View source for Whitetip reef shark

{{Distinguish|oceanic whitetip shark|whitetip weasel shark}}
{{Short description|Species of shark}}
{{Speciesbox
| name = Whitetip reef shark
| image = Carcharhinus albimarginatus-shark.jpg
| image_alt = Photo of a whitetip reef shark, a slender gray shark with a short head and white tips on its dorsal and caudal fins, resting inside a coral cave
| status = VU
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Simpfendorfer, C. |author2=Yuneni, R.R. |author3=Tanay, D. |author4=Seyha, L. |author5=Haque, A.B. |author6=Bineesh, K.K. |author7=, D. |author8=Bin Ali, A. |author9=Gautama, D.A. |author10=Maung, A. |author11=Sianipar, A. |author12=Utzurrum, J.A.T. |author13=Vo, V.Q. |date=2020 |title=''Triaenodon obesus'' |volume=2020 |article-number=e.T39384A173436715 |doi=10.2305/IUCN.UK.2020-3.RLTS.T39384A173436715.en |access-date=19 November 2021}}</ref>
| genus = Triaenodon
| parent_authority = [[Johannes Peter Müller|J. P. Müller]] & [[Friedrich Gustav Jakob Henle|Henle]], 1837
| species = obesus
| authority = ([[Eduard Rüppell|Rüppell]], 1837)
| range_map = Triaenodon obesus distmap.png
| range_map_caption = Range of the whitetip reef shark
| range_map_alt = A world map with blue shading around the periphery of the Indian Ocean, throughout Southeast Asia to northern Australia, over a large part of the central Pacific, and off the west coast of Central America.
| synonyms = 
''Carcharias obesus'' <small>Rüppell, 1837</small><br />
''Triaenodon apicalis'' <small>Whitley, 1939</small>
}}

The '''whitetip reef shark''' ('''''Triaenodon obesus''''') is a [[species]] of [[requiem shark]], in the [[family (biology)|family]] Carcharhinidae, and the only member of its [[genus]]. A small shark that does not usually exceed {{convert|1.6|m|ft|abbr=on}} in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the [[nostril]]s, oval eyes with vertical pupils, and white-tipped [[dorsal fin|dorsal]] and [[caudal fin]]s. One of the most common sharks found on [[Indo-Pacific]] [[coral reef]]s, the whitetip reef shark occurs as far west as [[South Africa]] and as far east as [[Central America]]. It is typically found on or near the bottom in clear water, at a depth of {{convert|8|-|40|m|abbr=on}}.

During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its [[gill]]s and lie still on the bottom. At night, whitetip reef sharks emerge to hunt [[bony fish]]es, [[crustacean]]s, and [[octopus]] in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individuals may stay within a particular area of the reef for months or years, frequently returning to the same shelter. This species is [[viviparous]], in which the developing [[embryo]]s are sustained by a [[placenta]]l connection to their mother.

Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, [[spear fishing|spear fishers]] are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though [[ciguatera poisoning]] resulting from its consumption has been reported. The [[International Union for Conservation of Nature|IUCN]] has assessed the whitetip reef shark as Vulnerable, noting its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to [[overfishing]].

