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Despite being lethargic, saltwater crocodiles are agile predators and display surprising quickness and speed when necessary, usually during strikes at prey. They are capable of explosive bursts of speed when launching an attack from the water. They can also swim at {{convert|15|to|18|mph|km/h|abbr=on}} in short bursts, around three times as fast as the fastest human swimmers, but when cruising, they usually go at {{convert|2|to|3|mph|km/h|1|abbr=on}}. However, stories of crocodiles being faster than a race horse for short distances across land are little more than urban legend. At the water's edge, however, where they can combine propulsion from both feet and tail, their speed can be explosive.
Despite being lethargic, saltwater crocodiles are agile predators and display surprising quickness and speed when necessary, usually during strikes at prey. They are capable of explosive bursts of speed when launching an attack from the water. They can also swim at {{convert|15|to|18|mph|km/h|abbr=on}} in short bursts, around three times as fast as the fastest human swimmers, but when cruising, they usually go at {{convert|2|to|3|mph|km/h|1|abbr=on}}. However, stories of crocodiles being faster than a race horse for short distances across land are little more than urban legend. At the water's edge, however, where they can combine propulsion from both feet and tail, their speed can be explosive.


Dr. Adam Britton, a leading crocodilian researcher, has also made studies on crocodilian intelligence.<ref>[http://crocodilian.com/big-gecko Big Gecko – Crocodile Management, Research and Filming]. Crocodilian.com. Retrieved on 2011-04-30.</ref> He has compiled a collection of Australian saltwater crocodile calls, and associated them with behaviors.<ref>[http://www.flmnh.ufl.edu/cnhc/croccomm.html Crocodile Communication: Crocodiles, Caimans, Alligators, Gharials]. Flmnh.ufl.edu (1996-03-05). Retrieved on 2011-04-30.</ref> One of his conclusions is that while crocodilian brains are much smaller than those of mammals (as low as 0.05% of body weight in the saltwater crocodile), saltwater crocodiles are capable of learning difficult tasks with very little conditioning. He also infers that the crocodile calls hint at a deeper language ability than currently accepted. They have also learned to track the migratory route of their prey as the seasons change. Britton believes that that saltwater crocodiles are especially clever animals that can possibly learn faster than laboratory rats.
Dr. Adam Britton, a leading crocodilian researcher, has studied crocodilian intelligence.<ref>[http://crocodilian.com/big-gecko Big Gecko – Crocodile Management, Research and Filming]. Crocodilian.com. Retrieved on 2011-04-30.</ref> He has compiled a collection of Australian saltwater crocodile calls, and associated them with behaviors.<ref>[http://www.flmnh.ufl.edu/cnhc/croccomm.html Crocodile Communication: Crocodiles, Caimans, Alligators, Gharials]. Flmnh.ufl.edu (1996-03-05). Retrieved on 2011-04-30.</ref> One of his conclusions is that while crocodilian brains are much smaller than those of mammals (as low as 0.05% of body weight in the saltwater crocodile), saltwater crocodiles are capable of learning difficult tasks with very little conditioning. He also infers that the crocodile calls hint at a deeper language ability than currently accepted. They have also learned to track the migratory route of their prey as the seasons change. Britton believes that saltwater crocodiles are especially clever animals that can possibly learn faster than laboratory rats.


=== Hunting and diet ===
=== Hunting and diet ===

Revision as of 17:42, 7 July 2013

Saltwater crocodile
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Reptilia
Order:
Crocodylia
Family:
Crocodylidae
Genus:
Crocodylus
Species:
C. porosus
Binomial name
Crocodylus porosus
Schneider, 1801
Range of the saltwater crocodile in black

The saltwater crocodile (Crocodylus porosus), also known as saltie, estuarine or Indo-Pacific crocodile, is the largest of all living reptiles, as well as the largest terrestrial and riparian predator in the world. The males of this species can reach sizes of up to 7 m (23 ft) and weigh as much as 2,000 kg (4,400 lb).[2] However, an adult male saltwater crocodile is generally between 4.3 and 5.2 m (14 and 17 ft) in length and weighs 400 to 1,000 kg (880–2,200 lb), rarely growing larger.[3] Females are much smaller and often do not surpass 3 m (9.8 ft). As its name implies, this crocodile can live in salt water, but usually resides in mangrove swamps, estuaries, deltas, lagoons, and lower stretches of rivers. They have the broadest distribution of any modern crocodile, ranging from the eastern coast of India, throughout most of Southeast Asia, stretching south to northern Australia, and historically ranging as far west as off the eastern coast of Africa and as far east as waters off the coast of Japan.

