Figure 2.

Distribution and estimated prevalence of pair bonding and parental care across select vertebrate lineages. Data sources: Pair bonding—mammals: [5–7]; birds: [8]; reptiles: [9–11]; amphibians: [12,13]; fishes: [14–16]. Parental care—mammals, birds, reptiles, amphibians, fishes: [17]. Representative pair bonding and parental species illustrated. All prevalence percentages are at the species level, except for parental care estimates of ray-finned fishes, which are at the family level. The absence of estimated prevalence percentage indicates it is unknown. *Among Westernized societies.