Chiropteran Diversity and Ecology in a Panamanian Cloud Forest
Aarhus, Angela J.
University of Wisconsin-Stevens Point, College of Natural Resources
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Habitat preference and vertical stratification were determined for bats ( order Chiroptera) residing in the cloud forests of Parque Internacional La Amistad m Western Panama. Between June and November 2001, bats were captured m understory and canopy mist nets placed across streams, trails, and forest gaps in both primary (3 sites) and secondary (3 sites) cloud forest habitat. Sampling took place during the wet season for a total of 56 nights or 2548 mist net hours (mnh). In all, 11 73 bats were captured, representing 15 species, two families, and ten genera. Diversity for the entire La Amistad bat community was estimated at H' = 1.58. Five phyllostomid species, Anoura geoffoyi, Sturnira hondurensis, Artibeus aztecus, Sturnira mordax, and Artibeus toltecus accounted for more than 98% of all captures and were present throughout the study period. Monthly capture rates for these common species varied over the wet season. At times of high abundance, large numbers of reproductively active females were observed for S. hondurensis, S. mordax, and A. geoffroyi. In the nectarivore, A. geoffroyi, this peak coincided with a time when flowers of the Majaguillo (Heliocarpus popayanensis) were abundant in the study area. Species diversity did not differ significantly between disturbed and undisturbed sites, however bats were substantially more abundant in secondary forest (58.4 captures per 100 mnh) than primary forest (23.6 captures per 100 mnh). Three of the five common species, A geoffroyi, S. hondurensis, and A. toltecus, preferred secondary forest, while the remaining two occurred in both forest types equally. Vertical stratification by bat species was biased to the canopy where 78% of all captures occurred. All common species were significantly more abundant at the canopy level, except for the frugivore S. mordax, which was captured equally in understory and canopy nets. Analysis of the La Amistad bat community via a feeding guild/body size niche matrix revealed that only five of the ten possible feeding guilds were represented in La Amistad and suggested that medium-sized members of the frugivore guild might be minimizing competition by using different food types and activity times. Habitat generalism in S. mordax may be a mechanism by which this species minimizes competition with its numerically dominant congener S. hondurensis for access to highly nutritious but patchily available Solanum fruits. Overall, this research suggests that bat species residing at high elevations might be generalists, capable of existing in both disturbed and mature cloud forest habitat, and might be coupling their energetically costly reproductive activities with local peaks in resource abundance.