Albatross expert Dr. Henri Weimerskirch, of the French National Centre for Scientific Research (CNRS), turned his favourite seabirds into spies two years ago by fixing them up with loggers that could detect the radar of illegal fishing vessels. The information from this project, known as OCEAN SENTINEL, has helped governments select which parts of the ocean to patrol. But Dr. Weimerskirch wanted to recruit another, possibly better, species to stealth operations. In late 2020, he returned to the remote Kerguelen Islands, in the southern Indian Ocean, to see if they would cooperate. He told Horizon about his expedition.