Communication Education news


8 April 2022
University of Ljubljana

The average wolf pack in Slovenia is estimated to have four members. Why then do we see footage of up to ten wolves? The answer lies both in their biology and in the reasons for their mortality. The fluctuations in wolf numbers are significant even over the course of a year. Read on to find out why!

Wolves are social animals and live in family communities – packs. A pack consists of a leading female and male and their offspring from one or more litters. Older offspring that have not yet left the parent pack help to care for younger siblings, while only the lead female and male breed. Wolves are highly territorial animals, which, among other things, hunt large herbivores within their territory to satisfy their dietary needs. However, they can only be successful and “sustainable” if they hunt alone (only their family – the pack) in that area. Therefore, they actively mark and defend their territory against other wolves and wolf packs, thus limiting their abundance (density) in a chosen area.

Wolf pack from Pokljuka.

When young wolves go in search of territory, this is called dispersal. Dispersal occurs most often between the ages of 11 and 24 months but can occur as early as 5 months (and very rarely, wolves stay in their parent pack for several years). They most often leave the parental pack at sexual maturation from early winter until the breeding season of the next litter, or in autumn (October, November) when their younger siblings start to grow up.

The time of territorial search is particularly vulnerable for young wolves, as they often travel long distances and are exposed to many factors, such as other territorial wolves, proximity to settlements and thoroughfares. Most young wolves therefore never form their own pack.

This image shows the Snežnik wolf pack with pups in October 2019, with 10 members still in the pack by October. In the following year, however, only 4 more individuals were detected in the area. The rest went into dispersal or died, including the telemetrically monitored wolf.

The mortality of young wolves is therefore quite high. A wolf may have 4 to 7 pups in a season (on average 5.5). In the period leading up to dispersal, about 65% of them survive, while in the period when they are searching for their territory, they have about a 50% chance of survival. To illustrate this with an example, it would look something like this: In a pre-breeding pack, there is a reproductive female, a reproductive male and two helpers (usually female). In the first half of May, 6 pups are born. Two pups die in the first month and one in the pre-dispersal period. This leaves 7 individuals in the pack. Of the three remaining pups, two will have dispersed by the time of the next litter and one will probably die within a year. This will leave 4 individuals in the pack over the winter, one of which will manage to establish a new territory in an unoccupied area. This means that within a season, wolf numbers increase, but also gradually decrease. Therefore, fluctuations in wolf abundance within packs can be large even within a year. With a high reproductive potential, the presence of the species, despite the high mortality of young wolves, has increased considerably over the last twelve years and has spread to areas where it was previously absent for several decades. The wolves in Slovenia are estimated at up to 150 individuals at the latest count and are part of the large Dinaric-Balkan population, which is estimated to be around 4 000 wolves in abundance.

Showing the variation in abundance within a pack over the course of a season.

More and more wolves are being spotted!

The increasing number of media and social media posts quickly gives us the impression that the density of wolves in Slovenia is high and that the chances of encountering a wolf in Slovenia are high. Even though the wolf is spreading into areas where it was previously absent for decades, the dynamics of wolf abundance are already significant within a year. Due to their biology (territoriality), wolves themselves limit their density in a chosen area. Observation of wolves in the wild alone is also not sufficient to determine their abundance. For this purpose, we need to use a range of scientific methods, as only these allow us to obtain accurate results and to understand the bigger picture. Now we invite you to get away from the computer and go for a walk in the forest! The chances of seeing a wolf are (unfortunately) almost zero.