When I was in college, I would stay with a friend of my dads during the summer and he had a helicopter round up business. Most of the ranches here in south Texas were getting over run with nilgai. He contracted with a meat packing company and ranches to shoot them. So that's what I would do during the summer. I was usually on the ground crew picking them up. When they would shoot them out of the chopper, they would radio use and we would come by and pick them up. Once we got about 5, we would take them in. They had refrigirated trailers and butchers on sight that would butcher them. I got to get in the chopper a few times and shoot and it's harder than it looks. All the shots had to be head shots or they wouldn't take them. We used a scoped AR-15. Everytime we went out, we would shot between 40 and 50 nilgai. And no, we weren't shooting out all the nilgai, just thinning out the herd. Some of these ranches are over run and 600 - 800 lb animals can really hurt working cattle ranches, especially on dry years.