Depleted wolf population leading to spread of jackals in Europe

The researchers discovered that interaction between the two species is very strong and that the decline in the wolf population had probably been the key factor facilitating the jackal's spread in Europe.

The results were presented in two articles published in acclaimed science journals Nature Communications and Hystrix. Krofel participated in both studies.

In the past wolves were present across Europe, with the exception of a few coastal areas and islands. During the 19th and 20th century people exterminated them or greatly reduced their numbers in a major part of their habitat.

This enabled jackal to spread and settle down in the vacated areas, explained Krofel, a researcher of the Forestry and Renewable Forest Sources department at the Ljubljana Biotechnical Faculty.

He said that while the golden jackal is a species endemic to Europe, its living space had been limited for thousands of years to coastal areas along the Mediterranean and the Black Sea. In recent decades the species has been spreading fast across the continent, including in Slovenia.

The researchers also examined what happens with jackals when wolves return to areas they had been driven away from in the past. They looked at eight areas in Europe where the wolf population recovered and found that jackals disappeared upon the return of the wolves or moved to the edges of the wolf territories.

The only area where the jackal persisted is a part of Serbia where wolves remain under strong culling pressure that does not allow them to create stable packs.

The researchers concluded that the mere presence of wolves is not enough to drive away jackals. Wolves need to have a chance to survive in sufficient numbers and form stable packs in order to perform their ecological function.

These findings were confirmed in a second study that looked not only at the interaction between wolves and jackals but also relations between other pairs of large and small predators. The results showed that controlling the numbers and territorial presence of smaller predators (jackals, coyotes and foxes) only becomes successful when large predators (wolves and dingos) live in natural densities across large areas.

There were around 60 wolves in Slovenia last year, while monitoring for this year is currently under way. Permanent territorial wolf packs are present in the south of Slovenia - in the Kočevska, Dolenjka, Primorska and Notranajska regions. Individual wolves also venture to Gorenjska, but generally wolf packs have not been present in the northern parts of Slovenia since they were exterminated in the 20th century, Krofel explained.

Presence of wolves and jackals identified by emulating their howling

There are several methods to examine the presence of territorial wolf packs. Slovenian researchers mostly use the method of howling emulation, which provokes responses that researchers can record. This is done in the field during the night, when the wolves are at their most active.

When howling, the researcher pretends to be a young wolf who arrived to a territory and wants to check whether it is still vacant.

If territorial wolves are present in the given area, they mostly respond with their own howling. "This is much like responding with 'no, no, this area is already occupied, go away or we will attack you'."

Occasionally the wolves move closer to the researchers. "But once they establish that these are people and not wolves, they turn around and escape. Wolves have a fairly strong fear of people. There is practically no danger of a healthy wolf attacking a person," Krofel stressed.

The best way to learn how to emulated wolf howling is listening to it in nature, while researchers also use recordings available online. Training is what matters the most, stressed Krofel, who usually practices at home or in his car.

Similar methods are used with jackals, but tape recordings are the preferred choice since it is harder to emulate jackals.

Large predators important for preserving equilibrium

Krofl explained that large predators like wolves are necessary to preserve a dynamic equilibrium in nature. One role performed by them is the ecosystem service of preventing the overpopulation of smaller predators, including jackals, he said.

Smaller predators have been under constant evolutionary pressure from large predators, which is why they did not develop strong self-regulation mechanisms. Large predators, on the other hand, were not subject to such pressure and had to develop their own self-regulation mechanisms. These mechanisms are usually based on territoriality.

"We know now that apex predators need to be preserved in stable groups and sufficient densities if we wish to benefit from this ecosystem service," Krofel stressed. If this is allowed, the wolves are much more effective in controlling jackal figures than culling, he explained.

Interfering in the natural state often has negative effects. Recent research has shown that culling, which was for a long time the basic approach to managing wolves and preventing attacks on domestic animals, is not effective in limiting damage. Once wolves lose a key member of the pack they become less effective in hunting their natural prey (deer, wild boar), which means culling can even lead to an increase in the predation of domestic animals.

On the other hand, experience from the field has shown that better protection of domestic animals, for instance with the right use of electric fencing and shepherd dogs, can reduce this type of damage significantly.

A Slovenian project has shown that the damage caused by wolves in Slovenia was reduced by more than 70% in this way, Krofel noted.

He argued that Slovenia is pretty advanced when it comes to the management of wild animals, including large carnivores. "We know now pretty well already what works and what doesn't and this is increasingly used in practice. I feel we're making good progress but there is still quite a bit of room for improvement."

Research abroad

Krofel is also active at the Berlin-based Leibniz Institute for Zoo and Wildlife Research, participating in fieldwork in Africa, where he is studying leopards and cheetahs, and in Mongolia, where he is studying snow leopards in the Altai mountains.

He said similar problems exist whenever there are large predators living in areas with livestock breeding, which leads to attacks on domestic animals and conflicts with breeders. "There, science also plays the important role of collecting information that can make management measures more effective and simplify the cohabitation of people and big cats," Krofel added.

Dr Miha Krofel

Dr Krofel is a researcher and associate professor at the Ljubljana Biotechnical Faculty, a lecturer at Primorska University, and a guest researcher at the German institute IZW conducting fieldwork in Africa.

His main research field are large carnivores, especially wolves, bears, lynx, jackals, as well as leopards, cheetahs and snow leopards. He devoted his PhD, finished in 2012, to the research of Eurasian lynx and its relationship with other animals in the Dinaric forests.