Letter: [copy] If I were a sloth, where would I defecate?

From Jane Lambert, Penzance, Cornwall, UK

I enjoyed Jason Bittel's article on sloths (23/30 December 2017, p 44). I was perplexed, however, by the statement that the reason sloths climb down to the forest floor to defecate, then bury the mess, “is still a mystery”.

If I were an extremely slow-moving animal with many predators I don't think I would drop my calling card from high in the forest canopy, allowing it to smear every leaf and twig as it fell and then lie at the foot of my tree.

Evolution has given the sloth the longest digestive process on record for a plant-eating mammal, so it doesn't have to make the descent too often.

The editor writes:
• This hypothesis is certainly appealing. Others include the idea that the excrement may contain something that allows sloths to communicate, which could explain why it is worth expending so much energy. We know of no one testing these ideas or others experimentally, which is what we would need to know for sure.