Flexibility in group formation and maintenance in grey wolf societies: lessons from Yellowstone

Over 30 years of research in Yellowstone National Park (YNP) has provided unique insights into the mechanisms of society formation and identity in grey wolves, Canis lupu s. Packs form when wolves disperse from natal packs, breed with unrelated individuals and establish a territory. In YNP's high wolf density system, new pack formation resulting from same-sex groups coming together from different packs predominates over pairs forming packs, which is commonly reported in this species. This strategy results in new packs starting with more than two members, an advantage at YNP, with its dense populations, given pack size is a critical factor in pack success and persistence. This also facilitates the formation of wolf packs complex enough to be treated as ‘societies’ in that they include offspring from multiple litters and generations. Group cohesion is reinforced through daily activities such as hunting, territorial patrolling and pup rearing, as well as other social behaviours like scent marking, howling and physical interactions. Dominance hierarchies emerge, and experienced leaders, generally the dominant breeding pair (often referred to as the alphas), play critical roles in maintaining stability and pack persistence in a territory largely through the matrilineal line. The cohesion and longevity of wolf societies is influenced by demographic factors, ecological conditions and the ability to maintain strong social bonds across generations that can persist for decades. As a result, wolves make a compelling taxon for inclusion in cross-disciplinary research on the evolutionary advantages of group identity and social belonging. • Grey wolves live in packs varying from simple to complex. • Complex packs include multiple age cohorts with varying levels of relatedness. • Wolf packs are societies that are aggressive towards other packs. • Wolves recognize pack members as part of their own society. • Long pack tenures are associated with pack members of advanced age.