==Taxonomy and phylogeny==
[[File:Triaenodon obesus drawing.jpg|thumb|left|Early illustration of a whitetip reef shark from ''Systematische Beschreibung der Plagiostomen'' (1841).]]
The whitetip reef shark was first described by the German naturalist [[Eduard Rüppell]] as ''Carcharias obesus'', in the 1837 ''Fische des Rothen Meere'' (''Fishes of the Red Sea'').<ref name="compagno">{{cite book |author=Compagno, L.J.V. |year=1984 |title=Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date |place=Rome |publisher=Food and Agricultural Organization |isbn=978-92-5-101384-7 |pages=535&ndash;538}}</ref> His choice of the [[specific name (zoology)|specific epithet]] ''obesus'' was curious, given that this shark is actually quite slender.<ref>{{cite book |title=Fishes of the Great Barrier Reef and Coral Sea |author=Randall, J.E. |author2=Allen, G.R. |author3=Steene, R.C. |name-list-style=amp |publisher=University of Hawaii Press |year=1997 |isbn=978-0-8248-1895-1 |page=22}}</ref> Later in 1837, [[Johannes Peter Müller|Johannes Müller]] and [[Friedrich Gustav Jakob Henle|Friedrich Henle]] moved this species into its own genus ''Triaenodon'', from the [[Greek language|Greek]] ''triaena'' meaning "trident", and ''odon'' meaning "tooth". As Rüppell did not originally designate a [[holotype]], in 1960 a 31-cm-long specimen caught off [[Jeddah]], [[Saudi Arabia]], was made the species [[lectotype]].<ref name="compagno"/> Other [[common name]]s for this shark include blunthead shark, light-tip shark, reef whitetip shark, and whitetip shark.<ref name="fishbase">{{FishBase |genus=Triaenodon |species=obesus |month=July |year=2009}}</ref>

Once placed in the family [[Triakidae]], the whitetip reef shark is now recognized by most authors as belonging to the family [[Carcharhinidae]] on the basis of [[morphology (biology)|morphological]] characters, such as a full [[nictitating membrane]], well-developed precaudal pit, strong lower [[caudal fin]] lobe, and scroll-like [[intestine|intestinal]] valves.<ref name="randall"/> Morphological and [[molecular phylogenetics|molecular phylogenetic]] analyses suggest the whitetip reef shark is grouped with the [[Negaprion|lemon sharks]] (''Negaprion'') and the [[sliteye shark]] (''Loxodon'') in occupying an intermediate position on the carcharhinid [[evolutionary tree]], between most [[basal (phylogenetics)|basal]] genera (''[[Galeocerdo]]'', ''[[Rhizoprionodon]]'', and ''[[Scoliodon]]'') and the most [[Synapomorphy|derived]] (''[[Carcharhinus]]'' and ''[[Sphyrna]]'').<ref name="carrier et al">{{cite book |title=Biology of Sharks and Their Relatives |author=Carrier, J.C. |author2=J.A. Musick |author3=M.R. Heithaus |name-list-style=amp |publisher=CRC Press |year=2004 |isbn=978-0-8493-1514-5 |pages=52, 502}}</ref>

==Distribution and habitat==
[[File:Triaenodon obesus malaysia.jpg|thumb|left|alt=Photo of a whitetip reef shark resting amongst many brightly colored corals, its head concealed in a cave|The whitetip reef shark almost exclusively inhabits coral reefs]]

The whitetip reef shark is distributed widely across the entire [[Indo-Pacific]] region. It was once thought to have existed in the [[Atlantic Ocean]], based on [[fossil]] teeth found in [[North Carolina]] dated to the [[Miocene epoch]], although subsequent research has suggested that the teeth are of a [[Lamniformes|mackerel shark]], and that the whitetip has never colonized the Atlantic.<ref name="whitney et al">{{cite journal |author1=Whitney, N.M. |author2=Robbins, W.D. |author3=Schultz, J.K. |author4=Bowen, B.W. |author5=Holland, K.N. |year=2012 |title=Oceanic dispersal in a sedentary reef shark (''Triaenodon obesus''): genetic evidence for extensive connectivity without a pelagic larval stage |journal=Journal of Biogeography |volume=39 |issue=6 |pages=1144–1156 |doi=10.1111/j.1365-2699.2011.02660.x|bibcode=2012JBiog..39.1144W |s2cid=59405419 }}</ref> In the [[Indian Ocean]],  whitetip reef sharks can be found off of northern [[KwaZulu-Natal]], [[South Africa]] and all along the [[East Africa|East African]] coast, from the [[Horn of Africa]] to the [[Red Sea]] and along the [[Indian subcontinent]] (including [[Sri Lanka]]). They are found near many major island chains as well, including [[Madagascar]], [[Mauritius]], [[Mayotte]], the [[Comoros]], the [[Aldabra Group]], the [[Seychelles]] and the [[Chagos Archipelago]]. 

