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From poison dart frogs to hagfish slime: 20 animal defenses

  • From poison dart frogs to hagfish slime: 20 animal defenses

    All animals need to defend themselves. Humans tend to think of nature as a place of freedom and beauty, but for an animal, it’s dangerous out there, and a lot of those threats are other creatures that want to eat you. So animals have evolved an amazing range of ways to counterattack or avoid being attacked in the first place. We've gathered 20 examples from scientific studies and natural-history literature—some representative of strategies found throughout the animal kingdom, and some pretty uniquely weird.

    While some say the best defense is a good offense, nature doesn't always agree. There are risks and costs to responding to every attack with a counterattack, especially if your opponent is bigger than you are. So some animals have evolved passive defense techniques. Maybe the most basic is to have a body that's covered with a barrier—a hard shell that's difficult to penetrate, or sharp points that make it hurt when another animal tries to grab or take a bite. Camouflage works, too: Avoid being attacked in the first place by simply not being seen because you blend into the background. Or, another way to use your appearance as a defense is to mimic another animal that your foe is afraid to attack. Predators know that certain species taste bad or sting, so looking like one of those nasty critters wards them off. These mimics are often so precise it's hard to believe, but evolution has produced them over and over: The more an individual looks like the avoided species, the likelier it is to survive and have offspring that look like it, so the imitation gets better and better over time.

    Other strategies are more active. There are animals that use chemical weapons, like venom or poison (yes, those are different, as we'll explain) and noxious sprays. Others rely on confusing or distracting their attacker: behaving like they're dead or injured, say, or blocking their vision with a cloud of ink. And some use physical counterattacks that are unusual to say the least, as you'll see.

    Read on to learn about 20 animal defenses. 

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  • Dart frog: poison

    Frogs in the family Dendrobatidae are known as poison dart frogs or poison arrow frogs because the toxin exuded by their skin was used by humans to poison the tips of arrows. Most are also brightly colored to warn predators that they are dangerous to eat. Dart frogs are widely kept as pets, which is perfectly safe: They are not poisonous in captivity because the toxin derives from the insects they eat in the wild.

  • Inland taipan: venom

    Venom and poison are not the same: Poison makes you sick if you bite the animal, and venom makes you sick if the animal bites you. The primary function of venom is to disable the snake’s prey but it can also serve as a defense against predators. Possibly the most dangerous venomous snake is the inland taipan of Australia, which has the most toxic venom and injects the largest amount with each bite.

  • Squid: ink

    Squid ink is more than an ingredient for pasta dishes: It’s an incredibly clever defense. A squid will squirt out a cloud of ink when being chased by a predator. This not only makes it harder for predators to see the squid, it may even fool them into biting at a glob of ink, thinking it’s the tasty creature they’re hunting.

  • Bombardier beetles: hot chemical spray

    Many insects use an irritating chemical called benzoquinone as a defense against predators, but bombardier beetles take this to the next level. They combine ingredients to produce it inside their bodies at the moment of use, and the chemical reaction heats almost to the boiling point and provides the pressure to eject a spray from their abdomen.

  • Hagfish: slime

    The hagfish is unusual in many ways, including its lack of a jaw and backbone, but most of all for its unique and uniquely gross defense. When it’s attacked or just stressed out, special glands produce about a teaspoon of slime that instantly expands in size 10,000 times. Even a shark will gag and spit the hagfish out and go look for a less slimy meal.

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  • Eurasian roller: vomit

    There’s a less fancy way to expel something repulsive as a defense: just throw up. The nestlings of the Eurasian roller upchuck noxious orange vomit when disturbed. Like the dart frog’s poison, it’s thought to contain chemicals derived from the insects in its diet, and experiments show that it’s distasteful to potential predators.

  • Clownfish: borrowed stings

    Sea anemones have stinging tentacles that they use to capture prey. The clownfish is immune to their toxin and lives among them, safe from predators. It’s not a one-way relationship, though: The clownfish pays back in several ways, including providing nutrients and helping provide oxygen, aerating the water with its swimming motions.

  • Three-banded armadillo: rolling into an armored ball

    All species of armadillo have a shell made of hard bony plates covered with a layer of keratin that provides a tough barrier to predators. The three-banded armadillo takes this defense a step further: It’s the only species that can roll up into a ball with its head and legs tucked inside. When they’re rolling up, the shell snaps shut on their assailant, providing an additional deterrent.

  • Robber fly: look like something dangerous

    Many animals defend themselves by looking like another animal that predators don’t want to mess with. The robber fly doesn’t have a sting, but it looks like a bumblebee, so insect-eating creatures leave it alone.

  • Stick insect: camouflage

    Looking like something else can also be a different kind of defense strategy: If predators can’t see you, they won’t know you’re there. Stick insects are found all over the world and have evolved to look like astonishingly precise imitations of the vegetation they live among. Some even add to the disguise with their behavior by gently waving like a leaf in the wind.

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