Suzi Eszterhas / Southern sea otter (Enhydra lutris) veterinarian Mike Murray performing surgery on captured otter to remove time depth recorder as part of long term study, Big Sur Coastline, California, USA September...

Suzi Eszterhas / Southern sea otter (Enhydra lutris) researcher Tim Tinker handing diver net for capturing sea otters for flipper tagging, blood sampling, and implantation of time depth recorder, Big Sur Coastline, Ca...

Suzi Eszterhas / Sea Otter (Enhydra lutris) researcher Tim Tinker holding captured otter in net for time depth recorder implanting, Big Sur, California

Suzi Eszterhas / Sea Otter (Enhydra lutris) captured in net by researchers for implanting a time depth recorder, blood sampling and flipper tagging, Big Sur, California

Suzi Eszterhas / Sea Otter (Enhydra lutris) captured in net by researchers for implanting a time depth recorder, blood sampling and flipper tagging, Big Sur, California

Juergen Freund / Depth and time recorder device for attachment to a shark, used in the Coral Reef census, Lizard Island, Queensland, Australia, April 2008

Flip Nicklin / Bottlenose Whale (Hyperoodon ampullatus) surfacing and about to be hit by suction-cup dart time depth recorder, Nova Scotia, Canada

Flip Nicklin / Bottlenose Whale (Hyperoodon ampullatus) surfacing and targeted by researcher with suction-cup dart time depth recorder, Nova Scotia, Canada

Jeff Rotman / Sealion places time-depth recorder on whale model while carrying video camera, CA, USA

Suzi Eszterhas / Sea Otter (Enhydra lutris) researcher Tim Tinker holding time depth recorder that was just removed from sea otter two years after being surgically implanted, Big Sur, California

Suzi Eszterhas / Sea Otter (Enhydra lutris) researcher Tim Tinker holding captured otter in net for time depth recorder implanting, Big Sur, California

Flip Nicklin / Bottlenose Whale (Hyperoodon ampullatus) researcher holds suction cup cross bow used to attach time depth recorder to whales, Nova Scotia, Canada