In the western and central Pacific Ocean, whitetips occur off [[South China]], [[Taiwan]], and the [[Ryukyu Islands]], south to the [[Philippines]] and throughout the entire [[Coral Triangle]], including the coastlines of [[Indonesia]], [[East Timor]] and [[Papua New Guinea]]. Their range continues south to the northern [[Australia]] and the [[Great Barrier Reef]]. Whitetips are also found around numerous Pacific [[Atoll|atolls]] and islands, including [[Melanesia]], [[Micronesia]], and [[Polynesia]], north to [[Hawaii]] and south to the [[Pitcairn Islands]]. They have also been sighted near [[Midway Atoll|Midway]] and [[Johnston Atoll|Johnston Atolls]] and [[Laysan]]. In the Eastern Pacific, they may be found off the west coasts of [[Costa Rica]] and [[Panama]] south to the [[Galápagos Islands]], and as far north as [[Isla Isabel National Park|Isla Isabel]], [[Socorro Island|Isla Socorro]], and the southern tip of [[Baja California peninsula|Baja California]] ([[Cabo San Lucas]] and [[Cabo Pulmo National Park|Cabo Pulmo National Marine Park]]).<ref name="compagno" />

Associated almost exclusively with [[coral reef]] [[habitat]]s, whitetip reef sharks are most often encountered around coral heads and ledges with high vertical relief, and additionally over sandy flats, in [[lagoon]]s, and near drop-offs to deeper water.<ref name="hobson"/> They prefer very clear water, and rarely stray far from the bottom during the day.<ref name="randall"/> The species is most common at a depth of {{convert|8|-|40|m|abbr=on}}.<ref name="compagno"/> On occasion, they may enter water less than 1 m deep when foraging; there is an exceptional record of a whitetip reef shark being captured from a depth of {{convert|330|m|abbr=on}} off the Ryukyu Islands.<ref name="randall">{{cite journal |author=Randall, J.E. |title=Contribution to the Biology of the Whitetip Reef Shark (''Triaenodon obesus'') |journal=Pacific Science |year=1977 |volume=31 |issue=2 |pages=143&ndash;164}}</ref>

==Description==
[[File:Triaenodon obesus moc.jpg|thumb|right|upright=1.2|alt=Frontal view of a whitetip reef shark, which has a wedge-shaped snout, oval eyes, and tubular flaps of skin next to the nostrils|The "face" of a whitetip reef shark is distinctive, with a broad snout, tubular nasal flaps, and oval eyes with vertical pupils.]]

A relatively small species, few whitetip reef sharks are longer than {{convert|1.6|m|ft|abbr=on}}. The maximum length this species attains is often given as {{convert|2.1|m|ft|abbr=on}}, though this was originally based on visual observations and may be dubious.<ref name="randall"/> The maximum reported weight is {{convert|18.3|kg|lb|abbr=on}}.<ref name="fishbase"/> The whitetip reef shark has a slim body and a short, broad head. The snout is flattened and blunt, with large flaps of skin in front of the [[nares]] that are furled into tubes. The eyes are small and oval with vertical [[pupil]]s and prominent ridges above, and are often followed by a small notch. The mouth has a distinct downward slant (imparting a disgruntled expression to the shark), with short furrows at the corners. There are 42&ndash;50 tooth rows in the upper jaw and 42&ndash;48 tooth rows in the lower jaw. Each tooth has a single narrow, smooth-edged cusp at the center, flanked by a pair of much smaller cusplets.<ref name="compagno"/>

