Patterns and drivers of female extra-pair mating in wild Kalahari meerkats

In many pair-living vertebrates, females commonly mate outside the pair bond, but when and why they do so is unclear. This behavior may stem from females seeking "good genes" or "compatible genes" from extra-pair mates superior to or less related than their partner. Variation in female ability to acquire extra-pair copulations, however, may also influence extra-pair paternity rates. We analyze 23 yr of parentage data to explore extra-pair paternity in wild Kalahari meerkats (Suricata suricatta), cooperative breeders where a single dominant pair monopolizes most reproduction in each group. When paired with a familiar breeding partner, females almost exclusively mate extra-pair to avoid inbreeding; however, even when paired with an unfamiliar male, extra-pair paternity still occurs. In our study of unfamiliar pairings, 14% of dominant female litters contained extra-pair paternity, with 90% of offspring sired by resident dominant males, 7% by extra-group males, and 3% by subordinate immigrant males. Results were not consistent with the compatible or good genes hypotheses: more closely related dominant pairs were not more prone to extra-group paternity; extra-group sires were not less related, heavier, or older than the resident dominant male; and offspring from extra-group matings did not demonstrate advantages over within-pair offspring. Extra-group paternity was more likely when dominant females were heavier, dominant males were lighter, more extra-group males visited, and few subordinate males resided in the group, suggesting extra-pair paternity rates are primarily driven by individual and social conditions. Whether females benefit from extra-pair paternity or simply mate with any available male remains unclear.