March 17, 2010
Elk pregnancy rates are typically high – almost 90% on average in the Rocky Mountains – but we have observed low pregnancy for several years in a portion of the Clarks Fork elk herd that migrates annually into Yellowstone Park. With the help of collaborators John and Rachel Cook, we are trying to understand what causes this low pregnancy rate, and in so doing we hope to improve the regional understanding of these questions. Two factors, drought and costly antipredator behaviors (i.e. habitat quality vs. ‘predator stress’), are leading hypotheses for why elk pregnancy might be low in some areas of Yellowstone. These two newspaper articles discuss some of the issues, including findings by other researchers in the region.