Bat sampling
We captured bats using four to six mist nets (6m – 12m) opened along trails and near watercourses in the study area from 18h – 22h. In addition, a canopy net and harp trap were used in 2009 but these had low capture rates and so were not used in 2015. Sampling took place in the dry season during January-February (Sector Santa Rosa of ACG) and Mar-Apr (La Selva) (2015), in the wet season May-Jul (Santa Rosa of ACG) (2009), and in the wet season July-August (Sector Santa Rosa of ACG) and September-October (La Selva) (2015). Sampling and bat identification during the normal year was conducted as described in Clare et al. (2019). Sampling effort using mist nets was equal to approximately 2,250 m2.hours within each season during the El Niño year, and approximately the same during the normal year. We collected wing punches for another study and these also served to avoid recaptures. We measured the forearm length with callipers (0.1 mm precision) and identified species following Reid (1997), Timm & Laval (1998) and Laval & Rodriguez-Herrera (2002). Bats were held in cloth bags for a maximum of two hours for the collection of faecal samples. All samples were frozen after collection (-20° C).