The saltwater crocodile is a formidable, opportunistic, and adaptable predator capable of taking almost any animal that enters its territory. It is an apex predator which preys on a variety of fish, crustaceans, reptiles, birds and mammals, including other predators. It is an ambush predator, waiting for a suitable moment to attack. It has the strongest bite of any animal today, but its teeth are not designed to rip flesh, but to hold onto the prey item, which is an advantage that reduces the animal's chance of escape.[4] These two properties allow the crocodile to catch and drag the animal into the water with the minimal possibility of losing its prey. Then, the prey item is swallowed whole or torn into pieces either by death roll or by sudden jerks of the head. Saltwater crocodiles are considered as the most dangerous species of crocodiles to humans, although attacks and killing are rare.[5]

Saltwater crocodiles are more territorial than other crocodilians, and are less tolerant of their own kind. Most crocodiles are social animals, sharing basking spots and food. Saltwater crocodiles do not fall into this category however, especially in the case of adult males of the species. They are extremely territorial and will fight off any intruders. The adult male will share his territory with a female. Saltwater crocodiles mate in the wet season, laying eggs in a nest made into a mound of mud and vegetation. The female guards the nest and hatchlings from predators. Conservation efforts were successful in this species, and it has recovered since the 1970s. Today, they aren't endangered in many countries. However, some populations are still at risk.

Characteristics

Saltwater crocodile skull from The Museum of Zoology, Russia
Head of a saltwater crocodile

The saltwater crocodile has a wide snout compared to most crocodiles. However it has a longer muzzle than the mugger crocodile; its length is twice its width at the base.[6] The saltwater crocodile has fewer armour plates on its neck than other crocodilians. On this species, a pair of ridges runs from the eyes along the centre of the snout. The scales are oval in shape and the scutes are small compared to other species.[7] The adult saltwater crocodile's broad body contrasts with that of most other lean crocodiles, leading to early unverified assumptions the reptile was an alligator.[8] The head is very large. Skull lengths more than 75 cm (30 in) have been confirmed for the species and mandibular length has been reported up to 98.3 cm (38.7 in) (female skull lengths of over 50 cm (20 in) are exceptional).[9][10] The teeth are also long, with the largest teeth (the fourth tooth from the front on the lower jaw) having been measured to 9 cm (3.5 in) in length.[11][12] If detached from the body, the head of a very large male crocodile can reportedly scale over 200 kg (440 lb) alone.[13]

Young saltwater crocodiles are pale yellow in colour with black stripes and spots on their bodies and tails. This colouration lasts for several years until the crocodiles mature into adults. The colour as an adult is much darker greenish-drab, with a few lighter tan or grey areas sometimes apparent. Several colour variations are known, and some adults may retain fairly pale skin, whereas others may be so dark as to appear blackish. The ventral surface is white or yellow in colour on crocodiles of all ages. Stripes are present on the lower sides of their bodies, but do not extend onto their bellies. Their tails are grey with dark bands.[14][15]

Size

Sweetheart, a large crocodile, at about 5.1 m (17 ft)

Newly hatched saltwater crocodiles measure about 25 to 30 cm (9.8–11.8 in) long and weigh an average of 70 g (2.5 oz).[16] By their second year, young crocodiles will grow to 1 m (3.3 ft) long and weigh 2.5 kg (5.5 lb).[17] Males reach sexual maturity at around 3.3 m (11 ft) at around 16 years of age, while females reach sexual maturity at 2.1 m (6.9 ft) and 12–14 years of age.[15] An adult male saltwater crocodile is normally 4.3 to 5.2 m (14–17 ft) long weighing 400 to 1,000 kg (880–2,200 lb). However, large, mature males can exceed 6 m (20 ft) in length and weigh more than 1,000 kg (2,200 lb). Largest living individuals can surpass 7.1 metres (23 ft). Due to extensive poaching during the 20th century, such individuals are extremely rare today, as it takes a long time for the crocodiles to attain those sizes. There is also the possibility of certain genes that allowed for such big sizes being lost in the overall gene pool due to trophy hunting. However, with recent restoration of saltwater crocodile habitat and reduced poaching, numbers of large crocodiles are increasing, especially in Odisha, India. Recently, Guinness has accepted a 7.1-metre (23 ft), 2,000-kg (4,400-lb) male saltwater crocodile living within Bhitarkanika Park in Odisha.[18] Although, due to the difficulty of trapping and measuring a very large living crocodile, the accuracy of these dimensions are yet to be verified. Currently, four other crocodiles over 6 m (20 ft) live in the Bhitarkanika Park. In the future, if conservation efforts pay off, these large individuals could be more common.[19] This species is the only extant crocodilian to regularly reach or exceed 5.2 m (17 ft).[13]

