Every year, millions of acres of tropical rain forest are cleared for timber and agriculture in Central and South America, and efforts are increasing to regrow the forests on these cleared lands. That's where bats and artificial roosts may play a vital role.
Researcher Detlev Kelm of Germany's University of Erlangen-Nuremberg has used Bat Conservation International research scholarships to explore and test the possibilities. He says that while the commitment to reforestation is growing throughout much of the tropics, we still lack practical and cost-efficient methods for kick-starting the process of forest regeneration.
The first step in regrowth on open land is seed dispersal. In tropical environments, fast-growing, light- and heat-tolerant pioneer plant species play a dominant role in restoring vegetation. Fruits of such plants turn out to be the main food source of an abundant and widely dispersed group of tropical bats that feed on the fruits and nectar and disperse the seeds.
Although these bats still seem to be abundant throughout the New World tropics, their local distribution depends on the availability of suitable daytime roosts, and most of the relevant bat species prefer caves or, especially in lowland areas, hollow trees. But only very old trees become large and hollow enough to serve as day roosts. Since loggers typically remove the largest trees, many areas now lack sufficient natural roost sites, so bat densities decline even through food sources could support many more bats.
Kelm's project, begun in 2000, designed artificial bat roosts for fruit-eating bats that roost in tree hollows and tested them in a lowlands area of Costa Rica, where the dominant land uses are cattle breeding and farming. The roosts proved surprisingly attractive to bats. Bats moved into most of them within a few weeks of installation, and these roosts have been permanently colonized for over three years.
The main resident is the short-tailed fruit bat (Carollia perspicillata). But nectar-feeding bats such as the brown long-tongued bat (Glossophaga commissarisi) - an important pollinator for a great number of plants - tiny common big-eared bats (Micronycteris microtis) and frog-eating bats (Trachops cirrhosus) have also been recorded.
An analysis of bat feces collected from inside the roosts revealed seeds of more than 40 different plant species, most of them fast-growing pioneer plants. The study showed that, on average, 10 short-tailed fruit bats bring more than five grams of seeds into their roosts every night. That's equivalent to an average of more than 2,000 individual seeds! Bats, of course, also disperse many seeds over their foraging areas, as well as below their feeding roosts.
Bats clearly can be major players in launching the regrowth of tropical forests in cleared areas, and Kelm has shown that artificial roosts can be effective in helping bats to recolonize areas where natural roosts are scarce. The next step would be to install these proven artificial roosts across fragmented tropical landscapes, thus giving bats a shelter and encouraging them to help us in our reforestation efforts.
You can help Bat Conservation International support this kind of critical research while preparing talented young biologists for leadership roles in the future. To support BCI's Student Scholarship Program, contact Nicole Daspit .
