European wild forest reindeer and wolves: endangered prey and predators

Managers are sometimes faced with a situation where one endangered species increases the vulnerability of another one. According to our late-winter helicopter survey of Finland's two small populations of wild-forest reindeer (Rangifer tarandus fennicus), the eastern one decreased by half during the last 7 years. This is probably due to the return of the wolf (Canis lupus) to the area. Our data show that the annual recruitment rate of reindeer is strongly correlated with wolf density. Calf mortality was high and stable during the first months after birth. The wolf is classified as an endangered species in Finland. Thereby, our study area provides an example of a triggered situation in which a locally abundant, endangered predator increases the vulnerability of a threatened prey. There are basically two policy options for avoiding extinction: (1) to directly control the predation risk or (2) to reach further out into the ecosystem to control those factors that have led to high abundance of predators. One potential direct management action is increased wolf control in the primary summer home ranges of female reindeer. In the long term, wolf predation on wild-forest reindeer would decline if the abundance of moose (Alces alces) could be lowered, because high moose density supports high abundance of wolves. Another noteworthy option is the reintroduction of reindeer into regions where the wolf still exists at low densities.