Actually, you are saving him from capture.
Although you follow Bigfoot in the Pacific Northwest, Gretchen Grimlock cages him and starts to take him away by helicopter. You will have to jump from your copter to hers, open her fuel tank, and cut the line to Bigfoot's cage with the gardening shears. You can parachute down with his cage.
A gorilla
You get the Island Medallion after you prove the existence of three of the four cryptids, and rescue Bigfoot from the evil Gretchen Grimlock. (see related question)
He is in the Pacific Northwest, where he lives in a cave. Once you have confirmed the other 3 cryptids, you can go there and follow him in the helicopter.
Yes, you can find proof of The Jersey Devil, Bigfoot, Nessie, and the Chupacabra. (see related question)
just wait for it to move the follow with helicopter
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
just keep following from a distance
After you have confirmed the other three cryptids (Nessie, Chupacabra, and the Jersey Devil), and brought back the inconclusive footprint from the Himalayas, Mews will send you in pursuit of Bigfoot, which is similar to the Yeti.
Reboot Poptropica if either the Helicopter or Bigfoot stops moving. This is a known glitch affecting less than 1% of Poptropica players on the island.
When you have gotten the footprint photo from the Himalayas, and confirmed the other three cryptids (Nessie, chupacabra, Jersey Devil), Mews will send you in pursuit of Bigfoot in the Pacific Northwest. You use the helicopter to follow Bigfoot as he moves through the forest, until he reaches his home in the caves. * If Bigfoot or the helicopter stops moving, you should reboot Poptropica and see if the game will progress. You may need to clear your browser cache. As a last resort, you can exit to the island map using the Haunted House card (350 credits in the store).
After you only get a footprint photo from the Himalayas, Mews decides that it is too difficult to track the Yeti. When you prove the other 3 cryptids, he sends you in search of Bigfoot, and you have to rescue the creature from the evil Gretchen Grimlock.
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.