crustaceans, although this appears to vary depending on the shark’s location.
Studies of the stomach contents of nurse sharks off the coast of Isla de la Juventud in Cuba found that “lobsters made up 50% of the prey items,” even though lobster doesn’t seem to appear on the nurse shark’s menu anywhere else in the world.
Other studies have found fish and invertebrates in the stomachs of mature nurse sharks, with teleosts and bony fish making up the lion’s share.
In addition to fish, crabs, clams, sea urchins, stingrays, and squid, scientists have also found algae and coral in the stomachs of nurse sharks, although these aren’t believed to be nutritional food sources.
Scientists believe the nurse sharks simply suck up the vegetation alongside their prey rather than targeting it as a food source.
Despite that, one nurse shark has adopted a completely vegetarian diet. Florence lives at the Birmingham National Sea Life Center in the UK prefers celery to cephalopods and must be tricked into eating fish.
Florence wasn’t always a vegetarian, but since undergoing an operation to remove a rusty hook from her mouth, she’s turned her nose up at meat and is sticking to a completely plant-based diet.
Nurse sharks have a unique way of hunting that distinguishes them from nearly all other shark species.
Rather than snatching and tearing its prey to pieces, the nurse shark uses suction to draw its prey into its mouth, where it crushes it with its multiple rows of small, serrated teeth.
What Hunts Nurse Sharks?
Nurse sharks have few predators, and no species is known to regularly prey on these slow-moving sharks.
There is some evidence to suggest that other predatory shark species will make a meal of a nurse shark if given the opportunity.
Lemon sharks, hammerheads, tiger, and bull sharks may all predate the nurse shark, but only infrequently.
Humans are the most dangerous predator for the nurse shark, targeting them both privately and commercially for their liver oil and hides.
The nurse shark has a thick, almost “armor-like” hide used to make high-quality leather products.
Although nurse sharks are “considered to be a species of least concern in the United States,” the grey nurse shark is Australia’s most endangered marine species.
They were extensively hunted for their fins, oil, and flesh and targeted because of their “fierce appearance.”
The short-tail nurse shark is also critically endangered due to “overexploitation by coastal fisheries and habitat degradation.”
Conclusion
The nurse shark is a slow-moving, bottom-dwelling shark that is rarely aggressive toward humans but can sustain a painful bite.
They are a robust species that handle captivity well, possibly because they have a smaller home range than most other sharks.
Nurse sharks reproduce relatively quickly, especially compared to species like the spiny dogfish shark, which is pregnant for almost two years!
This comparatively fast reproduction rate helps maintain a healthy global population, although the demand for its hide, oil, and fins continues to pressure the species.
Of the four species of nurse shark, the grey nurse shark is the most endangered, alongside the short-tail nurse shark.
The most common is the Atlantic nurse shark, or Ginglymostoma cirratum, which is frequently seen close to the Florida coastline.
Our ability to interact with the nurse shark has shed a lot of light on this particular species, which is better understood than many other types of shark.
However, that understanding doesn’t stop people from provoking it, and attacks are relatively frequent, despite the nurse shark’s non-aggressive nature.
Nicky is a British adventurer and animal lover who spends her time exploring the natural world and writing about her experiences. Whether on horseback, underwater, running, hiking or just standing with a fishing rod in hand, she embraces everything her adopted home of South Africa has to offer.