Tag Archives: Nectar

Fruit and nectar eaters are nature’s most resilient alcohol drinkers

New research at the University of Calgary in Canada has identified nature’s stoutest drinkers — unsurprisingly, they’re all fruit eaters.

Primates like humans, chimpanzees, gorillas, alongside other mammals whose diets contain lots of fruit such as bats are nature’s best drinkers, the paper reports. Such animals had an evolutionary incentive to develop the ability to metabolize alcohol, they explain, which created a selective pressure in favor of this ability. However, it’s not just mammals that partake — pound for pound, bees are known to be some of the heaviest drinkers out there.

It’s in my genes

“Being able to eat a lot of fruit or nectar without being subject to the effects of ethanol would certainly open up an important food resource,” explains lead author Mareike Janiak from the University of Calgary.

Fruits are very useful in one’s diet: they’re full of good nutrients and contain a lot of energy in the form of sugars. But bacteria also know this and are liable to start eating (fermenting) those compounds into alcohol. Alcohol concentrations in fruits past their prime can reach up to 8.1%, the study reports. Nectar, the sweet liquid flowers produce to attract pollinating insects, can still reach a respectable 3.1% alcohol concentration. For comparison, beers typically revolve around the 4.1% alcohol concentration mark.

It’s understandable, then, that fruit-eaters could be exposed to quite a generous helping of alcohol during breakfast, lunch, and dinner.

The ability to metabolize alcohol would, therefore, be quite desirable for fruit-eating species, the paper explains, as it would prevent them from getting completely smashed on a daily basis — which helps with things such as avoiding predators, impressing potential mates, or just maintaining basic motor coordination.

In order to understand how different species developed this ability, Janiak and her team studied genetic data for over 85 different mammal species looking for a gene called AHD7. This gene encodes the production of the enzyme alcohol dehydrogenase 7, which is part of a larger family of proteins that mediates chemical redox reactions. This particular one is specialized in alcohols and, in short, it allows bodies to either break it down into its constituent parts or recombine it from said parts. In short, AHD7 is what allows us to process alcohol (and its inebriating effects) out of our systems.

Mammal species who regularly consume fruit or nectar are more likely to have a variant of ADH7 that’s more efficient at processing alcohol, the team reports. Among the species that have this gene variant number bonobos, aya-ayes, chimpanzees, gorillas, as well as humans. They say it comes down to our shared genetic history, tied together by a common ancestor “at least 10 million years ago, long before we began fermenting beverages on purpose”.

However, “it is a fallacy to assume that other animals share our metabolic adaptations, rather than taking into consideration each species’ unique physiology,” the authors note.

Fruit- and nectar-eating bats are also very good at processing alcohol, the team found, likely because “being inebriated would be bad news for a flying mammal, so being able to better metabolize ethanol could be an important adaptation for them”.

In contrast, mammals who typically exclude fruits or nectar from their diet — including horses, cows, or elephants — are poor at metabolizing alcohol because they have lost their functioning version of ADH7.

The paper “Genetic evidence of widespread variation in ethanol metabolism among mammals: revisiting the ‘myth’ of natural intoxication” has been published in the journal Biology Letters.

No web, no worries — spiders also like to eat vegetarian

Spiders’ diets aren’t limited to juicy insect bits; they’ve been shown to occasionally consume fish, frogs or even bats before — but they spice up their menus with vegetarian courses too, zoologists from the US and UK have found.

Young jumping spider consuming a Beltian body (lipid and protein-rich detachable leaflet tips of acacias.)
Image credits Eric J. Scully/ Harvard University.

Spiders are traditionally viewed as insectivorous predators, dining on anything their webs can trap. But scientists are becoming increasingly aware that’s a skewed view of them, and that their diet is more diverse than we imagine. If available, spiders won’t shy away from eating fish, frogs, bats — all kinds of meat. But a team of zoologists from the University of Basel, Brandeis University and Cardiff University has now brought evidence of meat-eating spiders chowing down on plant-based foods too.

“The ability of spiders to derive nutrients from plants is broadening the food base of these animals; this might be a survival mechanism helping spiders to stay alive during periods when insects are scarce”, says lead author Martin Nyffeler from the University of Basel in Switzerland.

They gathered and documented all examples of spiders eating such items from scientific literature they could find. Their collection of data shows that spiders from ten families have been reported feeding on a wide range of plants such as trees, shrubs, ferns, flowers, weeds or grasses. And they aren’t picky, either; they’ll eat anything from nectar, sap or honeydew to leaves, pollen and seeds.

Jumping spider drinking nectar at extrafloral nectaries of a shrub.
Image credits David E. Hill, Peckham Society, South Carolina.

A family of diurnal spiders, the Salticidae, seem to be the most voracious plant-eaters of the Araneae order. These plant-dwelling, highly mobile foragers were attributed with almost 60 percent of the incidents documented in this study.

But such feeding habits aren’t a Salticidae-only thing. Plant-eating in spiders has been reported from all continents except Antarctica, but seems to be more common in warmer areas of the globe. As a larger number of the reports relate to nectar consumption (which has its core distribution in warmer areas where plants secreting large amounts of nectar are widespread) this isn’t too surprising.

“Diversifying their diet with plant is advantageous from a nutritional point of view, since diet mixing is optimizing nutrient intake,” Nyffeler concludes.

Currently, the extent to which different categories of plant-based food contribute to the spiders’ diet is still largely unexplored. But, as there currently is a known species of spider that is mostly herbivorous, the Central America indigenous Bagheera kiplingi, it can be assumed that in a pinch spiders can live on a full veggie diet for some time.

The full paper, titled “Plant-eating by spiders” has been published online in the Journal of Arachnology and can be read here.