Animals protect themselves from being eaten by other animals in countless ways. Some are commonplace. Others are unconventional. Camouflage and running are well-known defenses. Not being seen by a predator in the first place is an excellent strategy. Being able to outrun a threat is an effective backup plan. Body armor, biting, stinging and clawing are other familiar defenses that would-be prey employ to try to avoid becoming a meal. Any angler is aware of the needle-sharp, sometimes venomous, spines of salt- and freshwater fish. Other defensive tactics are less well known.

Chemical warfare is a widespread defense mechanism, and the delivery systems come in several different packages. For example, birds avoid eating monarch butterflies because the caterpillars feed on milkweed plants, which are poisonous to birds and mammals but harmless to butterflies. Skunks have another way of using chemicals in combat. Dogs and people usually need only one encounter with a skunk to learn not to mess with an animal that sports that do-not-mess-with-me coloration. Many frogs, including the common gray treefrogs of the eastern United States, have poisonous skin secretions that can cause major irritation of the eyes. And surely everyone is aware that spiders, scorpions and snakes can inject venom.

In a study published in the scientific journal Current Biology, Carlos Jared, Edmund D. Brodie Jr. and colleagues demonstrated that some frogs have taken a step forward in the arms race between predators and prey by being venomous rather than poisonous. These frogs actually inject a toxic substance, which is atypical of amphibians. Scientists studied two Brazilian frogs that have toxic skin glands on their head and bony spines on the skull that can penetrate skin. The combination allows the toxin to get into the bloodstream of the predator and qualifies the frogs as venomous. Drop for drop, the secretions are more toxic than the venom of tropical pit vipers such as the fer-de-lance.

The horned toad (which is actually a lizard) definitely makes the cut for odd and unusual defenses. Having bony spines on the head and body would be enough to deter some predators, especially a snake that swallows its prey whole. But what do these little armored tanks do with a fox or coyote that can chew them up first? They squirt blood from their eyes into the face of the predator. No one knows how effective this approach is at saving horned toad lives, but presumably it works enough of the time to remain part of the horned toad’s arsenal. Some animals considered prey may display the attributes of a threat themselves. The classic inflated neck and hissing of hognose snakes make them seem like formidable adversaries. A bird or mammal might have second thoughts, wondering whether the meal in front of them would be worth the price of admission. 

Morphing into a different body shape is a form of defense used as a last resort by many animals. Pufferfish, also known as blowfish, can change from a regular fish shape to softball-size or larger when threatened by a predator. They gulp in water, or even air, to inflate the stomach with the intent of becoming too large for their attacker to swallow. Common toads can fill up their bodies with air, a ploy that sometimes works with a snake that must swallow all of the prey or none of it. If the attempt to eat a toad continues, the snake or any other predator will get a taste of bufotoxin, a poison secreted from the large glands on top of a toad’s head. A dog that catches a toad in the yard will often foam at the mouth when they bite into the poisonous glands. Bufotoxin can be deadly for some predators.

Predators have many ways to get their prey, including brute force, venom and webs. Prey must be equally resourceful in their defense systems.

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