Alcohol discrimination and preferences in two species of nectar-feeding primate

Abstract

Recent reports suggest that dietary ethanol, or alcohol, is a supplemental source of calories for some primates. For example, slow lorises (Nycticebus coucang) consume fermented nectars with a mean alcohol concentration of 0.6% (range: 0.0–3.8%). A similar behaviour is hypothesized for aye-ayes (Daubentonia madagascariensis) based on a single point mutation (A294V) in the gene that encodes alcohol dehydrogenase class IV (ADH4), the first enzyme to catabolize alcohol during digestion. The mutation increases catalytic efficiency 40-fold and may confer a selective advantage to aye-ayes that consume the nectar of Ravenala madagascariensis. It is uncertain, however, whether alcohol exists in this nectar or whether alcohol is preferred or merely tolerated by nectarivorous primates. Here, we report the results of a multiple-choice food preference experiment with two aye-ayes and a slow loris. We conducted observer-blind trials with randomized, serial dilutions of ethanol (0–5%) in a standard array of nectar-simulating sucrose solutions. We found that both species can discriminate varying concentrations of alcohol; and further, that both species prefer the highest available concentrations. These results bolster the hypothesized adaptive function of the A294V mutation in ADH4, and a connection with fermented foods, both in aye-ayes and the last common ancestor of African apes and humans.

Physiology, ecology and industrial applications of aroma formation in yeast

“… 2008 ). Behavioral studies indicate that these nectar-seeking animals, specifically the primate slow loris ( Nycticebus coucana ) and the lemur aye-aye ( Daubentonia madagascariensis ), preferentially feed on nectar containing ethanol (Gochman, Brown and Dominy 2016 ). Interestingly, aye-ayes have a mutation in their ADH4 gene resulting in a 40-fold increase of their ethanol metabolism compared to most of the primates, potentially explaining why they do not get intoxicated on the high-alcohol food (Carrigan et al.…”

Feeding on ripening and over-ripening fruit: interactions between sugar, ethanol and polyphenol contents in a tropical butterfly

“…inverted U-shape response in relation to ethanol concentration with maximal positive effects for intermediate concentrations; Costantini et al, 2010;Dudley, 2004). However, other animals do not discriminate against food containing alcohol (Mazeh et al, 2008;Zungu and Downs, 2017), and some even actively seek such food (Gochman et al, 2016;Ogueta et al, 2010;Wiens et al, 2008), suggesting that energetic advantages may also overrule side effects.…”

Human Evolution and Dietary Ethanol

“…Diverse vertebrates consume food items containing low-concentration ethanol. [18][19][20][21][22][23][24][25] Ethanol acts as a feeding stimulant.…”

“…Although the animals never become overtly inebriated, hair samples contain high levels of a secondary metabolite of ethanol (ethyl glucuronide), consistent with high chronic exposure. Laboratory choice trials with two species of nectar-feeding primates indicate increasing preference for higher-concentration ethanol solutions [ 18 ] (see also [ 19 ] for analogous experiments with a primate frugivore). Additionally, wild chimpanzees consume anthropogenically sourced fermentations of palm sap within the tree canopy, at least at one site in West Africa [ 20 ].…”