I am stuck in the jungle on Zombie Island.

I've found the needle rock and put the marker on top.
But I cannot find my way to Camel back Mountain.

I can only enter and exit the bottom left of the screen that has the hole under the tree, no other exits show up.

Is this a bug with the Mac OSX version?

It's been awhile since I played this part of the game. I remember the Zombie Island portion of the game was kinda like a maze. It helped me to write down where every exit and entrance went. But also, when you see the little warthog, shoot an arrow at it. The boar will get mad and charge you. At this time, quickly interact with the tree branch above your head. This will open up another entrance that takes you directly to Camelback Mountain. It's probably a good idea to find the branch before you shoot the arrow at the boar. You won't have a lot of time once the boar is charging you.