Wolf recovery and population dynamics in Western Poland, 2001–2012
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Since the mid-twentieth century, under different management regimes (over 20 years of a wolf control program followed by 20 years of trophy hunting), wolves were absent or rare in Western Poland (hereinafter WPL). They became strictly protected in the whole country in 1998 and started to re-settle the vast forests of WPL, far (376 ± 106.5 km) from the source population in eastern Poland. In 2002–2012, the population increased from several to approximately 140 wolves living in 30 family groups, with an annual rate of increase of 38 % (λ = 1.38, SE = 0.10). The area of permanent occurrence increased from 600 to 10,900 km2, with an average density of 1.3 wolves/100 km2. The nearest neighbour distance between wolf territories decreased from 260 to 25 km. In 2001–2005, half of the settlement efforts by wolves failed after 1–2 years whereas in 2006–2009 only one fifth of newly settled wolves failed to persist >2 years. The number of wolves in groups varied from 2 to 9, and the mean group size increased from 1.8 in 2001 to 4.8 in 2012. The survival of pups from May to the end of November was 50 % (the mean number of pups per litter was 5.1 and 2.5, respectively). Of 28 wolves found dead, 65 % were killed by vehicles, 25 % were poached, and 7 % died because of diseases and natural factors. All road casualties were young wolves, most of them male (67 %), hit on roads on average 11.6 km from the centre of the nearest pack. The re-colonisation of WPL started from jump dispersal, which allowed wolves to establish packs in distant locations. As the recovery proceeded, the dispersal pattern shifted to being stratified, a mixture of diffusion and jump dispersal that resulted in the creation of packs in close vicinity to existing groups. After 12 years of re-colonisation, wolves in Western Poland occupied about 30 % of potential suitable habitats.