Sensory integration during foraging: the importance of fruit hardness, colour, and odour to brown lemurs

Animal reliance on fruit signals, such as hardness, colour, and odour, during foraging is poorly understood. Here, we present data on fruit foraging behaviour and efficiency (rate of fruit ingestion) of three groups of wild, frugivorous brown lemurs (Eulemur fulvus, N = 29 individuals) in Ankarafantsika National Park, Madagascar. We quantify fruit hardness using a modified force gauge, fruit colour using spectroscopy, and fruit odour using volatile organic compound (VOC) sampling with gas chromatography-mass spectrometry. We relate lemur foraging behaviour to fruit traits by calculating touching, visual inspection, and sniffing indices and relate lemur foraging efficiency to fruit traits by calculating acceptance indices. The use of different sensory modalities by lemurs is marginally predicted in one case by fruit traits—fruits with higher overall smell signals are sniffed less than fruits with lower overall smell signals. When controlling for all fruit traits, fruit size is the only significant predictor of fruit foraging efficiency—lemurs forage more rapidly on smaller fruits relative to larger fruits.