7 Impressive Animal Defense Mechanisms

NOAA Photo Library, Flickr // CC BY 2.0
NOAA Photo Library, Flickr // CC BY 2.0

The deep-sea squid known as Octopoteuthis deletron has a startling defense mechanism: When threatened, the squid attacks its predator and then pulls away, breaking off the tip of its own arm and leaving it behind as a diversion. As the arm continues to glow and twitch, the squid makes its escape.

But this squid isn't the only creature with a bizarre tactic for keeping itself alive. Here are several other animals with impressive defense mechanisms.

1. THE LIZARD THAT SHOOTS BLOOD FROM ITS EYES

The Texas Horned Lizard is a scary-looking creature. Brown, plump and perfectly camouflaged in its native sandy environment, its first line of defense is its spiky demeanor. If the sharp spikes and horns don't ward off predators, the lizard steps it up a notch and squirts a well-aimed stream of blood out of its eyes. The stream of blood, which can go as far as 5 feet, is mixed with a foul-tasting chemical that wards off predators. But this odd weapon comes at a cost: The lizard may release one-third of its total blood supply this way, amounting to 2 percent of its body mass. Unfortunately, its population numbers are dropping thanks to a threat that won't retreat after a well-aimed squirt: habitat loss due to rapid urbanization in the Lone Star State. 

2. THE HAIRY FROG THAT BREAKS ITS OWN BONES

Trichobatrachus robustus, aka hairy or horror frog

Emőke Dénes, Wikimedia Commons // CC BY-SA 4.0

What if every time you felt threatened, your first and only method of defense was to break your own bones and use them for weapons? Meet the hairy frog, a Central African species. When breeding, the male frogs develop thin strands of skin along the sides of their bodies that resemble hair. In theory, these strands also allow the frogs to take in more oxygen while they watch over their eggs. But what's really compelling about this frog is its ability to crack its own toe bones and push them through their skin to form sharp claws, which are great for warding off would-be attackers.

While it's not completely clear what happens to the bones after the threat of attack subsides, researchers believe the bones slide back under the skin when the frog's muscles relax.

3. THE NEWT THAT TURNS ITS RIBS INTO SPIKES

spanish ribbed newt

The hairy frog isn't the only amphibian that uses its bones for weapons. When attacked, the Spanish ribbed newt shifts its ribs forward at an angle and pushes them through its stretched skin. The resulting effect is a row of spikes on either side of its body. Like the hairy frog, the newt has to force the bones through its skin every time it is attacked, but the mechanism seems to cause little or no harm to the creature. Maybe one day it'll get its own robot protector: A team of researchers at the the Swiss university EPFL created a robotic salamander inspired by the newt, which they called the Pleurobot (after its scientific name, Pleurodeles waltl).

4. THE TERMITE THAT BLOWS ITSELF UP

Talk about taking one for the team. When under attack, a species of termites found in the French Guiana rain forests sends older worker bugs on suicide missions to defend the whole colony. These older bugs, no longer as useful to the pack as they once were, come equipped with "explosive backpacks" that, over a lifetime, fill with toxic crystals produced by glands in the abdomen. When mixed with salivary gland secretions, these crystals create a toxic liquid that explodes on enemies, paralyzing them and killing the worker at the same time. These termites aren't alone among insects in using a suicidal defensive tactic: When faced with a threat, an ant found in Borneo expands its abdomen until it ruptures, shooting out a toxic liquid

5. THE FISH THAT SLIMES ITS ENEMIES

Hagfish are eel-shaped marine animals with the incredibly useful ability to slime their enemies. When threatened, the hagfish emit a slime from their pores that, when mixed with water, expands into a gelatinous goo that can either trap predators or suffocate them by clogging their gills. The video above shows a hagfish being attacked 14 separate times by sharks and other big fish, and coming out completely unharmed. Each predator took one bite before immediately spitting the hagfish out and swimming away, gagging. The best time to encounter a hagfish is probably after it's emptied its slime glands withstanding such an onslaught; the glands take three to four weeks to refill.

6. THE SEA CUCUMBER THAT SHOOTS ORGANS OUT OF ITS ANUS

sea cucumber on coral reef
iStock

Sea cucumbers can seem pretty boring. There are some 1250 known species of these sedentary creatures in the world, and many of them do indeed look like cucumbers. But when it comes to survival, things get interesting. Like starfish and sea urchins, sea cucumbers are echinoderms, and they can regenerate lost body parts if necessary. This comes in handy when they're threatened. The sea cucumber will expel its internal organs, which are sticky and sometimes contain a toxic chemical that can kill predators. They don't have much of a defense against pollution though, which is a problem, because they're superstar ocean-floor cleaners.

