A lost whale - 6,000 miles from home

A grey whale, dubbed "Wally" by the marine biologists tracking it, is lost in the Mediterranean - and it must find its way home soon if it is to survive.

At this time of year, Wally should be 5,600 miles (9,000km) away, off the coast of Alaska. The species normally migrates up and down the cost of North America but melting ice in the Arctic has opened up previously closed off passageways to the Atlantic Ocean.

What happens if Wally can't get back?

Video by Joaquim Moreira Salles