The first [[dorsal fin]] is positioned well back on the body, closer to the [[pelvic fin|pelvic]] than the [[pectoral fin]]s. The second dorsal and [[anal fin]]s are large, about half to three-quarters as high as the first dorsal fin. The broad, triangular pectoral fins originate at or slightly before the level of the fifth [[gill slit]]. There is no ridge between the first and second dorsal fins. The lower lobe of the caudal fin is half the length of the upper, which has a strong notch near the tip.<ref name="compagno"/> The [[dermal denticle]]s are small and overlapping, usually with 7 horizontal ridges, giving the skin a smooth feel. The coloration is grayish to brownish above and white below, with a pattern of scattered small, dark spots unique to each individual. The tips of the first dorsal fin and upper caudal fin lobe, and sometimes also the second dorsal fin and lower caudal fin lobe, are bright white.<ref name="randall"/>

==Biology and ecology==
[[File:Triaenodon obesus guam.jpg|thumb|upright=1.2|left|alt=Three gray sharks lying beside each other on the sea bottom.|Whitetip reef sharks spend much of the day lying still on the bottom.]]
The whitetip reef shark is one of the three most common sharks inhabiting the reefs of the Indo-Pacific, the other two being the [[blacktip reef shark]] (''Carcharhinus melanopterus'') and the [[grey reef shark]] (''Carcharhinus amblyrhynchos''). The habitat preferences of this species overlap those of the other two, though it does not tend to frequent very shallow water like the blacktip reef shark, nor the outer reef like the grey reef shark.<ref name="compagno"/> The whitetip reef shark swims with strong undulations of its body, and unlike other requiem sharks can lie motionless on the bottom and actively pump water over its gills for [[aquatic respiration|respiration]].<ref name="compagno"/> This species is most active at night or during [[slack tide]], and spends much of the day resting inside caves singly or in small groups, arranged in parallel or stacked atop one another. Off Hawaii, these sharks may be found sheltering inside underwater [[lava tube]]s, while off Costa Rica they are often seen lying in the open on sandy flats.<ref name="martin">Martin, R.A. [http://elasmo-research.org/education/ecology/coral-whitetip.htm Coral Reefs: Whitetip Reef Shark]. ReefQuest Centre for Shark Research. Retrieved on August 7, 2009.</ref>

Whitetip reef sharks generally remain within a highly localized area; only rarely do they undertake long movements, wandering for a while before settling down somewhere new. One study at [[Johnston Atoll]] found that none of the sharks examined had moved more than {{convert|3|km|mi|abbr=on}} away from their original capture location over periods of up to a year.<ref name="randall"/> Another study at [[Rangiroa Atoll]] in [[French Polynesia]] found that, after more than three years, around 40% of the originally tagged sharks were still present on the same reef where they were first captured. An individual shark may rest inside the same cave for months to years. The daytime [[home range]] of a whitetip reef shark is limited to approximately {{convert|0.05|km2|mi2|abbr=on}}; at night this range increases to {{convert|1|km2|mi2|abbr=on}}.<ref name="martin"/> These sharks are not [[territoriality|territorial]] and share their home ranges with others of their species; they do not perform [[shark threat display|threat displays]].<ref name="compagno"/><ref name="hobson"/>

