For hundreds of years, the United States and countries around the world relentlessly hunted whales and other marine mammals for their oil, blubber and other byproducts. But today whales, dolphins and porpoises are widely viewed as intelligent creatures worthy of conservation and protection from commercial hunters. Scientists describe marine mammals as social animals that share characteristics with humans, including the ability to communicate in sophisticated ways. But Japan, Norway and Iceland still hunt whales, and Japan continues its controversial slaughter of dolphins for their meat, as dramatized by the Academy Award-winning documentary “The Cove.” Efforts to ban commercial whaling by the International Whaling Commission have failed because of political bickering and competing national interests. Meanwhile, climate change, entanglement in commercial-fishing gear and ocean noise pollution are adding to the peril facing marine mammals.