New research shows humans impact wolf packs in national parks

by Andria Waclawski, University of Minnesota
January 17, 2023

New research shows how humans are a substantial source of mortality for wolves that live predominantly in national parks — and more importantly, that human-caused mortality triggers instability in wolf packs in national parks.

Published today in Frontiers in Ecology and the Environment, the study was led by Kira Cassidy, a research associate at Yellowstone National Park, and included co-authors at five national parks and University of Minnesota Voyageurs Wolf Project researchers Thomas Gable, Joseph Bump and Austin Homkes.

“For gray wolves, the biological unit is the pack or the family. We wanted to focus on the impacts of human-caused mortality to the pack, a finer-scale measure than population size or growth rate,” said Cassidy. “We found the odds a pack persists and reproduces drops with more human-caused mortalities.”

While many studies have looked at how humans impact wolf populations, this study took a different approach and examined how human-caused mortality affects individual wolf packs. To do this, Cassidy and her team contrasted what happened to wolf packs after at least one pack member was killed by human-causes with packs where no members died of human-causes.

The researchers found that the chance a pack stayed together to the end of the year decreased by 27% when a pack member died of human causes, and whether or not that pack reproduced the next year decreased by 22%. When a pack leader died, the impact was more substantial, with the chance of the pack making it to the end of the year decreasing by 73% and reproduction by 49%.

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