Yes it is common courtesy to tip your driver, safari crew, guide and porter when on safari. Driver guides are a great source of information and if you tell them in advance what you want to see they will do their best to find it . However tipping is not mandatory.
Please see below some tipping guidelines, depending on the number of pax on a particular safari:
Porter/ Waiter: US $ 5 per service
Van driver/ guide/ crew: US $ 20 + per person , per driving day
Drivers tips are presented to the driver on the final day of driving.