Sunday, May 26, 2002		Nature

Novel ways to protect oneself from predators
Nutan Shukla

BUYING time, whether a lot or little, during an attack is always helpful. Many animals attempt this by two popular devices: sudden sounds and suddenly displayed fright-patterns.

Some animals, specially those that hide in dark dens or crevices, respond to the approach of a predator with an explosive spit and hiss. Suddenness of the action is very important because it can startle even the most determined predator. It is not hard to guess why this sudden display is so effective. Venomous snakes spit and hiss when they are cornered, and no predator likes to risk the possibility that a lurking shape may possess poisonous fangs.

This snake-mimicry is employed by many species, from the familiar domestic cat to less familiar finches (birds).

Visual displays that involve the sudden appearance of bright-coloured patches or conspicuous patterns, specially eye spots, also intimidate approaching killers. Because poisonous animals are often brightly coloured, as a warning to would-be-predators, there is a startle value in a prey species suddenly flashing a bright patch of colours, even if it is not poisonous. This is not simple mimicry, but a combination of mimicry and sudden exposure.

Some praying mantids open their wings and flash gaudy-coloured undersurfaces. The display is strengthened when the insect produces a hissing sound, by rubbing its abdomen rapidly between its wings. One species has brightly coloured legs, which it holds up to scare off predators. One was observed to see off a monkey.

Some butterflies open their wings and startle a predator by presenting it with large eye spots. Hawk moths at rest have their wings in the familiar triangular position, but if threatened, they open their wings wide to expose two large eye spots. These are not on the edge of the wings, like smaller eye spots, but are close to the abdomen where the combination of body parts resembles the face of something far bigger and more frightening. Underwing moths have camouflaged forewings. The hunter is either surprised and the moth escapes, or it pecks at the edge of the coloured wing without damaging the moth’s body.

The ultimate in caterpillars must be the way some of them mimic snakes. The sphinx caterpillar of Central America is the most skilled exponent. At rest it resembles a twig, but under threat its front end drops down from the branch and inflates into a triangular, snake’s-head shape, complete with eye spots and movements that resemble a snake striking.

One of the South American toads has eye spots painted on its bottom. If danger threatens, it raises its rear legs, blows up its body and turns its back on its assailant. If the predator persists, the toad produces an unpleasant substance from glands close to the false eyes.

Sometimes, the warning is genuine and the prey really does have something dangerous or obnoxious in reserve. One of the arctid moths opens its wings to display red or yellow blotches on its abdomen, while, at the same time, exuding a foul-tasting substance.

The skunk’s first line of defence is its conspicuous black-and-white fur pattern. It is a warning. If the colour code fails, the creature reinforces its warning. The large, striped skunk arches its back, stamps its feet, waves its head from side to side, and struts around with its tail and head in the air. If that fails to impress, it turns about and points its rear end at the aggressor, squirting a sticky, evil-smelling liquid from large anal glands. The spray can hit a predator 6 ft away with considerable accuracy and can reach one at 30 ft with a following wind. The spray itself contains proteins that latch on chemically to hair and are thus difficult to remove. A hunter that has received a faceful of ‘skunk juice’ is unlikely ever to forget it.