It's not fake as in CG or puppet snakes or a set or they dropped a bucket of snakes on an unsuspecting lizard, but video from different times spliced together to present a narrative that isn't what happened. Fake temporally at least. The producer has acknowledged this:

"Unfortunately lizards, snakes and iguanas aren’t good at 'takes'." She continued: "For continuity, it was better to crop the scenes together based off of the two cameras we had at the time to create the best possible scene."

https://www.independent.co.uk/arts-entertainment/tv/news/pla...