If I had center metered the scene wouldn't the snow have been blown out? I'm headed back in a few weeks and I'll experiment with some different exposure modes.
With automatic exposure modes like Aperture Priority, and the various metering strategies (matrix, center-weighted, etc.) it's tough to know exactly what balance the camera is going to make, and therefore how much you need to tweak it with EV Compensation.
But you're correct, metering that emphasizes the dark brown buffalo bodies has the potential of blowing out the snow, depending on what you do with EV Compensation.
The solution, when you have the luxury of a little time to tweak your settings, if you're using Av, is to make your best guess, and fine-tune it with a few test shots.
One of the reasons I shoot with Manual Exposure mode is that in the scene you shot, I only have to meter once, and that will be the correct exposure (assuming that the lighting conditions don't change) regardless of what I'm shooting - the snow, small buffalos in the snow, large buffalos in the snow, etc.
Food for thought.