Mixed lighting on safari

My photo tour group and I are now in South Africa at Sabi Sabi, a stunning private reserve adjacent to Kruger National Park. The game viewing here is different than in East Africa. In Kenya, for example, you can see for miles and miles, and game spotting is easy. Here the vegetation is more dense, and this often presents a challenge. However, the wildlife is so plentiful, and often so close, that we always get astonishing pictures. The first day on safari we were very lucky to see three different leopards. A male and female were in a tree and and third one sauntered by possibly to check out an impala kill that one of the other cats had dragged up into the tree. I took this picture at dusk, and with the assistance of a spotlight to add light to a very dark scene, the resulting images were wonderful. Because the spotlight was incandescent, I switched from daylight white balance to tungsten white balance (i.e. incandescent) so the colors on the leopard looked correct. This made the background become blue, but I liked the look of this. My settings were 1/640, f/4, and 8000 ISO. I used a Canon 500mm f/4 telephoto, hand held. l set the exposure mode to aperture priority and selected the largest f/stop because in this low light situation depth of field was not a luxury. The most important thing was keeping the shutter speed fast enough for a sharp picture, and I could only do that with a high ISO. I didn't want the artificial look of on-camera fill-flash.