The Art of Disguise - Camouflage in the Rainforest

Skyrail Nature Diary: August 2010

If an animal is camouflaged in the rainforest, it is at a huge advantage. Because of the high diversity and large number of organisms that live in tropical rainforests, many animals are either hunting or trying not to be hunted.

Animals are generally camouflaged with substrates or patterns common to their habitat - like the Leaf-tailed Gecko (Phyllurus cornutus) is camouflaged with moss covered bark (image 1). Camouflage can also incorporate mimicry to varying levels. Mimicry involves an animal or insect mimicking another species in order to disguise itself. Some species of mantis have young that mimic ants in the way they look and walk. Believe it or not, there are plant species which also possess this quality. Some plants which are not poisonous will mimic other plants which are, therefore benefiting by looking distasteful.

For animals to be camouflaged they need to be a colour that will help them blend into their surroundings, but also have a shape which is not easily recognisable by prey. Green-eyed Tree Frogs (Litoria genimaculata) are a good example of this. This species of frog has a fringe of frilly skin around the edges of its body to break up its visual outline as it sits on the bark of trees. This arboreal species has mottled green/grey, rough textured skin to match the mottled bark on which it lives (image 2). Usually active at night, being camouflaged helps it to ambush insects. However, Green Tree Snakes (Dendrelaphis punctulata) are one animal that can outsmart tree frogs. These animals have great eyesight and look just like a green vine. They have exceptionally good smell and can pick up the scent of a nearby frog by licking the air.

You may wonder why some birds, particularly Kookaburras (genus Dacelo), will perch in trees and stare at the ground, motionless. Although the Kookaburra doesn't have an impressive sense of smell, they have excellent eyesight and can detect incredibly small movements of potential prey, even when the prey is completely camouflaged.

The adult Bush Stone-curlew (Burhinus grallarius) looks remarkably like sticks and leaf litter, while their chicks are striped to blend in with grass and shadows. When threatened, the chicks lay their whole body flat on the ground and blend in perfectly. It would be extremely easy to walk straight over the top of them! Fortunately this species are common in the Barron Gorge National Park (North Queensland, Australia), but has dramatically declined in many areas further south of Australia. These areas have large numbers of foxes, which have no problem sniffing out camouflaged eggs, young and other ground nesting birds (image 3).

The Southern Cassowarry's (Casuarius casuarius) chicks are distinctly different to the adult. The chicks are light brown in colour and have black stripes, whereas the adult cassowary does not. Even though the paternal instincts of the father of the chicks is a good defence against predators, the stripes help the chick camouflage against the vegetation which is also often covered in stripes from shadows. However, this has little value in hiding the animals from the highly sensitive nose of feral pigs (image 5).

Whether it be hiding or hunting, being camouflaged is an extremely useful attribute to have for an animal living in tropical rainforests.

Photos courtesy of the Wet Tropics Management Authority: Image 2, Copyright Daryn Storch; Image 3, Copyright WTMA