Crocodile Attack in Australia: An Analysis of Its Incidence and Review of the Pathology and Management of Crocodilian Attacks in General
2005; Elsevier BV; Volume: 16; Issue: 3 Linguagem: Inglês
10.1580/1080-6032(2005)16[143
ISSN1545-1534
AutoresDavid Caldicott, David Croser, Charlie Manolis, Grahame J. W. Webb, Adam Britton,
Tópico(s)Forensic Anthropology and Bioarchaeology Studies
ResumoCrocodilians represent one of the oldest constant animal lineages on the planet, in no small part due to their formidable array of predatory adaptations. As both human and crocodilian populations expand, they increasingly encroach on each others' territories, bringing morbidity and mortality to both populations. In this article, the medical and herpetologic literature pertaining to injuries caused by crocodilians is reviewed, and the patterns of saltwater crocodile attacks in Australia from 1971 to 2004 are analyzed. In this review, we examine the features of crocodilians that contribute to explaining their evolutionary success, as well as the potential hazard they pose to humans. Only by understanding their capabilities is it possible to mitigate the potential threat to life and limb. Crocodilians represent one of the oldest constant animal lineages on the planet, in no small part due to their formidable array of predatory adaptations. As both human and crocodilian populations expand, they increasingly encroach on each others' territories, bringing morbidity and mortality to both populations. In this article, the medical and herpetologic literature pertaining to injuries caused by crocodilians is reviewed, and the patterns of saltwater crocodile attacks in Australia from 1971 to 2004 are analyzed. In this review, we examine the features of crocodilians that contribute to explaining their evolutionary success, as well as the potential hazard they pose to humans. Only by understanding their capabilities is it possible to mitigate the potential threat to life and limb. How doth the little crocodileImprove his shining tail,And pour the waters of the NileOn every golden scale!How cheerfully he seems to grin,How neatly spreads his claws,And welcomes little fishes in,With gently smiling jaws!—Alice in Wonderland by Lewis Carroll, 1866 Crocodilians are among the few species on the planet that cause reflexive fear in humans, perhaps because the fear of being eaten is greater than the fear of being bitten.1.Graham A. Eyelids of Morning: The Mingled Destinies of Crocodiles and Men. Chronicle Books, San Francisco, CA1990Google Scholar Many animals will bite, but only a few attack humans as they would other prey items. Fortunately, attacking and eating humans by crocodilians is an uncommon event. We review the features of crocodilians that make them such formidable predators, examine the incidence of saltwater crocodile attacks in Australia, and examine the pathology and management of this entity. The order Crocodylia comprises 23 species of extant crocodilians within 3 families: Alligatoridae (8 species; alligators and caimans), Crocodylidae (14 species; "true" crocodiles), and Gavialidae (1 species; Indian gharial)2.King F.W. Burke R.L. Crocodilian, Tuatara and Turtles Species of the World: A Taxonomic and Geographic Reference. Association Systematics Collections, Washington, DC1989Google Scholar (Figure 1). Crocodylomorpha, the broad taxonomic grouping that encompasses crocodilians and their known predecessors, can be traced back approximately 240 million years and has diversified into terrestrial, freshwater, and marine environments. The modern Crocodylia originated more than 100 million years ago, and its members have remained relatively unchanged since then. Crocodilians share their early archosaurian origins with dinosaurs and hence are more closely related to birds than other reptiles.3.Bellairs Ad'A. The Crocodilia.in: Webb G.J.W. Manolis S.C. Whitehead P.J. Wildlife Management: Crocodiles and Alligators. Surrey Beatty & Sons, Chipping Norton, Australia1987: 5-7Google Scholar The word crocodile is derived from the Greek word krokodeilos, which translates literally into pebble worm (kroko means pebble and deilos means worm or man), presumably referring to the appearance of a crocodile's skin. The word alligator