title

Large and small bears (Ursus arctos): are these features of the past and present?

author(s)

Igor Zagorodniuk (orcid: 0000-0002-0523-133X)

affiliation

National Museum of Natural History, NAS of Ukraine (Kyiv, Ukraine)

bibliography

Theriologia Ukrainica. 2025. Vol. 30: 3–17.

DOI

language

English, with Ukrainian summary, titles of tables, captures to figs

abstract

The hypothesis that the size of bears in Ukraine decreased over a century is considered, taking into account known facts, legends, statements, and assumptions about this phenomenon. The analysis was conducted considering studies of the variability of bear sizes (including geographical and sexual variation) from different neighbouring regions. The possible role of artificial selection through many years of hunting pressure with the removal of large individuals and ‘pseudo-selection’ through a decrease in the lifespan of animals due to environmental changes and population decline are analysed. Such hypotheses primarily concern the Carpathian region, unlike Polissia, where bears have always been smaller. An analysis of literature and factual data from different periods showed that sources from 100–150 years ago, which paid considerable attention to descriptions of notable trophies, feature specimens with large body sizes and weights (around 400–450 kg). Values of such magnitude have already disappeared in works from the middle and, even more so, the second half of the 20th century, despite the continuation of trophy hunting, which suggests a reduction in the size of these animals over time. As an alternative system for assessing the size structure of the population, it is proposed to use the analysis of paw print sizes (length of the hind foot and width of the front foot), which is successfully used in some regions of Europe and is a much more accessible type of data compared to body size or weight. Hypotheses for the shrinkage of body size are considered, including artificial selection (shooting of large individuals), the trophic hypothesis (deterioration of the food base), the climatic hypothesis (disappearance of the need to accumulate fat for wintering) and the statistical hypothesis. Obviously, all these processes are taking place, and the common denominator and additional general factor may be the disappearance of large-body-size (= not numerous) classes due to small population sizes. The decline in bear body size may reverse as a result of improvements (essentially a restoration) in the age structure of the population, the main factors being a triad of ‘population growth’ + ‘improvements in the food base’ + ‘reduction in disturbance factors’. The above is only possible with a reduction in anthropogenic pressures on natural complexes and an increase in the scope and network of protected areas.

keywords

brown bear, microevolutionary processes, long-term dynamics, Ukraine

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