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Blacktip reef shark Image Source: National Oceanic and Atmospheric Administration (NOAA) ; Wikimedia Commons The presence of sharks in a reef is a sign of a healthy ecosystem. As top predators they help keep other carnivores from becoming too numerous and depleting herbivorous species. They also weed out sick and weak fish, leaving the fittest tor survive. This helps keep the reef diverse and vibrant.
Over 160 species of sharks inhabit the Great Barrier.Reef. For the most part they not dangerous predators of humans. While they can indeed be efficient killing machines, their targets are their traditional prey. The top apex predator at the Great Barrier Reef is — as is the case with many other large reefs — is the tiger shark. Tiger Sharks can reach lengths of five meters. Attacks involving them are rare, still I would’t turn my back to one. [Source: Great Barrier Reef.com]
The most common species of shark found in the Great Barrier Reef is the whitetip reef shark, a relatively passive shark that grows to a maximum length of two meters. Hammerhead sometimes show up. They can grow up to four meters in length and rarely attack swimmers although they do have a reputation for being aggressive. Great white sharks are generally not found at tropical reefs.
Whitetip reef sharks, grey reef shark and blacktip reef shark (all described in more detail below) often occupy reefs together along with other sharks and predators. Often each species occupies a particular niche and location within the reef system. Whitetip reef sharks live among the coral reefs, most commonly between the depths of eight and 40 meters (26 and 131 feet). Blacktip reef sharks are more likely to be found in shallow, high-energy coastal waters. The grey reef shark sticks to deeper clear waters off the reef edge.
Websites and Resources: Shark Foundation shark.swiss ; International Shark Attack Files, Florida Museum of Natural History, University of Florida floridamuseum.ufl.edu/shark-attacks ; Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems
Lemon Sharks and Nurse Sharks
Lemon sharks (Scientific name: Negaprion brevirostris) are found mostly in tropical waters the eastern Pacific and the western and eastern Atlantic Oceans. Also known as galano and galano de ley, they are found around reefs and in shallow waters and can survive in brackish water in areas with low oxygen and feeds mainly on bony fishes, guitarfish and stingrays and may also eat crustaceans, mollusks and seabirds.
Nurse sharks(Scientific name: Ginglymostoma cirratum) are one of the most benign and sluggish shark species. Reaching a length of 4.3 meters (14 feet) and a weight of 150 kilograms (330 pounds), they spend much of their time cruising the bottom of the sea near the shore and searching through rocky crevices and caves for prey such as squid, crabs and lobsters. Their name comes from the powerful sucking sound made by their powerful throat muscle, small mouth and large pharynx which in the old days reminded some people who heard it of nursing children. They are also known as cat sharks. They source of the name nurse shark is a matter of debate.
See Separate Articles LEMON SHARKS ioa.factsanddetails.com NURSE SHARKS ioa.factsanddetails.com
Requiem sharks are sharks of the family Carcharhinidae in the order Carcharhiniformes. They are migratory, live-bearing sharks of warm seas (sometimes of brackish or fresh water) and include such species as the bull shark, tiger shark, silky shark, dusky shark, spinner shark, blacknose shark, blacktip shark, blue shark, copper shark and oceanic whitetip shark. Among those found around coral reefs are thelemon shark, grey reef shark, blacktip reef shark and whitetip reef shark. ,
Many requiem sharks look similar and are difficult to tell apart. Grey reef sharks (Carcharhinus amblyrhynchos), for example, can be easily mistaken for similar species of requiem sharks. The blacktip shark (Carcharhinus limbatus) and the blacktip reef shark (Carcharhinus melanopterus) can be distinguised by a black tip on the dorsal fin, while the dorsal fin of C. amblyrhynchos is white or grey. Similarly, the silvertip shark (Carcharhinus albimarginatus) has white tips on its pectoral and caudal fins, while the grey reef shark does not. [Source: Animal Diversity Web (ADW)]
Requiem sharks are among the top five species involved in shark attacks on humans; however, due to the difficulty in identifying individual species, a degree of inaccuracy exists in attack records. Requiem sharks (Carcharhinus spp.) have accounted for 46 non-fatal attacks and 5 fatal attacks for of total of 51 attacks. [Source: International Shark Attack Files, Florida Museum of Natural History, 2023, Wikipedia]
According to International Shark Attack Files: Due to the similarity of small coastal species in this group in tooth shape, body size, and appearance, it is often difficult to assign a species in bite cases. Based on life history traits, ISAF suspects blacktip sharks (C. limbatus) account for the majority of these requiem bites in Florida. However, these cases lack enough evidence to be conclusive.