7. THE OPOSSUM THAT PLAYS DEAD

possum playing dead in the grass
Tony Alter, Flickr // CC BY 2.0

You can't do a roundup like this without at least mentioning the opossum. We typically refer to this creature's infamous defense mechanism as "playing dead," but there's actually nothing playful about it; the act is completely involuntary. Under intense fear, opossums fall into a comatose-like state that can last for hours, long enough to convince any predator that the opossum is already dead. Also unappetizing: Fear causes these animals to emit a corpse-like smell that only adds to their act. Thank the opossum for providing some defense for us too: They eat venomous snakes and ticks, gobbling up to 4000 insects a week.

Why Do Dogs Lick?

iStock/MichaelSvoboda
iStock/MichaelSvoboda

​One of the more slightly annoying things our dogs do (or most adorable, depending on who you ask) involves their tongue obsessively licking every crevice of every spot possible in pretty much the whole world. From our faces to our furniture to themselves, some dogs are absolutely in love with licking anything and everything. Although it can be cute at first, it quickly gets pretty gross. So why do they do it?

According to ​Vetstreet, your pup's incessant licking is mostly their way of trying to show affection. When we pick up our dogs or give them attention, chances are we kiss or pat their heads, along with petting their fur. Their way to show love back to us is by licking.

However, there are other reasons your dog might be obsessively licking—including as a way to get attention. Licking can be a learned behavior for dogs, as they see that when they lick their owner, they get more attention. The behavior can seem like something humans want which, to an extent, it is.

Licking is also a sensory tool, so if your dog is licking random objects or areas of your home, they're probably just exploring. It's easier to get a feel for their surroundings if they can taste everything. But licking objects like your rug or furniture can also be indicative of anxiety or boredom (which can often lead to destructive behavior), and a recent study linked excessive licking of surfaces to certain gastrointestinal disorders.

Another reason for licking is your dog wanting to clean themselves and/or spots around them. They've seen it since they were born; animals lick things ritualistically for cleaning and care. If your dog seems to be obsessed with licking themselves or one particular thing, they probably are. (Yes, dogs can have OCD, too.)

As Vetstreet points out, "excessive" dog licking often only seems excessive to the dog's owner, not the pooch itself. But if it's bothersome enough to you, a trainer can often help curb your dog's enthusiasm for giving wet, sloppy kisses. And while strange behavior is not rare for pets, if your dog's licking seems odd or in any way concerning, there's no harm in taking your pet to the vet to check it out—even if it's just for peace of mind.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

5 Holiday Foods That Are Dangerous to Pets

iStock/svetikd
iStock/svetikd

One of the best parts of the holiday season is the menu of indulgent food and drinks that comes along with it. But while you enjoy that cup of spiked hot cocoa, you’ve got to be careful your dog or cat doesn’t nab a lick. Here are five holiday treats that are dangerous for your pets, according to Vetstreet.

1. COFFEE

Any coffee lover will agree that there’s nothing quite like an after-dinner cup of joe on a cold night. But pups, kitties, and other pets will have to sit this tradition out. Caffeine can prompt seizures and abnormal heart rhythms in pets, and can sometimes be fatal. Other caffeinated drinks, such as soda or tea, should also be kept away from your four-legged family members.

2. BREAD DOUGH

We know the threat that bread dough poses to the appearance of our thighs, but it’s much more dangerous to our furry little friends. Holiday bakers have to be careful of unbaked bread dough as it can expand in animal stomachs if ingested. In some dogs, the stomach can twist and cut off the blood supply, in which case the pup would need emergency surgery.

3. CHOCOLATE

Cat and dog in Santa hats chowing down on plates of food
iStock/TatyanaGl

A little chocolate never hurt anybody, right? Wrong. The sweet treat can cause seizures and even be fatal to our pets. Darker chocolate, such as the baker’s chocolate we love to put in our holiday cookies, is more toxic to our pets than milk or white chocolate. The toxic ingredients include caffeine and theobromine, a chemical found in the cacao plant.

4. MACADAMIA NUTS

Macadamia nuts, which are a common ingredient in holiday cookies and often put out to munch on as an appetizer, can be toxic to dogs. While poisoning might not always be easy to detect in a pet, clinical warning signs include depression, weakness, vomiting, tremors, joint stiffness, and lack of coordination.

5. ALCOHOL

Think back to when you first started drinking and how much less alcohol it took to get you tipsy, because you likely weighed less than you do now. Well, your pet probably weighs a lot less than you did, even back then, meaning it takes much less alcohol to make them dangerously sick. Keep those wine glasses far out of reach of your pets in order to avoid any issues. Well, maybe not any issue: We can’t promise that this will stop you from getting embarrassingly drunk at a holiday party this year.

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