Important predators of the whitetip reef shark include [[tiger shark]]s (''Galeocerdo cuvier''), [[Galapagos shark]]s (''Carcharhinus galapagensis''), and possibly also [[silvertip shark]]s (''Carcharhinus albimarginatus''), though they usually occur at depths greater than those favored by whitetip reef sharks. An {{convert|80|cm|in|abbr=on}} long whitetip reef shark has also been found in the stomach of a [[giant grouper]] (''Epinephelus lanceolatus''), though these groupers are unlikely to be significant predators of this species due to their rarity.<ref name="randall"/> Known [[parasite]]s of the whitetip reef shark include the [[copepod]] ''Paralebion elongatus'' and the praniza (parasitic) [[larva]]e of the [[isopod]] ''Gnathia grandilaris''.<ref name="bester">Bester, C. [http://www.flmnh.ufl.edu/fish/Gallery/Descript/WTReefShark/WTReefShark.html Biological Profiles: Whitetip Reef Shark]. Florida Museum of Natural History Ichthyology Department. Retrieved on August 7, 2009.</ref><ref>{{cite journal |author=Coetzee, M. |author2=N.J. Smit |author3=A.S. Grutter |author4=A.J. Davies |name-list-style=amp |title=A new gnathiid (Crustacea: Isopoda) parasitizing two species of requiem sharks from Lizard Island, Great Barrier Reef, Australia |journal=The Journal of Parasitology |date=June 2008 |volume=94 |issue=3 |pages=608&ndash;615 |doi=10.1645/ge-1391r.1|pmid=18605791 }}</ref> While resting during the day, these sharks have been observed being cleaned by the [[wrasse]] ''[[Bodianus diplotaenia]]'' and the [[goby]] ''[[Elacatinus puncticulatus]]''. Unusually, there is also a report of seven whitetip reef sharks adopting a cleaning posture (mouth agape and gills flared) in the midst of a swarm of non-cleaning [[Hyperiidae|hyperiid]] [[amphipod]]s; the mechanical stimulation from the moving amphipods are thought to have evoked this behavior through their similarity to actual cleaner organisms.<ref>{{cite journal |author1=Whitney, N.M.  |author2=P.J. Motta  |name-list-style=amp |title=Cleaner host posing behavior of whitetip reef sharks (''Triaenodon obesus'') in a swarm of hyperiid amphipods |journal=Coral Reefs |volume=27 |issue=2 |date=June 2008 |page=363 |doi=10.1007/s00338-007-0345-4|bibcode=2008CorRe..27..363W |s2cid=40111386 }}</ref>

===Feeding===
[[File:Triaenodon obesus JNC960 Lower jaw and teeth 2.JPG|thumb|The lower jaw and teeth of whitetip reef shark]]
With its slender, lithe body, the whitetip reef shark specializes in wriggling into narrow crevices and holes in the reef and extracting prey inaccessible to other reef sharks. Alternatively, it is rather clumsy when attempting to take food suspended in open water.<ref name="randall"/> This species feeds mainly on bony fishes, including [[eel]]s, [[squirrelfish]]es, [[Lutjanidae|snapper]]s, [[damselfish]]es, [[parrotfish]]es, [[surgeonfish]]es, [[triggerfish]]es and [[goatfish]]es, as well as [[octopuses]], [[spiny lobster]]s, and [[crab]]s.<ref name="compagno"/> The whitetip reef shark is highly responsive to the [[olfaction|olfactory]], [[acoustics|acoustic]], and electrical cues given off by potential prey, while its visual system is attuned more to movement and/or contrast than to object details.<ref name="hobson"/><ref>Nelson, D.R. and R.H. Johnson. (1970). Acoustic studies on sharks: Rangiroa Atoll, July 1969. ONR Technical Report 2, No. N00014-68-C-0138.</ref><ref>{{cite journal |author=Yano, K. |author2=H. Mori |author3=K. Minamikawa |author4=S. Ueno|author5=S. Uchida |author6=K. Nagai |author7= M. Toda |author8=M. Masuda |name-list-style=amp |title=Behavioral response of sharks to electric stimulation |journal=Bulletin of Seikai National Fisheries Research Institute |date=June 2000 |volume=78 |pages=13&ndash;30}}</ref> It is especially sensitive to natural and artificial low-frequency sounds in the 25&ndash;100&nbsp;Hz range, which evoke struggling fish.<ref name="martin"/>

