This interview is part of our Meet-a-Scientist series.
When you turn your lights off to go to bed, a bat’s waking day is just beginning.
As mostly nocturnal animals, bats are active at night and fly around in search of food. To navigate through the darkness, bats use echolocation. This process begins with the bat sending out a sound wave and when this wave hits an object far away, it produces echoes that the bat can hear.
Bats are incredibly loud – one of the loudest animals on the planet (even though the frequency they use is too high for us to hear). The more noise they make, the easier it is to find bugs to eat. And yet, most bats don’t echolocate louder than a certain level…how come?
In an article adapted by Science Journal for Kids, researcher Shannon Currie studied how much energy bats use when echolocating and discovered that both louder calls and echolocating while flying require extra energy.
Hi Shannon, can you tell us a bit about yourself?
I was born in the U.S. and spent most of my early childhood in Michigan. I have very fond memories of catching small toads and fireflies in my backyard. When I was 11 years old, my family moved to Australia and I spent most of the rest of my life there, running around in the eucalypts. When I was younger I wanted to become a dancer, and I still try to dance as much as I can in my spare time.
When I started university I was still confused about what I actually wanted to do. I was always a big environmentalist and advocate for animal welfare so I decided to look into conservation biology. But once I started learning more about physiology I was so fascinated I just wanted to learn more and more. I think that’s the true path of scientists. It’s just about curiosity and the drive to find answers.
What were your favorite subjects in school and during your early years in college?
In high school, my favorite subjects were actually in the performing arts (dance and drama), and my second favorite class was biology. When it came time to select my college courses I realized zoology was probably the best choice for me and when I finally got to study vertebrate anatomy and physiology I was hooked!
What is ecophysiology and what sparked your interest in this field?
Ecophysiology is the study of how animals have adapted their bodily functions to best survive in their environments. For example, how animals who live in desert environments balance their water by having very specialized kidneys and by being active when they will lose the least amount of water through evaporation.
I entered this field because it was my favorite subject at university and learning about all the amazing ways animals’ bodies work just fascinated me. In particular, I was drawn in by how the heart works in different species. This extremely important organ has to pump blood throughout the body constantly for the entire lifetime of an animal and in some species, it’s the size of a pinhead while in others, it can be as large as a car!
The heart is essential for providing nutrients to the body and is directly linked to energy expenditure so this is how I became interested in this field. But once I found out that a bat’s heart can beat over 1000 times per minute when they are flying and then the same animal can hibernate and its heart can go as slow as 5 beats per minute, I was blown away and knew that’s what I wanted to study.
What are you currently working on in the lab — can you describe what a typical day in the lab looks like?
Right now I am working on a project looking at fuel use (what source of energy is being used — fat, protein, or sugar) during long-distance migration of bats and birds. I have just returned from collecting data from the field, so I am sorting blood and breath samples and analyzing the data. For example, I am downloading temperature and humidity loggers that collect data every 10 minutes so we can understand whether the bats are flying at certain times based on environmental conditions.
How does echolocation help bats create a picture of their surrounding environment? How is echolocation similar or different from human sight?
When bats echolocate they use high-frequency sound to perceive their environment via the returning echoes. The information that they can gain from these calls can tell them about the size, distance, shape, and even texture of things in their surroundings. To get a more clear understanding of an object, bats can change the direction of their echolocation calls and the number of times they call (the pulse rate). That way they can get more echoes and more information – kind of like focusing your eyes on something to see it more clearly.
Vision and echolocation are two very different sensory systems but they can give similar information about the world. It’s a common misconception that bats are blind, but in fact many bats can see very well and so they use both their echolocation and sight to perceive their environment. Interestingly, many blind humans are known to use echolocation to find their way around. They do this by clicking their tongues or tapping on something. It’s a very natural phenomenon and obviously a great way to get around in the dark!
How loud are bats’ echolocation calls? Can people hear them? Do their high-pitched calls interfere with other animals?
Each bat species has a specific type of echolocation call that they use to navigate their surroundings, while most bats use echolocation calls that are very loud compared to humans (louder than a jack-hammer), the intensity can vary based on where the animal is flying (in dense forests or open fields) and what they are trying to do (find their way home or catch small insects). Most people cannot hear bats because they call in the ultrasonic range but some bats have part of their calls within our hearing frequency and young people in particular can sometimes hear bats chirping at night. Many people don’t even realize they are listening to bats at night and can confuse the calls of bats with crickets!
Can you tell us more about your experiment — where did it take place and where did you get the bats for it?
The experiment took place at the Max Plank Institute for Ornithology in Seewiesen, Germany at their wind tunnel facility. It was important for our study to have bats flying at a steady pace and the best way to do that is to train them to fly in a wind-tunnel. Wind tunnels are very large and sophisticated pieces of equipment and the Max Plank Institute is the only location in Germany with such a tunnel. We collected the bats for this study from their daytime roosts in known roost boxes within the forests near the institute. After the study was done the bats were released back into their roost boxes.
For some people, bats have a bad reputation. Is it deserved? What is it like to work with bats?
The bad reputation of bats is certainly not deserved and comes from very old and incorrect myths. These misconceptions arise from the fact that bats are active at night and most people know very little about them. There are more than 1400 species of bats in the world and only 3 of them drink blood and while some bats do carry diseases, they are not aggressive animals and are actually very shy. The one thing I think most people don’t know is that bats are very smart animals!
During our experiments we needed to teach the bats to fly in the wind tunnel, which is a new and potentially scary place for them. With birds sometimes it takes weeks for them to learn how to fly in the tunnel but with our bats it only took a couple of days. The funny thing then becomes realizing that if they don’t want to fly, the bats will always find a place to hang. Even though the wind tunnel is made from glass and smooth plastic the bats could find the tiniest spot to cling to, and this meant that sometimes I would have to climb into the tunnel to get them down from their hanging place!
In the era of climate change and as cities continue to grow, how would that impact bats?
There are a number of effects that climate change will have on bat populations worldwide, especially because bats are found on every continent except Antarctica. The two biggest threats to bats because of these processes are 1) a loss of habitat and 2) lack of food. Insect numbers and diversity are declining globally as we use more and more pesticides and as climate change brings extreme weather events that decimate populations. As insects are the main source of food for millions of bats this is extremely worrying. In addition, urbanization (the growth of cities) drives habitat loss and destroys food resources for both insect-eating and fruit-eating bats.
What does it mean to be a scientist to you?
To me, being a scientist means being constantly curious. I have always been interested in how things work, I love taking apart things and putting them back together and I’m always wondering how and why things are the way they are. Being constantly curious means every day at work is fun.
What advice do you have for students looking to get into science?
Science is such a broad field, and you can do so many amazing things when you have a career in science. It’s not just academia and working at university, scientists are needed in a wide range of fields and industries.
My advice for all potential scientists, but particularly young people from minority groups, try not to let anyone derail you from your path by asking you questions like “Are you sure … ?”. This is a very good question in science and you should do your research, but often this question is asked when you are at career-defining moments – “Are you sure you want to enter science?” or “Are you sure you want to get a PhD?” The more weight you give to this question the more likely you are to let it drive you away from this path, and it is asked to those in minority groups more often than others.
What are your future career goals?
In the future, I plan to run my own research lab continuing to study ecophysiology of small mammals and birds.
Conducted for SJK by Maxine Mouly
See all of our ‘meet-a-scientist’ interviews and read Shannon’s research paper below: