Brown bear

Ursus arctos

Adult females: approximately 100 kg

Adult males: 150–250 kg

Adult bears stand approximately 1 metre at the shoulder and measure around 2 metres in length from the tip of the snout to the base of their short tail.

20–25 years

In Greece, the brown bear is a strictly protected species under both national and international legislation. The species and its habitat are protected under the Greek Forest Code, the EU Habitats Directive (92/43/EEC), the Bern Convention, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). According to the Red Data Book of Threatened Animals of Greece (2009), the brown bear is classified as Endangered.

The earliest ancestors of today’s bears appeared during the Miocene epoch, approximately 25–30 million years ago, when vast open steppes dominated southern Europe and the Balkan Peninsula. Over this immense span of geological time, natural evolution, together with dramatic climatic and environmental changes, shaped the remarkable adaptability of the bear family (Ursidae), as it did for countless other living organisms on Earth.

The first bear to resemble modern bears in appearance was Ursus minimus, which lived in Europe between 3 and 8 million years ago. More recent fossil evidence, however, identifies a younger species, Ursus etruscus (the Etruscan bear), dating back around 2 million years, as the true ancestor of the modern genus Ursus. Since then, profound environmental changes have endowed bears with extraordinary adaptive capacity. As a result, today we find the polar bear thriving in the harsh conditions north of the Arctic Circle, while species such as the spectacled bear and the sun bear inhabit tropical environments.

Following the Ice Ages, vast treeless landscapes and severe climatic conditions dominated much of the northern hemisphere. The absence of forests—and therefore natural cover—combined with an abundance of large herbivorous prey shaped the earliest bears into predominantly carnivorous animals with a more aggressive behavioural ecology. As temperate and boreal forests gradually expanded across the Palearctic region, the brown bear adapted to these new conditions by evolving a series of remarkable survival strategies, including an omnivorous diet and winter hibernation. These adaptations enabled the species to occupy a wide range of habitats across the Northern Hemisphere and parts of North Africa.

Around 400,000 years ago, the ancestor of the modern brown bear began spreading westward from present-day western China. It reached North America by crossing the Bering Land Bridge and, approximately 200,000 years ago, expanded into Europe via the Aral–Caspian region.

The brown bear has the widest natural distribution of any bear species in the world. Until relatively recently, its range extended across most of North America, Europe, Asia, the Middle East, and North Africa. Today, however, its distribution has declined dramatically, particularly in North America and Europe.

The species disappeared from Denmark around 5,000 years ago, from Great Britain by the 10th century, and later became extinct in Germany, Switzerland, and Austria during the 18th, 19th, and 20th centuries, respectively. Over the past two centuries alone, Europe’s brown bear population is estimated to have declined by approximately 50%, while its suitable habitat has been reduced by nearly 60%.

The principal causes of this decline have been hunting—which was prohibited in Greece only in 1969—and the continued destruction and fragmentation of the species’ habitat. With the exception of the Eastern Balkan population and the Dinaric–Pindos population, both of which have recovered to viable numbers and are currently considered stable or increasing, the long-term outlook for brown bears in much of western and southern Europe remains uncertain.

In France, poachers killed the last female bear of the Western Pyrenees in 2004, resulting in the local extinction of the species in that region. In the Central and Eastern Pyrenees, however, long-term reintroduction programmes have successfully established a small but stable population of around 30 individuals. Similar conservation efforts in the Alps have also enabled the species to return, with the population now estimated at approximately 60 bears. In the Central Apennines of Italy, a small, isolated population of around 50 individuals survives, belonging to the endemic subspecies Ursus arctos marsicanus.

In Greece, systematic recolonisation of former habitats has been documented since 1995. Brown bears have naturally returned to areas where they had disappeared decades earlier, particularly throughout the southern Pindos mountain range and other mountainous regions, including Voras, Paiko, Vermio, Mount Olympus, Mount Oiti, and the mountains of Nafpaktia. For a large mammal such as the brown bear, recolonisation through natural dispersal is a gradual and entirely natural ecological process, supported by extensive scientific evidence.

According to the most recent studies, Greece’s brown bear population is now estimated at approximately 750 individuals (2022). The species’ permanent range extends across much of the Pindos Mountain Range and its surrounding mountains, as well as the Rhodope Mountain Range, covering an estimated 24,105 km².

Despite these encouraging developments, significant threats remain. Although the brown bear has enjoyed strict legal protection in Greece since 1969 and is listed as a priority species under the EU Habitats Directive (92/43/EEC), it continues to face serious risks from illegal killing and the use of poisoned baits. Road mortality is also a growing concern. Between 2003 and 2023, at least 125 collisions involving brown bears were recorded on the road network of northwestern Greece, highlighting the continuing need for effective conservation measures and wildlife-friendly infrastructure.

The brown bear has an average lifespan of 20 to 25 years. It is exceptionally intelligent and is widely regarded as one of the most intelligent mammals, surpassed only by primates, elephants, and dolphins. Bears possess excellent memory, advanced problem-solving abilities, and a remarkable capacity for planning and learning.

Physically, the brown bear is distinguished by its rounded head, powerful muscular body, prominent shoulder hump—formed by well-developed muscles and fatty tissue—and long, robust claws. It has small rounded ears, relatively small eyes, and a short tail. Its senses of hearing and smell are highly developed, while its eyesight is less acute. Although it can see clearly at distances of around 80 metres, it is unable to distinguish a person at approximately 300 metres.

Coat colour varies considerably, ranging from the typical shades of brown to lighter blond tones and darker colours approaching black.

Adult bears stand up to approximately 1.10 metres at the shoulder and measure between 1.70 and 2.20 metres in total length from the tip of the snout to the end of the tail.

A bear’s body weight fluctuates significantly throughout the year. It reaches its maximum in autumn, after accumulating substantial fat reserves for winter hibernation, and falls to its minimum in spring, when these reserves have largely been depleted.

Adult males generally weigh between 150 and 250 kg, although exceptionally large individuals have been recorded weighing up to 300 kg in spring and 400 kg in autumn. Adult females are considerably smaller, typically weighing around 100 kg. On average, males weigh nearly twice as much as females. The largest bears in the world are the Kodiak brown bear of Alaska and the polar bear, both of which may exceed 750 kg.

Although the brown bear appears slow and cumbersome because it moves both legs on the same side of its body in sequence, it is in fact remarkably agile and can reach speeds of up to 60 km/h. It is also an excellent climber, thanks to its exceptional muscular strength and powerful claws.

Another distinctive anatomical feature is that the brown bear is plantigrade, walking with the entire sole of each foot touching the ground, particularly its hind feet. This enables it to stand upright on its hind legs. Contrary to popular belief, this posture is not necessarily a sign of aggression. More often, bears stand upright to improve their awareness of their surroundings by making better use of their highly developed senses of smell and hearing. This behaviour is particularly common among females with cubs, whose strong maternal instinct keeps them in a constant state of vigilance.

The mating season, which extends from mid-May to mid-July, is the only period during which brown bears display social behaviour, as adult males and females actively search for mates. During this time, males may travel considerable distances in search of receptive females. This behaviour is made possible by the females’ pheromones, which can be detected thanks to the bear’s exceptionally well-developed sense of smell. Females generally reach sexual maturity between four and five years of age.

Although fertilisation occurs during the mating season, the fertilised egg does not immediately implant in the uterus. Instead, it remains in a dormant state until late autumn—approximately five months later—when actual pregnancy begins. This phenomenon, known as delayed implantation, is one of the brown bear’s most remarkable evolutionary adaptations.

By postponing embryonic development, the female has sufficient time to accumulate the fat reserves needed to sustain herself, support the developing embryos, and later nurse her highly vulnerable cubs during the winter months.

Unlike most large mammals, brown bears give birth in the middle of winter. The expectant female prepares a carefully selected den, lining it with leaves, branches, dry grasses, and moss to create a warm, well-insulated nesting chamber. Choosing a suitable den is essential, and particularly favourable sites may be used by successive generations of females, passing from mother to daughter.

During winter, snow often seals the den’s narrow entrance, creating a stable microclimate inside. The mother’s body heat transforms the den into a natural incubator for her newborn cubs, which are born blind, almost hairless, and weigh only 350–400 grams.

If food availability during the previous autumn has been insufficient, pregnancy may be terminated before implantation occurs and the embryo is naturally reabsorbed. This adaptation prevents females from investing energy in reproduction when survival conditions are unfavourable.

Cub mortality during the first year of life is naturally very high, reaching up to 50%. Human-related mortality adds a further 25%, meaning that only a relatively small proportion of cubs survive to adulthood.

Those that do survive, however, grow remarkably quickly thanks to the exceptionally rich nutritional value of their mother’s milk. By their first birthday, a cub’s body weight may have increased by up to fifty times.

Young bears remain with their mother for approximately one and a half to two years, during which she is solely responsible for their care and education. Adult males play no role in raising cubs and may even pose a threat to them, occasionally killing unrelated young.

From their very first spring, cubs accompany their mother through the forest, learning the essential skills they will need to survive independently. She teaches them how to recognise edible foods, where and how to find them, how to identify potential dangers, and what to avoid. This prolonged learning period is critical to their future survival. If it is interrupted—particularly during the first year, for example through the loss of the mother—the cubs’ chances of survival are greatly reduced.

Hibernation is one of the brown bear’s most remarkable adaptations to the harsh conditions of winter. During this period, the bear’s metabolism slows significantly, reducing energy expenditure and allowing it to survive for several months without feeding. At the same time, the carefully insulated microclimate of the den minimises heat loss, helping the bear conserve energy throughout the winter.

Brown bear hibernation differs fundamentally from the true hibernation observed in many other mammals.

In true hibernators, body temperature drops to near ambient levels—often approaching 0°C—while heart rate and respiration slow dramatically. In marmots, for example, the heart rate decreases from around 350 beats per minute to just 3–4, representing a reduction of approximately 95%. These animals periodically awaken to urinate and defecate before returning to hibernation.

