In March 2020, there were most probable 30 wolf packs in Finland (27–33 with a probability interval of 90%, Fig. 1), of which 24 (21–27) were completely on the Finnish side of the border. Six (5–7) packs were moving on both sides of the eastern border of Finland. The total number of packs increased from last year by approximately 25%.
There were more packs than before especially in western Finland, where there were most probable 18 (16–21) packs. For example, there were three large packs in the Laitila-Mynämäki-Pöytyä region. There were most probable 17 (13–20) wolf pairs, of which 15 (11–18) lived in Finland and two (1–3) moved on both sides of the eastern border of Finland.
The term “pack” refers to a group of three or more wolves that mostly move together and share the same territory, while “pair” refers to two wolves that move together and share a territory. A majority of the wolf population lives in packs or pairs during the wintertime.
No change in number of territories
There was no clear change from last year in the total number of territories. There was a change, however, in the structure of the wolf population that populates the territories. Compared to last year, there are more packs and fewer pairs in these territories. A large number of cubs were born in the spring of 2019, and the new cubs turned pairs into packs.
In March 2020, the total number of pack and pair territories was 43–49 with a probability of 90%. The map indicates the locations of the territories.
With a probability of 90%, the number of individual wolves in Finland in March 2020 was 216–246. The population was estimated at 185–205 in March last year.
The population estimate for March 2020 is based on a comprehensive set of data. Clearly more observations were saved in TASSU than last year (a link to a news article). Furthermore, approximately 40% more successful DNA analyses were performed than last year.
Forecast for March 2021: No major increase in the wolf population
According to the forecast model, the wolf population is not expected to experience any significant increase by March 2021. This is because the total number of pairs and packs capable of producing cubs remains at the same level as it was in the spring of 2019. The high number of cubs in 2019 can be realised as a more abundant population at the earliest in the spring of 2021 when the wolves that were born in 2019 reach sexual maturity.
The good cub yield of 2019 is expected to be reflected as a larger number of wolves in the summer of 2020 and as the taking over of new territories during the autumn and winter. The number of territories is at its highest during the early winter before the harshest winter conditions increase the mortality rate.
With a probability of 90%, there will be 57–71 territories in November 2020. The number of territories is expected to decrease to 42–69 in March 2021, of which the share of packs is expected to be 34–56%.
Probability distributions describe the accuracy of wolf population estimates
Over the past year, Luke has been developing the method used to estimate the wolf population by indicating the uncertainties of the estimate with a probability distribution. When dealing with animals living in the wild, there are always some uncertainties in the assessment of the population size. As more observation and research data on wolves is collected, the size of the population can be assessed with more certainty.
The probability distribution is described with a bar graph where the height of a bar indicates the probability of the number of individuals. For example, the most probable number of wolves in the Utajärvi territory in March was four, but there could have been five or six wolves within the territory with a probability of 18%. As the observation data indicates that there were at least four wolves in the territory, it could be deduced that there was a pack within this territory with a probability of 100%.
The new probability model was used to assess the territory-specific numbers of individuals once the territory limits had been outlined by reviewing the data. The model is a combination of the data provided by successful DNA samples and TASSU observations, as well as information on dead wolves and wolves that have leaved their territories.
The probability distributions for the number of territories inhabited by packs and pairs were determined by combining the territory-specific individual probability distributions.