Fake would be in a studio or a zoo and trying to pass it off as if it were in the wild. Fake is not setting up shots through painstaking planning.
Interesting you say that, for I've had that exact experience. In the Adelaide Zoo about 10-15 years ago, walking around with a bunch of kids as part of some school-holiday daycamp thingy (something my then-gf roped me in to help with).
We get to the Siamang section, and there's a camera crew there, looking rather bored. Being the nut I am, I start talking to the camera crew. They say they're working for a new David Attenborough series (which turned out to be 'Planet Earth'). They'd just spent weeks in the wild trying to find these monkeys to film, and given up, filming in the wild is damned expensive. On a hunch they thought they'd try the Adelaide Zoo, there's a really good habitat for them there.
So there they were, and the damned monkeys were silent, and the film crew were rather annoyed. But then the kids started yelling at the monkeys, and we being the 'responsible adults' were ridiculously embarrassed, trying to shut the kids up. But then the monkeys started yelling back. So as it turned out, we turned it into a game with the kids. Got them to yell for a bit, enough to get the monkeys started, then get the kids to shut up for a few minutes (the hardest part) while the film crew could get their shots, and repeat.
I always like it when that series comes on, because I can still pick the bits that were shot in the Zoo (you can kind of tell, the sky is really blue and it's shot from almost directly underneath and the monkeys are looking straight at the camera). Nowhere does it say in that scene that it's in a zoo, but nowhere does it also say it's in the wild. It mentions the Adelaide Zoo in the credits (either in the 'filmed on location' bit or the 'thanks to' bit), along with a whole lot of other zoos and wildlife parks.
I know it's nothing like when Attenborough was the first white guy to set foot in some remote forest to collect specimens for the London Zoo (which is how he started), but finding something classed as 'wild' is getting harder and harder these days. So I don't mind if stuff is filmed in Zoos or whatever. The only time I'd mind is if it was a faked one of those 'look at how these monkeys have started using tools in the wild', which it wasn't. In the end, there's only about 5-10s of stuff filmed there, spliced in with 'real' jungle footage, so who cares?
edit: I should call them Siamangs and not Howler Monkey, before some nerd picks me up on it