In the Atlantic and East Pacific, nurse sharks are a species of shark that are frequently seen in warm, shallow waters.
With a large head and rounded dorsal and pectoral fins, they are recognized for their striking appearance. These brown sharks can reach a maximum length of 10.1 feet.
The fact that nurse sharks are ovoviviparous—meaning that their fertilized eggs hatch inside the female—is an intriguing detail about them. Nurse sharks mate from the end of June to the beginning of July, and females can take up to 18 months to lay a fresh batch of eggs.
A typical litter size for nurse sharks is 21–29 pups after a six-month gestation period.
Despite their frightening exterior, nurse sharks are typically thought to be non-lethal to humans. It’s crucial to remember that they are still wild animals and should be respected as such.
The habitat, habits, and nutrition of nurse sharks will all be covered in this article. We will also go over their function in the environment and the reasons they should be protected as a species.
Table of Contents
Nurse sharks are a species of carpet shark that are slow-moving and have a broad head with a rounded snout.
They are typically brown or gray in coloration with a smooth skin texture. Here are some of the physical characteristics of nurse sharks:
Nurse sharks are typically between 7 and 9 feet long, but can grow up to 14 feet long in some cases.
The maximum adult length is currently documented as 3.08 m (10 ft 11⁄2 in), whereas past reports of 4.5 m (15 ft) and corresponding weights of up to 330 kg (730 lb) are likely to have been exaggerated.
Adult nurse sharks are solid brown in color, while juveniles are spotted. However, they lose the spotted pattern with age.
There are also reports of nurse sharks occurring in unusual colors, including milky white and bright yellow.
Jaws and Teeth
Nurse sharks have a curled, hinged mouth that allows them to suck prey from the sand.
They have small, serrated teeth that are used to crush the shells of crustaceans and mollusks, as well as to catch fish and other small prey. The teeth are arranged in rows that rotate into place as needed.
Nurse sharks have sensory barbels on their lower jaw that help them locate prey in the sand.
The barbels are covered in tiny taste buds that allow the shark to detect the chemical signals given off by potential prey.
Nurse sharks have rounded pectoral fins that are used for steering and maneuvering. The fins are located on either side of the shark’s body and are used in conjunction with the caudal fin to propel the shark through the water.
Habitat and Distribution
Nurse sharks are bottom-dwelling fish that inhabit warm tropical and subtropical waters off the coasts of the Atlantic and Pacific oceans.
They are found in a wide but patchy geographical distribution along the tropical and subtropical coastal waters of the Eastern Atlantic, Western Atlantic, and Eastern Pacific.
In the Eastern Atlantic, nurse sharks range from Cape Verde to Gabon, and are occasionally sighted as far north as France.
In the Western Atlantic, they are found from Brazil to North Carolina, with unconfirmed sightings as far north as Rhode Island. Nurse sharks are also found in the Eastern Pacific, ranging from the Gulf of California to Ecuador and the Galapagos Islands.
Nurse sharks prefer to live in warm, shallow waters close to the coastline. They are commonly found in coral reefs, mangrove islands, seagrass beds, rocky crevices, and ledges.
Juvenile nurse sharks prefer shallow reefs, mangrove islands, and seagrass beds, while adults tend to inhabit deeper waters.
Inshore and Offshore Waters
Nurse sharks can be found in both inshore and offshore waters, and are known to inhabit sandy and muddy areas.
They prefer to dwell near the sea floor and will use natural protections like caves and crevices to hide during the day. Nurse sharks are also known to migrate to deeper offshore waters during the winter months.
Behavior and Diet
Prey and Hunting
Nurse sharks primarily feed on bottom-dwelling invertebrates such as crustaceans, sea urchins, molluscs, and tunicates.
They are sluggish and slow-moving predators, and they prefer to hunt at night. Nurse sharks use their senses of smell and electroreception to locate prey, and they have strong jaws that can crush the shells of their prey.
When hunting, nurse sharks use suction to draw in their prey, which they then swallow whole.
They are known to specialize in feeding on octopi, expanding their pharynx to create an intense negative pressure that sucks them in. Other prey they consume include corals, crustaceans, sea urchins, small fish like queenfish, rabbitfish, surgeonfish, squids, and even sea snakes.
Groups and Social Behavior
Nurse sharks are social animals and rest in groups during the day. They do not hunt in groups, but when they have plenty of food, they will continue to hunt and sleep in the same reef or habitat for most of their lives.
Reproduction and Birth
Nurse sharks are ovoviviparous, which means that the eggs hatch inside the mother’s body and the young are born live.
The gestation period is around six months, and litters usually consist of 21 to 29 pups.
Mating cycles for nurse sharks occur every two years, and females give birth to their young in shallow waters. The pups are born fully formed and immediately able to swim and hunt for food.
Nurse sharks are listed as vulnerable on the IUCN List of Threatened Species due to overfishing and capture in fisheries.
They are also often caught as bycatch in shrimp trawls. Inactive and sedentary, nurse sharks are easy targets for fishermen, and their flesh is used for human consumption and their skin for leather.
Despite their docile nature, nurse sharks have been known to attack humans, although these attacks are rare.
It is important to respect their space and avoid disturbing them while diving or snorkeling. Conservation efforts are being made to protect nurse sharks and their habitats, such as through the creation of marine protected areas and regulations on fishing.