Bats have long suffered from an undeservedly bad reputation, stemming from largely unfounded fears. Rabies, for example, is often associated with bats, and yet, over 15 years in the U.S., an average of just two people per year died of bat-related rabies. Rarely do we hear of the services provided by bats: controlling pests and disease, pollinating plants, spreading seeds… Threatened by habitat loss, bats are moving out of their forests and into cities. Recognizing their important role, researchers aim to understand how they adapt to this new ecosystem and how humans can help.
Kathrin Barboza Marquez holds a piscivorous bat
Alright, I get it. I confess I can see why the animal pictured above has not found its way easily into the hearts of the public the way, say, a baby polar bear might. Especially if the creature has already found its way into someone’s home. Running into this fish-eating bat, or one of its cousins, in your living room has got to be slightly unsettling.
But, like any element of any ecosystem, bats are more than a simple nuisance, existing purely to disturb their human neighbors. Like every other organism, they participate in their environment, and, as it happens, in ways that are very important for us. Maybe they scare you, or you just can’t bring yourself to call them cute, but you are right now benefiting from the services provided by bats.
The UN Millennium Ecosystem Assessment recognized the importance of ecosystem services provided by species. These are defined as benefits people obtain from ecosystems. This could mean providing food or fresh water, regulating climate or disease, supporting soil formation or even cultural services like education and recreation. Many such services are provided by the 1,232 known bat species, about two-thirds of which eat insects, while others feed on fruit or nectar. Far from being miniature vampires who make a point of getting tangled in people’s hair, these flying mammals are responsible for, among other things, pollination of plants, for seed dispersal, and for consuming huge amounts of insects that can create major problems for humans. According to Bat Conservation International, the role of bats in distributing seeds into ravaged forestlands has earned them the nickname “farmers of the tropics”. By spreading pollen between plants, bats help them to bear fruit and contribute, along with insects, to maintaining genetic diversity in the plant species.
One of the most significant contributions of bats involves the voracious appetite of many species for insects. Often, these are insects that cause trouble for people. They may be pests that destroy agricultural crops or, like mosquitoes, carry diseases, such as yellow fever or dengue. Kathrin Barboza Marquez, a PhD candidate studying bats at the Bolivian Bat Conservation Program (PCMB) in Cochabamba, Bolivia, puts into perspective the aid to humans provided by the much-maligned bat: a single colony of one million moth-eating free-tailed bats in Texas has been estimated to eat the equivalent in weight of 25 elephants – every night. The moths in question are destructive to corn crops; imagine the pesticide it would take to do the same job. In terms of controlling disease, other species of bats that consume up to 600 mosquitoes per hour help limit the spread of dangerous illnesses, for free, in a 100% natural, chemical-free way.
The services provided by bats are well established. But, like so many other species, they suffer from loss of habitat due to increasing urbanization. Most insectivorous bats are at risk, although some species are managing to adapt and make the city their home. Kathrin Barboza Marquez wants to know how. What factors allow them to live there—what type of light, vegetation, food availability, shelter and moon phase, even—and what can be done to protect these vital contributors to a healthy ecosystem?
Kathrin studies several species of the Molossidae family of free-tailed bats, as well as the Vespertilionidae family. Out in the field, she captures bats with mist nets—like fishing nets, with very thin thread. She takes measurements of the bats she catches; records the sex, age and species; takes a tissue sample—a small piece of the wing membrane—and a fecal sample, before releasing the animal back into its habitat to continue on its way.
The species she looks at are, in fact, quite difficult to capture because they are able to detect the nets by echolocation. By emitting high frequency calls as they fly (like this) and listening to the echoes that return, bats are able to find their prey and avoid obstacles in flight. Kathrin Barboza Marquez makes use of the bats’ echolocation herself, to identify them, even when they can’t be seen or caught. This is especially the case in an urban environment, where the animals fly very high and are all the more elusive. She records their calls, and analyzes their duration and the frequency and shape of the sound waves. “These things are characteristic of a species,” she explains. “They allow me to identify the species present, and also to determine the habitat uses of the bats. Certain calls are characteristic of capturing insects, for example. All of this is important for understanding the ecology and the natural history of these species.”
Kathrin Barboza Marquez captures high frequency bat echolocation calls with a microphone and special detector.
To gain further knowledge about how bats manage to operate in an urban setting, Kathrin plans to compare aerial insectivorous bat populations in her native Cochabamba, Bolivia with those in a much bigger city: Madrid, Spain. With the support of a fellowship from the L’Oréal-UNESCO For Women in Science program, she will spend 6 months in the Spanish capital and 6 months in Cochabamba, locating urban bats, characterizing their shelters and available resources, examining their diet – assessing as many factors as possible to understand how they live. In the acoustics lab of Spain’s National Museum of Natural Sciences, she will analyze the echolocation calls of the Spanish bats. Her recordings will become part of the catalogsof bird, frog, and other animal sounds already in the collection, and will be available for other researchers to use.
Kathrin Barboza Marquez’s ultimate objective is to use all of the information she will have gathered to create conservation plans adapted to the lifestyle of the urban bat. While some types have succeeded in adapting to this new environment, the limited number of species spells trouble for diversity. Kathrin’s previous work already allowed her to put one species of bat back on the list in her country: In 2006, she and her colleague Aideé Vargas rediscovered the sword-nosed bat – a species that had not been recorded in Bolivia since 1932. Its only home, she found, was in two caves on the border with Brazil, and these were severely disturbed by human activities in the area. Their work helped convince the local community to save the tiny, endangered population, leading to the creation of the San Juan of Corralito Municipal Ecological Reserve.
The species Kathrin is concentrating on these days may be in less immediate danger than the sword-nosed bat, but it is no less important to work for their conservation. We may not even be aware of them as they swoop through our city skies at night, like so many Batmen, performing good ecological deeds for the humans below, but bats carry out a variety of vital functions that we would not want to do without. If we don’t take steps to protect them and their habitat, write bat researchers Thomas Kunz et al., “benefits that humans inadvertently and unsuspectingly derive from bats will be forever lost.”
To find out more :
Bat Conservation International – Conducting and supporting science-based conservation efforts around the world
Defenders of Wildlife: Bat Facts and Video
Year of the Bat 2011-2012: Bats and Biodiversity