But the target, a tiny fist-sized area between the shoulders, can only be reached when the animal's feet are together; and swift kills, which need strength as well as skill and nerve, don't always happen.
The animal isn't always swiftly killed. 
mnli hypothesis: The animal isn't always swiftly killed.  premise: But the target, a tiny fist-sized area between the shoulders, can only be reached when the animal's feet are together; and swift kills, which need strength as well as skill and nerve, don't always happen.