Although you have gotten the photo of the footprint from the Himalayas, the Yeti is not going to be proven. When you have proved the other three (Nessie, chupacabra, and Jersey Devil), Mews will send you to the Pacific Nortwest to chase Bigfoot.
Follow Bigfoot in the helicopter as he runs through the trees. When he arrives at the caves, Gretchen Grimlock cages him. Save him by jumping to her helicopter, opening the fuel tank, and cutting loose Bigfoot's cage. You and he float down safely.
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)
You still have to prove the chupacabra and the Jersey Devil. You can get a photo from the Himalayas, but it does not prove the Yeti. So when you have the other three proven, you will be sent to chase Bigfoot in the Northwest.
Yes, you can find proof of The Jersey Devil, Bigfoot, Nessie, and the Chupacabra. (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.
just wait for it to move the follow with helicopter
Some users reported that the helicopter or Bigfoot stops moving on the chase sequence. The only recourse is to reboot and replay the Northwest scene.
You have to chase him, then save him. You cannot get the proof you need for the Yeti. After you prove the other three cryptids (Nessie, Chupacabra, and the Jersey Devil), Mews will send you to the Pacific Northwest to pursue Bigfoot. Follow Bigfoot in the helicopter as he tries to hide under the trees. Gretchen will arrive and put him in a cage. Jump to her helicopter and click the fuel tank, then cut the rope holding the cage using the shears. You and Bigfoot float down safely.
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.