Maximum weight capacity of leaves used by tent-roosting bats: implicatons for social structure

ABSTRACT

Fewer than 2% of bats can modify their environment to construct roosts. Tent-roosting bats cut and fold leaves to form roosts called tents. Unlike the caves or hollow trees used by some bats, leaves possess an upper limit on their capacity to support weight. We tested the hypothesis that the maximum weight capacity that leaves can support limits the maximum social group size of bats that roost in them. We conducted research in the Tirimbina Biological Reserve (TBR), Sarapiquí, Costa Rica, between March and April 2012. We 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. 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.