South Asian river dolphin The sphincter-like structure is capable of sensing light, and may be able to sense the direction from where the light was emitted. However, the muddy waters, or low light conditions, that the "Platanista gangetica" inhabit negate the use of the little vision that remains. The Ganges subspecies shows object-avoidance behavior in both the consistently heavily murky waters of its habitat and in clear water in captivity, suggesting that it is capable of using echolocation effectively to navigate and forage for prey. However, there is limited information on how extensively vocalization is utilized between individuals. This subspecies of river dolphin is
Endangered Species Act of 1973 birds, 6 reptiles and amphibians and 22 fish. This first list is referred to as the "Class of '67" in "The Endangered Species Act at Thirty", Volume 1, which concludes that habitat destruction, the biggest threat to those 78 species, is still the same threat to the currently listed species. It included only vertebrates because the Department of Interior's definition of "fish and wildlife" was limited to vertebrates. However, with time, researchers noticed that the animals on the endangered species list still were not getting enough protection, thus further threatening their extinction. The endangered species program was expanded by the