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Nurse sharks are a type of shark that can be found in warm, shallow waters. They are known for their docile nature and nocturnal habits. Nurse sharks have a unique way of breathing, using muscles in their throats to pump water over their gills. They also have a special adaptation called spiracles, which allow them to take in water even while lying on the ocean floor. Nurse sharks feed primarily on crustaceans, mollusks, and small fish, using their powerful jaws to crush their prey. Despite their intimidating appearance, nurse sharks are not typically dangerous to humans unless provoked or stepped on.
Wild Creatures
The Size, Weight and Appearance of Nurse Sharks
The Structure of a Nurse Shark
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Even the relatively small nurse shark can appear enormous when encountered unexpectedly. Although there are reports of nurse sharks measuring up to 14 feet (4.3 meters) in length, marine scientists who have measured the species are more conservative [source: Castro]. It is agreed that the female nurse shark is always slightly larger than the male. A more realistic estimate puts the length of female nurse sharks at between just over 7 feet and just under 9 feet (2.2 to 2.7 meters) [sources: Guarracino, National Aquarium]. Males are generally about one-third of a foot shorter [source: Guarracino].
However, male nurse sharks weigh more than females, with males weighing between 200 and 267 pounds (90 to 120 kilograms) and females weighing between 167 and 233 pounds (75 to 105 kilograms) [source: Guarracino].
Nurse sharks can be different colors, from yellowish tan to dark brown, although most are closer to dark brown. Juvenile nurse sharks may have pigmentation in the form of small black spots and bands.
The dorsal fins of nurse sharks are rounded, not pointed like those in movies. The first dorsal fin is larger than the second. Nurse sharks have very long tails, and the caudal fin makes up over 25 percent of their body length [source: Guarracino]. The pectoral fin, located on the bottom, allows the nurse shark to hover and even walk along the ocean floor. This hovering motion sometimes helps nurse sharks find food, which we will discuss later.
Nurse sharks have a pharynx, a muscular cavity that can suck in food like a vacuum, to help with eating. You might also notice barbels, or whiskers, on the nurse shark’s snout; these help the nurse shark sense nearby food.
Since nurse sharks suck in food, they have a small mouth and simple teeth. The small mouth limits the size of the prey that’s available to the nurse shark, and the teeth are barely used in feeding because of the shark’s ability to draw food in with the pharynx. The teeth are small and non-serrated, which means they’re not ideal for cutting or tearing into their prey’s flesh [source: Matott, Motta, Hueter]. The nurse shark’s bite is strong, however, and surgical instruments may be required to free a human from the grasp of a nurse shark [source: Guarracino].
Nurse sharks are slow and lethargic, and they don’t put much effort into moving around. Unlike some sharks which must move continually to breathe, nurse sharks have respiratory systems that can pump water over their gill slits, allowing them to breathe without moving.
Perhaps the nurse shark never moves because it loves where it is. Discover where the nurse shark calls home on the following page.
FAQ
1. What are nurse sharks?
Nurse sharks are a type of shark found in warm, shallow waters in the western Atlantic and eastern Pacific Oceans. They have a distinctive appearance, with a broad, flat head and small eyes. Nurse sharks are generally slow-moving and docile, making them a popular attraction for divers and snorkelers.
2. How big do nurse sharks get?
Nurse sharks typically grow to be around 7-9 feet long, although some individuals have been recorded at up to 14 feet. They can weigh up to 330 pounds.
3. What do nurse sharks eat?
Nurse sharks are bottom-feeders, and their diet consists primarily of crustaceans, mollusks, and other small prey found on the ocean floor. They will also eat small fish and occasionally larger prey like stingrays or octopuses.
4. How do nurse sharks hunt?
Nurse sharks are nocturnal hunters and will usually hunt at night. They use their sense of smell to locate prey on the ocean floor and will suck it into their mouths using their strong suction power. Nurse sharks have small, serrated teeth that are adapted for crushing shells and other hard prey items.
5. Are nurse sharks dangerous to humans?
Nurse sharks are generally not considered to be a threat to humans. They are relatively docile and will usually swim away if approached. However, like all sharks, nurse sharks are wild animals and should be treated with caution and respect.
6. How do nurse sharks reproduce?
Nurse sharks are oviparous, which means that they lay eggs rather than giving birth to live young. Females will lay a nest of eggs, which are protected by a leathery case. The eggs will hatch after around 6-9 months, depending on water temperature.
7. What is the lifespan of a nurse shark?
The lifespan of a nurse shark is estimated to be around 25-30 years in the wild. However, their lifespan can be significantly longer in captivity.
8. What is the conservation status of nurse sharks?
Nurse sharks are listed as a species of “Least Concern” by the International Union for Conservation of Nature (IUCN). However, like all shark species, nurse sharks are vulnerable to overfishing and habitat destruction.
9. Can nurse sharks be kept as pets?
It is not recommended to keep nurse sharks as pets. They are large, powerful animals that require a lot of space and specialized care. Additionally, in many areas it is illegal to keep nurse sharks as pets without a special permit.
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