animal behaviour
edyong | July 19, 2009It seems like an uneven match. In one corner, the unassuming California ground squirrel (Spermophilus beechyi), 30cm in length. In the other, the northern Pacific rattlesnake (Crotalus oreganos), more than twice the length of the squirrel, and armed with hinged fangs that pack a lethal venom. But thanks to a cunning adaptation, the squirrel often gets an unexpected upper hand in this bout.
Ground squirrels live in a series of burrows that keep them out of reach of most predators. Snakes, however, have exactly the right body plan for infiltrating long sinuous tunnels, and it's not surprising…
neurophilosophy | July 17, 2009BATS use sonar, or echolocation, to navigate complex environments, and also to forage and then accurately pinpoint the flying insects on which they prey. Insects in turn have evolved various counter-measures to evade capture. Some species have ears which are in tune to the echolocation signals, while others are capable of performing complex evasive flight maneuvers in response to the clicks produced by attacking bats.
Tiger moths have evolved the ability to produce ultrasonic clicks in response to attacking bats. However, the function of these clicks was unclear, although decades of research…
edyong | July 17, 2009
Bats view the world in echoes, timing the reflections of their own ultrasonic calls to navigate and hunt. This biological sonar, or echolocation, has made them masters of the night sky; it's so sensitive that some species take moths and other insects on the wing, while others pluck spiders from their webs without entangling themselves in silk. But with such an efficient technology, it was only a matter of time before their quarry developed countermeasures.
Some insects gained ears; others simply rely on outmanoeuvring their attackers. But one group, the tiger moths, play bats at their own…
edyong | July 13, 2009While dogs can often be taught new tricks, cat-owners will be all too aware that it can be very difficult to persuade them to do something they don't want to do. Eddie Izzard summed it up best in his legendary Pavlov's cat sketch, where felines are quite capable of outfoxing (outcatting?) eminent Welsh-Russian psychologists. Real cats may be less devious, but only just - new research suggests that they are very skilled at getting their human owners to do their bidding.
When they want food, domestic cats will often purr in a strangely plaintive way that their owners find difficult to ignore…
edyong | July 5, 2009
Earlier today, I published a post on how Japanese honeybees defend themselves from hornets with a mass defence that relies on heat and carbon dioxide. This article was originally written two years ago, and describes the slightly different tactic of Cyprian honeybees.
When Oriental hornets attack, Cyprian honeybees mob them in a huge ball that targets the breathing apparatus in the hornet's abdomen. The hornets can't breathe without expanding their abdomens and with sheer numbers, the bees strangle the hornets to death.
Hornets are giant wasps that pack a powerful sting. To most people,…
edyong | July 5, 2009Rising temperatures and high carbon dioxide emissions are the means through which humans are inadvertently causing the decline of several species. But one animal actively uses both heat and carbon dioxide as murderous weapons - the unassuming honeybee.
With their stings and numbers, bees already seem to be well-defended but they are completely outgunned by giant hornets (right). These two-inch long monsters are three times longer than several times heavier than tiny honeybees and raiding parties can decimate entire hives. European bees mount little in the way of an effective defence, but…
edyong | July 1, 2009It's been just three weeks since I last wrote about the dark-footed ant-spider Myrmarachne melanotarsa, but this is one species that just keeps getting more and more interesting. To quickly recap, M.melanotarsa is a jumping spider that protects itself from predators (like other jumping spiders) by resembling an ant. Earlier this month, Ximena Nelson and Robert Jackson showed that they bolster this illusion by living in silken apartment complexes and travelling in groups, mimicking not just the bodies of ants but their social lives too.
Now Nelson and Robert are back with another side to the…
edyong | June 30, 2009In a classic episode of the Simpsons, Homer's brain explains to him that "money can be exchanged for goods and services". That's obviously true for humans (even cartoon ones) but monkeys use an altogether different form of payment - grooming. It's as close to a currency as monkeys have and it can be redeemed against a wide range of goods and services including more grooming, a free pass from aggression, permission to handle babies, back-up in fights and even sex.
The purposes of these exchanges go well beyond cleaning. Grooming, it seems, is also an enjoyable activity that releases brain…
edyong | June 29, 2009If the idea of a cold, motionless sexual partner isn't one of your turn-ons, then you're clearly not an echidna. The males of these spiny Australian animals will happily mate with females even if they're hibernating.
Gemma Morrow and Stewart Nicol from the University of Tasmania have spent the last decade studying the short-beaked echidnas of Tasmania. Over that time, they discovered many instances of males mating with torpid females in deep hibernation, or with females who roused themselves briefly only to re-enter their deep slumber. Over the last two years, the voyeuristic duo use a…
edyong | June 27, 2009
You don't have to be particularly intelligent to use tools - many animals do so, including some insects. But it takes a uniquely intelligent animal to be able to combine different tools to solve a problem. We can do it, the great apes can do it, and now the New Caledonian crow joins our exclusive club.
