Sea otters weigh about 50 to 70 pounds, they float on their backs and they spend most of their lives in the ocean. River otters are two or three times smaller, they swim with their bellies down and they live mostly on land but travel by water to find food. Sea otters nearly went extinct in the early 1900s because of the fur trade. River otters are common and of “least concern” in California, but are threatened or endangered in some other states. But Heath offered a warning. “They’ll hiss at you if you get too close,” she said. “They’re...