- Bats pollinate trees, disperse seeds, and eat insects, but most populations are declining due to hunting, spreading disease, and habitat loss.
- Scientists typically identify bats by their calls and want to standardize monitoring techniques to help reduce the natural variation in calls by the caller’s age, gender, and activity.
- iBats offers a free app that records, geo-locates, and uploads bat vocalizations to its web portal for use by scientists and others interested in exploring bat distributions and population trends.
With more than 1,300 species worldwide, bats make up over 25% of all mammals on Earth. They live on every continent except Antarctica, though more species live in warmer, tropical regions. The cold of northern winter that forces us indoors pushes bats, like bears and various other mammals, to hibernate.
The sensitivity of bats to human impact, their slow population growth rate, and their temperature-sensitive hibernation behavior, make them good indicators of a healthy environment.
In many environments, bats also serve as keystone species, contributing to ecosystem functioning through fertilization, pollination, and seed dispersal and providing these and other ecosystem services, such as pest control, to human landscapes.
Some plant species, such as the baobab tree in the East African savanna, depend almost exclusively on bats for pollination. Through seed dispersal, bats may also help to regenerate logged forests. Bats protect commercial plants by eating insects such as the corn earworm moth in North and South America. Bats are undeniably critical components of ecosystem health and human economies worldwide.
Despite their vital contributions to human and natural systems, bat populations are declining worldwide. Over 1,000 species (3/4 of all bat species) are listed as endangered or vulnerable on the IUCN Red List, while scientists lack data on the conservation status of hundreds more.
What threatens bats?
Bats face a range of threats, from disease to human-inflicted habitat loss, disturbance, and overhunting. The clearing of bat habitat worldwide for timber, agriculture, and development remains the most widespread threat, though people across the tropics, from Southeast Asia to Latin America to the Pacific Islands, also kill bats directly for sale on the commercial bushmeat market or for fear they are blood-sucking vampires, though (just three species actually feed on blood). Inappropriate winter tourism and guano mining scare bats from their hibernation roosts, forcing them to prematurely burn through their fat stores.
In North America, white-nose syndrome attacks hibernating bats with mortality rates approaching 100% at some sites. Even the environmentally promising installation of wind turbines has taken a toll on bat populations, killing hundreds of thousands of bats each year in the U.S. alone.
How do we know where bats are threatened?
We know populations from surveys. One of the biggest challenges to surveying bats, however, has traditionally been identifying them. At night.
Bats are nocturnal and difficult to capture, so scientists typically survey them acoustically, identifying individual bats by their species-specific echolocation calls. However, a bat’s habitat, its age and sex, its activity (e.g. socializing, searching, feeding), and the presence of other bats may cause calls to vary, making it difficult to identify species, even with ultrasonic detectors in the field and complex statistical models.
To better understand and protect bat populations worldwide, scientists want to standardize population monitoring techniques and encourage broader participation in surveying bats across the globe. The Zoological Society of London and the Bat Conservation Trust have partnered to establish the Indicator Bats Program, the first global bat acoustic monitoring program, as part of the Technology for Nature partnership. The project, known as iBats, was developed in 2011 to produce a standard, quantified, repeatable measure of identification, and has already succeeded in doing just that for 34 European species.
iBats encourages broad participation in bat surveys. It works with NGOs in Europe, Japan, and Taiwan to engage volunteers to monitor local bat populations using standardized monitoring protocols and openly available acoustic tools. Volunteers upload and manage their data on the iBats web portal, where they can also receive feedback about distribution of bats and population trends in their region.
The iBats program’s free app for both iPhone and Android-based smartphones allows participants to record sounds, location, and data with the same device, to allow more people to survey bats more easily. The app also allows the smartphone to connect directly to the ultrasonic detector, which allows a volunteer to record bat echolocation, conduct geo-location surveys, and automatically upload data to the iBats website. Here are some video tutorials for anyone interested in joining a bat survey project.
Says Kate Jones, manager of the iBats program at the Zoological Society of London, “British people are nuts about counting things. They will monitor slugs if you ask them to. There’s a huge interest here in natural activism, in the normal, everyday person going out and doing something.”
Since most volunteers live in human-inhabited places, the iBats program has created iBatsID. The tool helps scientists and their volunteers to classify and track different bat species across Europe, starting here with London:
|Searching for bats in Hyde Park, London.
Image credit: iBats
|Bats surveyed, data collected, time to head home.
Image credit: iBats
The iBatsID (Europe) classification tool uses groups of learning models called artificial neural networks (eANN’s) to automatically detect bat calls within long sound sequences and classify bat species. The system can discern calls in noisy, real-world situations and identify bats to species with an 83.7% success rate when used in conjunction with SonoBat software (Walters et al. 2012). The eANN’s are trained using twelve call parameters (such as a call’s maximum and minimum frequency, or its slope and duration) in order to maximize repeatability and ensure the tool is applicable at a continent-level scale.
iBatsID currently detects only 34 species, so it has a long way to go, and it seeks funding to broaden its coverage. The application promises major advancement in acoustic identification that has potential to cover a wide range of taxa and inform conservation decisions in the future.
Walters, C.L., R. Freeman, A. Colleen, C. Dietz, M.B. Fenton, G. Jones, M.K. Obrist, S.J. Puechmaille, T. Sattler, B.M. Siemers, S. Parsons, and K.E. Jones. 2012. A continental-scale tool for acoustic identification of European bats. Journal of Applied Ecology 49: 1064-1074.