50 years ago, the U.S. Navy enlisted sea lions and other marine mammals

Porpoises, sea lions and even whales have been trained to retrieve dummy rockets and other objects from the bottom of the ocean…. The animals, guided by a homing device, would carry grappling hooks to submerged objects.… But whales became too expensive and kept running off to mate, so research now concentrates on smaller sea mammals such as porpoises. Today, the U.S. Navy Marine Mammal Program, based in San Diego, trains bottlenosed dolphins and California sea lions to protect ships and harbors. Sea lions help retrieve equipment from the ocean floor, dolphins locate underwater mines and both species detect unauthorized swimmers. Animals in the program have also helped researchers understand dolphin echolocation, assess the impacts of human-generated noise on wildlife and more. Current projects are testing whether it’s possible to judge dolphins’ health based on their whistles and whether a video game system can provide Navy sea lions with cognitive enrichment.