An Ultrasonically Silent Night
THE TROPICAL DRY FOREST WITHOUT BATS
Richard K. LaVal
WITHOUT BATS, in their varied roles as pollinators of commercially important trees, seed dispersers critical for forest succession, and consummate predators of nocturnal insects, the tropical dry-forest life zone would be a vastly different place. Despite the unquestioned importance of these common mammals, few scientific papers have dealt specifically with bat conservation until very recently. Fenton (1997) has clarified the relationship between recent advances in bat biology and bat conservation, and a book edited by Kunz and Racey (1998) addresses bat conservation issues worldwide. Ceballos (1995) discusses vertebrate conservation in the dry forest, with special emphasis on the importance of bats.
For the purposes of this chapter, “dry forest” refers to a deciduous-forested life zone that extends at low elevations along the entire Pacific coast from west-central Mexico to northwestern Costa Rica, with rainfall mostly less than 1,500 mm. Much of this forest has been converted to nonforest land uses, primarily agricultural (Janzen 1988). Although a large portion of the land area included would be classified as tropical dry forest under the Holdridge Life Zone System (Holdridge 1967), there are areas of moist forest (to the south) and very dry forest (to the north) that I include in the dry-forest life zone because of floral and faunal similarities.
BATS IN THE DRY FOREST
Ninety-two bat species occur in the dry forest as defined in the previous paragraph (based primarily on maps in Hall 1981). Of these, 15 are endemic to the dry forest or nearly so. Sixteen are restricted to Mexico, 67 occur in both Mexico and Central America, and 9 are found only in Central America. Most Central American species also occur in South America. In comparison, there are 93 species in the tropical wet forest of the Caribbean lowlands, extending from east-