 As wilderness areas shrink, herpers are concentrated into smaller areas, and commercial collectors often encounter field biologists which may have quite different approaches to their study animals.Many species are also threatened or endangered and thus it is illegal to take them from the wild.Another consideration is spreading of diseases, such as the fungus "Batrachochytrium dendrobatidis" responsible for a worldwide decline in amphibian populations, which may be spread inadvertently by humans.