A decade ago, we set out to unravel deep ocean crime scenes we weren’t even sure existed. The crime? Endangered Steller sea lions were rapidly disappearing in parts of Alaska. Their numbers dropped by 80% in three decades, yet only rarely did anyone see or sample dead sea lions. Live sea lions studied in the summer when they haul out to breed seemed healthy and had healthy pups.
We wanted to know when, where, and why sea lions die. To unravel the mystery, we needed information from those animals that we don’t see, those that might not breed, those that might never come back ashore. So we ...