comes from the Spanish for lizard, el lagarto.4.Dodson P. Allure of El Lagarto: why do dinosaur paleontologists love alligators, crocodiles, and their kin?.Anat Rec A Discov Mol Cell Evol Biol. 2003; 274: 887-890Crossref PubMed Scopus (15) Google Scholar Modern crocodilians are geographically widespread in warm temperate and tropical climates.5.Ross J.P. Crocodiles: Status Survey and Conservation Action Plan. IUCN, Gland, Switzerland1998Google Scholar The 2 species of alligator, the Chinese alligator (Alligator sinensis) and the American alligator (Alligator mississippiensis), are distributed in more temperate climates and are exposed to relatively cold conditions during winter. It would seem that humans may have always had a healthy respect for crocodilians, judging by the paleontologic evidence that suggests that crocodilians preyed on human ancestors.6.Davidson I. Solomon S. Was OH7 the victim of a crocodile attack?.Tempus. 1990; 2: 197-206Google Scholar Crocodilians feature in the traditions and myths of many cultures around the world. For example, crocodiles (Crocodylus porosus, Crocodylus johnstoni) figure prominently in the dreamtime stories of a number of aboriginal clans in northern Australia7.Reed A.W. Crocodile people.Aboriginal Myths and Legends. Reed New Holland, Sydney, Australia1999Google Scholar, 8.Webb G. Manolis C. Australian Crocodiles. Reed New Holland, Sydney, Australia1998Google Scholar, 9.Lanhupuy W. Aboriginal attitudes to crocodile management.in: Webb G.J.W. Manolis S.C. Whitehead P.J. Wildlife Management: Crocodiles and Alligators. Surrey Beatty & Sons, Chipping Norton, Australia1987: 145-147Google Scholar and are of totemic significance to this day. To the Iban people of northern Borneo, it is taboo to kill crocodiles, except where one has killed a human.10.Ritchie J. Jong J. Bujang Senang Terror of Batang Lupar. Samasa Press, Kuching, Malaysia1993Google Scholar,11.Steubing R. Sarawak's killer crocodiles.Malayan Naturalist. 1983; 37: 17-23Google Scholar The Por people of the Cardomom Mountains in Cambodia revere Siamese crocodiles (Crocodylus siamensis), and the killing of one is believed to cause an ancestor's forest spirit to bring illness and death to the person or family responsible.12.Daltry JC, Chheang D, Em P, et al. Status of the Siamese Crocodile in the Central Cardamom Mountains, Southwest Cambodia. Cambodian Crocodile Phnom Penh: Conservation Programme, Fauna and Flora International, Cambodia Programme and Department of Forestry and Wildlife; 2003.Google Scholar In ancient times, Nile crocodiles (Crocodylus niloticus) in Egypt were worshipped and associated with the crocodile-deity Sobek, at the shrines of Kom-Ombo in Upper-Egypt, and in Crocodilopolis (Fayum).13.Morenz LD. Die Sobeks - Spuren von Volksreligion imägyptischen Mittleren Reich [The Sobeks–Traces of popular religion in the Egyptian Middle Kingdom]. IBAES IV Conference Proceedings. 2002; Berlin, Germany. Tierkulte im pharaonischen Ägypten, 83–97. Available at: www2.rz.hu-berlin.de/nilus/netppublications/ibaes4/morenz/text.pdf.Google Scholar The crocodile was thought to be responsible for the rains that overflowed the Nile River and left behind the rich mud that fertilized the land. At the same time, they were feared for their destructive power.14.Seawright C. Sobek, God of crocodiles, power, protection and fertility. Available at: http://www.thekeep.org/kunoichi/kunoichi/themestream/sobek.html. Accessed 2002.Google Scholar,15.Trompf G.W. Mythology, religion, art, and literature.Crocodiles and Alligators. Weldon Owen, New York, NY1989Google Scholar Early explorers reported the fear that Native American Indians showed toward alligators.16.Le Moyne J. Indorum Floridam proviniciam inhabitantium elcones.in: Byr T. Voyages en Virginie et eu Floride. Ducharte et Van Buggenhoudt, Paris, France1926Google Scholar More recently, humans have had the advantage. The overexploitation of crocodilians for their skins after World War II resulted in two thirds of the species being placed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 1973.17.Jelden D. Crocodilians within CITES.in: Crocodiles: Proceedings of the 17th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Darwin, NT, Australia. Gland, Switzerland2004: 