Blacktip Reef Sharks
blacktip reef shark Blacktip reef sharks (Carcharhinus melanopterus) are the most commonly encountered shark in tropical waters in the the Pacific and Indian Oceans. They are found around reefs and in shallow waters. Their dorsal and tail fins often project above the water and have black tips, hence its name. Blacktip reef sharks are regarded as inquisitive but not dangerous. They occasionally bite divers, surfers and waders, seemingly accidently, as they chase schools of bait fish near the shore but are generally not aggressive. Blacktip reef sharks have accounted for 14 non-fatal unprovoked attacks and zero fatal attacks on humans, according to the International Shark Attack Files, Florida Museum of Natural History, between 1876 and 2023.
Blacktip reef sharks reach lengths of two meters (six feet) and weight of about 45 kilograms. (100 pounds). They give birth to live young, have streamlined bodies and are excellent and powerful swimmers. Blacktip sharks are "gregarious creatures that travel in large groups and somersaults out of the water during feeding frenzies." Within their genus,, blacktip reef shark and sand tiger shark females illustrate their readiness to mate by reducing their speed and swimming with their tails in a more upward position and their snout pointing slightly down. The male will then come up to the female and place its snout below the female’s vent.
Studies of black tips indicates they head to warmer waters in the winter but return to their nursery ground when the weather warms. Research indicates they have a very sophisticated navigation system that allows them to migrate to certain points in the ocean at specific times. In waters off Aldabra Atoll in the Seychelles, blacktip reef sharks position themselves in water only a few centimeters deep and wait for the tide to refill the lagoon. According to National Geographic: With their bellies touching the sand, they point their snouts into the current to keep water flowing over their gills.
Grey Reef Sharks
Grey reef sharks (Scientific name:Carcharhinus amblyrhynchos) range across the Indian ocean, and the islands and atolls of Indonesia, the Philippines and the South Pacific. Attaining a length of six feet or more, these medium-size sharks prowl the reefs with "slow flicks of it black-edged tail." The longest known lifespan for a wild grey reef shark is 25 years. Their name is sometimes spelled gray reef shark. [Source: Bill Curtsinger, National Geographic January 1995]
Grey reef sharks are commonly seen by divers and snorkelers and usually present no problems they can be very aggressive. When an intruder such as a diver enters their territory, they often adopt an aggressive posture with their back arched, the pectoral fins lowered and snout raised, swimming from side to side in a "threat posture analogous to a rattlesnake.” Grey reef sharks have accounted for eight non-fatal unprovoked attacks and one fatal attack for of total of 9 attacks. [Source: International Shark Attack Files, Florida Museum of Natural History, 2023]
Grey reef shark are typically found at depths of zero to 280 meters (918.64 feet). They are widespread from the eastern Pacific Ocean (Costa Rica) through the western Pacific and Indian Oceans, and in the Red Sea. They are most commonly encountered off the islands of Tahiti, Micronesia, Fiji, Papua New Guinea, and Malaysia.[Source: Jessie Christel, Animal Diversity Web (ADW) /=]
Grey reef sharks are usually the top predators on coral reefs, controlling the fish populations under them. Their main known predators are larger sharks and orcas. The risk of predation for grey reef sharks decreases as they get older and bigger. Predation of grey reef sharks by silvertip sharks (Carcharhinus albimarginatus). has been observed in the Marshall Islands
Grey Reef Shark Characteristics
Grey reef sharks range in length from 1.22 to 2.55 meters (four to eight feet) and have an average weight of 18.5 kilograms (41 pounds). Males are larger than females. Males reach up to 2.55 meters (7.4 feet) in length, and are 1.3-1.45 meters (4.3-4.75 feet) long at sexual maturity, while females reach up to 1.72 meters (5.6 feet) and mature at 1.2-1.35 meters meters (3.9-4.4 feet). The maximum weight ever recorded for an individual was 33.7 kilograms (74 pounds), but big males may be heavier.
