New Guinea crocodiles are found in Papua New Guinea (mainland only) and in the Papua Province of Indonesia. This species has been divided into two genetically and morphologically distinct populations (northern and southern), divided by the main cordillera (central highlands) of New Guinea. Both forms are widespread and locally common, with the northern form being found in the Sepik and Ramu River systems and the southern form being found in the Fly and Bamu Rivers and their associated tributaries and lakes in the southwest region of the island, and the tidal forest zone of the Gulf of Papua in the south. (Bolton and Laufa, 1982; Cox, 2010; Hall, 1989)
New Guinea crocodiles inhabit freshwater lakes, swamps, and marshes. Larger crocodiles usually occupy main river channels, while juveniles and smaller individuals tend to inhabit nearby grassy wetlands. Seasonal changes in water levels have marked effects on population density and distribution. (Burgin and Pernetta, 1983; Cox, 2010; Montague, 1983)
This species is a small to medium-sized crocodile with maximum verifiable lengths of 3.5 m for males and 3 m for females. They have relatively narrow snouts and are brown to gray in color, with dark brown to black bands on their bodies and tails; banding is more visible on younger animals. These crocodiles have 66-68 teeth, of which 5 pairs are pre-maxillary, 13-14 are maxillary and 15 are mandibular. (Britton, 2012; Cox, 2010; Hall, 1989)
Northern and southern populations of New Guinea crocodiles differ slightly in morphology. The premaxillary symphysis (a fibrocartilaginous joint) of Southern populations is longer than the maxillary symphysis, while northern populations exhibit premaxillary symphyses that are shorter than the maxillary symphysis. Southern populations have 4-6 post-occipital scales on the neck, while northern populations always have 4 post-occipital scales. Relative skull measurements, however, are comparable between similar-sized individuals of both populations. (Burgin and Pernetta, 1983; Hall, 1989)
New Guinea crocodiles can be morphologically distinguished from saltwater crocodiles (Crocodylus porosus) by differences in the number of belly scales and the arrangement of scales on the nape of the neck. Furthermore, these species tend to prefer different (but overlapping) habitats, with saltwater crocodiles occupying deep freshwater pools and fast-flowing, rocky streams up to 700 miles inland, as well as brackish and coastal areas, and New Guinea crocodiles being found mainly in inland river systems and freshwater swamps and marshes. (Burgin and Pernetta, 1983; Hall, 1989)
Eggs are laid approximately two weeks after mating and incubation typically lasts for 12-13 weeks. Although the mode of gender determination has not been studied in this species specifically, it is nearly certain that they exhibit temperature-dependent sex determination, as do other crocodylians. In the closely related freshwater crocodile (Crocodylus porosus), intermediate incubation temperatures produce males, while lower and higher temperatures produce females. ("The management of crocodiles in captivity: 1. Captive breeding and the management of adult crocodiles", 1989; Britton, 2012; Burgin and Pernetta, 1983; Hall, 1991; Heiser, et al., 2012; Lang and Andrews, 1994)
Courtship behavior of New Guinea crocodiles seems to be triggered by the onset of the rainy season. Courtship and mating has not been observed in the wild, but observations under captivity report that mating individuals display head contact, a submissive display by a male to a female. A male may also blow bubbles underneath a female's body. If a female is willing to mate, she will lift her snout out of the water. A male will then circle and swim over her, pushing her into the water, where mating takes place. Size-specific dominance breeding hierarchies have been observed in captivity. (Burgin and Pernetta, 1983)
Reproductive activities occur throughout the year, with most breeding occurring from September to December. Northern populations form their nests during the dry season (June-October), while southern populations nest during the wet season (November-May). All New Guinea crocodiles form mound nests. Eggs are deposited in a central chamber, with a constant temperature maintained by the decomposition of surrounding organic materials. The majority of nests are constructed on land, above the previous year's high water mark and under the protection of overhanging vegetation, although some are built on floating masses of vegetation. Clutch and egg sizes vary depending on the population, with southern individuals laying fewer, larger eggs that hatch into larger juveniles. Clutch sizes can range from 10 to 48 eggs, with an average incubation time of 83 to 91 days. Egg mass averages 19.8-150.5 g, with a length of 60.0-116.0 mm and a diameter of 37.5-52.3 mm. Eggs exhibit high levels of mortality, due in large part to the high risk of nest flooding, as well as predation. The exact age at which New Guinea crocodiles reach sexual maturity is unknown, but measurements of sexually active individuals have been recorded. Females reach reproductive maturity once they have achieved 55-60% of their total length (1.4-2.0 m snout-vent length), while males reach sexual maturity at around 2.4 m snout-vent length. (Britton, 2012; Burgin and Pernetta, 1983; Cox, 2010; Hall and Johnson, 1987; Hall, 1991)
Hatchling size differs between southern and northern populations. Southern hatchlings range from 26-32 cm in length, about 5 cm longer than hatchlings from the northern population. (Cox, 2010; Hall, 1989)