The main determinant of weight is length. The weight of a crocodile will increase steeply as length increases. A 10 cm (3.9 in) increase in a 1 m (3.3 ft) crocodile would result in a 900 g (2.0 lb) increase in weight, but a 34 kg (75 lb) gain in the case of a 5 m (16 ft) long individual.[17] This explains 6 m (20 ft) individuals being more than twice the weight of 5 m (16 ft) individuals. Weight can also vary enormously based on condition and age; older males tend to outweigh younger ones since they maintain prime territories with access to better, more abundant prey. For example, crocodiles at 4.8 m (16 ft) long usually range in mass from 422 to 950 kg (930 to 2,094 lb). On average, though, these 4.8 m (16 ft) individual would weigh around 520 kg (1,150 lb), and at 5.5 to 5.8 m (18–19 ft) would weigh about 1,000 kg (2,200 lb).[8] This species has the greatest sexual dimorphism of any modern crocodilian, with the females being much smaller than males. Typical female body lengths range from 2.3 to 3.5 m (7.5–11.5 ft).[8] Females at 3 m (9.8 ft) in length, such as Connie and Cookie kept at the Australia Zoo, weigh 150 kg (330 lb).[20] A female of a median length of 2.7 m (8.9 ft) will weigh about 80 kg (180 lb) to 100 kg (220 lb).[17] The largest female on record measured about 4.2 m (14 ft).[13]

Distribution and habitat

Saltwater crocodile jumping up at Adelaide River
Video of a jumping crocodile at Adelaide River
Saltwater crocodile sunning itself
Large crocodile in park

The saltwater crocodile is one of the three crocodilians found in India, the other two being the more widespread, smaller mugger crocodile and the narrow-snouted, fish-eating gharial.[21] Apart from the eastern coast of India, the saltwater crocodile is extremely rare in the Indian subcontinent. A huge population, consisting of many large adults, several over 6 m (20 ft), including a 7 m (23 ft) male, is present within the Bhitarkanika Wildlife Sanctuary of Odisha and they are known to be present in smaller numbers throughout the Indian and Bangladesh portions of the Sundarbans.

In northern Australia (which includes the northernmost parts of the Northern Territory, Western Australia, and Queensland), the saltwater crocodile is thriving, particularly in the multiple river systems near Darwin (such as the Adelaide, Mary, and Daly Rivers, along with their adjacent billabongs and estuaries), where large individuals of more than 5 m (16 ft) in length are not uncommon. The saltwater crocodile population in Australia is estimated at between 100,000 and 200,000 adults. In Australia, the species coexists with the smaller, narrow-snouted Johnston's or freshwater crocodile. Their range extends from Broome in Western Australia through the entire Northern Territory coast all the way south to Rockhampton in Queensland. The Alligator Rivers in the Arnhem Land region are misnamed due to the resemblance of the saltwater crocodile to alligators as compared to freshwater crocodiles, which also inhabit the Northern Territory.[22] In New Guinea, they are also common, existing within the coastal reaches of virtually every river system in the country, along with all estuaries and mangroves, where they overlap in range with the rarer, less aggressive New Guinea crocodile. They are also present in varying numbers throughout the Bismarck Archipelago, the Kai Islands, the Aru Islands, the Maluku Islands, and many other islands within the region, including Timor, and most islands within the Torres Strait.

The saltwater crocodile was historically known to be widespread throughout south-east Asia, but is now extinct throughout much of this range. This species has not been reported in the wild for decades in most of Indochina and is extinct in Thailand, Laos, Vietnam, and possibly Cambodia. The status of this species is critical within much of Myanmar, but there is a stable population of many large adults present in the Irrawaddy Delta.[23] Probably, the only country in Indochina still harbouring wild populations of this species is Myanmar. Although saltwater crocodiles were once very common in the Mekong Delta (from where they disappeared in the 1980s) and other river systems, the future of this species in Indochina is now looking grim. However, it is also the least likely of crocodilians to become globally extinct due to its wide distribution and almost precolonial population sizes in Northern Australia and New Guinea.