Grey reef sharks are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature) and heterothermic (have a body temperature that fluctuates with the surrounding environment). According to Animal Diversity Web they have "sleek, fusiform bodies that are unmistakable for anything but a shark. Key physical features include the anal fin, five gill slits, and a mouth positioned behind the eyes and underneath the snout. Additionally, grey reef sharks appear grey from a distance, but show a bronze tint when viewed up close. They have a white underside and are distinguished by a broad black band on the edge of the tail and black markings on the tips of the pectoral fins. The dorsal fin is either grey or tipped white. They have a long, broadly rounded snout and round eyes. They are lacking an interdorsal fin. . Males are distinguished by the elongate mating claspers on their pelvic fins. /=\
Grey reef sharks sense using vision, touch, sound. vibrations, electric signals and magnetism. All of its senses are acute. Its vision is sensitive to blue-green and low light because there are many rod cells in the retina. These sharks are generally thought to be far-sighted, but they can hunt by starlight. Grey reef sharks "hear" by detecting sounds through vibrations using sensory pits called the lateral line system. They have inner-ear semicircular canals used for balance, motion, and vibration. Most unique is its electromagnetic sense. This is facilitated by pores known as "ampullae of Lorenzini" that are concentrated around the snout. As sharks move through the earth's magnetic field, they create an electric field. By sensing this field, they can detect the strength and direction of it. This is the grey reef shark's navigation system. /=\
Grey Reef Shark Behavior and Communication
Grey reef sharks are diurnal (active during the daytime), nocturnal (active at night), motile (move around as opposed to being stationary), sedentary (remain in the same area), territorial (defend an area within the home range) and social (associates with others of its species; forms social groups). No home range size has been specified. However, grey reef shark have been known to act aggressively towards other predatory sharks of similar size, perhaps to defend a territory. [Source: Jessie Christel, Animal Diversity Web (ADW) /=]
Grey reef sharks communicate with other sharks visually and by touch (see mating). They also utilize sound, chemicals usually detected by smelling and electric signals) and pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species). According to Animal Diversity Web: Grey reef sharks perceives its environment very much through its excellent sense of smell. It can detect very low concentrations of blood by swinging its head side to side and using both nostrils to sample the water.
Grey reef sharks are social, maintaining daytime schools, but becoming more active nocturnally. This species usually swims slowly (about 0.5 miles per hour), seemingly inactive. However, because of its extremely sensitive perception channels, it is always constantly aware of its surroundings. When food is near or tasted, this species will speed up and become more active very quickly. Additionally, when it feels the vibrations of a fish dying it becomes highly aggressive. These sharks can be territorial (defend an area within the home range). They have a very distinct agonistic display that they make to other sharks, and sometimes to human divers. A displaying shark will arch its back, point its pectoral fins completely downwards, and swing its head laterally in a slow pendulum-like motion as it swims.
Sleeping and Resting Grey Reef Sharks
Carribbean reef shark As we all know many sharks are “negatively buoyant.”and have to keep moving so that water flows through their gills to breathe and keep themselves from sinking. Sleeping sharks have been observed in Japan, the Yucatan and elsewhere. They extract oxygen from water carried through the gills by currents or use bubbling freshwater from fissures to remove parasites from their skin.
When grey reef sharks need a rest it “surfs” currents. According to Florida International University marine scientist and assistant professor Yannis Papastamatiou, who did a study on the topi published in June 2021 in the Journal of Animal Ecology it is similar to the way birds soar on wind currents, except they do it underwater.
