Pandas are an endangered species which feed exclusively on bamboo, of which they can consume up to 20kg per day. Their extra digit and mucus lined digestive system helps them process and gather these high levels. Although this is a large quantity to consume, bamboo has very low nutritional value. Therefore it has been a longstanding mystery as to how these creatures can survive with such a low energy input.
This week in Science researchers have uncovered the solution which underpins this panda puzzle. The team studied 8 pandas in total; 3 which were wild and the other 5 in captivity.
The secret it turned out was due to the creatures being ‘frugal with energy’ explained Professor John Speakman, the lead author of the study. The Pandas energy expenditure is only 38% of that of comparable sized mammals. In particular the bears in captivity had extremely low levels of energy expenditure – they were only off their bum for one third of the time they were being observed!
Pandas were found to be active only 49% of the time and when they were moving the speed was usually lower than 20 metres per hour. Additionally their levels of metabolism are very low as a result of a low level of thyroid hormone. This is a unique feature of Pandas which has arisen from a genetic mutation affecting thyroid hormone synthesis. The levels of thyroid hormone are so low they are comparable to a hibernating black bear. Similarly their overall energy expenditure is most similar to a three toed sloth famous for their lazy lifestyle!
So their bamboo diet can only be maintained by a low levels of thyroid hormone and in turn low metabolic levels and bamboo is unlikely to be a future fad diets!