'Born Survivor' Will Ferrell

Bear Grylls is teaching Will Ferrell how to survive in the wild.

The 'Anchorman' star is currently in a secret location with ex-SAS solider Bear, who is showing him how to survive in one of the world's harshest environments for a one-off episode of his TV show 'Born Survivor'.

A source said: "The appetite for Bear's show is massive so producers were looking at ways of making it even more exciting.

"Normally Bear and his film crew just head out and he shows viewers how to live in the wild. For the next episode he'll have an A-lister in tow so it will make things extra hard for him.

"Not only will he have to endure some pretty horrendous things himself, but he'll have to convince a celebrity to do it as well."

Bear has drank his own urine and slept inside a dead camel on previous episodes of 'Born Survivor'.

Although he displays incredible survival skills in his shows, Bear's reputation was rocked in 2007 by claims that during some trips he stayed in hotels rather than roughing it outdoors.