Bananas for Bats

For our independent study, we examined the effects of man-made trails on frugivorous bat foraging activity.  We compared foraging activity in 4 different treatments, two trails and their surrounding forests.  One trail, Camino Experimental, was narrow, and the other trail, Sendero Tres Rios, was wider.

Small pieces of banana were used as bait.  Every afternoon, we assembled 100 skewers with two chunks of banana each, and we placed these skewers in the forest, with 50 on each trail (25 skewers were placed 10m into the surrounding forest and 25 skewers were placed directly on the trail).  At night, we retrieved the skewers and checked them for marks from bat incisors, and if bats had eaten the bananas, we estimated the percentage consumed.  In total, we walked over 20 miles setting out and retrieving 280 banana skewers over 3 days.

In the end, we found increased foraging on the wide trail compared to foraging activity in the forest surrounding the wide trail as the mean percentage of the bananas consumed was greater on the trail compared to off the trail.  However, bat foraging activity was similar on the narrow trail compared to in the forest surrounding that trail.  This might be due to the fact that the wide trail had greater differences in structural complexity in comparison with its surrounding forest, whereas the narrow trail was closer in structural complexity to the forest surrounding it.

I had a lot of fun working on this project.  When collecting the banana skewers, it was always very exciting to find bat incisor marks, and we encountered many unique animals on our long walks through the forest at La Selva, including 5 different snake species.  I found all of our hard work to be very fulfilling, as this project has many meaningful implications for conservation.  For instance, I now realize the importance of making trails as narrow as possible.  Since bats defecate while flying, increased bat activity on wider trails means increased seed dispersal onto the paths where seed germination is inhibited.  Therefore, narrow paths are crucial for maintaining effective bat seed dispersal, which is key for conserving and restoring tropical forests.

Jamila Roth

Skidmore College

Photo credit to Jose Antonio Guzman and Christian Perez