several endangered animal and plant species now exist among the heavily fortified fences, landmines and listening posts. these include the extremely rare red-crowned crane (a staple of asian art), and the white-naped crane as well as, potentially, the extremely rare korean tiger, amur leopard and asiatic black bear. ecologists have identified some 2,900 plant species, 70 types of mammals and 320 kinds of birds within the narrow buffer zone. additional surveys are now being conducted throughout the region.