It turns out that elephants have a sixth toe. They’ve adapted one of their wrist bones into a strut that supports their giant squishy feet. I wrote about this for Nature (excerpt below), but here’s my full interview with John Hutchinson, the man behind the discovery, and the owner of (probably) the world’s largest collection of frozen elephant feet.
Elephants walk on the world’s biggest platform shoes. Now, John Hutchinson at the Royal Veterinary College in London and his team have found that their footwear also contains hidden stiletto heels.
Even though an elephant’s leg looks like a solid column, it actually stands on tip-toe like a horse or a dog. Its heel rests on a large pad of fat that gives it a flat-footed appearance. The pad hides a sixth toe — a backward-pointing strut that evolved from one of their sesamoids, a set of small tendon-anchoring bones in the animal’s ankle.
This extra digit, between 5 and 10 centimetres long, had been dismissed as an irrelevant piece of cartilage. Almost 300 years after it was first described, Hutchinson finally confirmed that it is a true bone that supports the squishy back of the elephant’s foot. The ones on the hindfeet even seem to have joints.
A leaf falls from the rainforest canopy, but it never hits the ground. Instead, it becomes trapped by nets of sticky fungi. While other lost leaves litter the forest floor, this one has joined the jungle’s mezzanine level – a layer of litter suspended in mid-air and hanging by a thread.
The fungi belong to a single genus called Marasmius, which extend networks of root-like filaments through the air. They act like a web that catches falling matter from the branches above. They have gone unappreciated, but Jake Snaddon from the University of Oxford has found just how important they can be.
By snaring leaves, the fungi provide room and board to insects, spiders and other canopy creepy-crawlies that might otherwise be confined to the ground. When Snaddon removed the fungi, the numbers of these animals plummeted by 70 percent.
Chillies come in many degrees of heat, from the sweet painless bell peppers to the “Trinidad Scorpion Butch T pepper”, a superlatively hot chili that needs to be handled with gloves. A less dramatic range also exists in the wild: some chillies are hot, and others are not. In supermarkets, the spectrum of heat is the result of clever breeding. It the wild, it’s due to a tension between two threats: drought and disease.
Hot chillies owe their mouth-watering bite to substances call capsaicinoids – a unique breed of chemical weapon wielded only by these plants. The weapon targets proteins that detect excessive heat, delivering an intense burning feeling without any actual burning. Birds, which pollinate chillies, don’t have these proteins and are immune to the fiery tastes. Mammals aren’t so fortunate; against them, capsaicinoids are an effective deterrent.
But pilfering mammals are not the biggest threats that wild chillies face. In 2008, Joshua Tewksbury at the University of Washington showed that their most important foe is a fungus called Fusarium semitectum, which rots the fruits and kills the seeds. Tewksbury showed that capsaicinoids kill the fungus, and chillies that lack their protection have half as many seeds in areas where Fusarium is around.
Many insects are armed with venom, which they can inject into their enemies via a sting. The African ant Crematogaster striatula is no exception, but its arsenal has a disturbing twist – its venom goes airborne. The ant can raise its sting and release its toxins as an aerosol spray. Its targets are termites, whose nests it raids. Even without making any contact, the ants can induce seizures in the termites, eventually paralysing them.
All Crematogaster ants have a mobile sting. The sting sits on the ant’s rear-end, which connects to its torso by a flexible stalk, so the ant can aim it in virtually any direction. Aline Rifflet from the Jean-Francois Champollion University Center saw this ability in action when she watched C.striatula take on termites.
The sickle-shaped “killing claws” of dinosaurs like Deinonychus and Velociraptor have captured the imagination for decades. They were held aloft from the second toe, and were far bigger than the neighbouring claws. In Jurassic Park, Alan Grant tells an annoying child that the dinosaurs used their claws to disembowel their prey with slashing motions. That seems unlikely – they didn’t have a suitable cutting edge. Others have suggested that they were used for climbing onto larger prey.
But neither idea made sense to Denver Fowler from Montana State University, who has put forward a very different idea about how these animals used their infamous claws. He compared the feet of extinct dinosaurs like Deinonychus to those of living dinosaurs like eagles, hawks and other birds of prey. Both groups are known as “raptors” and Fowler thinks that they share more than their nicknames.
In his vision, which he calls the “ripper” model, Deinonychus killed small and medium-sized prey in a similar style to a hawk or eagle dispatching on a rabbit. Deinonychus leapt onto its target and pinned it down with its full body weight. The large sickle-shaped claws dug into its victim, gripping tightly to prevent it from escaping. Then, Deinonychus leant down and tore into it with its jaws. The killer claws were neither knives nor climbing hooks; they were more like anchors.
It’s a simple idea, but a potentially important one, for it casts Deinonychus’s entire body into a new light. Fowler thinks that it flapped its large feathered arms to keep its balance while killing a struggling victim. And its feet, which were adapted for grasping prey, would have given its descendants the right shape for perching on branches. Fowler says, “It really helps to make sense of the weird anatomy of these little carnivorous dinosaurs.”
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.
In flight, the hovering hummingbird is more like a insect than a bird. Most most birds only create lift when they flap downwards. But the hummingbird, by flipping its wing before it flaps upwards, can create lift in both directions. Insects do the same thing, but their wings have no bones inside them. How does the hummingbird fly like a fly despite having the bones of a bird?
Tyson Hedrick has found out, by filming hovering hummers with high-speed X-ray cameras. I’ve written about the results in my new piece for Nature News, so go there and read the full story (including details about how hummingbird muscles work at high gear). The meat of it is this:
By filming ruby-throated hummingbirds (Archilochus colubris) in flight, Hedrick showed that the birds invert their wings by twisting their wrists. “It looks like it’s affecting the whole wing because the bird’s skeleton is very compressed and its wrist isn’t very far from its shoulder,” says Hedrick.
In most birds, the wrist collapses on the upstroke to draw the wing towards the body as it is raised. Hummingbirds have adapted the same movements to rotate their wings instead. “The usual mechanism makes the upstroke aerodynamically invisible,” says Hedrick. “The hummingbirds’ mechanism makes the upstroke aerodynamically effective.”
The videos also showed that hummingbirds flap their wings by twisting the humerus (upper arm bone), rather than flapping it up and down from the shoulder like other birds. To understand the difference, Hedrick recommends trying to mimic a bird by flapping your arms. “You’re doing something not too different to what a seagull’s doing,” he says. To mimic a hummingbird, “hold your upper arm close to your body with your elbow on your hip, and flap your forearms back and forth”.
Go try it. You can look as stupid as I did when I was writing about the paper.
Photo by Joe Schneid
We humans are often known as “naked apes”. It might seem like a deserved nickname; after all, we lack the lush coats of body hair that chimps, bonobos and gorillas have in abundance. But we are not naked. We actually have the same density of body hair as other apes of our size, but ours is largely fine and colourless rather than thick and dark. We are coated with a layer of short, fine hair, known technically as vellus hair and colloquially as peach fuzz.
Many scientists have speculated about why we humans have lost a thick coat of body hair. But very few of them have offered answers to an equally mysterious question: why have we kept our vellus coat? The fine hairs aren’t very good at preserving body heat, and they don’t make us more or less sexually attractive. They look like the results of a half-hearted evolutionary stab at becoming hairless. Some have suggested that they have no role at all.