Assertion: prairie dog's number | /r/CapableOf | decline by 87%
Facets:
value: from the 1920s
type: TEMPORAL
Source sentences:
text: However, it was recorded that Utah prairie dogs existed as far north as Nephi, and south to Bryce Canyon National Park, and Aquarius Plateau to the east in 1920, but the number declined from the 1920s to 1970s by 87%, and this was thought due to human settlers who caused overgrazing of soil, thus catalyzed the invasion of shrub to the grass land.