69-71Google Scholar No international trade is permitted under Appendix I (except animals derived from registered captive-breeding operations). Today, because of the efforts of conservationists, researchers, skin traders, and others, many crocodilian populations around the world have recovered.18.Hutton J. Webb G.J.W. Crocodiles: legal trade snaps back.in: Oldfield S. Trade in Wildlife: Regulation for Conservation. Earthscan Publications, London, England2003: 108-120Google Scholar The success of many of these management programs has led to increased interactions and conflicts between people and crocodilians, often promoting a negative reaction to their successful population recovery. In some countries, wildlife authorities have specific programs to remove nuisance alligators or problem crocodiles to improve public safety (eg, Australia, United States, Zimbabwe). With regard to unprovoked attacks on humans, 3 species are perhaps the best known—the American alligator, the Nile crocodile, and the saltwater or estuarine crocodile (C porosus). A number of other crocodilian species have been less commonly implicated in attacks on humans, including the black caiman (Melanosuchus niger),19.Evans P. Wilkinson P. Black caiman attack.Crocodile Specialist Group Newsletter. 1997; 16: 5-6Google Scholar,20.Hall P.M. Dangerous to man? A record of an attack by a black caiman in Guyana.Herp Rev. 1991; 22: 9-11Google Scholar Morelet's crocodile (Crocodylus moreletii),21.Marlin J.A. Marlin K.K. Platt S.G. A documented case of an attack by Morelet's crocodile (Crocodylus moreletii) on man.Bull Chicago Herp Soc. 1995; 30: 165-167Google Scholar, 22.Finger A.G. Rainwater T.R. McMurry S.T. Platt S.G. Rosado N. Windsor M. Mazzotti F.J. Human-crocodile conflict in Belize: a summary.in: Crocodiles: Proceedings of the 16th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Gainesville, FL. Gland, Switzerland2002: 198-199Google Scholar, 23.Huerta-Ortega S.M. Ponce-Campos P. Interacción hombre-cocodrilo en la costa de Jalisco, México.in: Crocodiles: Proceedings of the 16th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Gainesville, FL. Gland, Switzerland2002: 200-203Google Scholar American crocodile (Crocodylus acutus),24.Guggisberg C.A.W. Crocodiles: Their Natural History, Folklore and Conservation. Wren Publishing, Mt Eliza, Victoria1972Google Scholar,25.Vyas R. Recent cases of man-eating by the mugger (Crocodylus palustris) in Gujarat State.Hamadryad (Madras). 1993; 18: 48-49Google Scholar mugger (Crocodylus palustris),25.Vyas R. Recent cases of man-eating by the mugger (Crocodylus palustris) in Gujarat State.Hamadryad (Madras). 1993; 18: 48-49Google Scholar and the Indian gharial (Gavialis gangeticus).26.Bustard H.R. Singh L.A.K. Gharial attacks on man.J Bombay Nat Hist Soc. 1982; 78: 610-611Google Scholar Two cases of directed attacks by Australian freshwater crocodiles (C johnstoni) (in 1988 and 1990)27.Lindner G. Crocodile management: Kakadu National Park.in: Crocodiles: Proceedings of the 17th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Darwin, NT, AustraliaGland, Switzerland2004: 41-51Google Scholar appear to have been cases of mistaken identity, since this species is generally considered harmless unless provoked. The incidence of crocodile attacks in many countries is extremely difficult to quantify. Undoubtedly, many more people have been attacked by crocodilians than have been reported. At the turn of the century in the United States, current thinking was that crocodilians would not attack humans unprovoked.28.Carle W. Alligators DO attack!.Florida Wildlife. 1948; 2: 10-11Google Scholar, 29.Neill W.T. The Last of the Ruling Reptiles: Alligators, Crocodiles and Their Kin. Columbia University Press, New York, NY1971Google Scholar, 30.McIlhenny E.A. The Alligator's Life History. Society for the Study of Amphibians and Reptiles, Athens, Ohio1976Google Scholar This widely accepted opinion changed in 1973 with the death of a 16-year-old girl attacked by a 4-m-long alligator.31.Hines T.C. Keenlyne K.D. Alligator attacks on humans in Florida.in: Proceedings of the 30th Annual Conference Southeastern Association of Fish and Wildlife Agencies 30. 