Crocodiles Part 2:

Freshwater Crocodiles:

• In comparison to its relative, the Saltwater Crocodile Crocodylus porosus, the Freshwater Crocodile has a narrow snout and a smaller physique and overall size.

• It is grey to tan-brown in colour, with dark patches on the sides and top of the body.

• Even when the mouth is closed, the nostrils and eyes are visible at the top of the skull, and the fine sharp teeth are visible.

• Large triangular scales known as'scutes' run the length of the robust tail, which is nearly half the length of the animal.

• When the legs are spread out in the water, the hind limbs are significantly larger and longer than the forelimbs.

Habitat:

Freshwater Crocodiles inhabit various freshwater environments, including rivers, creeks, pools, billabongs, lagoons, and swamps. During the wet season these habitats become inundated with flood waters which allow the crocodiles to move throughout the flood plains. As the water levels drop the crocodiles tend to congregate in the larger and deeper water bodies, where they prefer to inhabit the shallower waters at the pool edges

Hunting and their diet:

In the wild, Freshwater Crocodiles will eat a variety of invertebrate and vertebrate prey, including crustaceans, insects, spiders, fishes, frogs, turtles, lizards, snakes, birds and mammals. Insects (both aquatic and terrestrial) appear to be the most common food item, followed by fish. Larger crocodiles tend to eat larger prey items, however the average size of prey for all Freshwater Crocodiles is generally small (mostly less than 2cm²). Small prey is usually obtained by a ‘sit-and-wait’ method, whereby the crocodile lies motionless in shallow water and waits for fish or insects to come within close range, before they are snapped up in a sideways action. However, larger prey like wallabies and waterbirds may be stalked and ambushed in a manner similar to that of the Saltwater Crocodile.

Other adaptations:

Freshwater Crocodiles can perform a ‘high walk’ to move overland, whereby the body is held high so that the belly and most of the tail is not touching the ground. Track marks indicate these crocodiles may walk considerable distances at the end of the wet season in search of a dry season refuge. When startled on land a Freshwater Crocodile may leap into a fast ‘gallop’ and rapidly sprint to the water.

Breeding Behaviour:

In the Northern Territory courtship and mating begins at the start of the dry season (June), with egg-laying taking place around 6 weeks later.

The egg-laying period typically lasts for four weeks through August and September. About three weeks before egg-laying starts the gravid female will begin excavating a number of ‘test’ holes at night, usually in a sandbank within 10m of the water’s edge.

Clutch size ranges 4-20, with on average a dozen eggs being laid. Larger females tend to have more eggs in a clutch than do smaller females. The hard-shelled eggs take between two to three months to hatch, depending on the nest temperature. Unlike Saltwater Crocodiles the females do not guard the nest; however they will return and excavate the nest when the eggs have hatched, honing in on the calls of the young inside. Once the young have been uncovered the female helps carry them down to the water and will aggressively protect them for a period of time.