animal behaviour
edyong | September 21, 2009This article is reposted from the old Wordpress incarnation of Not Exactly Rocket Science. The blog is on holiday until the start of October, when I'll return with fresh material.
The sabre-toothed cat is one of the most famous prehistoric animals and there is no question that it was a formidable predator, capable of bringing down large prey like giant bison, horses, and possibly even mammoths. The two massive canines - the largest teeth of any mammal - are a powerful visual. But while they were clearly powerful weapons, scientists have debated their use for over 150 years.
Now, a new study…
edyong | September 16, 2009
For humans and most other mammals, sex is a question is chromosomes. Two X chromsomes makes us female while an X and a Y makes us male. Birds use a similar but reversed system, where males are ZZ and females are ZW. But for reptiles, including crocodiles, turtles and many lizards, sex is determined not by genes, but by temperature.
In crocodiles, males hatch from eggs incubated at cooler temperatures while warmer conditions produce females. In turtles, it's the other way around, and lizards use a variety of criteria including some very complicated combinations of genes, temperature and…
edyong | September 9, 2009When food is precious, animals can resort to strange behaviours in order to satisfy their hunger. Take the great tit. Its usual diet of insects and creepy-crawlies is harder to come by in winter. But in one Hungarian cave, great tits, ever the opportunists, have learned to exploit a rich and unusual source of food. They kill sleeping bats.
Great tits are only about 5 inches long, but their prey - the pipistrelle bat - is smaller still, just an inch or two in size. The bats spend the winter months hibernating in rock crevices. They're well hidden, but when they wake up, they start making…
edyong | September 8, 2009When danger threatens many lizards can detach their tails, leaving them behind as decoys in the hope that the predator will attack it rather than the lizard itself. But the tail doesn't just lie there as bait. For half an hour after they've been severed, the disembodied tails perform a complex dance, flipping, lunging and jumping up to an inch in the air. These acrobatics serve to distract the predator even further.
For the first time, Timothy Higham and Anthony Russell have studied the movements of severed gecko tails to understand how they can move in such complex ways without any input…
edyong | September 4, 2009Domestic dogs are very different from their wolf ancestors in their bodies and their behaviour. They're more docile for a start. But man's best friend has also evolved a curious sensitivity to our communication signals - a mental ability that sets them apart from wolves and that parallels the behaviour of human infants. Dogs and infants are even prone to making the same mistakes of perception.
Like infants less than a year old, dogs fail at a seemingly easy exercise called the "object permanence task". It goes like this: if you hide an object somewhere(say a ball under a cup) and let the…
edyong | September 2, 2009Birds have a variety of alarm calls that warn other members of the flock about impending danger. But for some birds, the very act of taking off is enough to sound the alarm. Mae Hingee and Robert Magrath from the Australian National University have found that crested pigeons have modified wing feathers that produce distinct whistles when the birds take off quickly and steeply. That's exactly the sort of flight that they undertake when they're alarmed, and other pigeons treat the resulting whistles as cues to take to the skies themselves.
Crested pigeons are comical-looking birds that are…
neurophilosophy | August 26, 2009
THIS weird and wonderful creature is the star-nosed mole (Condylura cristata), a small, semi-aquatic mammal which inhabits the low wetlands of eastern North America. Like other moles, it ekes out an existence in a network of narrow underground tunnels, and digs shallow surface tunnels where it forages for insects, worms and molluscs. Living as it does in almost complete darkness, the star-nosed mole has poorly developed eyes, and is virtually blind. Instead, it relies heavily on its remarkable star-shaped nose. This organ enables the star-nosed mole to decide whether something is edible with…
edyong | August 21, 2009Viruses and bacteria often act as parasites, infecting a host, reproducing at its expense and causing disease and death. But not always - sometimes, their infections are positively beneficial and on rare occasions, they can actually defend their hosts from parasitism rather than playing the role themselves.
In the body of one species of aphid, a bacterium and a virus have formed a unlikely partnership to defend their host from a lethal wasp called Aphidius ervi. The wasp turns aphids into living larders for its larvae, laying eggs inside unfortunate animals that are eventually eaten from…
edyong | August 20, 2009
During chase scenes, movie protagonists often make their getaway by releasing some sort of decoy to cover their escape or distract their pursuer. But this tactic isn't reserved for action heroes - some deep-sea animals also evade their predators by releasing decoys - glowing ones.
Karen Osborn from the Scripps Institute of Oceanography has discovered seven new species of closely related marine worms (annelids) that use this trick. Each species pack up to four pairs of "bombs" near their heads - simple, fluid-filled globes that the worms can detach at will. When released, the "bombs" give…
edyong | August 20, 2009
In 2007, Jan Souman dropped three volunteers into the Sahara desert and watched as they walked for several miles, in an attempt to walk in a straight line. Souman was interested in the widespread belief that lost travelers end up walking in circles, a belief that has never been properly tested but has nonetheless become firmly entrenched in the popular consciousness. Just think about Frodo and Sam's hike through Mordor or the three hapless teens in the Blair Witch Project.
