It is very common on the net, to use images without checking the copyright. Not only images, sound, mp3 and videos, any kind of intellectual property is used without notice. But it is unbelievable how often this strange bat is stolen! Maybe not stolen, many sites owners are sure, this bat is in the public domain and therefore "free".
It is very interesting: you will find those bats not only on caving pages: biology and environmental pages, Gothic, horror and Halloween pages, even some TV stations use those batimations.