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 Scientists studying the endangered black-and-white bears said on
Thursday that while pandas almost exclusively eat bamboo, which
contains only tiny amounts of sugars, they showed a strong
preference for natural sweeteners in an experiment.
The researchers also examined panda DNA and found a match to the
same "sweet receptor" gene that humans possess that underpins their
ability to taste sugars.
Sweeter foods like fruit may have been part of the natural diet of
pandas before human activities helped drive the animals into their
current mountainous habitat where those foods are scarce, the
researchers said.
"Giant pandas love sweets," said behavioral geneticist author
Danielle Reed of the Monell Chemical Senses Center in Philadelphia,
who led the study published in the journal PLOS ONE.
"We are a bit surprised. However, given the anecdotal evidence that
they like apples, sweet potato and so on in captivity, we are not
completely surprised," added Monell molecular biologist Peihua
Jiang, another of the researchers.
Pandas, the rarest species of bear, reside primarily in bamboo
forests high in the mountains of western China. Understanding what
type of food pandas prefer may help determine what nutrients can be
used to supplement bamboo in their diet as part of efforts to
conserve them, Jiang said.
The study was conducted as part of long-term research aimed at
understanding how taste preferences and diet selection are affected
by taste receptor genes.
The researchers wondered if pandas were able to taste sweet stuff
because while pandas are plant eaters, their ancestors were
meat-eaters. Many strict carnivores have lost their sweet-tasting
receptor gene, called Tas1r2, and show no preferences for
sweet-tasting compounds.
For instance, their previous research showed that any type of cat,
from house cats to tigers, cannot taste sweets and, thus, do not
like them.
Their experiments involved eight giant pandas at the Shaanxi Wild
Animal Rescue and Research Center in China. The youngest was 3 years
old and the oldest was 22.
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The bears were given two bowls of liquid and permitted to drink for
five minutes. One was filled with plain water. The other contained
water mixed with one of six natural sugars: fructose, galactose,
glucose, lactose, maltose and sucrose.
The pandas liked all the sugar solutions better than plain water,
especially fructose and sucrose. "They often emptied the bowl
containing sugary solution," Jiang said.
The researchers then did the same tests with five artificial
sweeteners, but the pandas were far less interested in those.
Pandas previously lived in lowland areas, but human activities like
agriculture, forest destruction and development exiled them to their
current mountain terrain.
"We cannot travel back in time to understand what animals ate before
their habitats were disturbed by mankind. But we can look at their
DNA and their taste preferences and make inferences about their
ancient diet," Reed said.
"Giant pandas' ancient diet may have included more foods than just
bamboo — perhaps fruits, hence the sweet tooth. It may be that
bamboo is an everyday food for giant pandas, but when sweeter foods
are available, they go for them," Reed added.
(Reporting by Will Dunham; editing by David Gregorio)
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