The New World tropics are among the most diverse ecosystems on Earth, and an amazing number bat species play vital roles in preserving the health of these fast-disappearing forests. Some of the most important are the nectar-feeding bats that pollinate hundreds of rainforest plant species. Yet remarkably little is known about the symbiotic relationships between individual bat and plant species, how bats respond to seasonal changes in resources and the impact of human-caused landscape changes on these interactions.
Cullen Geiselman, a Columbia University graduate student, is working in the dense forests of French Guiana to begin filling some of those gaps in scientific knowledge. Bat Conservation International and the U.S. Forest Service International Programs supported her Ph.D. research through a BCI/U.S. Forest Service Bats in International Forestry Scholarship.
Geiselman’s work is crucial to effectively focusing future conservation efforts, especially as tropical forests are increasingly cleared and fragmented. Knowing which plants are most needed by which bats – and vice versa – can greatly improve the protection of bats, plants and habitat in fragmented forests.
In the past year, Geiselman netted bats in both wet and dry seasons at the new Nouragues Forest Reserve, a 385-square-mile preserve of lowland rainforest. She captured 135 bats of three nectivorous species: Geoffroy’s long-nosed bat (Anoura geoffroyi), chestnut long-tongued bat (Lionycteris spurrelli) and Thomas’ long-tongued bat (Lonchophylla thomasi).
Pollen was collected from the snout of each bat. The bats were also kept for up to two hours in numbered cloth bags to collect fecal samples that were later examined for pollen, insect parts and seeds. The bats were then identified, measured and released.
To identify the bat-borne pollen, and thus the plants being pollinated, she collected pollen from 93 flowering plants in the reserve. Though not all the pollen has been identified yet, the most common pollen found on the bats so far came from Eperua falcate (in the dry season), a tree known as the Wallaba and used for shingles and other construction materials; Lecythis poiteaui, a member of the Brazil-nut family (in the rainy season); and Inga trees, with commercially valuable flowers, that were also found in wet months.
Preliminary results included at least one surprise: pollen from one species (Psittacanthus acinarius) of a plant family pollinated primarily by hummingbirds and not known to be visited by bats was found in the fur and feces of Geoffroy’s long-nosed bats during the rainy season. This discovery of a new bat-pollinated species, genus and family highlights the importance of considering all flowering plants – not just those of typical types and forms – as potential food sources for nectar-eating bats. Geiselman predicts many more species will be added to the list of bat-pollinated plants as she and others shed new light on the complex web of bat/plant interactions.
Her continuing fieldwork and laboratory analyses are beginning to tease out details and test hypotheses about how these similar nectar-bat species can successfully coexist in the same habitat. She suspects that in the dry season, when flowers are abundant, the bat species mostly tap the same floral resources, while their diets diverge during wet months, when blooms are more limited. Geiselman found, for example, that while Geoffroy’s long-nosed bats were busily pollinating P. acinarius, no pollen was found on chestnut long-tongued bats. They were eating only insects during the wet season.
She hopes to solve these and other puzzles about these bats and flowers as she continues her research.
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