Sea lions learned to press a paddle for fish — to help scientists protect their hearing

Keepers at Sydney's Taronga Zoo trained two Australian sea lions and two long-nosed fur seals to press a paddle whenever they hear a tone — fish for every correct answer — in the first hearing tests ever done on these species. Led by Curtin University and published in peer-reviewed journals, the work found the animals hear best around 3.2 kilohertz, giving scientists a baseline for judging how ship traffic, boats, and coastal construction noise affects them. It matters most for the endangered Australian sea lion, down to about 12,000 animals.