You could get all you want because you actually have the whole creature at the end, before he is evidently released back into the wilderness.
When you first start the island and you get the paper about Mews needing the evidence of ONE cryptid to get your reward, you end up needing to search for 4: Bigfoot, the Loch Ness Monster, the Chupacabra, and the Jersey Devil.
Yes, you can find proof of The Jersey Devil, Bigfoot, Nessie, and the Chupacabra. (see related question)
first you have to find all the other cryptids then you go in the helicoptor to the new location and follow him to his cave
In the Pacific Northwest, follow Bigfoot in the copter as he moves through the trees. Be careful because he may trick you. You have to follow him until he reaches the caves.
You don't. However, you will later follow Bigfoot as he travels through the trees in the Pacific Northwest.
Not Bigfoot's footprint, but possibly that of the Yeti (a similarly described creature). It is above the monastery on a trail to the upper left. You need a photo of the footprint in the snow.
You can't, because it never appears. You do find Bigfoot at the end of the quest. All you can do at the Himalayas is get the lantern from the monastery and a photo of a footprint high up on the mountain. This is not enough proof. When you prove the other three cryptids, Mews will send you after Bigfoot instead.
You find him in the lab, where you first talked to him. From the helipad. it is just to the left.
Since the monks won't let you test the Yeti scalp, you have no proof. Once you have the lantern and the footprint photo, you can find nothing at the Himalayas. However, once you prove the other three cryptids (Nessie, Chupacabra, and the Jersey Devil), Mews will send you in pursuit of the similar creature, Bigfoot.
There are 3 you have to prove: Nessie (Loch Ness) Chupacabra (Puerto Rico) New Jersey Devil (New Jersey) You can't get what you need to prove the Yeti, so you are sent to find Bigfoot.
You take it to mews mansion and give it to him if its real you can analyze it if it is not he wont take it.
To win the island, you must find the proof that confirms the existence of three legendary cryptids : Nessie of Loch Ness, the Chupacabra, and the Jersey Devil. Then you have to rescue the 4th creature, Bigfoot, from the evil plans of Gretchen Grimlock. (see related solution question)