1976: 358-361Google Scholar Since then, more detailed records on alligator attacks have been kept,32.Conover M.R. Dubow T.J. Alligator attacks on humans in the United States.Herp Rev. 1997; 28: 120-124Google Scholar although with nowhere near the accuracy or detail of the record keeping of other animal attacks, such as the International Shark Attack File. The worst mass attack by crocodiles was said to have been on the night of February 19, 1945, when allegedly approximately 1000 Japanese soldiers found themselves pinned down in a mangrove swamp separating Ramree Island from the Burmese mainland. According to the British naturalist Bruce Wright, who was then a member of the British Armed Forces, only 20 Japanese allegedly escaped alive from the saltwater crocodiles.33.Wright B. Wildlife Sketches Near and Far. University of New Brunswick Press, Fredrickton, New Brunswick1962Google Scholar The veracity of this report has subsequently been called into question.34.Platt S.G. Ko W.K. Kalyar Myo M. Khaing L.L. Rainwater T. Man eating by estuarine crocodiles: the Ramree Island massacre revisited.Herp Bull. 2001; 75: 15-18Google Scholar A 5.8-m-long saltwater crocodile (named Whiteback due to distinctive white markings on his back) gained considerable notoriety in Sarawak, Malaysia, after killing 13 people.35.Iordansky N.N. The skull of the Crocodilia.in: Biology of the Reptilia. Vol 4. Academic Press, New York, NY1973: 201-262Google Scholar Accurate data collection concerning animal attacks does not usually occur until a species is protected and formal monitoring is introduced. The situation with saltwater crocodiles in northern Australia is no exception, and most detailed information on attacks has been recorded since the species was legally protected in the states or territories in which it occurs (Western Australia in 1969, Northern Territory in 1971, and Queensland in 1974).8.Webb G. Manolis C. Australian Crocodiles. Reed New Holland, Sydney, Australia1998Google Scholar Even so, detailed information on some attacks is not always available, and attacks that do not result in injury are not usually recorded. A review of crocodile attacks in northern Australia would not be complete without a brief summary of the features of crocodilians that make them such formidable predators. Crocodilian notoriety stems in part from their prominent teeth, the number of which varies between species.36.Richardson K.R. Webb G.J.W. Manolis S.C. Crocodiles: Inside and Out. Surrey Beatty & Sons, Chipping Norton, Australia2002Google Scholar Saltwater crocodiles possess between 64 and 66 teeth: 17 to 18 teeth on each side of the upper jaw (premaxilla and maxilla) and 15 on each side of the lower jaw (mandible). Designed to grab and hold onto prey, the teeth are constantly replaced through the animal's life. Massive pterygoid muscles37.Erickson G.M. Lappin A.K. Vliet K.A. The ontogeny of bite-force performance in American alligator (Alligator mississippiensis).J Zool (Lond). 2003; 260: 317-327Crossref Scopus (202) Google Scholar close the jaws with enormous force, and being bitten has been described like being hit with a hammer, patients often only realizing later that they have sustained a penetrating injury. Even bites from small specimens can have serious consequences. Recently, investigators measured the bite force of various crocodilian species, with particular attention to series of different sized American alligators and saltwater crocodiles. These results indicated that a 300-kg, 3.65-m-long American alligator could exert a force of just under 1000 kg, equal to the force required to lift a small utility vehicle.38.Cox D. Alligator's bite could lift a small truck. Science Daily 29/3/2002. Available at: www.sciencedaily.com/releases/2002/03/020328073614.html.Google Scholar Such forces can easily crush turtle shells and have been reported to be able to crush a pig's head with ease.8.Webb G. Manolis C. Australian Crocodiles. Reed New Holland, Sydney, Australia1998Google Scholar They also found that biting force was proportional to size. As in most vertebrates, the depressor muscles that open the crocodilian's jaws are much weaker than those that close the jaws, and it is common folklore that a strong elastic band can prevent even large crocodilians from opening their