Gray Whales were once nearly wiped out by commercial whaling. Once that ceased in the late 20th century, they staged a remarkable comeback, reaching a population of around 26,000 by 2016. But since then many have died on migration, and a new estimate indicates their population has been cut in half. We talk with Dr. Aimee Lang of the NOAA Southwest Fisheries Science Center about that estimate, and what might be causing the decline of these iconic marine mammals.