<P> It is generally accepted that sustainable gray wolf packs had been extirpated from Yellowstone National Park by 1926 , although the National Park Service maintained its policies of predator control in the park until 1933 . However , a 1975 -- 77 National Park Service sponsored study revealed that during the period 1927 to 1977 , there were several hundred probable sightings of wolves in the park . Between 1977 and the re-introduction in 1995 , there were additional reliable sightings of wolves in the park , most believed to be singles or pairs transiting the region . </P>
when was the last wolf pack killed in yellowstone
by 1926