The population is sporadic in Indonesia and Malaysia, with some areas harbouring large populations (Borneo and Sumatra, for example) and others with very small, at-risk populations (e.g., Peninsular Malaysia). Despite the close proximity to the crocodile hot-bed of northern Australia, crocodiles no longer exist in Bali. This species is also reportedly extinct on Lombok, Komodo and most of Java. A small population may remain within Ujung Kulon National Park in western Java. The saltwater crocodile is also present in very limited parts of the South Pacific, with an average population in the Solomon Islands, a very small and soon to be extinct population in Vanuatu (where the population officially stands at only three) and a decent but at-risk population (which may be rebounding) in Palau. They once ranged as far west as the east coast of Africa at the Seychelles Islands. These crocodiles were once believed to be a population of Nile crocodiles, but they were later proven to be Crocodylus porosus.[8]

On a beach in Darwin, Australia

Because of its tendency to travel very long distances at sea, individual saltwater crocodiles have been known to occasionally appear in areas far away from their general range. Vagrant individuals have historically been reported on New Caledonia, Iwo Jima, Fiji, and even in the relatively frigid Sea of Japan (thousands of miles from their native territory.) In late 2008/early 2009, a handful of wild saltwater crocodiles were verified to be living within the river systems of Fraser Island, hundreds of kilometres from, and in much cooler water than, their normal Queensland range. These crocodiles did indeed migrate south to the island from northern Queensland during the warmer wet season and presumably returned to the north upon the seasonal temperature drop. Despite the surprise and shock within the Fraser Island public, this is apparently not new behaviour, and in the distant past wild crocodiles had been reported occasionally appearing as far south as Brisbane during the warmer wet season.

Saltwater crocodiles generally spend the tropical wet season in freshwater swamps and rivers, moving downstream to estuaries in the dry season, and sometimes travelling far out to sea. Crocodiles compete fiercely with each other for territory, with dominant males in particular occupying the most eligible stretches of freshwater creeks and streams. Junior crocodiles are thus forced into the more marginal river systems and sometimes into the ocean. This explains the large distribution of the animal (ranging from the east coast of India to northern Australia), as well as its being found in the odd places on occasion (such as the Sea of Japan). Like all crocodiles, they can survive for prolonged periods only in warm temperatures, and crocodiles will seasonally vacate parts of Australia if cold spells hit.[24]

Biology and behaviour

A saltwater crocodile off Maconacon

The primary behavior to distinguish the saltwater crocodile from other crocodiles is its tendency to occupy salt water. Though other crocodiles also have salt glands that enable them to survive in saltwater, a trait which alligators do not possess, most other species do not venture out at sea other than extreme conditions. The only other species that exhibits regular seagoing behavior is the American crocodile, but still not considered as marine as the saltwater crocodile. As its alternate name "sea-going crocodile" implies, this species travels between areas separated by sea or simply uses the ease of traveling through water, to travel across long distances on the same land mass, such as Australia. In a similar fashion to migratory birds using thermal columns, saltwater crocodiles use ocean currents to travel long distances.[25] In a study, 20 crocodiles were tagged with satellite transmitters; 8 of these crocodiles ventured out into open ocean, in which one of them travelled 590 km (370 mi) in 25 days. Another specimen, a 4.84-m-long male, travelled 411 km (255 mi) in 20 days. Without having to move around much, sometimes simply by floating, the current-riding behavior allows for energy saving. They even interrupt their travels, when the currents are against the desired direction of travel, in sheltered bays, for a few days until the currents change direction.[25] Crocodiles also travel up and down in river systems, periodically.[25]

Generally very lethargic, a trait which helps it survive months at a time without food, the saltwater crocodile typically loiters in the water or basks in the sun through much of the day, preferring to hunt at night. A study of seasonal saltwater crocodile behaviour in Australia indicated they are more active and more likely to spend more time in water in the Australian summer and less active and spend relatively more time basking in the sun during the winter.[26] Saltwater crocodiles, however, are among the most active of all crocodilians, spending more time cruising and active, especially in water. They are much less terrestrial than most species of crocodiles, spending little time on land other than basking. At times, they can spend weeks at sea in search of land and in some cases, barnacles have been observed growing on crocodile scales, pointing out at the long periods they spend at sea.[27]

