What does the bat say? Listening to echolocating, insect-eating bats on Kent Ridge

More than two decades ago, my Vertebrate Flight and Echolocation lecturer at the NUS Department of Zoology David Lane, took us up the ridge to listen to bats. The 30+ of us third years crowded around him to listen to that single bat detector. It was a memorable evening.

I finally shared the experience with some students (07 Nov 2013) and Pearlynn Sim, Fung Tze Kwan and Hazel Peh walked the ridge in search of the call of insect-eating bats, armed each with a BatBox III D.

We didn’t have to wander far from the S2 stairs along Kent Ridge Road before we found two hot spots where the bats were flying and hunting insects by echolocation.

They were very active between 7.30pm – 8.15pm, and it was lovely to detect the increasing loudness of a bat’s call and then see them zoom past us! As they turned sharp angles and dived along the road, they reminded me of rebellion pilots making their torpedo run towards the Death Star’s exhaust port.

Our simple bat detectors scale the frequencies of bat calls down to an audible range. With four of us tracking various frequencies, we were able to cover a spectrum of frequencies (30-62 KHz, strongest between 35-40 KHz) and narrow down to active bands to enjoy listening and watching the microbats hunt.

After a peak of activity, it grew quiet and they left for hunting grounds elsewhere. I wonder how many insects they consume each night on the ridge!

LSM3261 Zoology Lecture 6 -  Sensory perception and feeding

Direct recordings are possible from this bat detector to the iPhone but this night I simply recorded sounds off the speakers with the iPhone’s Voice Memos app. When I imported the sound file to Audacity, I could examine the profile – lovely tools we have these days, to enhance our appreciation.

I played a sample of calls to the 3rd year LSM3261 Life Form and Function class (slide above). I first trained them with other bat calls, so they had a sound profile in their heads. Then they could listen for the terminal buzzes (last phase of a hunt) in the call of the Kent Ridge bats.

My three companions that night agreed evening bat walks on the ridge, after the monsoon, should be offered to NUS star and students. I could start with a 15-minute lecture at 7.00pm in Lab 7 like we did that evening, before heading off for the walk. It would complement the day walks in raising our appreciation for the ridge.

That night, as we walked and listened, I figured out the design for a practical for either the LSM3261 or LSM2251 class next year. It’d be great for them to spread out over NUS and Kent Ridge Park, listen, record and send their data to a common site for all to observe a profile of activity of the bats of Kent Ridge in one evening.

As we returned to the department that evening, the fruit-eating bats were fluttering in the bushes, bathed by the glow of the orange street lights. Certainly a lovely end to the walk in our backyard.

Tweets that night between 7.15pm – 8.15pm

  • Bat walk on Kent Ridge: insect-eating bats certainly are out hunting on this muggy night, 35-39 KHz
  • Bat valley at Kent Ridge Road, terminal buzzes, nice.
  • Glad they are back; vegetation allowed to grow, helps!
  • We’re detecting bats calls over a wide range: 30-62 KHz, but strongest between 35-40 KHz. Peak hunting was ~0730
  • My first KR Bat Walk was in 1989, the students with me were not born yet!
  • Insect-eating bats left the ridge by 8.15pm. All quiet now, but we see flutterings of megabats

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s