Thousands of eastern bent-winged bats hibernate in an artificial cave on Shikoku Island in Kochi, Japan. For several years the complete disappearance of the animals during the winter season baffled researchers as environmentalists could not locate their winter hideout. After much research, this massive colony of around 4,000 bats was found hiding on the island. (Photo by Kei Nomiyama/Barcroft Media)
