Bats ‘recognise other’s voices’

As if flying around in the dark swooping and diving to catch insects was not tricky enough, bats also listen for their fellow hunters.

A study has revealed how these winged mammals recognise other bats’ voices.

They are able to differentiate the ultrasonic “echolocation” calls that other bats make as they navigate.

In the journal PLoS Computational Biology, the scientists report that the bats have an internal “reference” call to which they compare others.

Yossi Yovel from the Weizmann Institute of Science, Israel, and his colleagues in Germany recorded the echolocation calls of five greater mouse-eared bats

The bats use these brief bursts of sound in sonar navigation - bouncing sound waves off their surroundings to find their way and locate prey.

Dr Yovel’s team tested the bats’ ability to identify the others by playing the recorded sounds to them.

“Each bat was assigned two others it had to distinguish between,” Dr Yovel explained. “So we trained bat A on a platform, playing a sound from bat B on one side and from bat C on the other. He had crawl to where the ‘correct’ sound was coming from.”

Each of the subjects was taught that a call from just one of the other bats was correct.
So during this training exercise, if the bat A made the right choice, and crawled towards the sound from bat B, it was rewarded with its favourite food - a mealworm.

“Then, in the next stage - the test - we rewarded them no matter what choice they made, and they still chose correctly more than 80% of the time,” said Dr Yovel.

“So we knew the bats were able to distinguish individuals. But it wasn’t clear what they’re using to discriminate one from the other.

“If you think of this in comparison with humans, it’s like being able to recognise a person just by listening to the same one-syllable yell in different voices.

“The bats learned the voice by listening to hundreds of very short ‘yells’, but they then were able to recognise an individual based on one single yell.”

Modelling sound

In the second part of the study, Dr Yovel’s team designed a computer model to mimic the way in which the bats compared the different sounds.

“The model takes all the calls the bat thought were A, and all the calls it thought were B, and tries to understand what differences it is using to match them up,” said Dr Yovel.

“Our analysis showed that each bat has a typical distribution in the frequencies it emits, probably a result of the differences in each animal’s vocal chords.”

He thinks the bats may have an internal “prototype” - a sort of reference sound against which they can compare these subtle differences.

This could explain how bats remain in a group when flying at high speeds in darkness, and how they avoid interference between each others’ echolocation calls.

Ranchers driving wind revolution

Texan cattle rancher Mike Baca seems an unlikely evangelist for the American green revolution.

When he voices a visceral dislike of the “Washington liberals” there seems to be little hint of the environmentalist beneath the cowboy hat and saucer-sized belt-buckle.

But Mike is proof that renewable energy now unites the partisan debate on climate change.

Many Republicans sceptical of climate science support a major expansion of renewables to ease their nation’s dependence on foreign oil.

In Mike’s case, the tantalising prospect of pocketing hundreds of thousands of dollars from wind turbines on his ranch proves an extra incentive.

The sprawling ranch lies in the Texas panhandle on the high plains near Amarillo. Mike will not say how much land he owns but it stretches way beyond the horizon in all directions.

These high plains were considered low-grade land until engineers developed the fan-shaped wind pump to suck water from the shallow Ogallala aquifer and create cattle country.
The aquifer is running dry but engineers have again harnessed the wind to bring income to the relatively small number of people who own these vast empty spaces.

Mike is one of them. His nearest neighbours are miles away.

From the porch of his ranch-house - Tuscan with a Texan twist - at the floor of a verdant canyon he can sip bourbon and watch the giant blades turning a perpetual profit.

“I like them. And I like the cheque that comes with them,” he says.

“I could do with a few more of them. We have to be concerned about what the world will be like for our grandchildren. If the turbines get noisy I can just switch on the fountain.”

Texas utilities are planning a high voltage loop around the Panhandle to carry the power to the population centres of Dallas-Fort Worth and Houston.
Donny Allred, the local county judge, is lobbying to lure the power lines to Amarillo.

“This is the most perfect marriage of two industries - wind and cattle ranching,” he says.

“They were made for each other.”

The power lines will carry about 50% wind power and 50% from coal and gas to ensure security of supply.

The great river of wind that flows from Texas to the Canadian border is one of the finest renewable energy reserves in the world and the American Wind Energy Association estimates that it could power America twice over.

Ranch land is plentiful and the cows don’t protest that their view is being spoiled - in fact they shelter in the shade of the turbine towers.

The profits are so easy that while energy investments have been plummeting worldwide, the high plains have been distracting the footloose energy giants from their planned offshore wind projects in the UK.

The Obama administration is now working with American utilities nationally to create interconnectors to get the power where it is needed to the great cities on the coasts.
Some of the “wind states” have passed local laws stipulating the use of wind energy but some have been slow to capitalise.

The Waxman-Markey Climate Bill going through Congress would mandate a minimum 20% renewables target for all states by 2020.

The proposal has been watered down from 25% renewables in 2025. It is resisted by some politicians in south-eastern states where there is high dependence on Appalachian coal and less plentiful wind or solar power.

The US energy secretary Steven Chu told BBC News that the 20% target was easily achievable. But environmentalists oppose it for that very reason.

They say many states are on track to achieve more than 20% renewables by 2020.
Jennifer Layke from the World Resources Institute in Washington told BBC News: “I think that we could do more with the emissions targets on the renewables front.

“I think this is a political compromise to manage issues associated with specific geographical concerns for the southern part of the United States and other areas.”

“As such, I think it creates the floor for action. That’s a big improvement. It does not necessarily create the exponential scale-up of renewable technology that we need to combat climate change.”

Either way, the renewable revolution has widespread support. At a rally of the Goldwing Road Riders in Amarillo we met bikers from both sides of the political divide. They were united over wind.

Biker Wayne Jones said: “Oh lord! Climate change. I think that the wind is better than oil. It is a whole lot cleaner. Mother nature has given you the wind. It is free energy.”

Deborah Jones, another biker at the rally, told BBC News: “We need to be self-sufficient. As a nation, we need to rely on the United States.”

India made 363 runs against Sri Lanka in 50 overs

Good Eveing friends, something I like to share. India made 363 runs against Sri Lanka in 50 overs.

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