Bats can jam other bats’ sonar

This video from the USA says about itself:

Flight of the Mexican Free-tailed bat at Bracken Cave

16 May 2011

We watched these Mexican Free-tailed bats flying out of Bracken Cave for over an hour. With an estimate of more than 20 million bats, this is the largest colony in the world. It takes around 4 hours for the entire colony to fly out to hunt. In this video, they are leaving to fly approximately 50 miles to feast on boll weevils in Texas cotton fields.

From New Scientist in the USA:

Bats jam each other’s sonar to steal meals

06 November 2014 by Penny Sarchet

Species: Mexican free-tailed bat (Tadarida brasiliensis)

Habitat: Large caves, hollow trees, bridges and attics ranging from Brazil to Nebraska in the US.

It’s frustrating when your smartphone loses its signal in the middle of a call or when downloading a webpage. But for bats, a sudden loss of its sonar signal means missing an insect meal in mid-flight. Now there’s evidence to suggest that bats are sneakily using sonar jamming techniques to make their fellow hunters miss their tasty targets.

Like other bats, the Mexican free-tailed bat uses echolocation to pinpoint prey insects in the dark. But when many bats hunt in the same space, they can interfere with each other’s echoes, making detection more difficult.

Jamming happens when a sound disrupts a bat’s ability to extract location information from the echoes returning from its prey, explains Aaron Corcoran of Johns Hopkins University in Baltimore, Maryland. Previous research has shown that Mexican free-tailed bats can get around this jamming by switching to higher pitches. Using different sound frequencies to map the hunting grounds around them allows many bats to hunt in the same space.

In these studies, jamming of each other’s signals was seemingly inadvertent – a simple consequence of two bats attempting to echolocate in close proximity. But Corcoran has found evidence of sneakier goings-on.

Sonar sabotage

Corcoran has found a second type of sonar jamming in these bats – intentional sabotage of a fellow bat. “In this study, the jamming is on purpose and the jamming signal has been designed by evolution to maximally disrupt the other bat’s echolocation,” he says.

Working with William Conner of Wake Forest University in Winston-Salem, North Carolina, Corcoran compared flight-path calculations with audio and video field recordings. They discovered that these bats emit special ultrasonic signals that interfere with the echolocation of other bats that are attacking insect prey.

“For this type of jamming, the interfering sound needs to overlap the echoes in time and frequency,” says Corcoran. This is unlike previously described accidental jamming, which covers only a single frequency, so can be avoided by shifting to another frequency. “This jamming signal covers all the frequencies used by the other bat, so there’s no available frequency to shift to.”

Vicious competition

Playing back recordings of these jamming calls was enough to make flying bats miss their insect targets. Corcoran suggests being jammed by another bat is like having your sense of where an insect is become blurry. “The bats know a moth is there, they just can’t quite know where it is with sufficient detail to capture it.”

He believes the bats do this to each other because they live together in huge numbers, putting them in tough competition for the same food. “This species has the largest aggregations of mammals on the planet – up to one million individuals in a single cave,” explains Corcoran. Leaving a moth for another bat and going to look for another costs more energy. “It’s all about efficiency of getting food. Under high levels of competition, it pays to stay and fight for a food item.”

But it’s a game that one insect has evolved to get in on too. Grote’s bertholdia moth (Bertholdia trigona) is the only moth known to jam bat echolocation to protect itself from being caught and eaten. Corcoran says it jams most bats that have been studied, by making a barrage of high-frequency clicks as a bat approaches them. Far above the range of human hearing, it’s a life-or-death audio battle out there.

Journal reference: Science, DOI: 10.1126/science.1259512

Bats at Terschelling island ice rink

This video from the USA is called Bat Biology in Pennsylvania. Part 1 of 2.

And this video is the sequel.

Dutch ecologist Reinier Meijer reports about bats on Terschelling island.

The Dutch Wadden Sea islands are not really good environments for bats, compared to the continental Netherlands, as temperature is often lower and wind is often stronger.

A good place for bats on Terschelling is the Hêdreederplak near Hoorn village. Most of the year, this is a pond. In cold winters, it becomes an ice rink.

Common pipistrelles are a common species at the Hêdreederplak.

Nathusius’ pipistrelles are rather frequent as well.

Serotine bats used to be there as well, but have not been heard by bat detectors there since 2011.

Parti-coloured bats have been recorded since 2012.

Also since 2012, a brown long-eared bat was heard. Probably there was more than one individual, but recording this species is not easy.

Bats’ brains, new study

This video from the USA says about itself:

Bat Biology 101

3 July 2013

Bat biologist Dr. DeeAnn Reeder gives a quick lesson on bat physiology and anatomy.

From Wildlife Extra:

New study gets inside the brains of bats

A groundbreaking new study at Technische Universität München in Germany has found that there’s more to bats’ use of echolocation that meets the eye (or ear).

The study set out to investigate spatial orientation in bats, and reveals for the first time that spatial maps representing different echo delays in the brains of bats adapts to external factors.

Of course the use of echolocation in bats is nothing new. It has long been known that bats measure the delay of their echoes in order to navigate and hunt prey, but just what goes on in their brains to enable them to map their surroundings so efficiently has been unclear.

The study – run by Dr. Uwe Firzlaff – reveals that when a bat flies too close to an object, the number of activated neurons in its brain increases, resulting in the object appearing disproportionately larger on the bat’s brain map than objects at a safe distance, as if it were magnified.

