SQUIRREL #10 - ROAD TO RUIN
When you get to the second checkpoint, stop your quad then bailout into the hole behind you.
As long as your vehicle doesn't fall in with you, a squirrel sign will be revealed on the side of the ruins.
Respawn and ride down the track, until the next squirrel appears as you're blown off your quad.
SQUIRREL #11 - STORMTROOPER
Ride to the front end of the metal track section after the initial jump, then stop and roll back down the track.
Keep going backwards until you end up at start of the track.
A squirrel will appear at the bottom of the hill.
SQUIRREL #12 - BASE INVADER
Following the ramp that launches you when you land on it, bailout from the top of the next jump with the 'Bay 2' in the background.
Hold Y/Triangle to grab the winch hanging above, then let go after it stops moving to drop onto the conveyor belt below.
This takes you deeper into the factory, where the next squirrel is revealed in a control room.