August 7, 2012
iBatsID: New Tool Can Differentiate Bats By Sound
Michael Harper for redOrbit.com — Your Universe Online
Have you ever tried to tell the difference between 34 different bat species?
Like a fingerprint or the specific pitch and timbre of a person´s voice can differentiate one human from another, so, too, can the subtleties in squeaks and squelches set one bat apart from the others. Now, a team of ecologists have built an echo-location tool which can identify specific bats based on their vocal signatures.
The new tool, called iBatsID, can be used for free all across Europe. Bat conservation efforts in this part of the world have become increasingly important in recent years as bats fall victim to diseases such as “white nose syndrome,” as well as other fatal illnesses.
Partnering with an international team of ecologists, PhD student and lead author Charlotte Walters from the Zoological Society of London (ZSL) pulled data from a set of 1,350 calls from more than 34 species of European bats. All told, Walters was able to build an international library of more than 200,000 bat calls.
Charlotte and team then analyzed these calls to distinguish the tiniest of differences between them. The team then determined which bat call characteristics were most useful in distinguishing the bat calls from one another.
In a statement, Walters described the process this way: “Lots of different measurements can be taken from an echolocation call, such as its maximum and minimum frequency, how quickly the frequency changes during the call, and how long the call lasts, but we didn´t know which of these measurements are most useful for telling different species´ calls apart.”
Of these distinguishing characteristics, Walters and team chose 12 with which to “train” the networks and processes behind the iBatsID tool. Armed with this information, iBatsID can successfully distinguish the vocal differences between 34 different species of bat across Europe. The bat detecting tool is so good at listening to bats, it can correctly distinguish between species with greater than an 80% accuracy. Though iBatsID usually guesses correctly, the accuracy of the tool can vary as some species are harder to distinguish than others.
“iBatsID can identify 83-98% of calls from pipistrelle species correctly, but some species such as those in the Myotis genus are really hard to tell apart and even with iBatsID we can still only identify 49-81% of Myotis calls correctly,” says Walters.
Another of the paper´s authors, chair of the Bat Conservation Trust Kate Jones, said iBatsID can be an important conservation tool, but it becomes even more important when everyone decides to use it.
“Acoustic methods are really useful for surveying and monitoring bats, but without using the same identification methods everywhere, we can´t form reliable conclusions about how bat populations are doing and whether their distributions are changing,” said professor Jones.
“Because many bats migrate between different European countries, we need to monitor bats at a European, as well as at country, scale. In iBatsID, we now have a free, online tool that works anywhere in Europe.”
As the number of bats in Europe continues to decline, the animals are now protected through the EU Habitats Directive. Many of these bats are finding it increasingly difficult to make their homes in Europe, facing challenges such as reducing feeding sites, fewer roosting sites and a decreasing insect population. Bats are quite important to the area, of course, pollinating plants and controlling the insect population as they go along.
Walters added: “Bats are very sensitive to changes in their environment, so if bat populations are declining, we know that something bad is going on in their environment. Monitoring bats can therefore give us a good idea of what is going on with biodiversity in general.”
The paper by Walters and Jones has been published today in the British Ecological Society´s Journal of Applied Ecology.