Beaked whales are the most mysterious of all marine mammals. So far, there are about 20 species known around the world. They inhabit deep, pelagic waters spending very little time at the surface.
As a consequence, scientists are developing technologies to learn more about these elusive toothed whales. Mark Johnson has designed a non-invasive way to study them using a device called the DTAG.
We join Mark, Natacha Aguilar de Soto and their team on El Hierro in the Canary Islands, Spain, as they search for beaked whales to study their movements, habitat use and vocalizations.