Masking: Animals in disguise

Masking: Animals in disguise
Some species push the defense tactics of hiding and camouflage to the max by actually wearing costumes. This behavior is known as masking.

The decorator crab, found in the eastern Pacific Ocean, is named for its habit of disguising itself. The crab picks seaweed, anemones, and sponges and puts them on its shell. Bristles on the shell work like Velcro to hold these items in place. In this disguise, the crab looks like another weed-covered rock. When the crab outgrows its shell and sheds it during molting, it takes the decorations off its old shell and plants them on its new one. Decorator crabs share the eastern Pacific with sharp-nosed crabs, which sometimes stick seaweed on the sharp front edges of their shells. Other species of crab disguise themselves, too. The camouflage crab of New Zealand adorns its shell and legs with seaweed (and sometimes snacks on bits of it). The sponge crab uses its hind legs to hold a live sponge on its shell. The shell is covered with algae, which has settled on the shell just as it would on a stone.

Hermit crabs sometimes plant anemones on their shells. Anemones have stinging cells in their tentacles, so they provide an extra layer of protection for the crab. In return, the crab takes them to new feeding grounds, and the anemones can dine on tidbits from the crab’s meals. Another species, the anemone crab, has claws equipped with hooks for gripping anemones. Any predator that approaches this crab will have the stinging anemones waved in its face.

Some insects also use masking. A wavy-lined emerald caterpillar cuts petals from the flowers it feeds on. Then it attaches the petals to spines on its body and fastens them in place with silk. When the petals wilt, it replaces them. This habit has earned the caterpillar the alternative name of camouflaged looper. Other kinds of looper caterpillars mask themselves with flowers, leaves, and bits of bark.

The larvae of many kinds of caddis fly mask themselves in camouflaged cases. The cases are made out of material from the larva’s freshwater habitat: grains of sand, small stones and shells, leaves, twigs, bits of wood, or pine needles. The materials are bound together with sticky or silky fluids produced by the larva’s body. A hooked pair of legs at the larva’s hind end hang on to the case as the larva creeps about in search of food.

Hiding, camouflage, and masking help animals avoid predators. Animals’ behaviors and bodies have changed over millions of years in ways that help them survive. Scientists call these changes adaptations. The process of change over time is called evolution.

Predators have also evolved so that they could keep finding prey. When they do, the prey must turn to another form of self-defense.

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