here's my favorite answer
1. Cattle are very expensive (each is worth several thousand dollars).
2. Insurance doesn't cover “range death†due to natural causes (eg. a cattle falling and killing themselves); however insurance does cover vandalism (eg. a vandal shooting a cow).
3. Remarkably enough, a space alien killing a cow will be considered as vandalism and covered by insurance - provided that a policeman will write the report up this way.
4. Space aliens mutilating cows seem to respect police jurisdiction lines (outside of which vandalism isn’t covered by insurance).
5. Relatively little blood leaks out of a dead cattle when it is cut or mutilated (because the heart isn't pumping).
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