Answer:A video I watched speculated that Eric was making his way through the jungle and came across the Rex. It is thought that he hid and while he was hiding the Rex peed. While he was hiding he noticed that some Compies close by fled at the smell so he decided to test if they were scared of it. When he knew for sure he bottled it up.
Chosen answer:It's never explained how he got it. Any explanation the filmmakers might give would probably be implausible.
Answer: A video I watched speculated that Eric was making his way through the jungle and came across the Rex. It is thought that he hid and while he was hiding the Rex peed. While he was hiding he noticed that some Compies close by fled at the smell so he decided to test if they were scared of it. When he knew for sure he bottled it up.