PLANET EARTH Caves

The bats can detect the snakes using echolocation, but the snakes are literally in the dark - they can see nothing. The strikes seem to be largely hit-and-miss（碰巧）, but the snakes have a secret weapon. They can actually sense each bat flying past. Receptors in the snake's head pick up the heat given off by the flying bats, as this thermal image（热成像图） shows.



To the snakes the bats are apparently glowing and this gives them something to aim at. This is the price that these cave commuters must pay for their daytime sanctuary on the ground. Small wonder then that there are other cave dwellers that stay put. Many caves are like islands - cut off from the outside world and from other caves.



This isolation has resulted in the evolution of some various strange creatures. They are the cave specialists - troglodytes（类人猿，同时有隐居者的意思）, animals that never emerge from the caves or see daylight. These troglodytes from Thailand are possibly the most specialized creatures on Earth for they live only in cave waterfalls. The entire population of these cave angel fish seems to be restricted to just two small caves.