Tuesday, May 25, 2021

Incredible Wolf Journeys: A Slovenian Wolf Treks 1,200 Miles

On December 19, 2011 a two-and-one-half-year-old wolf known as Slavc (pronounced: slouts) left his birth pack in the southwestern corner of Slovenia, near the eastern border of Italy. At 88 pounds, Slavc was an average sized male, about the size of the European wolf pictured above. But over the next three months he would prove to be well above average in his determination and ability to meet the challenges of an incredible biologically driven journey in search of a mate.

His 1200-mile trek was tracked by data from the collar he had been fitted with a few months before his dispersal. The collar transmitted data points seven times a day, making his route a connect-the-dots drawing on the computer screen of Hubert Potocnik, the biologist and researcher who had collared Slavc. 

The challenges of Slavc’s journey started on day one, when he bumped into the A1, a fenced, four-lane expressway. As Potocnik told a reporter for The Guardian, the wolf could only cross the A1 by underpass, overpass, or along a river. He chose the overpass and kept moving. (A sample section of the expressway is pictured below.)

A section of the A1. (via Wikipedia) 

A short time later Slavc crossed yet another wide and busy highway, the H4, using a 492-foot long bridge. The last data dots from day one placed him in the backyard of a house in a small town near the H4. Potocnik feared someone had shot the wolf, mistaking him for a stray dog because of his collar. But as the biologist fretted and even considered calling the police, fresh GPS dots appeared. Slavc was alive and on the move.

He moved mostly at night and found plenty of fuel for his journey. Slovenia has ample red deer (similar to elk), roe deer, and wild boar, prey that makes up about 90% of a typical wolf’s diet, according to Miha Krofel, a researcher and university professor. But again Slavc proved he was anything but typical. The GPS dots showed that he stopped near the Ljubljana airport for three days. Further investigation revealed that while there he caught and consumed two foxes. Fed and rested, he continued his journey toward points unknown. 

Slovenia highway map 

In just ten days Slavc had crossed Slovenia from its southwest corner to its northern border, somehow making his way safely through a network of major highways pictured on the map above. As with other wolves whose journeys I have studied, major highways may slow but not necessarily stop determined dispersers. That drive to find a mate is powerful. 


Once Slavc entered Austria, he intersected the Drava River. Though there was no bridge or overpass, he didn’t stop. When GPS dots appeared on one bank and then the other, Potocnik decided that Slavc had swum the 900-foot wide river. In December. I can picture Slavc standing on the bank, his legs spread as he shakes the river water off, looks around, and continues on his journey. 


With that river challenge behind him, he headed to the Austrian Alps to try his paw at crossing mountain ranges. In early January. He trudged through extreme alpine conditions where snow had accumulated up to 19 feet deep. He turned westward, passed a ski area, and made snowy tracks toward Italy. After climbing an 8,530-foot high pass, he ate a roe deer calf to recharge.  


Roe Deer (via CC BY-SA 3.0)

By late January, Slavc was deep in the Italian Alps, heading south, and skirting ski areas. By mid February, two months into his journey, he had passed the last ski area and exited the Italian Alps. On Potocnik’s computer screen, data from the collar created a connect-the-dots line pointed toward Italy’s Lessinia Regional Park in the upper reaches of the Lessini Mountains. When news of Slavc’s location got out, one of Potocnik’s colleagues sent him a video of wolves—including a female—in Lessinia Park. The biologists joked with each other that Slavc would surely find his female there.

But Slavc wasn’t ready to stop; he continued south and past the park. By March of 2012—after three months of crossing busy highways, a wide river, and wintery mountains—he reached the sunny countryside of Italy’s Valpolicella vineyard region. In doing so, he became the first wild wolf in that area in more than 130 years. 

But he wasn’t the only wolf. Slavc discovered a private animal park that contained three captive wolves, one a female. Perhaps hoping to connect, he remained in the area for twelve days. To survive, he killed his first livestock, two sheep and a goat, thus creating another first for the area. 

Eventually, he must have realized that those other wolves could not join him. Once again fed and rested, he continued his compelling search for a mate and territory. He headed back north for thirty some miles and this time he entered Lessinia Regional Park. That park, at 38 square miles, is about the size of Yellowstone’s Lamar Valley. A mountainous section of the park is pictured below. 


Monte-Grolia (Archive Lessinia Regional Park)

Back at his desk, Potocnik studied the GPS dots and asked a Lessinia Park manager to look for Slavc’s tracks in the park. She discovered two sets, one smaller than the other. After a 1200-mile trek, Slavc had found a female that was later found to be from the Apennine Mountains in southern Italy. As determined as Slavc, she had travelled about the same distance as he had to reach Lessinia and find a mate. The media named her Juliet because she was now near Verona, a city that contained the house of Juliet, the famous heroine from Shakespeare’s Romeo and Juliet.  


Juliet and Slavc created the first pairing of wolves in the Eastern Alps, according to a Lessinia Park press release. And the firsts kept coming. They produced the first pups—a litter of at least two—born in that region in many years. Their pups represented the first mixing of the DNA of two distinct wolf populations: Slavc’s DNA from Slovenia’s Dinaric-Balkan region and Juliet’s DNA from Italy’s Apennine region. 


That Slavc and Juliet were able to find each other and create a pack was possible because of how wolves were treated in Slovenia and Italy. 


In Slovenia, according to a journal article, wolves were never completely killed off, but their population came close to being eradicated. Just as in the US, Slovenian wolves were persecuted in the early twentieth century. As their numbers fell they retreated to the most remote parts of the Dinaric Mountains, Slavc’s home territory, in the southwestern corner of the country. In 1993 Slovenia declared wolves an endangered species and afforded them protection. By late 2019 Slovenia had 86 to 100 wolves.


In Italy, wolves faced similar challenges. Though once widespread, by early in the twentieth century wolves were extirpated in the Italian Alps (the area Slavc had passed through on his way to find Juliet). By 1970 Italy only had about 100 wolves, most in the central and southern Apennines, Juliet’s home territory. In 1971 wolves received their first protection. By 2019 a survey found that Italy had 1,500 to 2,000 wolves.


Slavc and Juliet helped increase Italy’s wolf population. They had seven pups in 2014 and seven more in 2015. But their story doesn’t end here. 


A son of Slavc and Juliet dispersed back to Slovenia in 2018, according to the European Wilderness Society. The son paired with a female from unknown origins and by 2019 they had mated and reproduced. So began the creation of another new mix of DNA and another new wolf pack. They lived in a forested plateau on the edge of Triglav National Park, Slovenia’s only national park, in the northwest corner of the country, far from where Slavc had begun his journey years earlier. 


The remarkable story of Slavc and Juliet and their offspring shows that when wolves are protected and allowed to safely disperse, they increase the size of the wolf population, the breadth of wolf country, and the health of the species.


Rick Lamplugh writes, photographs, and speaks to protect wildlife and wild lands.

His bestselling In the Temple of Wolves; its sequel, Deep into Yellowstone; and its prequel, The Wilds of Aging are available signed. His books are also available unsigned or as eBook or audiobook on Amazon.

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