Data from: The role of volatile plant secondary metabolites as pre-ingestive cues and potential toxins dictating diet selection by African elephants

Understanding the factors driving diet selection represents one of the
main thrusts of contemporary foraging ecology. Many studies have focussed
on nutritional factors and anti-nutritional factors (such as tannins) that
may describe diet selection of generalist mammalian herbivores, but these
often do not explain the observed feeding patterns. Alternatively,
generalist herbivores may be influenced by the presence, diversity, and/or
concentration of toxins. Plant volatiles have been understudied, yet may
play an important role in this context. We aimed to determine whether diet
selection by African elephants is better correlated with the presence and
concentration of toxic plant secondary metabolites (PSMs) than with
nutritional or anti-nutritional factors. We also aimed to identify the
specific aspects of the plant-odour profiles that were correlated with
dietary selection, which could be used as a pre-ingestive cue for food
selection. We found that elephant diet selection was not well described by
crude protein, in vitro digestibility, tannin concentration, and total
polyphenol concentration. Instead, the best predictors of elephant diet
choice were the number and absolute (total) emissions of potentially toxic
volatile PSMs, specifically monoterpenes. Elephants avoided plant species
that emitted a wider diversity of volatile PSMs, had higher total
emissions, and higher numbers and emissions of monoterpenes. This suggests
that PSMs with a high propensity to become toxins, such as monoterpenes,
are likely a better indicator for elephant diet avoidance than nutritional
or anti-nutritional factors. Moreover, we demonstrated that elephants can
differentiate between food items based on odour alone, specifically
volatile monoterpenes, suggesting that these animals are relying on
specific volatile cues emitted from plants to direct their foraging
choices prior to ingesting selected plants.