Group composition effects on aggressive interpack interactions of gray wolves in Yellowstone National Park

Behavioral Ecology
By: , and 



Knowledge of characteristics that promote group success during intraspecific encounters is key to understanding the adaptive advantages of sociality for many group-living species. In addition, some individuals in a group may be more likely than others to influence intergroup conflicts, a relatively neglected idea in research on social animals. Here we use observations of aggressive interactions between wolf (Canis lupus) packs over an extended period and use pack characteristics to determine which groups had an advantage over their opponents. During 16 years of observation in Yellowstone National Park from 1995 to 2010, we documented 121 interpack aggressive interactions. We recorded pack sizes, compositions, and spatial orientation related to residency to determine their effects on the outcomes of interactions between packs. Relative pack size (RPS) improved the odds of a pack displacing its opponent. However, pack composition moderated the effect of RPS as packs with relatively more old members (>6.0 years old) or adult males had higher odds of winning despite a numerical disadvantage. The location of the interaction with respect to pack territories had no effect on the outcome of interpack interactions. Although the importance of RPS in successful territorial defense suggests the evolution and maintenance of group living may be at least partly due to larger packs’ success during interpack interactions, group composition is also an important factor, highlighting that some individuals are more valuable than others during interpack conflicts.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Group composition effects on aggressive interpack interactions of gray wolves in Yellowstone National Park
Series title Behavioral Ecology
DOI 10.1093/beheco/arv081
Volume 26
Issue 5
Year Published 2015
Language English
Publisher Oxford Journals
Contributing office(s) Northern Prairie Wildlife Research Center
Description 9 p.
First page 1352
Last page 1360
Country United States
State Wyoming
Other Geospatial Yellowstone National Park
Online Only (Y/N) N
Additional Online Files (Y/N) N
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