Written by and Photos courtesy of Alyson Brokaw
It`s just after 8 o`clock in the evening and the forest is slowly growing darker. With the help of the students, we just opened the mist nets and are waiting for our first catch of night. Tonight we are on transect in the core zone of the Calakmul Biosphere Reserve. Earlier in the afternoon, we set out 6, 6-meter long nets across the path and between trees, approximately 900 meters down the trail. Our furthest nets are set near a hidden limestone cliff. As the forest darkens completely, the bats are out in full force, emerging from cliff crevices, tree hollows and leaves to start their nightly foraging. We watch as they dip, dive and maneuver their way through the dense understory and around our mist nets.
As part of the biodiversity monitoring project run by Operation Wallacea, our goal is to document the abundance and diversity of bats in the reserve. Worldwide, bat numbers are on the decline, facing habitat loss, disease and persecution. However, bats place an important role in maintaining the health of ecosystems, like those found in the reserve. The Neotropics (Mexico throughout Central America and South America) are a hotspot for bat biodiversity, where they act as pollinators, seed dispersers and insect control. Long term monitoring projects like this one are increasingly important in determining trends in populations, species distribution and abundance, and help reserves and conservationist make land management decisions.
Together with the group of high school students, we check to see if we have caught any bats in our mist nets. The first check proves a success, with several bats caught in the nets. Most are the same species, the Jamaican fruit-eating bat (Artibeus jamaicensis). A large, stocky bat with velvety fur, the Jamaican fruit-eating bat is an important seed disperser of fruiting trees. We work quickly to remove the tangled bats from the net and place them into cloth bags to carry them back to our processing station. Once we have removed a bat from the net, we record the weight and forearm of each bat, as well as sex, age, reproductive status and species. The students help us with measuring, weighing each bat and bag with a spring scale and measuring forearm using calipers.
Amongst the bats of our first check is a different species, a favorite amongst bat biologists who work in the Neotropics. The wrinkle faced bat (Centurio senex) lives up to its name, with a face that looks like it has been hit with a frying pan. Usually uncommon or rare, this bat is consistently captured in nets at Calakmul. This bat is a frugivore, specializing on overripe or rotten fruit. It bites into and sticks its face into the fruit. It is hypothesized that the wrinkles on its face acting as funnels, directing the fruit juices into its mouth.
However, the most exciting is yet to come. Another net check finds a great false vampire bat (Vampyrum spectrum) caught in the net. The largest bat in the Americas, the great false vampire bat has a wingspan of almost a meter. It is also carnivorous, feeding on birds, reptiles, small rodents and even other bats. A powerful bat, it takes two hands just to hold it during processing. The great false vampire bat belongs to the family of bats called Phyllostomidae, or the leaf nosed bats. It is a highly diverse group, characterized by a triangle of flesh that sticks up straight from its nose. Unlike most bats, the leaf nosed bats echolocate with their nose, leaving their mouths free to carry fruit or prey back to a feeding roost. Before we release the bats, we mark them with a small amount of colored nail polish. Each transect is assigned a different color and allows us to know if we recapture a bat later in the night.
We keep the nets open until 2 am, collecting and processing bats throughout the night. As our night ends, we round up the sleepy students, collected our equipment and make the trek back to the truck. A quick jungle shower and we crawl into our sleeping bags, dreaming of bats and what new and interesting species will greet us the next night.