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Asked by to Thon, Catherine, James, Natalie, Shaylon on 24 Jun 2014. This question was also asked by .
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James Bell answered on 24 Jun 2014:
Good question – for some reason, Pandas have evolved only to eat bamboo and this is confusing for a number of reasons…
1) All other large bears are carnivores or omnivores and don’t ever depend upon a single food source. Pandas in the wild will occasionally eat eggs, fish and other things but their diet is around 99% bamboo
2) Pandas have carnivorous teeth which are rubbish for chewing tough plant material
3) Pandas have short guts, so they can’t digest plant material properly – this means they have to eat 10 or 15 kilos of bamboo a day to get enough nutrition (but also that they poop more than 20x a day)
4) The quality of the diet is so poor that Pandas both cannot hibernate (they must eat all year round rather than hibernate as other large bears do) but also can’t produce good quality milk for their babies so have to spend much longer looking after their young.This dependence on bamboo (and the amount they need to eat) means Pandas need big territories and are also very limited in where they can live (particularly as conflict with human land uses increase)
All this amounts to the conclusion that Pandas are highly vulnerable to extinction (they are even the mascot of the WWF) and only really stand a chance of survival through human intervention. However, some biologists might argue that actually, in a constantly changing world, the panda’s time is limited anyway. Even without human impacts, they’d be at risk – they reproduce slowly and have to maintain huge territories.
I realise I haven’t actually answered your question 😛 It’s not really clear why the Panda depends so heavily on bamboo (or at least I don’t know the reason, someone else probably does). It is possible that they simply took advantage of a resource that is very plentiful in their habitat and gradually became more dependent on it. Bears like the Grizzly will eat lots of different things (mainly salmon) but and the Panda probably did something similar at one point but has gradually grown more and more dependent on bamboo (which might just have been the only plentiful food)
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Anthony Caravaggi answered on 24 Jun 2014:
That’s a very good question indeed. James has covered a lot of the ground, here, but I should be able to throw out a few thoughts on the subject.
In 2010, scientists in China found that pandas seem to have lost the ability to taste savoury flavours, like meat, due to an inactive gene in their DNA. Taste is important in telling us what we like to eat, so modern pandas may not like to eat meat, even if it is available. They will and do eat some of course, but occasional meat makes up a very, very small part of a panda’s diet. This gene stopped working around 4 million years ago, which is about the time a lot of other animals died out. If your food disappears, you’re going to eat whatever is around, and bamboo was everywhere.
Since switching to bamboo, pandas have evolved extremely strong jaws which allow them to grind their food really well, getting as much nutrition as possible when it’s digested. They also have a sort of thumb, which helps them be a bit pickier about how they eat. They eat the leaves of the bamboo first, and only go for the harder stem centres later. The ‘thumb’ allows them to manipulate the bamboo while they feed.
Another group of scientists found that bamboo might produce a reward response in the panda’s brain. To explain what this means, think of how much most people like sugary and fatty foods. There’s a simple explanation for this – eating these foods leads us to produce a chemical called dopamine, which makes us feel good. Our brain then remembers that we felt good and encourages us to eat more of the feel-good food when it’s available. It turns out that pandas don’t produce dopamine properly and so don’t have a normal feel-good reaction. Chemicals in bamboo might help pandas make more dopamine. In short, eating bamboo might make the panda’s brain think that as far as food goes, bamboo is pretty fantastic.
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