You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2 below.
Australia's camouflaged creatures
Many species of animal in Australia protect themselves by using camouflage — a way of “hiding” by blending into the surroundings.
A
Most species use camouflage to some extent. If they are convincing, they survive to pass their genes on to future generations. After generations of natural selection, animals can develop astonishingly complex camouflage techniques, manipulating shape, colour and movement. The principle of camouflage is to make it economically unviable for a predator to pursue a particular species of prey, explains Professor Mark Elgar of the University of Melbourne. Camouflage increases search time and, as a consequence, the predator will simply target another species, either because it doesn't see the camouflaged individual or it finds something more obvious.
B
The easiest way for an animal to disguise itself is to be invisible in its surroundings. To that end, stick and leaf insects have evolved complex camouflage to hide themselves from predators. Many have the texture of sticks or dry leaves, while others imitate living foliage, even the veins in a leaf. Some insects develop blemishes to match spots caused by disease. A convincing appearance only works if its owner also acts the part, so during the day the creature stays motionless or sways like a dead leaf in the breeze. If disturbed, it falls to the ground and stays still. Entomologist Paul Zborowski rates the desert insects of Central Australia as the most convincingly disguised creatures he has seen. Most behave like stones and do not move all day, feeding only at night.
C
A tawny frogmouth sitting motionless on a stump also illustrates the importance of pairing a persuasive costume with behaviour. Professor Gisela Kaplan of the University of New England says the frogmouth's skill at camouflaging is learned behaviour. While posing may be a reflex observed in a hatchling's first week, the ability to choose a matching backdrop develops after 4–6 months. When chicks land they are usually highly conspicuous, and their parents signal them to move to safer locations.
D
Fixed camouflage is only effective against a relatively unchanging environment, so some animals such as the cuttlefish have evolved an adaptable disguise. The cuttlefish can almost instantly change its colour, pattern and texture to match surroundings using specialised cells and muscles. In Queensland reefs, another fish, the bluestriped fangblenny, alters its colouration to mimic other species, gaining safety in numbers.
Its most impressive impersonation is of the black-with-neon-blue striped cleaner wrasse, which eats parasites on larger fish. The fangblenny benefits from reduced predation and also gets closer to prey, darting out from the cleaning station to nip at passing fish.
E
The most famous form of mimicry is Batesian mimicry, where harmless animals imitate dangerous ones using conspicuous colours. The harlequin snake eel imitates the toxic yellow-lipped sea krait, preventing attacks. However, success depends on the ratio of mimics to originals; if predators see too many harmless ones, they stop fearing the pattern.
F
An imitation of a dangerous creature does not need to be exact, just enough to make predators hesitate. The hawk moth caterpillar has markings resembling snake eyes. When threatened, it pulls in its head and the “eyes” appear, startling predators and allowing escape.
G
The chameleon gecko has another defence. Its body is brown but its tail is black and white. If attacked, it drops its tail, which wriggles and even squeaks as bones rub together. The predator becomes distracted while the gecko escapes. The regrown tail is brown like the body. Such tricks show the limits of natural disguise, and only the most successful survive.