Michelle Marchante wrote in the Miami Herald: “The discovery was made during a visit to the southern channel of Fakarava Atoll in French Polynesia, where more than 500 grey reef sharks gather to hunt. During the daytime dives that Papastamatiou noticed that many of the sharks remained in the small channel, even though they weren’t hunting. Then he noticed something else: The sharks had developed a “conveyor belt” like system. When one shark reached the end of the line, it allowed the current to carry it back to the beginning, he said. So did another shark. And another. And another. Many barely moved their tails. They looked almost motionless, like they were floating. [Source: Michelle Marchante, Miami Herald, June 16, 2021]
“But they weren’t sleeping. To figure out what was happening, the team used a variety of tools, including animal-borne cameras, special tags to gather data on the sharks activity and swimming depths, and a detailed map to predict and model where possible updrafts might appear, depending on the direction of the tide. The data confirmed what researchers noticed during their underwater observations: “The sharks were using the updrafts to “surf the slope” and cut their energy usage by at least 15 percent, which is significant for a species that can never stop swimming, said Papastamatiou.
“How deep the sharks went also depended on the updraft. During incoming tides, with strong updrafts, the sharks would go deeper where the current was weaker, he said. During outgoing tides, when there was turbulence — enough to have the sharks bouncing around like they were on a bad flight — the sharks would move closer to the surface for a smoother ride. Papastamatiou said it seems that sharks, at least some of them, like to congregate in places where there are high currents, and expects that this finding could help researchers predict and understand why sharks might prefer a certain area over another.
Grey Reef Shark Food, Eating Behavior and Feeding Frenzy
Grey reef shark primarily prey on bony reef fishes less than 30 centimeters (three feet) in length. They also eat crabs, octopus, squid, lobsters, and shrimp and snatch their food with their powerful jaws for their size and sharp teeth. When hunting, they have been observed swimming at speeds of up to 48 kilometers per hour (30 miles per hour). [Source: Jessie Christel, Animal Diversity Web (ADW) /=]
A study was conducted that studied the attack behavior of grey reef sharks.. The sharks’ body starts to move in a spinning and winding motion. At the same time, its body moves in a back and forth motion. They swim in an almost disoriented way instead of a fluid motion. Their path of motion is in a circular pattern, with their snout pointing upward. It is thought that bull shark attacks may follow similar behavioral patterns.
Describing an encounter with grey reef sharks lured by a bucket of dead fish, Peter Benchley wrote in National Geographic, "Before we could clear out masks grey reef sharks were on us — quick, curious, unafraid darting around us like a pack of wild dogs." After the bucket was open, "The ocean exploded. Sharks swarmed like enraged bees — dozens of them, scores perhaps’snapping and biting and twisting and tearing, their bodies torqued in impossible contortions, their jaws extended, their eyes partly covered by nictitating membranes that gave them the look of murderous cats. They were a tightly wrapped ball of frenzy.The bucket rose in the water and spun, throwing off a cloud of blood. Sharks charged it, and disappeared in a flurry of bodies. A shark grabbed one of David's fins and worked it, as a dog worrks a bone. Another shark opened its mouth, turned towards me and lunged, trying to force its way between David and me. I struck it with the heel of my hand, and it sped away...And then it was over. In an instant they were gone."
Grey Reef Shark Mating, Reproduction and Offspring
Grey reef sharks 1) are viviparous (give birth to live young that developed from eggs in the body of the mother); 2) employ sperm-storing (producing young from sperm that has been stored, allowing it be used for fertilization at some time after mating); and 3) engage in internal reproduction in which sperm from the male fertilizes the egg within the female. This differs from most fish who engage in external reproduction in which the male’s sperm fertilizes the female’s egg outside her body. [Source: Jessie Christel, Animal Diversity Web (ADW) /=]
Females and males reach sexual or reproductive maturity at seven to 7.5 years. The average gestation period is 12 months. The number of offspring ranges from one to six. According to Animal Diversity Web: As in all sharks, male grey reef sharks have paired reproductive structures called "claspers," located between the pelvic fins. A groove in each clasper directs sperm into the female's cloaca during mating. Sperm may fertilize the egg then, or may be stored until an egg is released. /=\
When a female is ready to mate, she gives off behavioral and chemical cues (pheromones, chemicals released into air or water that are detected by and responded to by other animals of the same species). When the male senses these cues, he pursues her and seizes her with his teeth, which can actually cause serious wounds. Females have thicker skin on their backs than males do, probably to protect them from male biting. There is little or no information on the seasonality of mating in this species, or how many mates males or females have when breeding.
