Category: Animal defences

Why porcupine quills slide in with ease but come out with difficulty

By Ed Yong | December 11, 2012 8:00 am

A shorter version of this story appears at Nature News.

In August of this year, Allison Noles rushed her bulldog Bella Mae to the vet. The dog’s face looked like a pincushion, with some 500 spines protruding from her face, paws and body. The internet is littered with such pictures, of Bella Mae and other unfortunate dogs. To find them, just search for “porcupine quills”.

North American porcupines have around 30,000 quills on their backs. While it’s a myth that the quills can be shot out, they can certainly be rammed into the face of a would-be predator. Each one is tipped with microscopic backwards-facing barbs, which supposedly make it harder to pull the quills out once they’re stuck in. That explains why punctured pooches need trips to the vet to denude their faces.

But that’s not all the barbs do. Woo Kyung Cho from Harvard Medical School and Massachusetts Institute of Technology has found that the barbs also make it easier for the quills to impale flesh in the first place. “This is the only system with this dual functionality, where a single feature—the barbs—both reduces penetration force and increases pull-out force,” says Jeffrey Karp, who led the study.

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Fossil insect hid by carrying a basket of trash

By Ed Yong | December 10, 2012 2:00 pm

If you travelled back to Spain, during the Cretaceous period, you might see an insect so bizarre that you’d think you were hallucinating. That’s certainly what Ricardo Pérez-de la Fuente thought when he found the creature entombed in amber in 2008.

The fossilised insect of the larva of a lacewing. Around 1,200 species of lacewings still exist, and their larvae are voracious predators of aphids and other small bugs. They also attach bits of garbage to tangled bristles jutting from their backs, including plant fibres, bits of bark and leaf, algae and moss, snail shells, and even the corpses of their victims. Dressed as walking trash, the larvae camouflage themselves from predators like wasps or cannibalistic lacewings. And even if they are found, the coats of detritus act as physical shields.

We now know that this strategy is an ancient one, because the lacewing in De la Fuente’s amber nugget—which is 110 million years old—also used it. It’s barely a centimetre long, and has the same long legs, sickle-shaped jaws, and trash-carrying structures of modern lacewing larvae. But it took camouflage to even more elaborate extremes. Rather than simple bristles, it had a few dozen extremely long tubes, longer even than the larva’s own body. Each one has smaller trumpet-shaped fibres branching off from it, forming a large basket for carrying trash.

De la Fuente called it Hallucinochrysa diogenesi, a name that is both evocative and cheekily descriptive. The first part comes from the Latin “hallucinatus” and references “the bizarreness of the insect”. The second comes from Diogenes the Greek philosopher, whose name is associated with a disorder where people compulsively hoard trash.

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Spiny mice defend themselves with self-flaying skin and fast healing factors

By Ed Yong | September 26, 2012 1:00 pm

When Marvel Comics created a short superhero who could heal horrific injuries, perhaps instead of “Wolverine”, they should have named him “African spiny mouse”. These tiny rodents can jettison strips of skin from their own hides when captured by predators, and heal those same wounds with extraordinary speed.

Healing powers are common in the animal world. Salamanders and starfish can regrow lost limbs, while some flatworms can regenerate their bodies from a single cell. But mammals lag behind – while some species can grow back a lost tail, when most of us lose our body parts, we do so permanently. The spiny mice are an exception.

Biologists have noted that these rodents have very weak skin, which seems to slough off easily when they are handled. Led by these anecdotal reports, Ashley Seifert from the University of Florida has studied the skin-shedding ability in greater depth, focusing on two species: Kemp’s spiny mouse (Acomys kempi); and Percival’s spiny mouse (Acomys percivali).

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Deep-sea squid can break off all its arms onto an enemy

By Ed Yong | August 1, 2012 9:00 am

If you grew up on a diet of 1980s cartoons, as I did, you will have seen many a giant robot shoot many a rocket-propelled fist into many a big monster. Sadly, there are no rocket punches in the real world, but I can give you the next best thing: a squid that can grabs its enemies with flashing, writhing, self-amputating arms.

The squid in question is Octopoteuthis deletron, a beautiful red animal with hook-lined arms, which grows to around five inches in length. I’ve written about it before – the males have a tendency to indiscriminately implant members of both sexes with sperm.

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Aging termites put on suicide backpacks full of chemical weapons

By Ed Yong | July 26, 2012 2:00 pm

Termite workers don’t get to peacefully retire. As they age and their bodies can work no more, some of them are fitted with suicide backpacks and conscripted for war.