jaws. With relatively undifferentiated teeth, crocodilians waste little time processing prey before swallowing it. The jaws and teeth crush flesh, carapace, and bone enough to render prey small enough to be swallowed. Larger prey items are broken into smaller chunks by rolling the entire body (termed the death roll) and also by using a whipping action of the head.39.Grenard S. Handbook of Alligators and Crocodiles. Krieger Publishing Co, Malabar, FL1991Google Scholar Contrary to what might be assumed by their large size, crocodilians are surprisingly agile and explosively fast over short distances. Some species have been observed "galloping" at speeds up to 17 km/h (10.6 mph),40.Webb G.J.W. Gans C. Galloping in Crocodylus johnstoni: a reflection of terrestrial activity?.Rec Aust Mus. 1982; 34: 607-618Crossref Google Scholar and even large crocodilians can move rapidly across land at speeds of up to 10 km/h (6.2 mph). The ability to move very quickly over a short distance (eg, an entire body length in less than half a second) contributes to their success as ambush predators. Most adult crocodilians are threatened only by other crocodilians and humans. Generally, the larger species of crocodilians see humans as a potential food source. The average maximum size of male saltwater crocodiles is 5 m, and some individuals may exceed 6 to 7 m.10.Ritchie J. Jong J. Bujang Senang Terror of Batang Lupar. Samasa Press, Kuching, Malaysia1993Google Scholar,41.Webb G.J.W. Messel H. Crawford J. Yerbury M. Growth rates of Crocodylus porosus (Reptilia: Crocodilia) from Arnhem Land, northern Australia.Aust Wildlife Res. 1978; 5: 385-399Crossref Scopus (68) Google Scholar Nile crocodiles typically average 3.5 m in length, although some males may reach 5 m.42.Groombridge B. The distribution and status of world crocodilians.in: Webb G.J.W Manolis S.C. Whitehead P.J. Wildlife Management: Crocodiles and Alligators. Surrey Beatty & Sons, Chipping Norton, Australia1987: 9-21Google Scholar Male American alligators average approximately 3 m, and some occasionally reach 4.5 m.43.Joanen T. McNease L. The management of alligators in Louisiana, USA.in: Webb G.J.W. Manolis S.C. Whitehead P.J. Wildlife Management: Crocodiles and Alligators. Surrey Beatty & Sons, Chipping Norton, Australia1987: 33-42Google Scholar The success of crocodilians as predators is due largely to the shape of their body and their ability to expose only a small part of it (the head), while the bulk of the body remains hidden underwater. The positioning of the internal nares behind the palatal valve and the development of a secondary palate have been instrumental in their success, enabling this minimum exposure posture of eyes, ears, and nostrils above water that lends a crocodilian its stealth profile.8.Webb G. Manolis C. Australian Crocodiles. Reed New Holland, Sydney, Australia1998Google Scholar A palatal valve at the back of the tongue serves to seal the mouth off from the palate and trachea, enabling the jaws to be opened fully underwater without allowing water to enter the throat and trachea. This minimum exposure posture leaves the well-developed sense organs exposed and continually sensing the environment.36.Richardson K.R. Webb G.J.W. Manolis S.C. Crocodiles: Inside and Out. Surrey Beatty & Sons, Chipping Norton, Australia2002Google Scholar Daytime vision is good, and night vision is enhanced by a layer of guanine crystals in the retina (the tapetum lucidum) that reflect light that enters the eye back over the visual sensory cells a second time.36.Richardson K.R. Webb G.J.W. Manolis S.C. Crocodiles: Inside and Out. Surrey Beatty & Sons, Chipping Norton, Australia2002Google Scholar,44.Bellairs Ad'A. The senses of crocodilians.in: Crocodiles: Proceedings of the First Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, New York. Gland, Switzerland1971: 181-190Google Scholar Crocodilian hearing apparatus is the most developed of all reptiles, and its sensitivity is on a par with most mammals. Research has also shown their olfactory and gustatory senses to be highly developed. Recent studies of sense organs in the skin around the jaws (dermal pressure receptors) show the organs' ability to detect very subtle pressure changes in the water—alligators