Cooperatively breeding animals live in social groups in which some individuals help to raise
the offspring of others, often at the expense of their own reproduction. Kin selection—when …

Reproductive inequality, or reproductive skew, drives natural selection, but has been difficult
to assess, particularly for males in species with promiscuous mating and slow life histories …

Highlights•Cooperation between males in reproductive contexts is an underappreciated and
puzzling behaviour.•We define male–male cooperation in reproduction and identify different …

Social animals often form long-lasting relationships with fellow group members, usually with
close kin. In primates, strong social bonds have been associated with increased longevity …

Variation in group size is ubiquitous in social animals, but explaining the range of group
sizes seen in nature remains challenging. 1–3 Group-living species occur most frequently in …

Highlights•Cooperative groups of greater anis compete for nesting areas.•Groups may
destroy entire clutches laid by neighbouring groups.•Length of tenure on the nest site, not …

Cooperatively breeding societies show distinct interspecific variations in social and genetic
organization. Long-term studies provide invaluable data to further our understanding of the …

Most cooperatively breeding birds live in family groups, in which a breeding pair is assisted
by genetically related “helpers” who do not reproduce. In some species, however, several …

Communal nesting, where several mothers regularly pool and cooperatively rear offspring,
is unusual in mammals. This type of crèching behavior is especially rare among primates …

Small populations that have experienced a bottleneck often suffer from low genetic diversity
and inbreeding, the effects of which may further threaten persistence over time. The iconic …