Modern rainforest plants are almost identical to those growing 70 million years ago. This means rainforests are one of Earth’s oldest ecosystems outliving many others found in the fossil record. Emerging with these ancient habitats into the modern world come ancient predators like rainforest crocodiles. Rainforest crocodiles are the ancient predators of this primeval habitat, belonging to the same group as the now extinct dinosaurs, the Archosauria.
If you are going to the Amazon Rainforest, rainforest crocodiles are a popular animal to encounter when night spotting for wildlife. This activity is offered by many Amazon Jungle tours.
In this article, I will be giving information on crocodilians then a species overview of some crocodilians found in the world’s rainforests. The term rainforest crocodiles will be used to describe all rainforest crocodilians, including caiman.
Although an old lineage, crocodilians are just as adapted now as ever. They have outlived humans, the dominant predator today, by about 199 million years. Despite this ancient bloodline, crocodilians have an advanced anatomy from an evolutionary perspective. They have features more similar to mammals and birds than to other reptilians. For example, like mammals and birds crocodilians possess a four chambered heart, whereas non-crocodilan reptiles have the less efficient three chambers. Other crocodilian features are their short legs, webbed toes, and long powerful tail.
There are 23 species of crocodilian, which all have a similar shape and colour with the males being the larger sex. One of their main differences is size and this ranges considerably. The smallest is Cuvier’s dwarf caiman (Paleosuchus palpebrosus) of the Amazon Rainforest reaching about 1.5 meters (five feet) and the largest is the imposing saltwater crocodile (Crocodylus porosus) that can reach around 8.5 metres long and lives in the tropical Indopacific realm.
Distribution and Evolution
Most crocodilians are found in tropical areas and all living species are semi-aquatic, but a fully land based crocodilian may have lived in New Caledonia as recently as 3000 years ago. This completely terrestrial way of living can be envisaged when looking how the freshwater crocodiles moves about on land.
In the Triassic period (about 245 million years ago) crocodiles were fully land based and had traits for agility across land, like slender legs, a different angle of the legs, and less digits. However, in the Cretaceous (145 mya) fossils show crocodilians had become amphibious and possessed characteristics adapted to this lifestyle. All crocodilians are lowland creatures and none are thought to have ever passed 1000m above sea level.
Crocodilians eat basically anything they can, dependent on the predator’s size, taking insects, fish, reptiles, mammals (including the odd human) birds and a variety of crustaceans.
There is a softer side to crocodilians, as females are very protective with young. The female crocodilian picks up her hatchlings in her mouth and gently carries them to the water’s edge. Females stay close to their eggs during the nesting months offering protection from predators, which include male crocodilians.
Caiman are commonly found in the Amazon Rainforest and are in the alligator family of crocodilians. Spotting for caiman is a popular nocturnal activity among Amazon Jungle tours. In the Amazon region, the dominant (although sadly now rare) rainforest crocodilian is the black caiman (Melanosuchus niger). This is the only reptile in the alligator family posing the same risk to humans as large crocodiles. Spectacled caiman, however, are common and are one of the many Amazon Rainforest Attractions.
The largest and reportedly most aggressive species is the saltwater crocodile (Crocodylus porosus). You can see this species in the Australian Wet Tropics. This is the probably the best known animal of the Australian tropics although they range well beyond this area. Saltwater crocodiles live around Australia (north of Mackay), the tropical wilderness of New Guinea, throughout Indonesia to India.
Try not to let their name fool you, as saltwater crocodiles are just at home in fresh as they are saltwater. The best time to see wild crocodiles in the Australian Wet Tropics is the dry season, as the temperature is just right for crocodiles to bask on river banks.
If you are in the salty’s territory, as they are known in Australia, a healthy respect for this species can prove life saving. Fatalities are not uncommon but are usually linked to careless or ill-informed behavior.
Saltwater crocodiles can live up to around 100 years, but many of these old timers were hunted and killed during the 1970s. This period contains records of crocodiles up to 8.5 metres in length, whereas nowadays the majority are about 5 to 6 metres long. Thankfully, they are fully protected and well regulated farms were set up for crocodile meat and leather.
You can distinguish a saltwater crocodile from Australia’s freshwater crocodile (Crocodylus johnsoni) by its wide snout. Freshies are a smaller species reaching around 3 metres. This crocodile is only found in Australia, but you wont find them in Australia’s Daintree rainforest as the saltwater crocodile is the dominant species, excluding them from mutual habitat.
All crocodilians are meat eaters. Instead of chewing their food, they grip it with their strong jaws and rip bits off using body movements or swallow it whole. They don’t feed that often and studies on Nile crocodiles (Crocodylus niloticus) found feeding took place as few as 50 times a year.
Morbidly, estimates show that about 200 people are eaten each year by the Nile crocodile, mainly because humans have severely encroached on their habitat making encounters a frequent part of life. This is Africa’s largest crocodile and reaches about 6 meters long. They also live in Madagascar’s river systems and swamps.
Usually solitary, rainforest crocodiles do group together if food is plentiful and even communicate with others. Dominant individuals swim higher up in the water column and mark their territory by splashing their heads onto the water, but in severe drought, territories are ignored and large numbers can be spotted in small bodies of water.
Books on Wildlife
Here is a selection of good books and guides on wildlife to help you learn more about animals and plants in their natural environment.