The recovery, distribution, and population dynamics of wolves on the Scandinavian peninsula, 1978-1998

Abstract

In 1966 the gray wolf (Canis lupus) was regarded as functionally extinct in Norway and Sweden (the Scandinavian peninsula). In 1978 the first confirmed reproduction on the peninsula in 14 years was recorded. During 20 successive winters, from 1978–1979 to 1997–1998, the status, distribution, and dynamics of the wolf population were monitored by snow-tracking as a cooperative Swedish–Norwegian project. After the 1978 reproduction in northern Sweden, all new pairs and packs were located in south-central parts of the Scandinavian peninsula. Between 1983 and 1990 wolves reproduced each year except 1986, but in only one territory. There was no population growth during this period and the population never exceeded 10 animals. In 1991 reproduction was recorded in two territories. After that there were multiple reproductions each year and the population started growing. In 1998 there were 50–72 wolves and six reproducing packs on the peninsula. Between 1991 and 1998 the annual growth rate was 1.29 ± 0.035 (mean ± SD). A minimum of 25 litters were born during the study period. The early-winter size of packs reproducing for the first time was 6.2 ± 1.4 wolves (n = 9), and this decreased with time during the study. The size of packs that had reproduced more than once was 6.4 ± 1.8 wolves (n = 12), and this increased with time over the study period. All but 1 of 30 reported wolf deaths were human-caused. The annual mortality rate was 0.13 ± 0.11, and this decreased with time during the study period. The minimum dispersal distance was 323 ± 212 km for males and 123 ± 67 km for females. Of 10 new wolf territories where breeding occurred, only 1 bordered other, existing territories. The distance from newly established wolf pairs to the nearest existing packs was 119 ± 73 km. Simulation of population growth based on known reproductions and mortalities showed a close similarity to the results from population censuses up to the mid-1990s. To what extent this population is genetically isolated is at present unclear.