There are thousands of termite species, and many engage in chemical warfare. Some squirt noxious chemicals from nozzles on their heads. Others violently rupture their own bodies to release sticky immobilising fluids, sacrificing themselves for the good of their sisters. Their range of weapons is astounding, and Jan Sobotnik from the Academy of Sciences of the Czech Republic and Thomas Bourguignon from the Université Libre de Bruxelles have just found a new one.

They were studying the termite Neocapritermes taracua when he noticed that some workers have a pair of dark blue spots in the gap between their torsos and abdomens. When other termites attack their colony, the blue workers bite the intruders and burst, releasing a drop of fluid that soon becomes sticky gel. Watch it happen in the video below – the black dot in the middle of the droplet are intestines and other internal organs).

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Flying plankton take to the air to flee from fish

By Ed Yong | March 20, 2012 8:00 pm

Even the topmost layer of the ocean, just millimetres below the air above, is full of life. This zone, where two worlds meet, is home to small creatures like animal larvae, algae, bacteria, and other plankton. Among the most abundant residents of this zone are copepods – tiny relatives of crabs and shrimp. And some of them have the ability to leave this world altogether, and take to the air.

When threatened by fish, some copepods can jump straight out of the water and shoot over many times their own body lengths. From the fish’s point of view, its prey suddenly disappears.  Flying fish use the same tactic to escape from predators. Now, we know that one of the most common groups of ocean animals shares their strategy.

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Giant squid, what big eyes you have. All the better to spot sperm whales with, my dear.

By Ed Yong | March 15, 2012 12:40 pm

The giant squid sees the world with eyes the size of soccer balls. They’re at least 25 centimetres (10 inches) across, making them the largest eyes on the planet.

For comparison, the largest fish eye is the 9-centimetre orb of the swordfish. It would fit inside the giant squid’s pupil! Even the blue whale – the largest animal that has ever existed – has measly 11-centimetre-wide eyes.

So why the huge leap in size? Why does the giant squid have a champion eye that’s at least twice the size of the runner-up?

Dan-Eric Nilsson and Eric Warrant from Lund University, Sweden, think that the squid must have evolved its eye to cope with some unique challenge that other animals don’t face. They suggest that the world’s biggest eyes evolved to spot one of the world’s biggest predators – the sperm whale.

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Death in the octopus's garden

By Ed Yong | December 14, 2011 9:00 am

Two turtles washed up dead in Moreton Bay, Australia, with no obvious signs of injury or illness. What killed them? I tell the story in a guest-post for Last Word on Nothing, my favourite science blog network. Here’s how it starts; do go and read the full thing.

There is an old story about a scorpion and a turtle. Variants abound, but the basic tale revolves around an unusually talkative scorpion that asks a turtle for a lift across a river. The turtle refuses at first, fearing the scorpion’s sudden but inevitable betrayal. The scorpion insists, the turtle relents, and the two get halfway across before the scorpion predictably stings the turtle. As they sink to their mutual deaths, the turtle asks, “Why did you do it?” The scorpion simply replies: “It’s my nature.”

This story is similar, except an octopus plays the role of the scorpion, and no one talks.

Moreton Bay, on the eastern coast of Australia, is home to around 20,000 green turtles. Kathy Townsend found one of them on October 11, 2008, washed up on a sand bank and dead. Townsend had been studying the links between human activity and sea turtle deaths, but it was clear that this turtle was not killed by people. On the surface, it had no signs of injuries, and it seemed perfectly healthy. “By all rights, it should have still been alive,” says Townsend.

She started cutting.

Burgling beetle targets plants with the heaviest security

By Ed Yong | November 24, 2011 9:30 am

Heavy locks, imposing gates and motion-sensing lights can help to fortify your home and safeguard your belongings against thieves. On the other hand, they can also advertise the fact that you have stuff worth stealing. Extra security can be a double-edged sword.

This is as true for plants defending their tissues as it is for humans defending their homes. Maize plants, like many others, protect themselves with poisons. They pump their roots with highly toxic insecticides called BXDs, which deters hungry mandibles. But these toxins don’t come free. The plant needs energy to act as its own pharmacist, so it distributes the poison to the areas that deserve the greatest fortification – its crown roots.

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Spiders coat their silk with an ant-repellent

By Ed Yong | November 23, 2011 9:30 am

Spider webs are great at catching flying insects, but they’re an inviting target for walking ones. The spider sits pretty in the middle of its home, surrounded by the pre-packaged morsels of the insects it has caught. It’s an all-you-can-eat buffet, and ants should easily be able to raid it. Ants are excellent predators, they hunt in large numbers, and they can negotiate their way along the non-stick parts of the web. And yet, there are very few reports of ants successfully pillaging spider webs. Why?

Shichang Zhang has found one possible answer: some spiders lace their silk with an ant-repelling chemical. Their sticky webs, which so effectively trap some insects, can also deter others.

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