Take The Plane Down 20
Land the plane without hitting an obstacle
Fairly shortly after starting the game you will flash back to the plane crash that stranded you in this situation. Just avoid hitting the mountains before the end of the level and this should unlock. It is however a little glitchy and may not unlock as it should, likely due to some finicky hit detection. But, since the flashback is practically at the start of the game, just load up chapter one and try again.
Gold All The Way 30
Obtain gold medals in all Trek Shooting Galleries
Trek galleries are the easiest of the three types of galleries. They only last a few minutes and the required score is low enough that platinum is almost a given. You get one runthrough of the map, but the biggest threat is not missing the required score, but being killed by a predator. Playing on Hard will make this easier since you get more points per kill. Tips can be found HERE
Finish all Shooting Galleries one time
There are 27 galleries in total, 9 of each type. To play them you will need to first unlock them by getting the appropriate collectible. See "Fill the Pocket" for more info on where to find them. To finish the gallery, you need to have a score recorded. For Survival, that means just continuing until you die, but for Trek that means finishing the map. If you die in Trek, you will not get credit for finishing the level. For Quick Draw, you must reach the maximum required score to get credit for finishing the gallery. See "Hunting for Gold," "Gold all the Way" and "Keep Them Comin'" for more information.
Mush Mush Mush! 20
Successfully complete one dog sledding event without taking any damage
There are two dog sled sections during the game, niether of which are particularly difficult. All you are doing is steering left or right to avoid obstacles on the path. If you miss either of them, just start up Level 2. There is a sledding section right at the beginning of the level, so you should have few issues making it through after a little practice.