Saltwater crocodile with a GPS-based satellite transmitter attached to its head for tracking

Despite being lethargic, saltwater crocodiles are agile predators and display surprising quickness and speed when necessary, usually during strikes at prey. They are capable of explosive bursts of speed when launching an attack from the water. They can also swim at 15 to 18 mph (24 to 29 km/h) in short bursts, around three times as fast as the fastest human swimmers, but when cruising, they usually go at 2 to 3 mph (3.2 to 4.8 km/h). However, stories of crocodiles being faster than a race horse for short distances across land are little more than urban legend. At the water's edge, however, where they can combine propulsion from both feet and tail, their speed can be explosive.

Dr. Adam Britton, a leading crocodilian researcher, has studied crocodilian intelligence.[28] He has compiled a collection of Australian saltwater crocodile calls, and associated them with behaviors.[29] One of his conclusions is that while crocodilian brains are much smaller than those of mammals (as low as 0.05% of body weight in the saltwater crocodile), saltwater crocodiles are capable of learning difficult tasks with very little conditioning. He also infers that the crocodile calls hint at a deeper language ability than currently accepted. They have also learned to track the migratory route of their prey as the seasons change. Britton believes that saltwater crocodiles are especially clever animals that can possibly learn faster than laboratory rats.

Hunting and diet

Feeding young adult in captivity, Western Australia

The saltwater crocodile is an opportunistic apex predator capable of taking nearly any animal that enters its territory, either in the water or on land. Like most crocodilians, they are not picky eaters and readily vary their prey selection based on availability, but are not voracious eaters, as they are able to survive on relatively little food for a prolonged period. The saltwater crocodile may take animals of almost any variety as it becomes available to them and due to the enormous power, aggression and size of the species, it may take the broadest of prey species of any modern crocodilian.[24] Hatchlings are restricted to feeding on smaller animals, such as small fish, frogs, insects and small aquatic invertebrates. In addition to these prey items, juveniles also take a variety of freshwater and saltwater fish, various amphibians, crustaceans, molluscs, such as large gastropods and cephalopods, birds, small to medium-sized mammals, and other reptiles, such as snakes and lizards. The larger the animal grows, the greater the variety of animals it includes in its diet, although relatively small prey are taken throughout the lifetime of a crocodile even as an adult. Among crustacean prey, large mud crabs of the genus Scylla are frequently consumed especially in mangrove habitats. Ground-living birds, such as emu and different kinds of water birds, are the most commonly preyed upon birds, due to the increased chance of encounter.[30] Even swift-flying birds and bats may be snatched if they come close to the surface of water,[24] as well as wading birds, while the birds are patrolling the shore, looking for food.[17] Mammalian prey of juveniles and subadults are usually up to the size of small species of ungulates, such as the greater mouse-deer and hog deer, seldom attacking larger animals. Various mammalian species including, crab-eating macaques, gibbons, porcupines, wallabies, mongoose, civets, flying foxes, hares, rodents, badgers, otters, fishing cats and chevrotains are readily taken when encountered. Large specimens, even the oldest males don't pass on the opportunity to catch small species when the opportunity arises.

C. porosus tearing apart a pig carcass for consumption

Adult saltwater crocodiles often prefer larger prey such as large mammals, to save energy. They can potentially eat any animal within their range, including other predators. Animals taken by adult crocodiles include, deer, such as sambar, muntjac and chital, wild boar, tapirs, monkeys, kangaroos, dingos, dholes, jackals, orangutans, turtles, pythons, monitor lizards, Asian antelopes, such as serow and nilgai, and large bovines, such as banteng, water buffalo, and gaur. As a seagoing species, the saltwater crocodile also preys on a variety of salt water bony fish and other marine animals, including sea snakes, sea turtles, which are usually taken during mating season when the turtles are closer to shore, sea birds, dugongs, rays, and small sharks,[24][31] which are usually coastal species, such as reef sharks, nurse sharks, and even small bull sharks.[32] Any type of domestic livestock, such as chicken, sheep, pigs, horses, and cattle, or pets may be taken opportunistically as prey. Saltwater crocodiles are also dangerous to humans if they feel threatened.[19][24] They are dominant over other crocodilians, regularly outcompeting and occasionally killing and eating other species, as has been recorded largely with freshwater crocodiles in Australia.[8] Other large predators within their range, like sun bears, leopards and tigers[33] are occasionally taken by adult crocodiles. Water buffalo and gaur, which may weigh over a ton, are considered conventionally as the largest prey taken by male crocodiles. Perhaps the only nonmarine animal in this species' range this crocodile has not been known to prey on is the Asian elephant. It is an extremely powerful animal; in one case, a one-tonne Suffolk stallion known to haul over two tonnes was pulled into water to its demise by a large male saltwater crocodile.[13]

