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  Section: General Zoology » Animal Defense Mechanism
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Spikes And Spines

Animal Armor
Spikes And Spines
Armored on the Inside
Insect Armor
Scales, Scutes, and Skin
Penetrating the Armor
Rolling up as a Defense

A caterpillar’s bristles, like those of this gypsy moth caterpillar, can be used as a defense against predators
A caterpillar’s bristles, like those of this gypsy moth
caterpillar, can be used as a defense against predators.

Spikes And Spines
Most insects have thick outer skeletons that serve as armor. These exoskeletons may also boast spikes and spines, which add to an insect’s defense. Many species of crickets and grasshoppers, for example, have spines on their legs and backs. Many ants have spines in the middle of their back that protect them from other insects’ nipping jaws. Praying mantises have spurs on their claws that not only help in grabbing prey, but also inflict wounds on predators.

Caterpillars typically have soft bodies. This makes them tempting morsels for predators. But most caterpillars have other ways to protect themselves. Some have spikes or spiny, hair-like bristles. Caterpillars can be so bristly that they appear to have fur. The bristles irritate a predator’s skin and eyes. If a predator accidentally inhales some bristles, they can hurt its nose, throat, and lungs.

Other small animals have spines, spikes, and bristles, too. The spined spider has an array of big, red spines on its body. Millipedes have bundles of barbed bristles along their bodies and on their hind ends. These bristles come off and get stuck in the faces and jaws of ants and other predators.

Large spiders called tarantulas also defend themselves with bristles. A tarantula uses two of its hind legs to rub bristles off its abdomen, which sends hundreds of the tiny barbed bristles at the attacker. The bristles irritate its eyes, nose, and mouth.

Sea urchins, like this common sea urchin found along the coast of Scotland, use their bristles for moving as well as defense
Sea urchins, like this common sea urchin found
along the coast of Scotland, use their bristles for
moving as well as defense.

Spikes and spines also protect animals that live underwater. The tiny young, or larvae, of crabs have spines that help them float while also repelling fish. Likewise, spiny lobsters are protected by spines that line their antennae and point forward along their shells. The crown-of-thorns sea star is also spiny. This sea star has as many as 19 arms, with sturdy pink or yellow spines poking out of its orange, red, and purple skin. The spines not only pierce skin, but also deliver a dose of painful venom.

Sea urchins are like living pincushions. Their hard, round bodies bristle with spines. An urchin uses its spines to help it move. The sharp spines also keep many predators at bay. Some sea urchins’ spines are connected to glands that make venom. Long-spined hatpin urchins have venomous spines that can be up to 12 inches (30 cm) long. Some species of fish and jellyfish hide in hatpin urchins.

Stonefish have spines connected to venom glands, too. These are well-camouflaged fish that lie on the seabed in some tropical waters. Their spines pierce and kill predators that grab them. Surgeonfish, which also live in tropical waters, have a pair of razor-like spines on either side of the tail. The fish slashes at attackers with these spines.

Sticklebacks are named for the spines that stick up on their backs. A stickleback can lock these spines in an upright position. The number of spines varies, as shown by their names, which range from three- to fifteen-spined stickleback.

The porcupine fish’s name is likewise a clue to its defense. This fish is covered with sharp spines. When threatened, the fish inflates its body with water, and the spines stick out in all directions. This makes the fish too big for some predators to swallow. It startles other predators, which may decide not to tackle the suddenly enlarged prey.

A variety of lizards also wear spike-studded armor. The well-named thorny devil resembles a miniature dragon as it strolls across the Australian sand, looking for ants to eat. Spikes of many sizes jut from its legs, sides, tail, back, and head. Despite its name, a thorny lizard is not aggressive. If threatened, it tucks its head between its front legs. This makes a large, spiky bump on its neck stick out—a bump that looks like an even more unappetizing head than the lizard’s actual one.

This thorny devil shows off its spikes of many sizes as it walks along a street in the Northern Territory, Australia
This thorny devil shows off its spikes of many sizes as it
walks along a street in the Northern Territory, Australia.

Just as prickly are the horned lizards of dry lands and deserts in parts of Mexico and the southwestern United States. A horned lizard has spines running down its sides, back, and tail. Strong, sharp horns jut from its head, making it look like a tiny triceratops. If a predator threatens it, a horned lizard puffs up its body so that its spines stick out. It also turns its head to present its horns. Some species can also squirt blood from the corners of their eyes. The blood can shoot out up to 3 feet (1 m). The blood tastes bad, so the squirt both surprises and disgusts a predator.

The armadillo lizard of southern Africa is also spiky. It makes the most of its spikes by rolling into a ball and grabbing its tail in its mouth when threatened. This turns the lizard into a prickly doughnut.

Mammals also make use of spines for protection. Porcupines, for example, fend off predators with spines called quills. There are about 25 species of porcupine. About half of them are found in Europe, Asia, and Africa. The rest are found in Central and South America, with one species living in North America.

A North American porcupine is covered with about 30,000 long, sharp quills. The quills range from half an inch (1.3 cm) to 5 inches (12.7 cm) long. A porcupine warns enemies before they attack. It lowers its head, lifts its tail, and raises its quills and rattles them. It also clacks its teeth, stamps its feet, and gives off a very strong smell from a patch of skin on its back.

If the attacker persists, the porcupine will back up toward it and whack it with its tail. The quills, which are barbed at the end, pop off the porcupine and stick in the attacker’s skin. They are painful and can actually drill deeper into skin and muscles over time.

The African crested porcupine also warns predators not to mess with it. It shakes its tail, making a loud rattling noise with a clump of special, hollow quills. This porcupine also raises quills on its back that can be up to 20 inches (50 cm) long and are boldly striped in black and white. As a last resort, it will run sideways or backward to jab its quills into its foe.

Hedgehogs are also prickly. A European hedgehog has about 5,000 short, sharp spines. Unlike a porcupine’s quills, hedgehog spines do not come out of the skin when used for jabbing.

A hedgehog usually flees or hides in the face of danger. If it is cornered, it raises its spines and then rolls into a ball, protecting its soft belly and its head. A hedgehog can stay rolled up for many hours, and a predator is likely to give up prodding the unresponsive, prickly ball. An uncurled hedgehog, however, may leap backward into a predator or thrust its spiny body into its face.

Spines also protect spiny anteaters called echidnas. Echidnas are Australian monotremes (egg-laying mammals) that eat insects, snaring them with their long, sticky tongues. Hundreds of spines cover an echidna’s body. A spine can be about 2 inches (60 mm) long. If threatened, an echidna digs quickly into the ground, leaving only its spiny back showing. It can also roll up into a ball or wedge itself into a crevice among rocks.

The army of spiny mammals includes the spiny rats of Central and South America. Some species of spiny rats have sturdy spines, while others have stiff, bristly hair. Spiny rats can also shed their tails to escape a predator’s grip. Another group of spiny mammals, the tenrecs, is found on Madagascar, an island off the east coast of Africa. A tenrec can roll up into a ball like a hedgehog. It also has a powerful bite and will butt its enemy in the neck with its spiny head.


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