"Using records from archives detailing bounties for wolves killed in northern Spain during the eighteenth and nineteenth centuries, we investigated demographic and spatial distribution parameters of the population to determine whether direct persecution or prey availability was
responsible for the observed population decline. Captures of adult, subadult, and young individuals, including those of litters, showed a downward trend. Progressive decreases in age ratio and litter size, and the increase in the proportion of males, were compatible with a population under food stress, driven by the extinction of wild ungulates, the sharp reduction in livestock numbers, and the lack of alternative prey. The immigration and dispersal process does not seem to have functioned under such conditions. In the study area, where strychnine was not used until the end of the nineteenth century, the broadly accepted idea of human persecution having an exclusive or primary role in wolf decline does not necessarily apply."
José María Fernández & Nerea Ruiz de Azua: Historical dynamics of a declining wolf population: persecution vs. prey reduction (2009) http://bit.ly/RwL8BU European Journal of Wildlife Research 56, 2 (2009) 169-179 (Un documento de PEER (Publishing and the Ecology of European Research http://peer.ccsd.cnrs.fr/ )