could detect a droplet of water hitting the surface near their head through the resulting pressure waves alone.45.Soares D. Extinct crocodiles had specialized sensory organs to detect water surface disruptions.in: Crocodiles: Proceedings of the 16th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Gainesville, FL. Gland, Switzerland2002: 131Google Scholar Crocodilians can remain underwater for extended periods, which allows them not only to drown prey but also to remain concealed. The amount of time that an animal can stay underwater without surfacing increases with increasing body size. Although most crocodiles stay underwater for an average of 15 minutes per dive, large crocodiles (>4 m in length) are able to stay underwater for up to 2 to 3 hours.46.White F.N. Redistribution of cardiac output in the diving alligator.Copeia. 1969; 1969: 567-570Crossref Google Scholar Following a voluntary dive, heart rate decreases markedly and can drop to as low as 1 to 2 beats/min. Unlike other reptiles, crocodilians have a 4-chambered heart that possesses unique valves both within the heart (cog valve) and in the twin aortas leaving it (foramen of Panizza).47.Webb G.J.W. Comparative cardiac anatomy of the Reptilia, III: the heart of Crocodylus porosus with notes on the complete interventricular septum of crocodiles and birds.J Morph. 1979; 161: 221-240Crossref Scopus (77) Google Scholar The heart's structure serves to divert oxygenated blood flow away from peripheral and nonessential organs during diving, maximizing available oxygen to the brain and other vital organs. Crocodilian hemoglobin has 12 unique bicarbonate binding sites, allowing far more oxygen to be released from the molecule for a given oxygen tension than from the human equivalent. A hybrid human-crocodilian hemoglobin (Hb-Scuba) has been developed and has potential as a synthetic hemoglobin.48.Deepthi S. Johnson A. Sathish R. Pattabhi V. Purification, crystallisation and preliminary x-ray study of haemoglobin from Crocodylus palustris and Crocodylus porosus.Biochim Biophys Acta. 2000; 1480: 384-387Crossref PubMed Scopus (9) Google Scholar One characteristic that is relevant to the analysis of crocodile attacks is that crocodilians will intentionally eat stones, which are stored within the stomach. These stones appear to act as gastroliths to assist in the breakdown of ingested food,8.Webb G. Manolis C. Australian Crocodiles. Reed New Holland, Sydney, Australia1998Google Scholar although a hydrostatic function has also been suggested.49.Cott H.B. Scientific results of an enquiry into the ecology and economic status of the Nile crocodile (Crocodylus niloticus) in Uganda and northern Rhodesia.Trans Zool Soc Lond. 1961; 29: 211-357Crossref Scopus (358) Google Scholar The propensity of crocodilians to retain heavy objects in the stomach means that items such as bullets and lead shot imbedded in prey or carrion remain in the stomach well after the food has been completely digested. A coroner's examination of crocodilian stomach contents that contain human remains may become "complicated" if such items are also present (Figure 2).8.Webb G. Manolis C. Australian Crocodiles. Reed New Holland, Sydney, Australia1998Google Scholar A review of the available literature on Australian crocodile attacks was completed from a variety of sources. The extensive records at Crocodylus Park (Darwin, Northern Territory) were cross-referenced against a Nexis/Lexis and NewsText electronic search of newsprint articles. Crocodile attack has only been coded as a separate injury mechanism since the introduction of the International Classification of Diseases, Tenth Edition in 1997, but data from the National Injury Surveillance Unit were further cross-referenced to the newsprint data. The medical literature was searched using the PubMed database for all references to crocodile or alligator. The herpetologic literature was searched using the Biosis Previews, Zoological Record, and Wildlife and Ecology Studies Worldwide databases for crocodile or alligator attacks. Finally, the Google search engine was used to search for all instances of crocodile attack or alligator attack. All references obtained using this search strategy were then subsequently hand searched