Fast lane: A Glossophaga soricina, nectar-feeding bat smothered with pollen from a flowering tree – Palo Verde National Park, Costa Rica. The long-tongued species is a significant rainforest pollinator.
Credit: Christian Voigt
SYDNEY: Nectar-feeding bats burn energy faster than any other mammal or bird on Earth, and three times faster than human athletes.
A new study reveals that tiny bats metabolise sugar at an incredible rate, and as a result of their reliance on this rapidly deplenished fuel, they are highly sensitive to any small changes in their environment.
"These bats live on the fast track of the metabolic autobahn," said Christian Voigt from the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany. "From a conservation aspect this study highlights the importance of intact forest ecosystems. If these bats don't find sufficient nectar every day, they starve."
Floral energy drink
Voight and John Speakman, of the University of Aberdeen in Scotland, are authors behind the study detailed today in the journal Functional Ecology. The biologists studied a captive breeding colony of 56 nectar-feeding bats of the Central and South American species Glossophaga soricina. These bats weigh in at less than 10 g and are among the smallest of all living mammals.
These nocturnal bats, can consume up to 150 per cent of their body weight in a single sitting, by hovering at flowers to feed on simple sugars – such as fructose, glucose and sucrose – found in the nectar. To maximise the energy extracted from their food, they metabolise most of the sugars immediately rather than converting them to fats for storage.
Researchers fed the bats sugar labelled with carbon-13 (a harmless isotope of carbon that can be tracked because of the faint radioactivity that it emits) and then used to detect the amount of sugar in the bats' breath and how rapidly it appeared; much like breathalysing a suspected drink driver. The pair then followed this up by measuring the rate the bats used up their fat stores.
Important rainforest pollinators
They discovered that the nectar-feeding bats were tapping into the sugar supplies mere minutes after drinking it. In less than 30 minutes, the bats were able to fuel themselves entirely from their latest meal. The study also revealed that bats burn their fat stores rapidly, depleting them by up to 60 per cent in a day.
In contrast, elite human athletes, can only get a maximum of 30 per cent of their fuel directly from energy drinks, the rest has to come from stored reserves.
These "phenomenal rates are still barely enough to sustain their metabolism when nectar is absent", wrote the researchers, who noted that the nectar feeding bats are the only mammals capable of hovering, much as hummingbirds do.
The study underlines how vulnerable the bats could be to even small changes in their habitat – possibly due to climate change.
"The ramifications of such an effect would be enormous," said Speakman, "because these bats are important pollinators of many rainforest plants."
