My gaming group (and some NPCs) are shipwrecked on a deserted island. I'd like the characters cooperate to survive in this hostile environment, because I want to make the game world really dangerous (so they have to cooperate or die).

But two players ("lone wolves") have broken away from the group and entered the jungle alone.

Now, I have always encouraged the betrayal and division among the players, but not so soon. If I offer to these "lone wolves" challenges appropriate to their abilities, they hardly feel the need for a group. But if I do otherwise, they will likely die at 1st level.

Furthermore, I will have to tell two stories in the same session.

Does anyone have any suggestions? I have to force the meeting of the two groups or leave the "lone wolves" to die in the jungle.