for further relevant references. There have been 62 definite, unprovoked attacks by wild saltwater crocodiles, resulting in injury or death to humans, between 1971 and 2004 (Table 1). One attack on a researcher (collecting crocodile eggs, 1986), 2 attacks on wildlife rangers (capturing crocodiles, 1993 and 2002), and 1 attack on a crocodile farmer (collecting crocodile eggs, 2004) that occurred during their work with wild crocodiles were excluded. Likewise, attacks by captive crocodiles were excluded from the analysis.Table 1Saltwater crocodile attacks in the wild, in northern Australia, 1971–2004 The Northern Territory, which contains the largest wild population of saltwater crocodiles within Australia, has accounted for most (63%) attacks, followed by Queensland (24%) and Western Australia (13%) (Table 1). Notwithstanding the relatively low number of attacks during the 34-year period, there has been a tendency toward increasing numbers of nonfatal attacks over time (from 0.1 per year in 1971 to 1980 to 3.3 per year in 2001 to 2004) and relatively stable numbers of fatal attacks over time (mean, 0.5 per year) (Table 2).Table 2Mean number of saltwater crocodile attacks per year in the Northern Territory and Australia The wild population of saltwater crocodiles in the Northern Territory has increased from an estimated 3000 to 5000 in 1971, when the species was protected after 26 years of unregulated hunting, to 50000 nonhatchlings in 198450.Webb G.J.W. Manolis S.C. Whitehead P.J. Letts G.A. A Proposal for the Transfer of the Australian Population of Crocodylus porosus Schneider (1801), from Appendix I to Appendix II of C.I.T.E.S. Technical Report 21. Conservation Commission of the Northern Territory, Darwin, Australia1984Google Scholar and 75000 nonhatchlings in 2000.51.Webb G.J.W. Britton A.R.C. Manolis S.C. Ottley B. Stirrat S. The recovery of Crocodylus porosus in the Northern Territory of Australia: 1971–1998.in: Crocodiles: Proceedings of the 15th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Varadero, Cuba. Gland, Switzerland2000: 196-235Google Scholar The recovery of the population has been characterized by a marked increase in the average size of the saltwater crocodile in the population.51.Webb G.J.W. Britton A.R.C. Manolis S.C. Ottley B. Stirrat S. The recovery of Crocodylus porosus in the Northern Territory of Australia: 1971–1998.in: Crocodiles: Proceedings of the 15th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Varadero, Cuba. Gland, Switzerland2000: 196-235Google Scholar Whether the increased numbers of crocodiles and greater numbers of large crocodiles are implicated in the increased frequency of attacks is unclear. Andau et al52.Andau P. Ambu L. Tsubouchi T. Indication of crocodile recovery and management implications in crocodile conservation in Sabah.in: Crocodiles: Proceedings of the 17th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Darwin, NT, Australia. Gland, Switzerland2004: 204-207Google Scholar concluded that the increased number of saltwater crocodile attacks in Sabah, Malaysia, were the result of increasing numbers of crocodiles. Glasgow53.Glasgow V.L. A Social History of the American Alligator. St Martins Press, New York, NY1991Google Scholar relates how increasing numbers of American alligators and an expanding human population in Louisiana in the 1970s resulted in increased interactions with alligators. The reasons why saltwater crocodile attack humans without any provocation are thought to be as follows:1.Defense of territory: Saltwater crocodiles are highly territorial.8.Webb G. Manolis C. Australian Crocodiles. Reed New Holland, Sydney, Australia1998Google Scholar,54.Lang J.W. Crocodilian behaviour: implications for management.in: Webb G.J.W. Manolis S.C. Whitehead P.J. Wildlife Management: Crocodiles and Alligators. Surrey Beatty & Sons, Chipping Norton, Australia1987: 273-294Google Scholar Males and females establish territories55.Kay W. Fitzsimmons N. Grigg G. Movements of Crocodylus porosus in the Kimberley region of Western Australia: integrating genetic and radio-tracking data.in: Crocodiles: Proceedings of the 17th Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN, Darwin, NT,
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