Summary report: Pronghorn antelope abundance survey in south-central Washington March 16-17, 2017

By the start of the 20th century, pronghorn antelope had become extirpated from Washington. Ninety-nine pronghorns were reintroduced onto the Yakama Reservation, Washington in 2011; these pronghorns have since dispersed from their release locations and increased in abundance. We conducted aerial surveys on March 16-17, 2017 in Benton, Klickitat, and Yakima Counties in south-central Washington, both on the Yakama Reservation and off the Reservation. The objective of the survey was to obtain a minimum population estimate for pronghorn. We counted a total of 116 pronghorns during our aerial survey and an additional 5 from ground surveys, for a total minimum population estimate of 121 pronghorns. The true abundance is likely to be underestimated because small group sizes made detecting pronghorns difficult and they may reside in locations outside of our survey area. Despite the harsh winter of 2016-2017, there is little evidence that the pronghorn population has declined since 2015. Human-induced mortality must be kept low to protect this small population. The Yakama Nation and Washington Department of Fish and Wildlife (WDFW) consider that the population will require a few more years of growth before recreational harvest should be considered.