“The map is similar to the navigation systems used in cars in that it shows bats the terrain in which they are moving,” Firzlaff explains. “The major difference, however, is that the bats’ inbuilt system warns them of an impending collision by enhancing neuronal signals for objects that are in close proximity.”

In essence, bats in flight are constantly evaluating their movement and mapping it against their distance to objects. “Our research has led us to conclude that bats display much more spatial information on their acoustic maps than just echo reflection,” says Firzlaff. “We may have just uncovered one of the fundamental mechanisms that enables vertebrates to adapt flexibly to continuously changing environments,” he concludes.

See also here.

The new research was published here.

Bat boxes in Britain

This video is called hy Do Bats Need Cowpats? – The Animal’s Guide To Britain, Episode 2 – BBC Two.

From the RSPB in Britain:

Build a home for bats

Bats are finding it hard to find food to eat, plus many of their natural sleeping places are being damaged and destroyed.

Simply putting up a bat box will help these night-time creatures have somewhere safe to raise a family and sleep during the day.

You’ll want to keep an eye out for common pipistrelles – they are our smallest bats, weighing the same as 10 paperclips and are small enough to fit in a matchbox!

RSPB bat boxes: see here.

Helping bats in the Netherlands: here.

Bolivian golden bat discovery

This video says about itself:

Golden Bat Revealed As ‘New Species

4 August 2014

From the BBC:

4 August 2014

Bolivian golden bat revealed as ‘new species’

By Michelle Warwicker, BBC Nature

A golden bat from Bolivia has been described as a new species by scientists.

Myotis midastactus had previously been classified as another bat found in South America called Myotis simus.

But examination of a collection of museum specimens suggested the existence of a different species, thought to live only in Bolivia.

Its most distinctive characteristic is its golden-yellow, very short and woolly fur.

This bright colouration – which is unique among New World Myotis species – earned the bat its new name midastactus, after the Greek legend of King Midas and his golden touch.

There are over 100 species of Myotis – or mouse-eared bats – in the world.

In the wild, Myotis midastactus lives in the Bolivian savanna. It eats small insects and roosts during the day in holes in the ground, hollow trees and under thatched roofs.

The full description of the species, published online in the Journal of Mammalogy, was carried out by Dr Ricardo Moratelli and Dr Don Wilson, from Fundacao Oswaldo Cruz (Oswaldo Cruz Foundation), Rio de Janeiro, Brazil and the Smithsonian Institution in Washington, US respectively.

Dr Moratelli built on a paper he published in 2011 suggesting differences in bats from Bolivia to others found in the Amazon basin.

The team carried out detailed morphological and morphometric statistical analyses of 27 museum specimens kept in several museums in the US and Brazil, to confirm the existence of a distinct species.

Dr Moratelli admitted he has been unable to capture living specimens of Myotis midastactus, despite having spent two months trying to do so. However he highlighted the importance of museum specimens as a resource for studying biodiversity: “I can confidently say that many new species from different zoological groups are in museum cabinets around the world, awaiting recognition and formal description.”

He added: “Discovering new species is the most exciting part of my research, and in some cases describing a new species can be the first step to preserve others.”

According to the new study, the conservation status of Myotis midastactus is not yet clear. But it acknowledges that scientists previously described Myotis simus living in Bolivia (now believed to be Myotis midastactus) as “near threatened”.

The new study also suggests Myotis simus – also known as velvety Myotis – does not live in Bolivia, although it is found in Argentina, Brazil, Ecuador, Paraguay and Peru.

Myotis midastactus is the fifth new species of bat Dr Moratelli has described. Others include Myotis diminutus, a tiny bat species found in the Ecuadorian Andes; Myotis lavali from north-eastern Brazil, Myotis izecksohni found in Atlantic forest in southern Brazil, and Myotis handleyi from the mountains of northern Venezuela.

The new discovery is the latest development of a larger project which aims to find out more about mouse-eared bats living in the neotropical ecozone.

First bat ever seen on St Kilda island

This video is called Nathusius’ pipistrelle bats advertising for mates.

From the BBC:

1 July 2014 Last updated at 08:54 GMT

Bat recorded for the first time on St Kilda

A bat has been recorded for the first time on the remote Scottish archipelago of St Kilda.

The Nathusius’ pipistrelle, which is a rare sight on the UK mainland, was spotted by visitors last month.

The bat was found on St Kilda’s main island of Hirta, resting on the wall of a small, stone-built store known as a cleit.

Nathusius’ pipistrelles are a migratory species and were first recorded in Britain in Shetland in 1940.

Individual animals have been recorded on North Sea oil platforms and the Shetland and Orkney islands, according to the Bat Conservation Trust.

The only mammals previously found on St Kilda, which lies 41 miles (66km) east of the Isle of Lewis, were Soay sheep and the St Kilda field mouse.

The islands once had house mice, but they died out after the last human residents abandoned St Kilda in 1930.

The National Trust for Scotland, which manages St Kilda, said it was not known from where the bat had flown.

Bats in Friesland, the Netherlands

This video from The Netherlands says about itself:

After sunset, the common noctules leave their home.

Ecologists from Friesland in the Netherlands report about bats in the north east of that province.

Six bat species were found.

They were (in order of numbers, with the most common species first): common pipistrelle, Nathusius’ pipistrelle, serotine bat, common noctule bat, Daubenton’s bat and particoloured bat.

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