helicopter gun ships were being used as well as all sorts of automatic weapons on the ground by the u.s. and the united nations. by september 2012, the game had sold 3.5 million copies. from 1 october 1980, the original 20 series sleeping cars were replaced by 24 series sleeping cars. in 2011 it was removed from the endangered species list. plants in the exhibit include palms, pomegranates, and ferns. sloths can reduce their already slow metabolism even further and slow their heart rate to less than a third of normal, allowing them to hold their breath underwater for up to 40 minutes. 