There are now an estimated 12,000 wolves in Europe, leading to calls for the animal to lose its "strictly protected" status.
See also: Norway clashes with environmentalists over wolf cull
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A wolf was spotted on Belgium's border with Luxembourg for the first time in 118 years last month.
Vanessa Ludwig, a biologist who monitors the growing wolf population, said: "In Europe, the wolf is at the top of the predatory chain. It has no enemies except humans.
"We have not reached the legal limit in wolf numbers which would allow for culling, so the species is, by its nature, destined to spread across the continent."
With more than 9,000 sheep killed this year in France alone, farmers are desperate to halt the rise of the wolf population.
Wolves are protected by the Bern Convention Act.
In 2000, the first wild pups were born in Germany since 1904 and by 2015, the country had about 35 packs and around 400 wolves.
Conservation, the loss of human population in rural areas and the spread of forests on the continent has helped them spread.
Wolves feed mostly on game. Roe deer account for just over half of the wolf's diet, followed by red deer and wild boar.