Whitetip reef sharks hunt primarily at night, when many fishes are asleep and easily taken. After dusk, groups of sharks methodically scour the reef, often breaking off pieces of coral in their vigorous pursuit of prey.<ref name="ferrari">{{cite book |author1=Ferrari, A. |author2=A. Ferrari |name-list-style=amp |title=Sharks |url=https://archive.org/details/sharks0000ferr/page/186 |url-access=registration |publisher=Firefly Books |year=2002 |isbn=978-1-55209-629-1 |pages=[https://archive.org/details/sharks0000ferr/page/186 186&ndash;187] }}</ref> Multiple sharks may target the same prey item, covering every exit route from a particular coral head. Each shark hunts for itself and in competition with the others in its group.<ref name="hobson"/> Unlike blacktip reef sharks and grey reef sharks, whitetip reef sharks do not become more excited when feeding in groups and are unlikely to be stirred into a [[feeding frenzy]].<ref name="hobson">{{cite journal |author=Hobson, E.S. |year=1963 |title=Feeding Behavior in Three Species of Sharks |journal=Pacific Science |volume=17 |pages=171&ndash;194}}</ref> Despite their nocturnal habits, whitetip reef sharks will hunt opportunistically in daytime.<ref name="randall"/> Off [[Borneo]], this species gathers around reef drop-offs to feed on food brought up by the rising current.<ref>{{cite book |author=Bight, M. |title=The Private Life of Sharks: The Truth Behind the Myth |publisher=Stackpole Books |year=2000 |isbn=978-0-8117-2875-1 |pages=123&ndash;124}}</ref> Off [[Hawaii]], they follow [[Hawaiian monk seal]]s (''Monachus schauinslandi'') and attempt to steal their catches.<ref name="carrier et al"/> A whitetip reef shark can survive for six weeks without food.<ref name="randall"/>

===Life history===
[[File:Triaenodon obesus group.jpg|thumb|upright=1.2|left|alt=Four sharks cruising amongst shallow rock outcrops|Gregarious in nature, whitetip reef sharks are often found in groups.]]
Like other members of its family, the whitetip reef shark is [[viviparous]]; once the developing [[embryo]]s exhaust their supply of [[yolk]], the [[yolk sac]] is converted into a [[placenta]]l connection through which the mother delivers nourishment for the remainder of [[gestation]]. Mature females have a single functional [[ovary]], on the left side, and two functional [[uterus]]es. The reproductive cycle is biennial.<ref name="robbins"/>

===Mating===
Mating is initiated when up to five males follow closely behind a female and bite at her fins and body, possibly cued by [[pheromone]]s indicating the female's readiness.<ref>{{cite journal |author=Johnson, R.H. |title=Copulation and possible olfaction-mediated pair formation in two species of carcharhinid sharks |journal=Copeia |volume=1978 |issue=3 |pages=539&ndash;542 |year=1978 |doi=10.2307/1443626 |author2=Nelson|jstor=1443626 }}</ref> Each male attempts to seize the female by engulfing one of her pectoral fins; at times two males might grasp a female on both sides simultaneously. Once engaged, the sharks sink to the bottom, whereupon the male (or males) rotates one of his [[clasper]]s forward, inflates the associated siphon sac (a subcutaneous abdominal organ that takes in seawater that is used to flush [[sperm]] into the female), and attempts to make contact with the female's vent. In many cases, the female resists by pressing her belly against the bottom and arching her tail; this may reflect [[mate choice]] on her part. The male has a limited time in which to achieve [[copulation (zoology)|copulation]], as while he is holding the female's pectoral fin in his mouth he is being deprived of [[oxygen]]. On the other hand, if the female is willing, the pair settles side-by-side with their heads pressed against the bottom and their bodies at an upward angle.<ref name="whitney et al 2">{{cite journal |author=Whitney, N.M. |author2=H.L. Pratt (Jr.) |author3=J.C. Carrier |name-list-style=amp |title=Group courtship, mating behaviour and siphon sac function in the whitetip reef shark, ''Triaenodon obesus'' |journal=Animal Behaviour |year=2004 |volume=68 |pages=1435&ndash;1442 |doi=10.1016/j.anbehav.2004.02.018 |issue=6|s2cid=3399520 }}</ref><ref name="tricas and le feuvre">{{cite journal |author1=Tricas, T.C.  |author2=E.M. Le Feuvre  |name-list-style=amp |title=Mating in the reef white-tip shark ''Triaenodon obesus'' |journal=Marine Biology |volume=84 |pages=233&ndash;237 |year=1985 |doi=10.1007/BF00392492 |issue=3|bibcode=1985MarBi..84..233T |s2cid=83826865 }}</ref>