Adult male saltwater crocodile in captivity, Australia

A crocodile usually waits for its prey to get close to the water's edge before striking, using its great strength to drag the animal back into the water. Many prey animals are killed by the impact of the great jaw pressure of the saltwater crocodile, although some animals are killed by drowning after the crocodile has pulled them into the water.[34] The saltwater crocodile's typical hunting technique with large prey is known as the death roll; it grabs onto the animal and rolls powerfully. This throws any struggling large animal off balance, making it easier to drag it into the water.

Like all extant crocodilians, the sharp but peg-like teeth are well-suited to seize and kill various prey, but they are not well-suited to tearing flesh off of large prey items as is the dentition and claws of many mammalian carnivores, the hooked bills and talons of raptorial birds, or the serrated teeth of sharks. However, this is an advantage rather than a disadvantage to the crocodile since the properties of the teeth allow it to hold onto prey with the least possibility of the prey animal to escape. Otherwise combined with the exceptionally high bite force, the flesh would easily cut through, creating an escape opportunity for the prey item. Prey such as fish, crabs, and small mammals are swallowed whole, while larger prey are thrashed around after they are killed, often either in a death roll-like action or by being flung back and forth in the air, until a limb or chunk of flesh separates and can be swallowed.

Bite

Crocodilians have the strongest bite of any extant animal. A large crocodile can crush a full-grown bovid's skull between its jaws. A 5.2 m (17 ft) long saltwater crocodile has been confirmed as having the highest bite force ever recorded for an animal in a laboratory setting. It was able to apply a bite force value of 3,700 lbf (16,000 N), and thus surpassed the previous record of 2,125 lbf (9,450 N) made by a 3.9 m (13 ft) long American alligator.[35][36] Taking the measurements of several 5.2 m (17 ft) crocodiles as reference, the bite forces of 6 m (20 ft) individuals were estimated at 7,700 lbf (34,000 N).[4] The study, lead by Dr. Gregory M. Erickson, also shed light to the larger, extinct species of crocodilians. Since crocodile anatomy has changed only slightly for the last 80 million years, current data on modern crocodilians can be used to estimate the bite force of extinct species. An 11 to 12 m (36–39 ft) long Deinosuchus would apply a force of 23,100 lbf (103,000 N), twice that of the latest, higher bite force estimations of Tyrannosaurus rex.[4] The extraordinary bite of crocodilians is a result of their anatomy. The space for the jaw muscle in the skull is very large, which is easily visible from the outside as a bulge at each side. The nature of the muscle is so stiff, it is almost as hard as bone to touch, as if it were the continuum of the skull. Another trait is that most of the muscle in a crocodile's jaw is arranged for clamping down. Despite the strong muscles to close the jaw, crocodiles have extremely small and weak muscles to open the jaw. The jaws of a crocodile can be securely shut with several layers of duct tape.

Reproduction

Hatchling in an aquarium, bred in captivity
Young saltwater crocodiles

Saltwater crocodile mate in the wet season, when water levels are highest. In Australia, the male and female engage in courtship in September and October, and then the female lays eggs between November and March. The female selects the nesting site, and both parents will defend the nesting territory, which is typically a stretch of shore along tidal rivers or freshwater areas. The nest is a mound of mud and vegetation, usually measuring 175 cm (69 in) long and 53 cm (21 in) high. The female typically lays from 40 to 60 eggs, but some clutches have included up to 90. The eggs measure on average 8 by 5 cm (3.1 by 2.0 in) and weigh 113 g (4.0 oz) on average. These are relatively small, as the average female saltwater crocodile weighs around five times as much as a freshwater crocodile, but lays eggs that are only about 20% larger in measurement and 40% heavier than those in the smaller species.[17] Although the female guards the nest for 80 to 98 days, the loss of eggs is often high due to flooding and occasionally to predation. As in all crocodilians, sex of the hatchling is determined by temperature, with relatively low temperatures producing mainly females, and high temperatures producing mainly males. In Australia, goannas commonly eat freshwater crocodile eggs (feeding on up to 95% of clutch if discovered), but are relatively unlikely to eat saltwater crocodile eggs due to the vigilance of the imposing mother.[17]

