Sweet tooth: Elephants detect fruit sugar levels based on scent alone

Abstract

The ability to assess food quality is crucial to all organisms. Fleshy fruits are a major source of nutrients to various animals, and unlike most food sources, have evolved to be attractive and to be consumed by animals to promote seed dispersal. It has recently been established that fruit scent—the bouquet of volatile chemicals emitted by ripe fruit—is an evolved communication system between plants and animals. Further, it has been argued that chemicals that are synthesized from sugar and its products may be an honest signal for sugar content and fruit quality. Elephants are important seed dispersers for numerous species and possess an olfactory system that is likely to outperform most other animals. We tested the hypothesis that fruit scent signifies sugar content and that elephants are capable of assessing fruit sugar levels based on scent alone. Using a paired‐choice test of marula fruits ( Sclerocarya birrea ) by semitame African elephants, we show that elephants are capable of identifying more sugar‐rich fruits based on scent alone and that this is likely based on two chemical compounds: ethanol and ethyl acetate, both downstream products of sugar fermentation. These results shed light on the mechanisms driving elephant feeding ecology, plant signaling, and the coevolutionary process between angiosperms and animal seed dispersers.

Anatomy and dietary specialization influence sensory behaviour among sympatric primates

“…Our data, although limited to three species, suggest that nasal turbinate volume may not be useful for predicting active sniffing in a fruit foraging context, and might be a better metric of other aspects of olfaction, an idea that invites future study. Olfactory perception remains a poorly understood area and is influenced by diverse factors, including the shape of the turbinates and nasal cavity, air flow rate across the olfactory epithelium, olfactory neuron density, OR diversity and their responsiveness to natural odours [ 27 , 32 , 59 , 60 ]. While we examined a narrow ecological context (e.g.…”

The Olfactory Landscape Concept: A Key Source of Past, Present, and Future Information Driving Animal Movement and Decision-making

“…the smell of ripe fruit, the odor of predators in the distance) (Nevo et al. 2020 ). Whether an animal is navigating within a patch, between patches, or across entire landscapes (Senft et al.…”

The promise of an evolutionary perspective of alcohol consumption

“…For example, Peris et al 24 looked at the dietary habits of wild seed disperser and pulp feeding species across two biomes and found that rotting fruits inoculated with Penicillium digitatum fungus were overwhelmingly preferred by local frugivores. Others found that African elephants (Loxodonta africana) could identify fruit sugar content based on scent alone, with volatile ethanol in the scent plume accounting for nearly 50% of the variance in which fruits were preferred 27 . Similarly, two nectar-feeding primates, the slow loris (Nycticebus coucang) and ayeaye (Daubentoniab madagascariensis), were found to prefer 1%-5% v/v ethanol solutions over sucrose-sweetened control solutions in a two-choice test 28 .…”