After a [[gestation period]] of 10&ndash;13 months, females give birth to litters of 1&ndash;6 (usually 2&ndash;3) pups. The number of offspring is not correlated with female size; each female produces an estimated average of 12 pups over her entire lifetime.<ref name="robbins"/> Parturition occurs from May to August (autumn and winter) in French Polynesia, in July (summer) off [[Enewetak Atoll]], and in October (summer) off Australia.<ref name="compagno"/><ref name="robbins"/> Females give birth while swimming, making violent twists and turns of their bodies; each pup takes under an hour to fully emerge.<ref>{{cite journal |author=Schaller, P. |title=Husbandry and reproduction of Whitetip reef sharks ''Triaenodon obesus'' at Steinhart Aquarium, San Francisco |journal=International Zoo Yearbook |volume=40 |issue=1 |pages=232&ndash;240 |year=2006 |doi=10.1111/j.1748-1090.2006.00232.x}}</ref> The newborns measure {{convert|52|-|60|cm|in|abbr=on}} long and have relatively longer caudal fins than adults. This shark develops slowly compared to other requiem sharks; newborns grow at a rate of {{convert|16|cm|in|abbr=on}} per year while adults grow at a rate of {{convert|2|-|4|cm|in|abbr=on}} per year.<ref name="randall"/> [[Sexual maturity]] is reached at a length of around {{convert|1.1|m|ft|abbr=on}} and an age of 8&ndash;9 years, though mature males as small as {{convert|95|cm|in|abbr=on}} long have been recorded from the [[Maldives]], suggesting regional variation in maturation size.<ref name="fowler et al"/> On the [[Great Barrier Reef]], males live to 14 years and females to 19 years; the maximum lifespan of this shark may be upwards of 25 years.<ref name="randall"/><ref name="robbins"/> In 2008, a whitetip reef shark produced a single pup through possibly [[asexual reproduction|asexual]] means at the Nyiregyhaza Centre in [[Hungary]]; previous instances of asexual reproduction in sharks have been reported in the [[bonnethead]] (''Sphyrna tiburo'') and the [[blacktip shark]] (''Carcharhinus limbatus'').<ref>{{cite journal |author=Holtcamp, W. |title=Lone Parents: Parthenogenesis in Sharks |journal=BioScience |volume=59 |issue=7 |pages=546–550 |date=July–August 2009 |doi=10.1525/bio.2009.59.7.3|s2cid=86322298 }}</ref>

==Human interactions==
The white tip reef shark is more harmless and is seldom aggressive unless provoked. They are also fearless and curious, as the whitetip reef sharks may approach swimmers closely to investigate. However, these sharks readily attempt, and quite boldly, to steal catches from [[spear fishing|spear fishers]], which has resulted in several people being bitten in the process.<ref name="randall"/> In some places, local whitetip reef sharks have learned to associate the sound of a [[speargun]] discharge or a boat dropping anchor with food and respond within seconds.<ref name="martin"/> As of 2008, the [[International Shark Attack File]] lists two provoked and three unprovoked attacks to this species.<ref>[http://www.flmnh.ufl.edu/fish/sharks/statistics/species2.htm ISAF Statistics on Attacking Species of Shark]. ''International Shark Attack File, Florida Museum of Natural History, University of Florida.'' Retrieved on August 7, 2009.</ref> Whitetip reef sharks are well-suited to [[ecotourism]] diving, and with conditioning they can be hand-fed by divers.<ref name="compagno"/> In [[Hawaiian mythology]], the fidelity (i.e. "loyalty") of whitetip reef sharks to certain areas of the reef for years at a time may have inspired belief in ''[[aumakua|ʻaumākua]]'', the spirits of family ancestors that take animal form and protect their descendants.<ref name="taylor">{{cite book |title=Sharks of Hawaii: Their Biology and Cultural Significance |author=Taylor, L.R. |publisher=University of Hawaii Press |year=1993 |isbn=978-0-8248-1562-2 |pages=20&ndash;21}}</ref>

