The Lord of the Rings star has a love for creepy crawlies that terrify most people, but he admits there is one thing that scares him - looking down.
Revealing he inherited a fear of heights from his mother, the Brit admits he was terrified when he learned he would have to clamber up a 120-foot (36.5-metre) tree in Malaysia while filming his new docu-series.
He tells WENN, ""(Producer) Paul (Kilback) told me that I was going to have to go about 120 feet into a tree to get close to these giant honey bees because they live in the highest trees in the jungle.
""So the day before we went up there, we did a little minor test run, which we filmed, of me being hoisted 30 feet into a tree, and I am just terrified, like white knuckles; I was sweating like a cat stuck to a tree, trying to grab it with my feet and with my knees and stuff like that. I couldn't relax.
""I'd go up 30 feet, and Paul was like, 'That's fine. That's as high as we are going to go. Just relax.' I remember looking down and saying, 'I can't relax. I can't.' I was, like, gripping the tree. I came down and realised, 'Well, I'm going to have to travel at least three or four times that tomorrow. Paul and I sat down that night, and he said, 'Do you have any requests?' And I said, 'Let's do it first thing. Let's have it be the first thing that we do. We'll grab a quick breakfast, harness me up, and I'll go up into the tree.'
""I said, 'The only other thing that I'd like would be a bottle of whiskey!' So we got those two things, and I was ready to go. Paul is an experienced climber so he kind of talked me through it as best he could.""
And now Monaghan accepts he'll have to confront his fear of heights again if the nature show is picked up for another series - because some of the creatures he's keen to discover don't live on the ground.
He adds, ""I'm trying to create positive pathways. I'll get there eventually, but I have to continue to expose myself to it, and that's hopefully what I'm doing with Wild Things.""