The New Guinea crocodile is a small species of crocodile found on the island of New Guinea. It is grey to brown in color, with darker bandings on the tail and body which become less noticeable as the animal grows. Longitudinal ridges in front of the eyes and some granular scales on the back of the neck between four large scales are distinctive features of this species. The snout is pointed and relatively narrow during juvenile stages and becomes wider as the animal matures.
New Guinea crocodiles occur on the island of New Guinea north of the mountain ridge that runs along the center of the island. They inhabit freshwater swamps, marshes, and lakes. They have been known to enter brackish waters but are generally very rare in coastal areas.
New Guinea crocodiles have a mostly aquatic lifestyle and are largely nocturnal. They spend much of the day underwater, often with their nostrils and eyes above the surface. Powerful side-to-side movements of their tails propel them through the water and they use both tail and legs to steer. When on land, they favor shady, dense areas of undergrowth. They tend to bask in a group during the day, dispersing at night to feed. These crocodiles catch their prey by stealth with a flick of their head, impaling it with their sharp teeth and gripping and crushing it. They are surprisingly agile and can lunge their body upward into the air to catch bats, flying birds, and leaping fish. They can also probe into the mud at the bottom of a river or swamp with their snout to search for crabs and mollusks. New Guinea crocodiles use various vocalizations to communicate with each other. An adult female can produce a repeated throaty "roar" when approached by another adult. The young start communicating with each other while still in the egg; this may help synchronize hatching. Newly hatched juveniles use various yelps and grunts. When startled, a warning sound emitted by one will send all the juveniles diving to the bottom of the water. Adults in the vicinity respond with growls, threats, and attacks.
New Guinea crocodiles are carnivores. Adult feed largely on fish, shrimps, crabs, frogs, snakes, birds, and medium-sized mammals. Newly hatched crocodiles feed on aquatic insects, spiders, tadpoles, freshwater snails, frogs, fish, and small mammals.
New Guinea crocodiles are polygynous meaning that males mate with more than one female in a single mating season. In the northern population, breeding usually takes place during the dry season between August and October. A floating nest composed of vegetation is made in shallow water in an overgrown channel, at the edge of a lake, on a scroll swale, or beside a stream. The female lays a clutch of between 22 and 45 eggs and covers it with further vegetation. The southern population prefers to breed during the wet season. The nest is sometimes built in similar locations to the northern nests but is more often on land, and a smaller number of rather larger eggs is laid. In both populations, the mother stays near the nest during the incubation period, which lasts about 80 days. When the eggs start to hatch, the emerging young are quite vocal, and both male and female crocodiles transport hatching and newly hatched young to open water, carrying them delicately in their mouths. Females become reproductively mature when about 1.6-2 meters (5 ft 3 in-6 ft 7 in) long and males at about 2.5 meters (8 ft 2 in).
The New Guinea crocodile was over-hunted for its valuable skin in the mid 20th century and some eggs and hatchlings are still removed from the nest and raised in enclosures.
According to the IUCN Red List, the total population size of the New Guinea crocodile is 100,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.