The whitetip reef shark is taken by [[fishery|fisheries]] operating off [[Pakistan]], [[India]], [[Sri Lanka]], [[Madagascar]], and likely elsewhere, using [[longline fishing|longlines]], [[gillnet]]s, and [[trawl]]s. The meat and [[liver]] are eaten, though sharks from certain areas present a substantial risk of [[ciguatera poisoning]] (especially the liver, which contains a much higher concentration of the toxin than the meat).<ref name="compagno"/><ref name="randall"/> The [[International Union for Conservation of Nature]] (IUCN) has assessed this species as Vulnerable, as its numbers have dropped in recent decades due to increasing, and thus far unregulated, fishing pressure in the tropics.<ref name="fowler et al">{{cite book |author=Fowler, S.L. |author2=R.D. Cavanagh |author3=M. Camhi |author4=G.H. Burgess |author5=G.M. Cailliet |author6=S.V. Fordham |author7=C.A. Simpfendorfer |author8=J.A. Musick |name-list-style=amp |title=Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes |publisher=International Union for Conservation of Nature and Natural Resources |year=2005 |isbn=978-2-8317-0700-6 |page=314}}</ref> Its restricted habitat, low dispersal, and slow reproduction are factors that limit this shark's capacity for recovering from [[overfishing]].<ref name="iucn status 19 November 2021" /> On the Great Barrier Reef, populations of whitetip reef sharks in fishing zones have been reduced by 80% relative to no-entry zones. Furthermore, populations in no-take zones, where boats are allowed but fishing prohibited, exhibit levels of depletion comparable to fishing zones due to [[poaching]]. Demographic models indicate that these depleted populations will continue to decline by 6.6&ndash;8.3% per year without additional conservation measures.<ref name="robbins">Robbins, W.D. (2006). Abundance, demography and population structure of the grey reef shark (''Carcharhinus amblyrhynchos'') and the white tip reef shark (''Triaenodon obesus'') (Fam. Charcharhinidae). PhD thesis, James Cook University.</ref> In June 2018 the New Zealand [[Department of Conservation (New Zealand)|Department of Conservation]] classified the whitetip reef shark as "Vagrant" under the [[New Zealand Threat Classification System]].<ref>{{Cite book|url=https://www.doc.govt.nz/globalassets/documents/science-and-technical/nztcs23entire.pdf|title=Conservation status of New Zealand chondrichthyans (chimaeras, sharks and rays), 2016|last1=Duffy|first1=Clinton A. J.|last2=Francis|first2=Malcolm|last3=Dunn|first3=M. R.|last4=Finucci|first4=Brit|last5=Ford|first5=Richard|last6=Hitchmough|first6=Rod|last7=Rolfe|first7=Jeremy|publisher=Department of Conservation|year=2018|isbn=978-1-988514-62-8|location=Wellington, New Zealand|pages=11|oclc=1042901090}}</ref>

==See also==
{{Portal|Sharks}}

*[[List of sharks]]

==References==
{{Reflist|colwidth=30em}}

==External links==
{{Commons category|Triaenodon obesus|Whitetip reef shark}}
* [http://fishbase.org/Summary/speciesSummary.php?ID=907 Whitetip reef shark (''Triaenodon obesus'')] at [http://www.fishbase.org/search.php FishBase]
* [http://www.flmnh.ufl.edu/fish/Gallery/Descript/WTReefShark/WTReefShark.html Whitetip reef shark (''Triaenodon obesus'')] at [http://www.flmnh.ufl.edu/fish/ Florida Museum of Natural History Ichthyology Department]
* {{SealifePhotos|214557}}

{{Carcharhinidae}}
{{Taxonbar|from=Q695344}}
{{Good article}}

{{DEFAULTSORT:shark, reef, whitetip}}
[[Category:Carcharhinidae|whitetip reef shark]]
[[Category:Fish described in 1837|whitetip reef shark]]