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"You Callin' Me A Liar?!"
"You Callin' Me A Liar?!"
Yes, indeed, we are. When in a tight corner, it can be really useful to lie through your teeth. Humans are experts at using our voices to deceive, as anyone who's been on the wrong end of a scamming sales call will know. But animals do it, too.
Some creatures sound a false alarm to scare off the competition, effectively crying wolf. The males of some species can mimic the call of a fearful predator in order to scare a female – who might freeze in fear long enough to allow the male an opportunity to mate with her. And some animals can even call out in a way that makes them sound like they taste bad. Here are some animals that have turned verbal deception into an art form.
Bats Be Jamming
Bats have their own sonic tricks up their sleeve. Many navigate by echolocation, sending out pulses of ultrasonic sound and listening for them to bounce back from objects. As a result, they are vulnerable to dirty tricks by some of the moths they are attempting to grab. That dirty trick is called jamming – a siren-like noise given at close range – that messes up the bats' ability to interpret its echolocation signals.
Jamming of bat signals by moths has been known for some time, but recently, while studying Mexican free-tailed bats, observers discovered that it wasn't just moths doing the jamming. While videotaping moths jamming bats, "we kept hearing this funny signal that the bats were making." This signal turned out to be a method of competitive jamming: bats foiling other bats as a way to snatch each other's food. "Imagine two bats approaching a target. The one in the front is just about ready to catch the target moth. The one in the back sends out the jamming signal. It jams the guy in the front, and the guy in the front misses [the target], and then the guy in the back comes in and cleans up." It's the first time this has been documented in animals.
It's unclear how jamming works. One idea is that jamming signals create a "phantom echo" that sends the recipient in the wrong direction. However, biologists now think jamming is not really a deceptive signal, but a way to block signals from being interpreted correctly.
Monkeys That Lie For Bananas
In Aesop's fable of The Boy Who Cried Wolf, a shepherd boy pranks his neighbours with false alarms. He gets his comeuppance when a real wolf appears and no one believes his cries for help. However, in nature some animals win out by raising false alarms.
Tufted capuchin monkeys are masters of false alarms, using deceptive alarm calls to grab extra food.
In Iguazú National Park in Argentina, a team was studying how the capuchins respond to predators, using experimental feeding platforms strung up in the treetops. The platforms were stocked with bananas, which the capuchins "are completely insane for". The highest ranking capuchins would "just sit there and eat as much as they want, and subordinate individuals just sit on the outside watching them." Occasionally the junior monkeys tried to reach in for a piece, but when they did, the senior capuchins often bullied them.
But something odd was going on. Capuchins make hiccup-like alarm calls to warn of an approaching wild cat, and observers heard these calls much more often at the feeding platforms than elsewhere. They suspected that the junior capuchins were crying wolf to scare their elders away from the bananas. In a series of experiments, it was almost always the low ranking individuals that were giving the false alarm calls. What's more, they used the fake calls more when the food was clumped on just one or two platforms. With more platforms, even the low ranking individuals don't need to deceive to get access.
The senior capuchins are not deceived for long, so it's a snatch and grab operation for the deceiver, maybe yielding only a handful of bananas. It works because the threat of predators is very real. The price of ignoring a genuine warning may be death, so they may accept being duped occasionally.
Duping By Dastardly Drongos
African birds called fork-tailed drongos run a food-stealing racket similar to the capuchins'. In the dry savanna of the southern Kalahari, observers have studied what they get up to.
Individual drongos hang out with lots of other bird species in mixed-species flocks. In those flocks, the drongos are security guards. They warn everyone within hearing distance about approaching predators, allowing the other birds to flee. Thanks to the drongos, birds like southern pied babblers and other animals like dwarf mongooses can spend less time standing guard and, at least in the case of the babblers, more time stuffing their faces with food.
But fork-tailed drongos also use false alarm calls to steal food, by scaring their competitors out of the way. Earlier this year, observers reported that drongos can mimic the warning sounds of about 45 other species, including the bark of a meerkat. This sounds like bad news for the other animals, but the drongos may be a good thing overall. In another recent study, the team looked at how one of the most common species in the flocks, the sociable weaver, responds to the drongos.
Sociable weavers build massive communal nests that house between 20 and 500 individuals. They normally feed within 1.5 km of this home base. The team followed foraging flocks of weavers and observed their feeding habits. By recording drongo calls in the presence or absence of weavers, they discovered that the drongos have a special call that they only use when weavers are around. Perhaps surprisingly, the weavers were attracted to these sentinel calls. They seemed to be an "all clear" signal, calling the weavers back if they had scarpered – including on occasions when the alarm call had been a fake. It seemed the weavers preferred to have the drongos around. When they did, the weavers spent more time foraging and less time standing guard.
It seems the sociable weavers put up with the manipulative drongos, even though they use sneaky tricks to steal food, because they also prevent others from being eaten. And the arrangement with the multi-species flock clearly works for the drongos. They obtain nearly a quarter of their total food intake by crying wolf.
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Source: http://bbc.in/1ybOxxC
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