You must have travel insurance for your trip. It must cover medical care, repatriation, cancellation, curtailment, loss and theft.
Flight Centre normally suggest "Cover More" insurance. Consider either single trip insurance or annual cover which is not much more expensive and covers any other overseas trips over 12 months.
You will need to tell the insurers:
If you already have insurance or want to take it out with another company, that is fine but it must cover the duration of your trip, and cover repatriation, safari, chimpanzee tracking and white water rafting (1-5).