Animals can use tools using little more than pre-programmed behaviour patterns that require little intelligence. But combining tools, or using one tool on another (a metatool, if you will), is a different matter entirely - that takes reasoning. This type of intelligence has been the engine…
edyong | June 25, 2009You've got to feel sorry for the female seed beetle. Whenever she mates with a male, she has to contend with his spiked, nightmarish penis (remember this picture?). And despite the damage that it inflicts, one liaison just isn't enough; female seed beetles typically mate with many males before they lay their eggs. Surely, she must benefit in some way?
The most likely idea is that she somehow ensures that her eggs are fertilised by sperm from males with the "best" genes - those that either make for particularly fit and healthy young, or that are a compatible match for the female's own genes.…
edyong | June 16, 2009Underwater, fish make very difficult prey. When they sense sudden disturbances in the water around them, they respond within five thousandths of a second with a defensive reflex called the C-start. Their body contorts into a C-shape and with a flick of the tail, they rapidly zoom away from the potential threat. But one predator has a way of turning the fish's defence against it, persuading the fish to swim towards danger. It's the tentacled snake.
The tentacled snake (Erpeton tentaculatum) is a bizarre species, easily recognised by the pair of short "tentacles" on the front of its head.…
edyong | June 7, 2009Where there are plants, there are almost certainly aphids feeding on them. These ubiquitous insects are banquets for many predators, and some have evolved incredible defences against them. The cabbage aphid, for example, is a walking bomb.
Its body carries two reactive chemicals that only mix when a predator attacks it. The injured aphid dies. But in the process, the chemicals in its body react and trigger an explosion that delivers lethal amounts of poison to the predator, saving the rest of the colony.
The aphids' chemical weapons are stolen from the plants they eat. Far from being…
edyong | June 5, 2009For humans, sex is a simple matter of chromosomes: two Xs and we become female; one X and a Y and we develop into males. But things aren't so straightforward for many lizards - many studies have found that the temperature of the nest also has a say, even overriding the influence of the chromosomes. But the full story of how the lizard got its sex is even more complicated. For at least one species, the size of its egg also plays a role, with larger eggs producing females, and smaller ones yielding males.
The discovery comes from Richard Shine's group at the University of Sydney. In earlier…
edyong | June 4, 2009 If you tickle a young chimp, gorilla or orang-utan, it will hoot, holler and pant in a way that would strongly remind you of human laughter. The sounds are very different - chimp laughter, for example, is breathier than ours, faster and bereft of vowel sounds ("ha" or "hee"). Listen to a recording and you wouldn't identify it as laughter - it's more like a handsaw cutting wood.
But in context, the resemblance to human laughter is uncanny. Apes make these noises during play or when tickled, and they're accompanied by distinctive open-mouthed "play faces". Darwin himself noted the laugh-like…
edyong | June 3, 2009The animal world is full of harmless liars, who mimic species more dangerous than themselves in order to avoid the attention of predators. But none do it quite like the dark-footed ant-spider Myrmarachne melanotarsa.
As its name suggests, this small species of jumping spider, discovered just nine years ago, impersonates ants. In itself, that's nothing special - ants are so aggressive that many predators give them a wide berth and lots of species do well by imitating them. The list includes over 100 spiders but among them, M.melanotarsa's impression is unusually strong. It doesn't just mimic…
edyong | June 2, 2009In the darkness of the deep ocean, some animals create their own light. Among these is the Hawaiian bobtail squid Euprymna scolopes, which forms a partnership with the luminous bacterium Vibrio fischeri. The squid houses colonies of these bacteria in special light organs, and it can control the brightness and direction of their illuminations. But these organs do much more than produce light - they detect it too.
Deyan Tong from the University of Wisconsin has discovered that the organs generate nervous signals when they sense light and they're loaded with proteins responsible for detecting…
edyong | June 1, 2009Chimps are known to make a variety of tools to aid their quest for food, including fishing sticks to probe for termites, hammers to crack nuts and even spears to impale bushbabies. But a taste for honey has driven one group of chimps in Gabon's Loango National Park to take tool-making to a new level.
To fulfil their sweet tooth, the chimps need to infiltrate and steal from bee nests, either in trees or underground. To do that, they use a toolkit of up to five different implements: thin perforators to probe for the nests; blunt, heavy pounders to break inside; lever-like enlargers to widen…
edyong | May 23, 2009
Two years ago, a group of Ugandan chimps provided a blow to the idea that humans are the only animals that truly behave selflessly to one another. These chimps showed clear signs of true selflessness, helping both human handlers and other unrelated chimps with no desire for reward.
The question of why we help each other, instead of looking out for ourselves, is one of the most compelling in modern biology. Evolutionary and game theory alike predict that selfish behaviour should be the rule with altruism the exception, and animal experiments have largely supported this idea. Nature, 'red in…
edyong | May 19, 2009While the rapid expansion of human cities has been detrimental for most animals, some have found ways of exploiting these brave new worlds and learned to live with their prolific inhabitants. The Northern mockingbird is one such species. It's very common in cities all over America's east coast, where it frequently spends time around humans. But Douglas Levey from the University of Florida has found that its interactions with us are more complex than anyone would have guessed.
The mockingbird has the remarkable ability to tell the difference between individual humans, regardless of the…