Genetic monitoring

What is genetic monitoring of brown bears?

Genetic monitoring is a modern and scientifically based approach to monitoring wild animal populations, enabling accurate assessment of their numbers, structure, and long-term trends without direct interference with the animals. In the case of the brown bear, which is a large and mobile species with extensive home ranges, traditional counting methods are not reliable. This is why genetic monitoring has become a key component of brown bear population monitoring in Slovenia.

Genetic monitoring is based on the non-invasive collection of genetic samples, most commonly feces, but also hair or tissue from dead animals. These samples contain DNA, from which the genetic record of an individual can be obtained in the laboratory. Each bear has a unique genetic “fingerprint”, which enables reliable differentiation between individuals, determination of their sex, and monitoring of their presence in space and time.

Samples are collected systematically throughout the entire range of the species. Hunters, foresters, and other field workers who are familiar with the terrain and signs of bear presence play a key role in this process. The collected samples are then sent to specialized genetic laboratories, where complex and lengthy procedures of DNA extraction, genotyping, and data quality control are performed.

Once the genetic profiles of individual bears have been determined, statistical and mathematical data processing follows. This involves the capture-mark-recapture method, which is based on the fact that some individuals appear multiple times in the sample, while others do not appear at all. Based on the frequency of repeat detections, it is also possible to estimate the number of bears that were not detected during sampling and thus calculate the total population size.

A particular advantage of genetic monitoring is that it allows differentiation between different seasons. The most commonly reported is the so-called autumn abundance estimate, which represents the lowest annual population abundance, as it already includes all recorded mortality in the current year and applies just before the birth of young. With additional calculations, it is also possible to estimate the spring population size, which is the highest in the annual cycle.

In addition to numbers, genetic monitoring also provides insight into the sexual structure of the population, the spatial distribution of individuals, their spread into new areas, and long-term changes in the population. Since the methods are standardized, it is possible to directly compare results between individual years. This allows for the detection of monitoring trends—growth, stabilization, or decline of the population—over a longer period of time.

In Slovenia, genetic monitoring of brown bears was carried out in 2007, 2015, and 2023, representing one of the longest and most consistent series of such studies in Europe. These data have shown that the brown bear population in Slovenia has grown in recent decades, while also revealing spatial constraints, the impact of infrastructure, and the importance of cross-border connectivity with populations in other countries.

Genetic monitoring is therefore not only a tool for counting bears, but also forms the basis for professional and sustainable population management. It enables objective decision-making, reduces uncertainty in management measures, and provides transparent and scientifically verifiable data that is crucial for both species conservation and the coexistence of humans and bears.