To see how non-fictional humans would fare, Souman tracked a group of volunteers using GPS as they walked through a…
edyong | August 18, 2009Several million years ago, at a time when dinosaurs walked the earth, a flying reptile - a pterosaur - came in for a landing. As it approached, it used its powerful wings to slow itself down and hit the ground feet first. It took a short hopping step before landing a second time. On solid ground, it leant forward, put its arms down and walked away on all fours.
The landing made quite an impression on the underlying limestone mud and in the following millennia, the creature's tracks became fossilised. Now, they have been unearthed by Jean-Michel Mazin from the University of Lyon at a site…
edyong | August 13, 2009They say that imitation is the sincerest form of flattery and it appears that capuchins believe it too. These very sociable monkeys gravitate towards humans that mimic their actions, spending more time in their company and even preferring to trade with them.
Annika Paukner, who studied this monkey business, thinks that imitation is a type of social glue that binds groups of monkeys together. It says, "We are alike," and in doing so, it lays the foundation for acts of selflessness by providing a means for two individuals to form an empathic connection.
Certainly, imitation is very much a…
edyong | August 12, 2009In a French laboratory, a team of ants is attempting a daring rescue. One of their colony-mates is trapped in a snare - a nylon thread that dastardly researchers have looped around its waist and half-buried in some sand. Thankfully, help is at hand. A crack squad of rescuers work together to dig away at the sand, expose the snare, and bite at the threads until their colleague is liberated.
Many animals help each other but actual rescue attempts, even between individuals of the same species, are rarely documented. Among back-boned animals, dolphins are famously said to help injured comrades…
edyong | August 10, 2009This article is reposted from the old Wordpress incarnation of Not Exactly Rocket Science.
In the Alien movies, the eponymous monster killed shipmates and marines with a fearsome set of double jaws. That may have been science fiction but science fact isn't too far off. In our planet's tropical oceans, moray eels use a ballistic set of second jaws to catch their prey.
These 'pharyngeal jaws' are housed in the eel's throat. When the main jaws close on an unlucky fish, the second set launches forward into the mouth, snags the prey with terrifying, backward-pointing teeth and drags it back into…
neurophilosophy | August 6, 2009NOT so long ago, the idea that birds might possess some form of what we call intelligence seemed quite ridiculous. Yet this view has changed dramatically in recent years, with numerous studies showing that some bird species are capable of complex cognition. Members of one family of birds in particular - the Corvidae, which includes crows, rooks and ravens - have an ability to make and use tools which is at least as sophisticated as that of chimpanzees.
Two new studies, published this week, provide yet more demonstrations of the remarkable cognitive abilities of this group of birds. One shows…
edyong | August 6, 2009Aesop's fable "The Crow and the Pitcher" has been confirmed in a wonderful experiment. In the classic tale, a thirsty crow uses stones to raise the level of water in a pitcher until it rises within reach of its beak. This is no mere fiction - rooks, close relatives of crows, have the brains to actually do this.
The aptly named Chris Bird, along with Nathan Emery, gave four captive rooks (Cook, Fry, Connelly and Monroe) a chance to reach a small worm floating in a cylinder of water, with nothing but a small pile of stones sitting on the side. All of them solved the task, and Cook and Fry…
edyong | August 4, 2009You'll sometimes hear people lowering their voices to make themselves sound tougher or more commanding. We're not the only ones - it seems that our close relatives, the orang-utans, pull the same trick, and they use tools to do it. Madeleine Hardus from the University of Utrecht has found preliminary evidence that young orang-utans use leaves for deception, in order to make lower-pitched calls that seem to come from a much larger animal.
While many animals are accomplished tool-users, most use their utensils to find food. A few populations of orang-utans, living in Borneo, are the only…
edyong | July 31, 2009This article is reposted from the old Wordpress incarnation of Not Exactly Rocket Science.
An ant nest is sheltered, well defended and stocked with food, but one that takes time to build and protect. That's why some species of ants don't bother to do it themselves - they just squat in the nests of others.
These ants are 'social parasites' - they don't feed off their hosts' tissues, but instead steal their food, sleep in their homes and use their resources. They're like six-legged cuckoos
An ant colony is too dangerous a target to victimise lightly and the social parasites use several…
edyong | July 29, 2009This article is reposted from the old Wordpress incarnation of Not Exactly Rocket Science.
Fizzy drinks like Perrier and Coca-Cola are targeted at a huge range of social groups, but if fruit flies had any capital to spend, they'd be at the top of the list. Unlike posh diners or hyperactive kids, flies have taste sensors that are specially tuned to the flavour of carbonated water.
Humans can pick up five basic tastes - sweet, salty, sour, bitter and umami (savoury). But other animals, with very different diets, can probably expand on this set. And what better place to start looking for these…
edyong | July 23, 2009Relative 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…