FBI Animal Mutilation Investigation

The FBI's Animal Mutilation Investigation — initiated by DoJ counsel Philip Heymann in 1979 and conducted through the Carter administration — examined a wave of cattle and livestock mutilations in the western United States, with particular focus on Native American reservations. The files run roughly 130 pages across five parts and remain the most-cited single FBI tranche on the topic.

Read across all five parts as one investigation. The investigative theory shifted multiple times — predator action, cult activity, helicopter-based perpetrators — without converging. UAP-adjacent because the contemporaneous folklore connected mutilations to UFO sightings, but the FBI's framing throughout is law-enforcement, not UAP.