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Tuesday, February 28, 2017

Toad Tales

Saltwater crocodile

From Wikipedia, the free encyclopedia
The saltwater crocodile (Crocodylus porosus), also known as the estuarine crocodileIndo-Pacific crocodilemarine crocodilesea crocodile or informally as saltie, is the largest of all living reptiles, as well as the largest riparian predator in the world. Males of this species can reach sizes up to at least 6.30 m (20.7 ft) and possibly up to 7.0 m (23.0 ft) in length. However, an adult male saltwater crocodile rarely reaches and exceeds a size of 6 m (19.7 ft) weighing 1,000 to 1,200 kg (2,200–2,600 lb). Females are much smaller and often do not surpass 3 m (9.8 ft). As its name implies, this species of crocodile can live in marine environments, but usually resides in saline and brackish mangrove swampsestuariesdeltaslagoons, 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, and northern Australia.
The saltwater crocodile is a formidable and opportunistic hypercarnivorous apex predator. Most prey are ambushed and then drowned or swallowed whole. It is capable of prevailing over almost any animal that enters its territory, including other apex predators such as sharks, varieties of freshwater and marine fish including pelagic species, invertebrates, such as crustaceans, various reptilesbirds and mammals, including humans. Due to their size, aggression and distribution, saltwater crocodiles are regarded as the most dangerous extant crocodilian to humans.
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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. 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 either small compared to other species or commonly are entirely absent. In addition, an obvious gap is also present between the cervical and dorsal shields, and small, triangular scutes are present between the posterior edges of the large, transversely arranged scutes in the dorsal shield. The relative lack of scutes is considered an asset useful to distinguish saltwater crocodiles in captivity or in illicit leather trading, as well as in the few areas in the field where sub-adult or younger saltwater crocodiles may need to be distinguished from other crocodiles. 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. The head is very large. The largest skull sized that could be scientifically verified was for a specimen in the Muséum national d'Histoire naturelle sourced to Cambodia, the skull length for this specimen was 76 cm (30 in) (female skull lengths of over 45 cm (18 in) are exceptional), with a mandibular length of 98.3 cm (38.7 in) and a maximum width across the skull (near the base) of 48 cm (19 in). The length of the specimen this came from is not known but based on skull-to-total-length ratios for very large saltwater crocodiles its length was presumably somewhere in the 7 m (23 ft 0 in) range.
 Although it is the largest overall living crocodilian and reptile, other crocodilians may have a proportionately longer skull, namely the gharial (Gavialis gangeticus) and the false gharial (Tomistoma schlegelii), skull lengths in the latter have been verified up to 84 cm (33 in) (the largest crocodilian skull verified for a living species), although both of these thin-snouted species have less massive skulls and considerably less massive bodies than the saltwater crocodile. The teeth are also long, with the largest teeth (the fourth tooth from the front on the lower jaw) having been measured at up to 9 cm (3.5 in) in length.  If detached from the body, the head of a very large male crocodile can reportedly weigh over 200 kg (440 lb) alone, including the large muscles and tendons at the base of the skull that lend the crocodile its massive biting strength.
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Saltwater crocodiles, even adults, can breach out of the water in upwards direction to capture food, although are most often seen to do so when enticed by bait as seen here.
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 seasonally vacate parts of Australia if cold spells hit.
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A saltwater crocodile will usually loiter in the water or bask in the sun during much of the day, preferring to hunt at night. A study of seasonal saltwater crocodile behaviour in Australia indicated that they are more active and more likely to spend time in the water during the Australian summer; conversely, they are less active and spend relatively more time basking in the sun during the winter. 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 less time on land except for basking. At times, they tend to spend weeks at sea in search of land and in some cases, barnacles have been observed growing on crocodile scales, indicative of the long periods they spend at sea.
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Saltwater crocodiles hold the record for the highest bite force ever recorded in any animal, with a peak bite force of 16,414 N (3,690 lbf), far surpassing the highest recorded value in the spotted hyena of 4,500 N (1,012 lbf). 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 extremely stiff, almost as hard as bone to the touch, such that it can appear to be 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.

1 comment:

Ur-spo said...

Awesome and fascinating !