You must be smarter than the bats

AKA – How we catch bats (or attempt to)

The goal of the Nicaraguan research project is to compare bat species diversity and activity between varying levels of fragmented forest (ex: highly fragmented such as near agricultural fields or homes, slightly fragmented such as a small tract of forest on the outskirts of town, and un-fragmented such as a contiguous tract of forest within a nature preserve).  Multiple sites have been selected within each fragmentation level for acoustic and mist-netting surveys.

The acoustic surveys are accomplished by placing Anabat microphones at the site. Anabats are able to record the echolocation calls of the bats and record them to compact flash (CF) cards. The CF cards are downloaded daily to computers and the echolocation calls are analyzed. Some bat species have unique echolocation calls while other species have such similar calls that it is difficult or impossible to make a species determination. Jose and Marlin are college students (undergraduate level) that have been hired to move the Anabats between survey points on a daily basis. They will continue the Anabat monitoring through this spring, even after our mist-netting surveys have been completed.

Marlon and Jose, the two undergraduate Nicaraguan employees running the Anabat surveys.

Mist netting involves placing nets in flyways such as streams and roads. A mist net is similar to a volleyball net but is taller (about 2.6 meters) and has much smaller holes. Mist nets range in length between 2.6m and 18m. The length of net we use is determined by the habitat in which we’re placing the nets.

The mist nets are strung between 2 poles and vary in height between “single high” nets and “triple-high” nets. Single highs are simply 1 net strung between 2 poles and triple highs are 3 nets stacked on top of each other strung between 2 poles that have a pulley-like system allowing the nets to be raised and lowered to remove captured bats.

Single-high mist net being deployed by one of our awesome US bat biologists.

Triple-high mist net. The white pvc rings have carabiners on them that the nets clip on to.
The rings are on a pulley system so the nets can be raised and lowered to remove bats.

The mist nets are placed in flyways (areas where bats fly - comparable to a human “highway”) where overhanging vegetation creates a small space through which the bats fly (called a funnel). Many bats are able to avoid the nets by pulling u-turns or going over the nets, however bats that aren’t paying close attention or can’t correct their flight path in time are captured in the nets.

The captured bats are removed from the mist nets and identified to species. We also determine the sex, reproductive status (if the females pregnant, lactating, or post-lactating, and if the males are non-reproductive or actively reproductive), and basic measurements such as weight, forearm (from elbow to wrist), thumb, ear, and foot are taken. If the bat is unusual or a new species for us we’ll usually take photographs of the bat (and us with the bat) and marvel over it before releasing it.

Removing a bat from the mist net.

Measuring a bats forearm (from their elbow to wrist). Several species that are
look identical are split into different species based on this measurement.

All of the mist netting surveys are conducted by bat biologists from the US that have volunteered for the project. These surveys began around the beginning of December and will continue through the end of January.

The acoustic and mist netting techniques don’t vary much between countries. Once the sun goes down and netting begins it is easy to forget we are in a foreign country thousands of miles away from whichever place each of us calls home. The night sounds that serve as our backdrop vary between the familiar such as the hooting of owls and the chirping of the frogs and insects and the unfamiliar such as the roar of the howler monkeys. We haven’t had any close encounters with the howlers (which is good since they’re known to fling objects ranging from tree branches to their own poo at unsuspecting people) but I enjoy their noises and tend to smile when I hear their husky voices.

There are security precautions we take in the field for the sake of our equipment and our own safety. The field trucks are always locked with all items removed from the truck beds. In high-risk areas a guard is left to watch over them. We also have a local field guide with us each night. The guide ensures we are on the correct property, interacts with landowners and local people, and watches over the group alert for any possible problems. We are surveying field sites farther away from our villa (about an hour and a half drive), close to the Costa Rican border. Drug runners are common, so Don Miguel is our guide for that locale. Don Miguel is known as “el jefe” in the area and is very respected by the locals.

“Don” and “Dona” are titles used here to denote men and women who are very well respected; they are often heads of their households and have a high social ranking within a community.

Time is running short as we are approaching the end of January. I am trying to not let thoughts of home intrude on my time and experience here but I know this will be harder as it gets closer to the time I need to leave. In the meantime, we are busy netting with an occasional night off. We are hoping for an arribada tonight or the following night.