During the pre-fertilization and pre-birth stages provisioning and protecting is done by females. Grey reef sharks females nourish their offspring while they are still inside them. Embryos are connected to a placenta-like yolk sac from which they are nourished. . Young are born alive and free-swimming, not in an egg. They are usually sized between 46 and 60 centimeters (1.5 to two feet). Once they are born they are have to fend for themselves, feeding on their own with no help form their parents and protecting themselves from a host of predators.
Humans and Grey Reef Sharks
Humans utilize grey reef shark for tourism, research and education. Since grey reef sharks are generally a harmless and inquisitive species, studies are conducted on them quite easily. Ecotourism in the form of "shark diving" that includes them is popular. Grey reef shark bite incidents involving humans most often occur during spearfishing, when the sharks become aggressive in the presence of food. Careless divers who corner the animal in a reef canyon may also be attacked in self-defense. There are particularly areas, notably in eastern Micronesia and the Marshall Islands, where these sharks have a reputation for being aggressive toward humans. /=\
International Union for Conservation of Nature (IUCN) Red List list grey reef shark as “Near Threatened”. They have no special status according to the Convention on the International Trade in Endangered Species (CITES). Decreases in numbers of the species have been observed around the Maldive Islands, and may be occurring in other places too. There are several characteristics and behaviors of this species that make them vulnerable to over-fishing: 1) they are found relatively near shores; 2) individuals tend to stay in one area; 3) and they gather in predictable locations, making them easier to catch. Females mature relatively slowly, and have small litters, which means slower population growth compared to other large fish.
Attacks By a Grey Reef Shark
Describing an attack by a grey reef shark, Curtsinger wrote: the shark "tore open my left hand, I remember feeling as if I'd been hit by a sledge hammer. Such was the shock, I don't recall the actual bite." The incident took place in 1973 in waters off a South Pacific atoll. "It was 20 feet away and closing. I saw it sweeping its head back and forth; its back was arched like a cat's. The shark was speaking to me, but at the time I didn't know the words."
"The shark came at me like a rocket. I had time only to lift my hand, the shark ripping it with its teeth. As I swam frantically toward the boat, I saw that each dip of my hand left a cloud of blood in the water. the shark struck again, raking my right shoulder. At that moment a friend in a dingy rescued me." Now Curtsinger sometimes wears a steel mesh diving suit or a protective plastic "shark scooter."
Describing another attack by a grey reef shark that he believed was injured, photographer Mike deGruy said, "I raised my camera and took a picture and it ripped up my right arm and then my left scuba fin. Luckily, it grabbed my fin and not my thigh. I came to the surface spewing blood everyplace. I swam with my left leg back to the boat."
"Three quarters of the way to the boat, I felt I might make it." Suddenly he wondered: "Why am I not being eaten? Then, it was like an epithet. 'Phil!' They're eating Phil!" His diving partner Phil was seriously injured. DeGruy required 11 operations over a year and a half to repair the damage that was done to him.
Whitetip Reef Sharks
Whitetip reef shark Whitetip reef sharks (Scientific name: Triaenodon obesus) are found mostly in tropical waters in the Indo-Pacific region. Their dorsal and upper tail fins have distinctive white tips, hence their name. Also known a bluntheads and white-tipped shark, they reach a length of 2.1 meters and a weight of about 20 kilograms. They are slender and give birth to live young. Unlike most sharks which need to swim continuously to keep oxygen flowing through their gills, whitetip reef sharks can pump water across their gills and thus rest on the ocean floor.
