I use Nikon equipment but have used Sony and Minolta gear in the past. I still have my other gear as back up but prefer to use my Nikon gear for all my wildlife shooting.
I have been shooting wildlife with a camera for more-or-less the last fifteen years. Wildlife photography is a very challenging endeavor, requiring specialized skills and equipment. One does not simply pick up the camera used for family vacation photos and capture compelling wildlife images.
Wildlife photography is regarded as being one of the more challenging forms of photography. As well as needing sound technical skills, such as being able to expose correctly, wildlife photographers generally need good field craft skills. For example, some animals are difficult to approach and thus a knowledge of the animal's behaviour is needed in order to be able to predict their actions. Photographing some species may require stalking skills or the use of a hide/blind for concealment.
You must be able to react quickly when photographing most animals in the wild. Getting the eyes in focus is key to capturing a photo of an animal. It's human nature to look at the eyes. It's how we determine emotion and how we connect.
Above all you must have patience. Just when you give up on a situation and prepare to leave the scene something always happens. You can not rush nature.