A clever cow has taught itself how to turn on a water tap.The animal apparently taught itself how to sip water from the roadside tap after "years of watching humans", locals said.The cow - called Moo - can be seen using the tap in a video, turning it back on after a passer-by shut it off, in Cortalim, Goa, on December 22.Local vet Fayaz Ahmad said: "Animals tend to learn through observation. It is one of the observational learnings.