The relationship between population density and body size of wolverines Gulo gulo in Scandinavia

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Abstract
The number of wolverines Gulo gulo in Scandinavia has declined dramatically since the middle of the last century, and the numbers killed continued to decrease until the species was protected. In 1968 the species was protected in Sweden; in 1973 the wolverine was given full protection in southern Norway and protection during the breeding period in northern Norway; and in 1982 the species was also given full protection in northern Norway. The protection has resulted in some increase in number, but the population density remains much lower than at the turn of the century, and the wolverine has yet not reoccupied all of its former range. Our analyses show that body size, as reflected by skull characters, was inversely correlated with population density from the mid-nineteenth to the mid-to late twentieth century. In contrast we found a strong decline in body size in the decades after ca 1960. The unexpectedly low wolverine resilience in this century may be explained by an energy-restricted model whose main factors include: 1) habitat fragmentation, 2) loss of habitat, 3) extinction of the dominant predator, the wolf Canis lupus, and 4) a maximised turnover in managed ungulate populations that has resulted in less natural mortality and fewer weakened animals available for scavengers and less efficient predators like the wolverine.