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  • Thumbnail for Maximum weight capacity of leaves used by tent-roosting bats : implications for social structure and plant species usage
    Maximum weight capacity of leaves used by tent-roosting bats : implications for social structure and plant species usage by Parker-Shames, Phoebe Amelia

    Fewer than 2% of bats have the capacity to modify their environment to construct roosts. Tent-roosting bats cut and fold leaves to form roosts called “tents” and often use specific plant species for this purpose. Unlike the caves or hollow trees used by some bats, leaves possess an upper limit on their capacity to support weight. I tested the hypothesis that the maximum weight capacity that leaves can support limits the maximum social group size of bats that roost in them. I tested a secondary hypothesis that the bat Dermanura watsoni would preferentially use the plant species that can support more weight. I conducted research in the Tirimbina Biological Reserve (TBR), Sarapiquí, Costa Rica, between March and April 2012. To test the first hypothesis, I added weight incrementally to new leaves of three plant species until the angle of the leaves fell below that which bats naturally use. Philodendron fragrantissimum and Heliconia imbricata support one-third more weight than Asterogyne martiana. To address the second hypothesis, I determined plant abundance by systematic-random plot sampling along main paths in the reserve and systematically surveyed tents along the same paths. Patterns of leaf use by D. watsoni suggest a preference for A. martiana and complete avoidance of H. imbricata. Dermanura watsoni did not show a preference for plant species that support a greater maximum weight capacity. This study demonstrates that the maximum weight that the leaves can support is similar to the mean social group weight of D. watsoni and Ectophylla alba reported in the literature for these plant species and lower than the maximum reported social group weights. Therefore, it is possible that the maximum weight capacity of the leaves used to construct roosts limits the maximum social group size but may not be an important factor used for plant selection.