Part of taking proper care of the cattle on a range is eliminating all dangerous vermin or predators both for the safety of self and cattle.
Rattlesnakes are the worst example, and most rangeland owners in the US will eliminate them on sight, some even sweeping entire areas to keep the population down.
From what I understand, Jews are only allowed to slay kosher animals via schechita, and many not slay any others aside from immediate self-defense. I understand that killing any animal in the wild unless it is attacking you is considered 'hunting', causing unnecessary suffering to the animal and therefore prohibited.
But it would seem that a rattlesnake is so dangerous that it is an intrinsic danger and should always be killed when seen to protect livestock or handlers.
Can a Jewish ranger only shoot the rattlesnake immediately threatening him, or can he traverse the range periodically to seek out and destroy all he sees?