sentence: marine mammals as a class ( whale , porpoise , seal , and polar bear ) , for the most part , found protection under the passage of the marine mammal protection act ( public law 92-522 ) of 1972 , which prevented extinction or depletion from indiscriminate taking , including hunting , harassment , capture , and killing ( permitted takings , including for subsistence and research purposes , must be accomplished humanely , with '' the least degree of pain and suffering practicable to the animal '' ) .