Nectar drinking efficiency in lonchophylline and glossophagine bats: are “pump-like” or “mop-like” tongues better? are "pump-like" or "mop-like" tongues better?

Nectarivory has independently evolved twice in the bat family Phyllostomidae, resulting in elongated tongues with 2 contrasting morphologies. Glossophagines have lapping "mop-like"tongues with terminal papillae, while lonchophyllines have non-lapping "pump-like"tongues that pull nectar through lateral grooves. Using flight-cage experiments, we measured maximum tongue extension and compared the nectar extraction efficiency of glossophagines and lonchophyllines in flowers with different morphologies and nectar depths. We studied 3 co-existing species in a cloud forest in the Ecuadorian Andes: 2 glossophagines (Anoura caudifer and A. cultrata), and 1 lonchophylline (Lonchophylla robusta). We found that maximum tongue extension is associated with nectar extraction efficiency across the 3 species in that L. robusta, with an intermediate tongue extension, was also intermediate in extraction efficiency. Additionally, within the 2 species of Anoura, individuals with greater tongue extension had greater extraction efficiency. We also found that, across all species, extraction efficiency declined at a similar rate with increasing nectar depths. However, the mechanism behind this decline was different for the glossophagines - which increased visit duration the deeper the nectar - versus L. robusta, which instead decreased visit duration with deeper nectar but simultaneously showed a much sharper decrease in amount of nectar consumed per visit. Our results suggest that bats with "pump-like"and "mop-like"tongues have comparable nectar extraction abilities across a variety of floral shapes, despite the large differences in behavior and tongue morphology. Instead, tongue extension appears to be a better predictor of nectar extraction efficiency, although data from more species are needed to be able to generalize these results.