Ultrathin Nets Catch Overlooked Bats

Gloriana Chaverri and her students confirmed a hunch about trapping bats. They hung nets in Costa Rican foliage and got 125 bats. The nets captured 90 of the flying mammals from 14 species. In Royal Society Open Science, her team from the University of Costa Rica explores how equipment choice can influence what scientific expeditions reveal. The researchers had to pay more attention to extract bats from the tangle-prone web and so there was less chatting.

Scientific American spoke with Chaverri about bat-catching protocols, elusive insectivores and what new takes on old technology can reveal about the inhabitants.

How do you catch bats in the wild?

The best places are not so cluttered because the bats are not flying along those routes. The bats will detect the net if the area is devoid of vegetation. If you are not experienced, stretching the nets takes a long time because they get tangled in your clothes.

The best time to open a net is at sunset because the bats are so hungry by the end of the day that you get the majority captured between six and eight. We try to stay until midnight. The regular nets people have been using for years are resistant to bites from most species of bats, so we open them and visit them every 15 to 20 minutes.

What made you want to test the differences between the older, thicker nets and the monofilament ones?

The first time I saw this type of net was at a bat meeting in Costa Rica. I always like to try new things, so I bought one. When I went out one time, I placed the net, and all of a sudden, I was able to capture some species that I had never before. I began to think: "Hmm, this is interesting."

I did a project in Uruguay a few years ago, and we only purchased nets. I showed the nets to the other bat researchers and they were very excited to see them. I think this should be published because a lot of people don't know about this other net.

When you compared the two nets, what did you find?

The differences were noticeable. The regular nets are missing a lot of the insectivorous bats that we normally see. It is more difficult to untangle bats from a net. The soft tissues of the bat make it difficult for researchers to see the threads.

A recent study found that very fine nets were less successful than other designs. Why do you think that is?

The bats are good at chewing. The nets were checked by the other team every 15 or 20 minutes, compared to the two to five minutes we did. Sometimes you don't have enough field personnel to check the nets. The combination of our two papers shows the pros and cons of using the nets and will allow a lot of people to start thinking about what equipment to use. People place traditional nets and assume that whatever they get is what's out there. Many studies show that it is not true, but we still use them.

Equipment choices like these play a big role in what you learn.

They play a big role. The papers suggest that we are missing a big part of the bat assemblages that we have. I think the monofilament nets are one of the instruments that we have to take advantage of because they are cheap and easy to use. I tell everyone about these nets. I think it's a good thing that I can help researchers reach conclusions that are closer to the truth.