Family living: an overlooked but pivotal social system to understand the evolution of cooperative breeding

Abstract

Cooperative breeding occurs in several major animal phyla, predominantly in arthropods and chordates. A number of comparative analyses have focused on understanding the evolution of cooperative breeding, yielding mixed, inconclusive, and often phyla-specific findings. We argue that much of this ambiguity results from an erroneous classification of social systems into noncooperatively and cooperatively breeding species. The shortcomings of this assumption are apparent among birds where noncooperative species constitute a heterogeneous group: some species are clearly non-family living, with offspring dispersing at or shortly after nutritional independency, whereas other species form persistent family groups through offspring delaying their dispersal substantially beyond independency. Here, we propose an objective, life history-based criterion classifying noncooperative bird species into non-family living and family living species. We demonstrate that by using the family time (the time offspring remain with its parent/s beyond independence) and body size-scaled reproductive investment, we are able to differentiate 2 groups with contrasting life histories. Our classification matches seasonal environmental variation experienced by different species: family living species postpone dispersal beyond the onset of less favorable autumn conditions. We discuss the consequences of this new social system classification for evolutionary and ecological research, potentially allowing solutions to some of the most intriguing riddles in the evolutionary history of birds-and cooperative behavior itself.

Looking for unity in diversity: human cooperative childcare in comparative perspective

“…In species where nonparents help, it is most often a family or extended family affair where offspring remain with their parents beyond independence and assist them in raising younger siblings [26]. Nevertheless, it is quite rare for helpers to only direct their care towards offspring of their own parents, but they direct it towards offspring with varying degrees of kinship.…”

Family living sets the stage for cooperative breeding and ecological resilience in birds

“…We posit that, by considering only 1 transition from noncooperative breeding to cooperative breeding, prior studies may have obscured the role of potential ecological and life history drivers because the factors that promote family living may have been inadvertently confused with those that promote helping at the nest [14,18]. Thus, a more nuanced understanding of the evolutionary steps through which cooperative breeding arose may help clarify the current debate on the conditions favoring its evolution [6,7,9,10].…”

The importance of the altricial – precocial spectrum for social complexity in mammals and birds – a review

“…Valuable relationships may occur among pair partners, direct family members or distantly related kin [86, 97, 98] as well as between unrelated individuals [71, 99] and may involve coalition and alliance formation [100, 101], communal defence [102, 103], communal or cooperative breeding [98, 104–110], conflict resolution [74, 111–115], and social support ([116, 117] and references therein) (see Table 1 for a complete overview). We found support for all these aspects in both altricial and precocial mammals and birds (Table 1).…”