Tag: animals

The pressure of a watching audience can have positive or negative effects on human performance, and it turns out the same is true of our closest relatives.

Christen Lin at Kyoto University, Japan, and his colleagues tested a group of six chimpanzees housed at the university’s primate research institute on three numerical tasks with varying difficulty.

In the first task, the numbers 1 to 5 appeared on the screen in random locations and the chimps simply had to touch the numbers in the correct order to get a food reward.

In the second task, the numbers weren’t adjacent: for example, 1, 3, 5, 7, 11 and 15 might appear on the screen. Again, the chimps had to press the numbers from smallest to largest in order to receive a reward.

Finally, in the hardest test, when the first number in the sequence was pressed, the rest of the numbers were hidden behind chequered squares on the screen. This meant the chimps had to memorise the location of the numbers in order to press them in the correct order.

The chimps were tested on the tasks thousands of times over a six-year period with varying audiences – from one to eight human observers, some familiar to the chimps and others who were new.

When the task was easy, the chimps performed worse when there were more people watching. But on the most difficult task, all six of the chimps did better as the size of the audience grew.

“It was very surprising to find a significant increase in performance as human experimenter numbers increased, because we might expect more humans being present to be more distracting,” says Lin. “However, the results suggest that this may actually motivate them to perform even better.

“For the easiest task, the humans may be distracting to them, but for the most difficult task it is possible that the humans are a stressor that actually motivates them to perform better.”

Team member Shinya Yamamoto, also at Kyoto University, says they were very surprised to find this effect in the chimps.

“Such an audience effect is often thought to be unique to humans, who live in a reputation-based normative society, where we sometimes perform better in front of an audience and sometimes perform worse than we expected,” he says. “But our study shows that this audience effect may have evolved in the ape lineage before the development of this kind of normative society.”

Yamamoto says it is difficult and sometimes dangerous to draw direct implications for humans from non-human studies. “But, in a casual way, we may be able to ease the tension of those who are extremely nervous in public by saying chimpanzees are the same!”

Miguel Llorente at the University of Girona, Spain, suggests further studies could explore how the audience effect is related to chimpanzees’ individual personalities.

“It would also be fascinating to explore these effects with chimpanzee audiences to understand more fully how these dynamics play out in a natural social context in order to generalise these results to the natural behaviour of chimpanzees,” he says.

Elephants are masters at using a hose – considered a complex tool because of its flexibility, length and the physics of flowing water.

Researchers studying three Asian elephants (Elephas maximus) at Berlin Zoo were surprised to see how nimbly they manipulated a hose to shower themselves and seemed to understand how to get the best use out of it. They even appeared to play pranks on each other by stopping the flow mid-shower – either by kinking the hose or compressing it with their trunks.

To reach more distant parts of the body, the elephants used a lasso-like technique, holding the hose further from the end and swinging it over their backs.

Michael Brecht at the Humboldt University of Berlin says the elephant behaviour around hoses reminded the team of the way children might play together.

“Elephants are exceptionally good with hoses and we very much wonder if this is related to the functional similarity of trunks and hoses,” he says.

Just as humans are either left-handed or right-handed, African and Asian elephant individuals are either left or right “trunkers”, preferring to bend their trunk in one direction. The researchers noticed that the elephants also had a side preference when they manipulated the hose. One of the elephants, named Mary, used her trunk for showering the right side of her body but used the hose more for the left side.

Another of the elephants, named Anchali, showed five different behaviours to disrupt water flow when Mary was trying to shower – hose positioning, lifting, kinking, regrasping the kink and compressing.

“This sabotage-like behaviour, if that’s what it is, has been seen in only very few animals,” says Brecht.

Brecht’s previous research suggests elephant trunks are one of the most sensitive body parts in the animal kingdom, enabling them to handle objects with similar precision to the human hand.

“The research reiterates the idea that elephants show very sophisticated trunk behaviours,” he says.

https://www.youtube.com/watch?v=VIKS6pXvays

Experiments with vampire bats running on treadmills have revealed they have a highly unusual method of getting energy from protein, due to their specialised diet.

Most mammals get the bulk of their energy for movement from fats and stored sugars, but the three species of vampire bats subsist on a diet of blood drawn from their victims, which is rich in proteins but low in fats and sugars. How their metabolism works is therefore unclear, as amino acids, which make up proteins, typically supply less than 10 per cent of animals’ energy during exercise.

To learn more about their metabolism, Kenneth Welch and Giulia Rossi at the University of Toronto in Canada studied 24 adult common vampire bats (Desmodus rotundus) captured in Belize. The bats were fed on cows’ blood containing amino acids with labelled carbon atoms, then placed on a treadmill in a small box.

The bats’ metabolic rate was measured by tracking oxygen intake and carbon dioxide expiration while they ran on the treadmill at speeds of up to 30 metres per minute. By analysing the carbon isotopes in the exhaled breath, the researchers found that they were drawing energy from their recent meal rather than stored fats or sugars.

Welch conceived of the experiment 20 years ago while researching how hummingbirds made use of the sugar in nectar, and discovering that there was a similarity with nectar-feeding bats. He knew that the tsetse fly (Glossina morsitans) fed on blood and was unusual in that it didn’t make use of fats or carbohydrates, but instead used proteins, and wondered if vampire bats would be similar.

But while hummingbirds and some nectar bats can hover in flight, making experiments possible without a large and expensive wind tunnel, vampire bats cannot. However, they do have the ability to run at speed, which they use to track prey on the ground, so Welch and Rossi could put them through their paces on a treadmill instead.

Drawing most energy from amino acids is unusual in the animal kingdom, confined to blood-feeding insects, emperor penguins during long periods of fasting and hibernating bears. “What’s different here is that this seems to be what this animal is going to do all year round, every day when it feeds, and that it’s making use of the protein in that blood meal that it ingested just minutes before,” says Welch. “That’s what really separates these animals from most of the rest of us.”

While most animals can turn nutrients into sugars and fats and store them away, vampire bats have evolved a different strategy that leaves them far more susceptible to starvation – in fact, they are at risk of starvation after only 24 hours without feeding, says Welch. To compensate for this, they have developed strong social bonds and will share meals with each other when one member of the group has failed to find food, regurgitating some of their own blood meal into another bat’s mouth to sustain it.