keep your distance
When it comes to photography, angle makes all the difference. Being at eye level gives the viewer the impression that they were right there and adds some character to the image. However, when taking photos of dangerous animals, it is not a good idea to get out of the vehicle and lie on the ground - especially when the subjects are a lioness and her cubs. You could just end up helping the little ones grow up to be adults by being their next meal. Instead, try keeping your distance and place the vehicle in a position that may drop the angle. You will need bigger camera lenses here to assist with framing. The photographers I was driving here were using their 600mm lenses to get nice and tight on the mother and cub. But the further you are from the subject the more it will appear as though you are on the same plane as them.
In my case I was using my 70-200mm with a 1.4x converter. This, coupled with my dx body which gives me a further 1.6x crop factor, meant that effectively I had a 400mm lens to work with. I was taking the pictures with an aperture of f6.3 so that I had enough depth of field. I bumped the ISO up to 640 to ensure that my shutter speed was up to 1/1000th of a second to capture any action like this bit of aggression towards the cub.
Expose your balance
Richard de Gouveia