i dont believe they are sterile, but i do believe they dont tend to survive very well as whitetails and mulies are suited for a very different ways of survival. i believe they also have a VERY hard time escaping preditors due to w/ts tend to use there speed to put as much distance between themselves and the hunter as possible(ive witnessed this WAY too many times) whereas mulies cant think of the word stottle? (bounce) to put objeects between them and the hunter. apparently the hybrids have a very hard time deciding how they are supposed flee so they tend to just bounce around like retards lol kinda funny really