I would check out what your ops manual, and the appropriate aaviation authority say about crew rest and fitness to fly. If they say something along the lines that you should have 8 hours of undisturbed rest in a 24 period, then you have a more than reasonable argument that your rest is being disturbed by the lions etc, and therefore you are not in accordance with the rules. If the buck stops with the captain, (as it always will) to say if he is fit to fly, then you should report yourself as unfit if you dont sleep. Then, they will either fix the problem or they sack you, depending on the company attitude!