If you pay attention to the credits, there is a "Survivor Expert" credit which has a different name for each episode. You'll also notice that Bear Grylls is credited as "Presenter". I do believe he has experience, but I think he is trained and informed of the area and its animals in great detail before he is dropped off. The whole point of the show is to inform us, which is why I think him being credited as "Presenter" is very appropriate.
I noticed this in the Ecuador Episode, and I actually searched the survival expert for that episode, which was Hazen Audel.
Turns out that Hazen Auden is a Teacher and has extended knowledge on rain forests and its animals.
Here is a link explaining his participation in the show.
http://www.spokesmanreview.com...al/story.asp?ID=199486
Full article
http://www.spokesmanreview.com...story_pf.asp?ID=199486
Quotes from article
Audel would talk to producers about indigenous practices, like using a bow and arrow to kill a particular fish, and would make all the props for the next shoot, sometimes while everyone else was eating dinner.
Not everything on the show is authentic, however.
Producers insisted on having piranhas and electric eels in the Rio Napo for Grylls to face, even though they're not native to the part of the river where filming took place.
"I had to contact my friends that live four days way downriver in a motorized canoe to go catch piranhas and electric eels for the shoot," Audel said. "It became really involved. It was an adventure on its own."
While demonstrating for the film crew how Grylls could show the fish's teeth on camera, the piranha bit the end of Audel's thumb. Audel said it became a joke among the producers that their expert got his thumb bitten off.
After filming the eels and piranhas, which were kept in a designated area, the crew ate them to avoid releasing them into the river where they didn't belong.
"It's definitely Hollywood," Audel said of the program.
It has to be, though.
"You can't just have one guy with a camera shooting, because it would just bore people to death," he said.