As in all crocodilian species, the female saltwater crocodile exhibits a remarkable level of maternal care for a reptile. She excavates the nest in response to calls from the hatchlings, and even gently rolls eggs in her mouth to assist hatching. The female will then carry the hatchlings to water, and remains with the young for several months. Despite her diligence, losses of baby crocodiles are heavy due to various predators and unrelated crocodiles of their own species. Around 1% of the hatchlings will survive to adulthood.[37] The young naturally start to disperse after around 8 mo, and start to exhibit territorial behaviour at around 2.5 yr old. However, even females will not reach proper sexual maturity for another 10 years. Saltwater crocodiles that survive to adulthood can attain a very long lifespan, with a life expectancy of at least 70 years, and some individuals possibly exceed 100 years.[38][15] While adults have no natural predators, baby saltwater crocodiles may fall prey to monitor lizards, predatory fish, various aquatic and raptorial birds, larger crocodiles, and many other predators. Juveniles may also fall prey to tigers and leopards in certain parts of their range, although encounters between these predators are rare and cats are likely to avoid areas with saltwater crocodiles.

Conservation status

Saltwater crocodile

In addition to being hunted for its meat and eggs, the saltwater crocodile has the most commercially valuable skin of any crocodilian, and unregulated hunting during the 20th century caused a dramatic decline in the species throughout its range, with the population in northern Australia reduced by around 95% by 1971. Illegal hunting still persists in some areas, with protection in some countries ineffective, and trade is often difficult to monitor and control over such a vast range. Despite this, the species has since made a dramatic recovery in recent decades. Because of its resurgence, the species is considered of least concern for extinction. Currently, the species is listed in CITES as follows:

  • Appendix I (prohibiting all commercial trade in the species or its byproducts): All wild populations except for those of Australia, Indonesia and Papua New Guinea
  • Appendix II (commercial trade allowed with export permit; import permits may or may not be required depending on the laws of the importing country): Australia, Indonesia and Papua New Guinea wild populations, plus all worldwide populations bred in captivity for commercial purposes

Habitat loss continues to be a major problem. In northern Australia, much of the nesting habitat of the saltwater crocodile has been destroyed by the trampling of feral water buffalo, although buffalo eradication programs have now reduced this problem considerably. Even where large areas of suitable habitat remain, subtle habitat alterations can be a problem, such as in the Andaman Islands, where freshwater areas, used for nesting, are being increasingly converted for human agriculture. After the commercial value of crocodile skins waned, perhaps the greatest immediate challenge to implementing conservation efforts has been the occasional danger the species can be to humans and the resulting negative view of the crocodile.[37]

Relationship with humans

Attacks on humans

Saltwater crocodiles have a strong tendency to treat humans in their territory as prey, and have a long history of attacking humans who stray into their territory. Given their power, size, and speed, survival of a direct predatory attack is unlikely if the crocodile is able to make contact. In distinct contrast to the American policy of encouraging a certain degree of habitat coexistence with alligators, the only recommended policy for dealing with saltwater crocodiles is to avoid their territory whenever possible, as they tend to be highly aggressive when encroached upon.[39]

No Swimming sign from the Kakadu National Park.

Exact data on attacks are limited outside of Australia. In Australia, attacks are fairly rare and usually appear in national news publications when they occur; about one or two fatal attacks are reported per year.[40] The low level of attacks may be due to extensive efforts by wildlife officials in Australia to post crocodile warning signs at many at-risk billabongs, rivers, lakes, and beaches. In the large Aboriginal community of Arnhem Land, attacks frequently go unreported. Also, recent, less-publicised attacks have been reported in Borneo,[41] Sumatra,[42] eastern India (Andaman Islands),[43][44] and Burma.[45]

