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Marlotte in the field in one of ConFoBi's 135 plots

A bat-logger in the field.

Analyzing the bat sound for different characteristics

What’s it like to be one of the ‘bat guys’…

Studying nocturnal flying creatures requires some special tools. Instead of wandering around the forest in the middle of the night, Marlot makes use of ultrasonic sound recorders, so called ‘bat-loggers’. Certain sound characteristics like frequency, call duration and distribution of energy, are used to identify bat species and even behavior. In the end, Confobi project B5 hopes to give some insight on how bat diversity is related to forest structural element and the surrounding landscape.

Doing fieldwork can be quite tricky, and there can be many obstacles out there once you leave the safety of the lab. Follow Marlot on one of her “ordinary day” in the field: 


August 14th

Its Monday and my week starts great. It’s little past 9 when I step out the door and find 3 garbage men discussing around my newly-acquired 20 years old VW-bus. Apparently, the combination of this street, my parking and passing garbage trucks didn’t work well this morning. The police is alerted and on the way.

Let the day begin…’

It’s almost noon when I’m finally off to work. I decide to change plans by not going to the University first but straight into the field instead. The pressure is on, the weather is still nice and in a few days, it could be raining again. Like most humans, bats don’t like it when it’s too cold, wet or windy. Therefore we need calm nights to make useful ultrasonic sound recordings.
What do we actually record? In order to ‘see’ in the dark bats have evolved echolocation. With their voice, bats emit sounds and based on the reflection (echoes) of their surroundings they are able to navigate and hunt at night. These calls can be recorded and analyzed afterwards to determine the species. My field work consists of driving around the research area, setting up bat loggers, leave them there for a few days and pick them up again. I have a great team that helps me out, because doing this on 135 different plots can be quite a logistic challenge.

I reach my first plot after approximately one hour of driving. I meet the forester on location, whom I (due to my spontaneous change of plans and slightly chaotic character) did not inform properly in advance. He is very friendly as he offers me some mushrooms (pfifferlinge) and we talk about the ConFoBi-project, the materials I use and the bats I’m after.

At a certain point the forester expresses the notion that bats are not so vulnerable, because like mice there are many and they are really common. I’m noticeably shocked and even though ‘bats’ are called ‘winged-mice’ in German (and Dutch) they are a totally different group of animals. Most notably in this regard, they differ hugely in reproduction strategy: mice get a lot of babies per year (easy over 50) whereas bats have only one young per year. During the early summer groups of females get together to give birth and raise their young, so called ‘maternity colonies’. Depending on the species these can be in buildings or in trees. Because of these colonies, taking down a single tree could potentially have a huge impact on the local population.

After my musings on bat reproduction with the forester we both get to work. I install the loggers and continue my journey to the next plot, a few kilometers down the forest road. But today I don’t get very far. At some point the road is blocked by 3 cars. On a wooden bench, five men are enjoying the sun. On the table in front of them are flowers, grapes and some salty snacks. It seems like they are enjoying the little pleasures of life. The gentlemen collectively insist that I should join them for a while before they let me pass. They offer me some ‘medicine’ and it tastes great. Their main topic of discussion is ‘hunting’ and how nowadays there are too many hunting events, but people don’t shoot enough at one event. Everyone seems to agree and I wonder if I should open up the discussion with the returning wolf… but I decide against it. I enjoy these spontaneous encounters and social interactions with these frequent visitors of the forest, and would love to listen longer to the stories. Unfortunately, I have to continue my work. And after continuously politely rejecting the refill of the ‘medicine’ they happily move the cars so I can pass, and can continue my path to the next plot.

135 plots, 135 adventures…’
I park the car on the middle of the road. On my hands and feet, I start to crawl up the hill and search for the poles I have left on this plot last time: To set up the bat-loggers in the field I attach the microphone to a wooden pole at approximately 1,8m height.  I take the loggers out of my bag, switch them on, check if the settings are okay and screw my microphones on the poles. Done. Next plot.

On my way to the last plot I find out that my charger doesn’t work and my smartphone is going to die soon. I use it for navigation, and of course today I didn’t bring my GPS or printed maps as a backup. I stare at my phone in full concentration and try to memorize the route to the next plot as good as I can. 7,2 km… first left, second right…. Take the 3 turn to the…  It’s hot, but I repeat the steps in my head and start driving. A few seconds later the screen turns black. I try hard to picture the map and memorize the steps. It should be here somewhere… wait.. is it..? yes! There it is! I am relieved when I find the pink border marking.

Around six o’clock, three plots are done. I laugh at myself, realizing that I’m an idiot but proud that I found my way. I step in the car, open the window, feel the sun on my face and smell the freshly mown grass. At this moment, I’m quite convinced that I have the best job ever.

by Marlotte Jonker (B5)