Factors influencing red wolf-coyote hybridization in eastern North Carolina, USA

Understanding the mechanisms that govern interspecific hybridization is vital to mitigating its impacts on endangered species. Research suggests that behavioral mechanisms such as mate choice and social disruption can regulate the rate at which hybridizing species interbreed. We investigated hybridization events between endangered red wolves (Canis rufus) and coyotes (Canis latrans) in eastern North Carolina to evaluate potential factors that may promote hybridization between these species. Specifically, we examined spatial location, breeding experience, breeder origin (captive vs wild), breeder ancestry (pure vs hybrid), and past history of the animal. There were over four times (126 vs 30) as many red wolf litters as hybrid litters over a 13 year time period. Over half of the hybridization events followed the disruption of a stable breeding pair of red wolves due to mortality of one or both breeders. Of these 69% were due to anthropogenic causes, primarily gunshot mortality prior to the red wolf breeding season. Both male and female red wolves interbred with coyotes, although a majority (90%) of the events we observed involved females. Wolves that produced hybrid litters tended to be young, first-time breeders with slightly higher levels of coyote ancestry. Only 16% of the hybrid litters were produced in the inner core of the red wolf recovery area. Our results suggest that disruption of stable breeding pairs of red wolves facilitates hybridization, jeopardizing future recovery of the red wolf. They also indicate the importance of behavioral forces, especially social stability, in regulating hybridization.