Many attacks in areas outside of Australia are believed to go unreported, with one study posting up to 20 to 30 attacks occur every year. Some attacks appear to be territorial rather than predatory in nature, with crocodiles over two years in age often attacking anything that comes into their area (including boats). Humans can usually escape alive from such encounters, which comprise for about half of all attacks. Non-fatal attacks usually involve crocodiles of 3 m (9.8 ft) or less in length. Fatal attacks, most likely predatory in nature, commonly involve larger crocodiles with an average estimated size of 4.3 m (14 ft). Under normal circumstances, Nile crocodiles are believed to be responsible for a considerably greater number of fatal attacks on humans than saltwater crocodiles. This is most likely because of the plethora of people in Africa who rely on riparian areas for their livelihood, which is less prevalent in most of Asia and certainly less so in Australia.[46]

During the Japanese retreat in the Battle of Ramree Island on 19 February 1945, saltwater crocodiles may have been responsible for the deaths of over 400 Japanese soldiers. British soldiers encircled the swampland through which the Japanese were retreating, condemning the Japanese to a night in the mangroves which were home to thousands of saltwater crocodiles. Another notorious crocodile attack was in 1985, on ecofeminist Val Plumwood, who survived the attack.[47][48]

In search for the largest living crocodile

The largest size recorded of a saltwater crocodile is the subject of considerable controversy. The reason behind unverified sizes is either the case of insufficient/inconclusive data or exaggeration from a hunter's point of view. This section is dedicated to examples of the largest saltwater crocodiles recorded by any individual, amateur or professional, with the aim of satisfying the public interest without creating data pollution. Below, in the order starting from the largest, are some examples of large crocodiles, confirmed or unconfirmed, recorded throughout history.

  • James R. Montgomery, who ran a plantation near to the Lower Kinabatangan Segama Wetlands in Borneo from 1926–1932, claimed to have netted, killed, and examined numerous crocodiles well over 6.1 m (20 ft) there, including a specimen he claims measured 10 m (33 ft). However, no one scientifically confirmed any of Montgomery's specimens and no voucher specimens are known.[13]
Lolong, the largest live-caught saltwater crocodile
  • A crocodile shot in the Bay of Bengal in 1840 was reported at 10 m (33 ft).
  • A crocodile shot in Queensland in 1957, nicknamed Kris the croc, was reported to be 8.63 m (28.3 ft) long, but no verified measurements were made and no remains of this crocodile exist.[49][50] A "replica" of this crocodile has been made as a tourist attraction.[51][52][53]
  • The skull of crocodile shot in Odisha, India,[54] was claimed to measure 7.6-metre (25 ft) in life, but when given scholarly examination, was thought to have come from a crocodile of a length no greater than 7 m (23 ft).[55]
  • A reported 7.6-m crocodile was killed in the Hooghly River in the Alipore District of Calcutta. However, examinations of the animal's skull actually indicated it ranged from 6.0 to 6.7 m (19.7–22.0 ft).[13]
  • The record size in Papua New Guinea was 6.32 m (20.7 ft) for a specimen shot in May 1966 along the northeastern coast. This specimen had a belly girth of 2.74 m (9.0 ft)[13]
  • Another notable New Guinea giant, which drowned after entanglement in a fisherman's net in 1979, measured 6.2 m (20 ft), with a skull length of 72 cm (28 in).[13]
  • In September 2011, a 6.17 metres (20.2 ft) specimen was captured alive in the Philippines, making it one of the largest specimens ever reliably measured snout-to-tail. This specimen, nicknamed Lolong and weighing roughly 1,075 kg (2,370 lb), had a past as a possible man-eater and was being kept alive as an attraction in a local zoo.[56][57][58][59][60][61] Lolong died on 10 February 2013.[62]
  • The official record length for a crocodile from Australia was 6.15 m (20.2 ft) for a specimen killed in the McArthur River in June 1960.[13]
  • Another Australian giant shot 16 years after that, an old male nicknamed "Big Gator" that had become a habitual predator of local cattle, was found after being shot to have measured 6.1 m (20 ft) and weighed 1,097 kilograms (2,418 lb).[13]

See also

References

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  40. ^ Caldicott, David G.E. (2005). "Crocodile Attack in Australia: An Analysis of Its Incidence and Review of the Pathology and Management of Crocodilian Attacks in General". Wilderness & Environmental Medicine. 16 (3): 143–159. doi:10.1580/1080-6032(2005)16[143:CAIAAA]2.0.CO;2. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
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  56. ^ “Lolong” holds world record as largest croc in the world. Pawb.gov.ph (2011-11-17). Retrieved on 2012-05-24.
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