Six million years ago, Argentina was ruled by ‘terror birds’. These giant flightless hunters, standing one to three metres tall were at the top of the food chain and killed using a massive, hooked beak, up to two feet in length. The murderous beaks are certainly evocative, but they were no blunt instruments. They were precision weapons, used with finesse and wielded with speed and agility.
Federico Degrange analysed the skull of a medium-sized terror bird called Andalgalornis and found that it was incredibly strong when biting straight down, but far weaker when being shaken from side to side. If the bird tried to subdue a struggling victim, its beak would probably have snapped under the strain. So despite its size, Andalgalornis probably danced around its prey, advancing and retreating while dispatching it with quick, well-aimed strikes – more Muhammad Ali than George Foreman.
Relative to its body size, the huge beak of the toco toucan is the largest of any bird. It allows the toucan to eat both fruit and small animals, and display to both mates and rivals. Darwin himself speculated that it acts as a billboard, shaped by sexual selection to display bright colours that could be attractive to potential mates. But the toucan’s bill has another function that has only been discovered. Like the ears of an elephant, the toucan’s bill is a radiator.
It certainly has all the characteristics of a biological radiator. It’s big and has a surface area that’s 25-40 times larger than normal for a bird of its size; in fact, the bill accounts for 30-50% of the bird’s total surface area. It also lacks any insulating layer of fat, feathers or fur, and beneath its horny exterior, lies a rich network of blood vessels.
These vessels are the means through which the toucan exchanges heat. When it’s warm, it widens the vessels and allows the heat of its blood to radiate into the atmosphere. When it’s too cold, it limits the loss of heat by shutting down the blood flow to its bill.
The giant cephalopods (squids and octopuses) of the deep sea have captured the imagination for centuries. But despite our fascination with these creatures, they are still enigmas, their behaviour illuminated only by the occasional lucky video or the presence of scars on animals they fight with. For many species, including the famous giant squid, we still know relatively little about what they eat and what position they occupy in their ecosystems.
Yves Cherel from the Centre d’Etudes Biologiques de Chize has some new answers about the behaviour of deep-sea cephalopods and they came from a most unorthodox technique– he studied remains recovered from the stomachs of dead sperm whales.
It’s clear that sperm whales feed on squid and octopuses. Sucker-shaped scars along the backs of some individuals have led people to picture titanic battles between the whales and their giant prey. Once eaten, the cephalopods’ soft bodies are easily digested, but they also have hard, parrot-like beaks that aren’t easily broken down.
By looking in the stomachs of three sperm whales stranded in the Bay of Biscay, Cherel recovered hundreds of beaks from 19 separate species – 17 squids including the giant squid, the seven-arm octopus (the largest in the world) and the bizarre vampire squid. Together, these species represent a decent spread of the full diversity of deep-sea cephalopods.
Imagine that you hand is made of jelly and you have to carve a roast using a knife that has no handle. The bare metal blade would rip through your hypothetical hand as easily as it would through the meat. It’s clearly no easy task and yet, squid have to cope with a very similar challenge every time they eat a meal.
The bodies of squid, like those of their relatives the cuttlefish and octopus, are mainly soft and pliant, with one major exception. In the centre of their web of tentacles lies a hard, sharp and murderous beak that resembles that of a parrot. The beak is a tool for killing and dismembering prey and the large Humboldt squid (Dosidicus gigas) is known to use its beak to sever the spinal cord of fishy prey, paralysing them for easy dining.
The Humboldt squid’s beak is two inches long and incredibly hard (difficult to dent or scratch), stiff (difficult to bend out of shape) and tough (resistant to fractures). This combination of properties makes the beak harder to deform than virtually all known metals and polymers. That’s all the more remarkable because unlike most animal teeth or jaws, it contains no minerals or metals. It’s made up solely of organic chemicals and manages to be twice as hard and stiff as the most competitive manmade equivalents.
By comparison, the mass of muscle that surrounds and connects to the beak is incredibly soft, the equivalent of a jelly hand gripping a bare metal blade. With such mismatched tissues, how does the squid manage to use its killer mouth without tearing the surrounding muscle to shreds?