Crocodylus novaeguineae

Geographic Range

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.

• Biogeographic Regions
• australian australian
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

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.

• Habitat Regions
• terrestrial terrestrial
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• marsh marsh
• swamp swamp

Physical Description

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.

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.

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.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Development

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.

• Development - Life Cycle
• temperature sex determination

Reproduction

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.

• Mating System
• polygynous polygynous

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.

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

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.

• Parental Investment
• male parental care male parental care
• female parental care female parental care
• pre-hatching/birth
  • protecting
    • female
• pre-weaning/fledging
  • protecting
    • male
    • female
• pre-independence
  • protecting
    • male
    • female

Lifespan/Longevity

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.

Behavior

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.

• Key Behaviors
• terricolous
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

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.

Communication and Perception

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.

• Communication Channels
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • piscivore piscivore
  • insectivore insectivore

• Animal Foods
• birds
• amphibians
• reptiles
• fish
• insects
• other marine invertebrates

Predation

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.

Ecosystem Roles

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.

• Ecosystem Impact
• keystone species keystone species

Economic Importance for Humans: Positive

There is a large industry for crocodile skin in Papua New Guinea and crocodile hunting is a major source of income in small villages.

• Positive Impacts
• food food
• body parts are source of valuable material

Economic Importance for Humans: Negative

There are no adverse effects of New Guinea crocodiles on humans.

Conservation Status

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.

Additional Links

Encyclopedia of Life

Contributors

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.

References

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Burgin, S., J. Pernetta. 1983. The status and ecology of crocodiles in the Purari. Monographiae biologicae , 51: 409-428.

Cox, J. 2010. New Guinea Freshwater Crocodile Crocodylus novaeguineae . Pp. 90-93 in Crocodiles: Status Survey and Conservation Action Plan, Third Edition . Darwin, Australia: Crocodile Specialist Group. Accessed June 17, 2013 at http://www.iucncsg.org/365_docs/attachments/protarea/16_C-9056770a.pdf .

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Hall, P. 1991. Estimation of nesting female crocodilian size from clutch characteristics: correlates of reproductive mode, and harvest implications. Journal of Herpetology , 25/2: 133-141. Accessed June 17, 2013 at http://www.jstor.org/stable/1564639 .

Hall, P. 1989. Variation in geographic isolates of the New Guinea crocodile ( Crocodylus novaeguineae Schmidt) compared with the similar, allopatric, Philippine crocodile ( C. mindorensis Schmidt). Copeia , 1: 71-80. Accessed June 17, 2013 at http://www.jstor.org/stable/1445607 .

Heiser, J., C. Janis, F. Pough. 2012. Vertebrate life . United States of America: Pearson Education.

Johnson, C. 1973. Thermoregulation in crocodilians - I. head-body temperature control in the Papuan-New Guinean crocodiles, Crocodylus novaeguineae and Crocodylus porosus . Comparative biochemistry and physiology , 49/1: 3-28.

Junker, K., J. Boomker. 2006. A check-list of the pentastomid parasites of crocodilians and freshwater chelonians. Onderstepoort Journal of Veterinary Research , 73: 27-36. Accessed June 19, 2013 at http://ojvr.org/index.php/ojvr/article/viewFile/167/161 .

Ladds, P., L. Sims. 1990. Diseases of young captive crocodiles in Papua New Guinea. Australian Veterinary Journal , 67/9: 323-330. Accessed June 19, 2013 at http://www.ncbi.nlm.nih.gov/pubmed/2264804 .

Lang, J., H. Andrews. 1994. Temperature-dependent sex determination in crocodilians. Journal of Experimental Zoology , 270/1: 28-44.

Montague, J. 1983. Influence of water level, hunting pressure and habitat type on crocodile abundance in the Fly River drainage, Papua New Guinea. Biological Conservation , 26/4: 309-339.

de Magalhaes, J. 2013. "AnAge entry for Crocodylus novaeguineae " (On-line). The Animal Ageing and Longevity Database. Accessed June 19, 2013 at http://genomics.senescence.info/species/entry.php?species=Crocodylus_novaeguineae .

Food and Agriculture Organization. The management of crocodiles in captivity: 1. Captive breeding and the management of adult crocodiles. FAO Conservation Guide 22. Rome, Italy: Food and Agriculture Organization of the United Nations. 1989. Accessed June 19, 1913 at http://www.fao.org/docrep/006/t0226e/t0226e00.htm .