Read more: “Minimals: Meet the smallest critters of all“
WALKING back to camp as night fell in Papua New Guinea, Christopher Austin heard a high-pitched, insect-like call coming from the forest floor. He and his companions were there to hunt for new species, so they started searching through the leaf litter.
“But we didn’t find anything,” says Austin. “We repeatedly did that during the night and weren’t able to find out what was making the call. So we ended up just grabbing a whole handful of leaf litter and throwing it into a plastic bag.”
Back in camp, with the benefit of better lighting, they slowly went through their haul. It soon became clear why they hadn’t been able to find anything out in the rainforest. The creatures that were making the noise were just 7.7 millimetres long. Yet they were not insects but fully grown frogs. “It was obvious that they were adult male frogs, as they were calling to attract a mate,” says Austin.
This minute amphibian, found in 2009, is the latest in a string of miniature vertebrates discovered in the past few years. The discoveries have sparked something of a race to find the world’s smallest – and although they had no idea at the time, Austin’s frog is a leading contender for that title. It could well be smaller than the previous record holder, a tiny freshwater carp from Sumatra in Indonesia described in 2006.
So are there even smaller vertebrates out there waiting to be found? What are the limits on how small a vertebrate can get?