Whitetip reef sharks were originally described by Eduard Ruppell in 1837. They have been around a long time. Fossils of them have been found in North Carolina from the Miocene Period (23 million to 5.3 million years ago) indicating that the shark existed in the Atlantic Ocean several million years ago; though they are not found there now. Their lifespan in the wild is estimated to be up to 25 years. The most dangerous predator of the whitetip reef shark is humans but they can be preyed upon by large sharks, such as the tiger shark and silvertip shark.[Source: Andrew Feldkamp, Animal Diversity Web (ADW)]
Whitetip reef shark are important predators in reef ecosystems. They use coral reefs as a habitat, as well as a source for food. Their predation of fishes may serve as a sort of population control. This is particularly important in those fishes, such as the parrotfish, that consume the coral. /=\ However the whitetip reef shark does occasionally have a negative effect on the coral, damaging iti n their aggressive pursuit of prey fish. The whitetip reef shark also serves as host to small cleaner fish such as gobies or striped cleaner wrasses who feed on the parasites infesting the shark.
Whitetip reef sharks live in tropical, saltwater, and/or marine environments and they are found in reefs, coastal areas and on or near the sea bottom as well as in caves at depths of one to 330 meters (3.28 to 1082.68 feet) at an average depth of 8-40 meters (26-131 feet). Found in both the Indian and Pacific oceans, they have been spotted as far west as the coasts of South Africa and Sri Lanka in the Indian Ocean and have been observed as far east as the coasts of Costa Rica and Panama in the Pacific Ocean. They are most numerous around Indo-Pacific islands and along the southern coast of the Indian sub-continent.
Whitetip Reef Shark Characteristics and Behavior
Whitetip reef sharks reach lengths of 213 centimeters (84 inches), with their average length being 165 centimeters (65 inches). They reach weights of 27.7 kilograms (61 pounds), with their average weight being 20 kilograms (44 pounds). Males are larger than females. [Source: Andrew Feldkamp, Animal Diversity Web (ADW)]
The whitetip reef sharks are grey in color with a white belly and characteristic white tips on its first dorsal, upper caudal and occasionally the pelvic fins. According to Animal Diversity: The snout is short and broad with a mouth full of smooth edged teeth on both jaws. Both the mouth and nostrils are located on the underside of the head. The skin is very tough and the lateral fins are highly flexible. Both of these characteristics allow them to exist more easily among the rough and jagged edges of a coral reef. A diagnostic feature that distinguishes Whitetip reef sharks from the similar silvertip and oceanic whitetip sharks is the second dorsal fin. In the whitetip reef shark it is significantly larger in comparison to the other species.
Whitetip reef shark are nocturnal (mainly active at night), occasionally motile (move around as opposed to being stationary) and occasionally sedentary (remain in the same area). Their average territory size is two square kilometers. They are considered docile and non-aggressive. Being nocturnal, they spend much of the day in caves and deep crevices in coral reefs and coral reef lagoons.
Whitetip reef sharks have the ability to pump water across their gills without moving forward, so they can sit motionless on the sea floor. However the shark prefers the safety and seclusion of caves when they are hunting and return to the same cave day after day for several months. Whitetip reef sharks remain in a relatively small area throughout their life. The longest recorded travel over the coarse of a year by an individual was three kilometers. The whitetip reef shark is non-territorial. It sharing its range with other whitetip reef sharks and sharks of other species.
Whitetip reef sharks communicate with vision, touch and chemicals usually detected by smelling and sense using vision, touch, sound, chemicals detected by smelling and electric signals. /=\ As with most sharks the main form of perception is visual. Their eyes are large and oval in shape. They share caves, and occasionally hunt together, however how they communicate is not well understood. Tactile communication — the male biting the fins of the female — is employed during mating.
