How do we capture bats?

 

To capture bats we set up mist nets made of very thin nylon thread that the bats only detect when they are too close and get tangled. This fine mesh is very soft and does not harm them in any way. We remove the bats out of the net making sure they do not get any more entangled. To do this, first we look for the direction in which the animal flew into it. The last body parts to come in contact with the net are the feet and back. We look for these and hold them tight without squeezing the bat and making sure it does not bite us. We gently pull it away from the net and we begin to release the rest of the body. The thread is pushed up its head and removed as if we were taking off a T-shirt, the wings are the last part to come out.

Some nights when the bat activity is at its peak or if we are near a roosting site, more than one bat is captured at the same time. As soon as we release one animal we put it in a fabric bag and continue to release the rest of the other bats that may have been caught. We have to be very efficient and organized, some nights we can capture up to 100 individuals! While some people are taking out bats from the nets others record body measurements and collect samples.

I collect tissue samples from the wings. I use a biopsy punch to take small circles of skin of about 3 mm in diameter. These holes are so little that they do not affect the bat's ability to fly. In nature, bats injure their wings with tree branches or spines but these injuries heal quickly usually within 2-3 weeks. Bats are commonly captured with holes in their wings that are much larger than those inflicted by wing punching.

Apart from skin, we sometimes collect other samples that are useful for other researchers (e.g feces, urine, parasites, pollen). We also take measurements of the forearm length and the overall size of the body to determine their life stage ( adult or juvenile). We weight them, determine their sex, and their reproductive status. For example, pregnant females have a round and swollen abdomen that if touched gently the fetus wings can be felt! Lactating females have a nipple under each wing, close to the armpit, that drips milk. Males during the reproductive season have swollen testicles. All this information is important to keep track of the timing of reproduction during the year. The samples are stored in a special liquid or in alcohol at -20°C to keep nucleic acids stable before DNA is extracted in the lab.

After we have finished collecting samples and taking measurements we release the bats back to their habitat!