Genetic monogamy in long-eared owls

We used DNA fingerprinting to study genetic parentage in socially monogamous Long-eared Owls (Asio otus). We detected no extra-pair fertilizations (EPFs) in 59 nestlings from 12 nests. One of these nests was solitary, but the other 11 had from one to five pairs of owls nesting simultaneously within 30 to 250 m. Thus, despite the presumably high potential for extra-pair matings, the Long-eared Owls that we studied were genetically monogamous. In addition, based on low band sharing among adults, we found no evidence that nesting aggregations were composed of close relatives. Genetic monogamy appears to be the rule for socially monogamous raptors. We suggest that the high rate of male parental effort in raptors selects against EPFs because females that engage in extra-pair activities risk losing parental investment by males whose confidence in paternity is reduced owing to the behavior of their mates.