Whitetip Reef Shark Food and Eating Behavior
According to Animal Diversity Web: Despite the docile nature of this shark during the day, during feeding at night they become very aggressive. It will thrash through coral reefs looking for food. The whitetip reef shark usually hunts alone but will work with other sharks to pursue prey throughout the coral reefs. Sometimes in pursuit of a fish, the shark will wedge the front half of its body into a crack or crevice on the reef and stay there until it catches the fish. [Source: Andrew Feldkamp, Animal Diversity Web (ADW)]
Horn shark The whitetip reef shark is considered clumsy and slow in open water, however it is still considered a pelagic (living in the open ocean, far from land) predator. It is capable of catching fish in coral reefs because of its maneuverability. Despite its ability to catch fish, it specializes in bottom feeding. Its ventrally located mouth is ideal for picking crab, lobster and octopi off the sea floor, but its primary source of food is several types of boney fishes including but not restricted to damselfish, parrotfish, surgeonfish, goatfish, triggerfish, squirrelfish and eels
The large eyes are particularly useful to the whitetip because it is a nocturnal animal that does most of its hunting and traveling at night. Like other sharks, they have very strong chemosensory systems as well. This is most useful to the whitetip reef sharks in hunting and eating. Whitetip reef sharks respond to sounds in the water. They are believed to be attracted to the sounds of spearfishing in the water. Like other sharks, this species also has electroreceptive abilities to help them detect prey.
Whitetip Reef Shark Mating, Reproduction and Offspring
Whitetip reef sharks are viviparous (they give birth to live young that developed in the body of the mother) and iteroparous (offspring are produced in groups such as litters). They engage in internal reproduction in which sperm from the male fertilizes the egg within the female and engage in seasonal breeding but there is not enough evidence to indicate how often this species breeds. Fertilization occurs seasonally in autumn and winter. This is between May and August in the Southern Hemisphere. The number of offspring ranges from one to five, with the average number of offspring being two to three young each measuring about 60 centimeters (two feet) each. . The average gestation period is five months. On average males and females reach sexual or reproductive maturity at age five years. [Source: Andrew Feldkamp, Animal Diversity Web (ADW)]
According to Animal Diversity Web: Male whitetip reef sharks have been known to school in groups of nearly a hundred in pursuit of a female ready to mate. The sharks orient themselves parallel to each other and at about a 45 degree angle to the water column during copulation. They position themselves with their snouts in the sea floor, maintaining this vertical position with occasional simultaneous undulations of their bodies. The male then bites the pectoral fin of the female and inserts his clasper into the cloaca. This ritual of biting the female’s pectoral fin to hold position is common to several species.
During the pre-birth stage provisioning and protecting is done by females. While in the embryo stage, the juvenile receives all its nutrients from the mother via a yolk sac placenta. When the female has a a litter of shark pups insider her, she slower and less maneuverable and thus more vulnerable to attacks by predators. Juveniles are born alive and fully functional. Resembling mini-versions of adults, they are completely independent and capable of surviving on their own. They grow relatively slowly and reach sexual maturity at around age five.
Whitetip Reef Sharks and Humans
Whitetip reef sharks are regarded as not dangerous, passive and calm — easily approachable by divers. They are only a problem to humans if provoked and may attack in defense if they are cornered and escape is not possible. The sharks are attracted by boat engines, presumably by an opportunity for a free meal, often show up when fish are speared, and occasionally bite divers in struggles over possession of speared fish. It has been suggested that the sound of spear fishing arouses these sharks to leave their cave and pursue the speared fish. In April 2001, a surfer was bitten on the left hand by a small white-tip reef shark in 10-foot waters off Ewa Beach in Hawaii Whitetip reef sharks have accounted for five non-fatal unprovoked attacks and zero fatal attacks according to International Shark Attack Files.
White tips have been overfished. Many have been harvested for their fins. Although there are reports that their body parts, particularly the liver, may be toxic, the flesh of these sharks is sometimes eaten for food. The International Union for Conservation of Nature (IUCN) Red List: lists whitetip sharks as “Near Threatened.” They have no special status according to the Convention on the International Trade in Endangered Species (CITES). The shark currently have a wide tropical distribution however their slow rate of reproduction makes them vulnerable to overfishing.
Image Source: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated March 2023