What happens when your last monkey dies?

[DAN-di-WARhol]

As above

[RCMidas]

It's effectively a game over, but you can reload the game from the last time it did save - which is usually at the moment the penultimate ape died - and try to rescue your last survivor. It is entirely possible that they are in too bad a shape to be rescued, of course. In which case, start over and use what you have learned to be better next time.