Like most crocodiles, New Guinea crocodiles exhibit parental care. Females construct nests from surface litter, soil, and plant debris near mixed swamp woodland-forest, providing shelter and food for hatchlings. These crocodiles do reuse nests, but it is not known if the same females return to the same specific nests. Females remain near the nest while eggs are incubating, although it is unknown if they defend their nests as aggressively as other species. It is assumed that hatchlings of this species use vocalization to stimulate one or both of the parents to excavate the nest, after which they guide the hatchlings to the water. Adults of both sexes typically defend their young, both from potential predators and other adults. ("The management of crocodiles in captivity: 1. Captive breeding and the management of adult crocodiles", 1989; Britton, 2012; Burgin and Pernetta, 1983; Hall and Johnson, 1987; Heiser, et al., 2012)
There is little information available regarding the lifespan of this species. In general, mortality is greatest during the early life stages, with adults suffering little mortality outside of predation by humans. There is a record of this crocodile reaching 24.6 years of age in captivity. (Burgin and Pernetta, 1983; de Magalhaes, 2013)
These crocodiles are semi-aquatic, with well-developed limbs that allow them to move easily through the water and over land. They thermoregulate by seeking shade, submerging in water, elevating their head above the substrate, and gaping their mouths. They are primarily nocturnal, tending to remain in covered, protected areas during the day, and are rarely found basking. (Britton, 2012; Johnson, 1973)
There is no reported information on the home range of the species. They are not known to defend specific territories, outside of nests while eggs are incubating. (Britton, 2012; Hall and Johnson, 1987)
While this species' methods of communication have not been specifically studied, it is likely that they employ similar communication methods to other crocodiles. In general, crocodiles communicate through vocalization, using sound extensively in their social behavior. Male crocodiles emit a variety of sounds during courtship and territorial displays. They also slap their heads and tail against the water as territorial displays. Hatchlings emit calls to stimulate adults to excavate nests, and juveniles may use distress calls to attract adult protection. Crocodiles also have musk glands beneath their throats and inside the cloaca, likely used for communication via scent. Their eyes, protected by a nictitating membrane, allow a wide field of binocular vision. ("The management of crocodiles in captivity: 1. Captive breeding and the management of adult crocodiles", 1989; Heiser, et al., 2012)
New Guinea crocodiles are opportunistic feeders. Hatchlings feed on mosquitos, grasshoppers, water bugs, and other aquatic invertebrates, and small juveniles feed heavily on schools of small fish. Adults have been reported to eat insects, fish, frogs, turtles, water snakes and lizards, rails, grebes, and ducks. (Britton, 2012; Burgin and Pernetta, 1983; Montague, 1983)
Adult New Guinea crocodiles have no predators other than humans; however, they are vulnerable to predation from a number of sources before they reach maturity. Eggs are at risk of predation from wild pigs, monitor lizards, and humans. Meanwhile, juveniles may suffer harassment from larger conspecifics and even cannibalism. Other predators of young crocodiles include accipitrid birds of prey and sharks. (Burgin and Pernetta, 1983; Hall and Johnson, 1987; Montague, 1983)
New Guinea crocodiles are considered apex predators and therefore are important in maintaining ecological balance. As juveniles, it is likely they help regulate insect populations and as adults, they help regulate populations of fishes, waterfowls, and amphibians. These crocodiles may serve as a host to a number of parasites. Animals in captivity are particularly susceptible to bacterial and parasitic infections. (Britton, 2012; Junker and Boomker, 2006)
There is a large industry for crocodile skin in Papua New Guinea and crocodile hunting is a major source of income in small villages. (Montague, 1983)
There are no adverse effects of New Guinea crocodiles on humans.
There are worldwide pressures on crocodiles from hunting and displacement by humans. Crocodile hunting is the only means of income for many villages in Papua New Guinea and the majority (75-95%) of the crocodiles being hunted are New Guinea crocodiles. While crocodiles in Papua New Guinea are plentiful and play an important role in the economy, increasing rates of crocodile harvesting could diminish population densities. There are many government regulations in place that help to protect this species of from overhunting. (Bolton and Laufa, 1982; Britton, 2012; Cox, 2010)
Vi Tran (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Jeremy Wright (editor), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
parental care is carried out by females
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
An animal that eats mainly insects or spiders.
animals that live only on an island or set of islands.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).
parental care is carried out by males
marshes are wetland areas often dominated by grasses and reeds.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an animal that mainly eats fish
having more than one female as a mate at one time
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
Living on the ground.
uses sight to communicate
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