Hi Greg,
I never pretend to be an expert on wildlife photography; there are some good photographers out there with a stack more experience on this subject than me, so please take my advice with a pinch of salt!
That said, one thing I would like to see in this photograph is less grass in front of the lion's face. If, as you suggest in your comments, you can see the anxiousness in the lion’s face then we need to be able to see that too. More often than not, this simply involves patience for the right moment – or just repositioning yourself or the vehicle if possible.
One thing I noticed when looking at the numbers on this photograph is that you took the photograph at 1/1600s while shooting at 1600 ISO. In a situation like this where the lion is not moving fast and you have the advantage of an image-stabilised lens, I would be inclined to bring the ISO back down to 400 or 800. This will bring your shutter speed down to 1/400 or 1/800 of a second respectively but you should get a better quality photograph.
Managing noise does not matter too much if you are mainly working with small photographs, but I think if you were to crop this photograph and enlarge it you would benefit from a lower ISO setting.
Cheers, Anthony.