In less than two decades, Germany's wolf population has jumped from somewhere approaching zero to numbers in the thousands, and they have a surprising ally to thank – the military. That's according to research recently published in Conservation Letters.  

After being completely eradicated in the 19th century, wolves (Canis lupus) are now experiencing something of a revival, encouraged by positive public attitudes towards conservation and changes to legislation in the eighties and nineties. 

Individual pups began making their way across the German-Polish border at the turn of the millennium. By 2016, numbers had climbed to include 47 packs and 21 pairs covering seven out of the country's 16 federal states. 

Scientists from Lupus, the German Institute for Wolf Monitoring and Research in Spreewitz, Germany, have been monitoring their progress over the last two decades or so, and Ilka Reinhardt, a biologist there, told Science the latest estimates suggest there are currently 73 packs and 30 pairs of wolves in the country. "Twenty years ago, no one would have expected this," she said. "It shows how adaptable wolves are."

If research conducted by Reinhardt and colleagues is anything to go by, part of that progress has been aided by the German military.

The team calculated wolf population growth between 2000 and 2015/16, tracked wolf mortality rates over that same time period, and collected information on wolf territory types, categorized as either "protected area", "military training area", or "other".

The study shows an exponential growth in population numbers, which increased (on average) 36 percent year-on-year. But perhaps even more surprisingly, 16 out of a total 79 territory establishments occurred in military training areas, compared to a relatively meager nine that took place in protected areas. The remaining 54 were on land described as "other". 

Interestingly, 13 out of 21 (or 62 percent) military training areas 30 square kilometers (11.5 square miles) or more were occupied by wolves during that time, compared to just eight out of 55 (or 14 percent) protected areas of that size. So, what is going on?

The researchers found little evidence to suggest it had to do with differences between the two types of territory – in terms of forest cover and road density, they were virtually the same. Instead, they suspect it has more to do with us.

Anthropogenic (aka human-caused) mortality was the prevailing cause of death in 80 percent of recorded deaths in territories, but rates in protected areas were higher than those in military training areas. Poaching, in particular, was a major cause of death in protected areas. And yet, not one incident of poaching was reported in military training areas, where there are heavy restrictions placed on hunting and other forms of human activity.

In short, and perhaps unsurprisingly, wolves prefer areas with less interference from people.

The study authors say that these relatively undisturbed military zones acted like "stepping-stones". As they explain, "Once wolves established territories and bred on MTAs [military training areas] a subsequent diffusion like range expansion around these initial colonization areas could also be observed."