Brown bears, however, enter a different physiological state. During hibernation, their body temperature decreases by only 1–2°C, remaining close to the normal 38°C. Heart rate falls from approximately 52 beats per minute to around 24, a reduction of about 43%, while respiration slows without reaching the extremely low levels observed in true hibernators.

Because bears remain in a relatively light state of hibernation, they can wake easily if disturbed. Once awakened, they often struggle to return to hibernation, forcing them to consume valuable fat reserves at a time when food is scarce. This unnecessary energy loss can significantly reduce their chances of surviving until spring.

The first snowfalls and the onset of low temperatures are the main environmental cues that trigger the search for a winter den. The duration of hibernation varies according to climate and latitude. In northern regions with long, severe winters, such as Scandinavia, hibernation may last up to six months, whereas in southern Europe, where winters are milder, it generally lasts two to three months.

In Greece, the average duration of hibernation has been estimated at 84 days. However, not all bears hibernate for the same length of time. Adult individuals have occasionally been observed becoming active again during mid-winter, either after being disturbed—most commonly by hunting activity—or because of unusually mild weather conditions. Pregnant females, by contrast, remain in their dens throughout the winter until their cubs are born.

During hibernation, brown bears neither eat nor drink, nor do they urinate or defecate. This extraordinary physiological adaptation has attracted considerable scientific and medical interest. Unlike any other mammal, the bear functions as a virtually closed biological system, recycling metabolic waste and converting potentially toxic compounds into reusable nutrients without suffering the harmful effects that would normally result from prolonged waste retention.

Understanding these unique biological mechanisms has important implications for medical research, particularly in the treatment of kidney disease, as well as for space medicine and the development of technologies that may one day support long-duration human space travel.

The brown bear is an omnivorous species whose diet consists predominantly of plant matter, which accounts for approximately 85% of its food intake. To maintain its large body size and energy requirements, it consumes substantial quantities of food throughout the year.

Its diet includes a wide variety of forest fruits and nuts, such as blackberries, cornelian cherries, wild cherries, apples, pears, raspberries, rowan berries, rose hips, wild strawberries, acorns, and beechnuts, as well as bulbs, roots, grasses, and other herbaceous plants. It also supplements its diet with honey, insects—particularly ants—small and large mammals, and occasionally tortoises.

Spring is the most challenging season for the brown bear. Emerging from hibernation after losing as much as 30% of its body weight, it faces a landscape where fruit-bearing trees and shrubs have not yet begun producing food. During this period, bears rely on alternative food sources, including fresh vegetation, bulbs, roots, and insects. They also take advantage of fruits that have remained preserved through the winter, such as wild apples, wild pears, rose hips, and acorns, which provide an important source of nutrition until fresh food becomes available.

It is during this season that the first cases of damage to beehives and livestock are typically recorded. Small agricultural plots located adjacent to forests—particularly those cultivating cereals such as wheat and maize, legumes such as clover, and fruit trees—also provide valuable feeding opportunities. The close proximity of farmland to forest habitats creates an ideal combination of food availability and shelter for the species.

Autumn is the period of hyperphagia, when bears spend most of their time foraging and consuming food. During this critical phase, the abundance of autumn fruits allows them to build the fat reserves essential for surviving the winter months. Among the most important food sources at this time are acorns and beechnuts, which are especially rich in energy.

Thanks to its exceptionally well-developed sense of smell, the brown bear can detect fruits at their optimal stage of ripeness. Studies of feeding ecology have shown that the species’ diet in Greece includes at least 67 species of plants and animals, reflecting its remarkable dietary flexibility and its ability to adapt to changing environmental conditions.

The brown bear also plays a vital ecological role in forest ecosystems. As it moves across the landscape, it unintentionally disperses seeds through its droppings, while passage through its digestive system often increases seed germination rates. In this way, bears contribute to the regeneration of forests by facilitating the growth of shrubs and young trees, whose root systems help stabilise soils and retain water within forest ecosystems.

The brown bear is primarily a forest-dwelling species, inhabiting extensive deciduous and mixed forests—dominated by oak and beech—as well as coniferous forests of black pine, fir, spruce, Bosnian pine, and other native tree species found in Greece’s mountainous and semi-mountainous regions.

Brown bears use different forest habitats according to their ecological value and the resources they provide throughout the year. Their movements are closely linked to their biological needs, including access to food, shelter, breeding sites, and suitable hibernation dens.

Because food availability is the primary factor shaping the bear’s annual cycle, the composition and structure of forest vegetation have a direct influence on its movements. Bears show a clear preference for deciduous forests, particularly those dominated by beech and oak, as these habitats provide abundant seasonal food resources. In some areas, they also benefit greatly from small-scale agricultural fields located adjacent to forests. The close proximity of woodland and farmland creates an ideal combination of shelter and reliable food sources throughout much of the year.

The brown bear is generally a solitary animal. It is most active during the early morning, at dusk, and throughout the night, when human disturbance is typically lower.

In Greece, annual activity peaks during two distinct periods: early summer, which coincides with the breeding season, and autumn, when bears enter the period of hyperphagia in preparation for hibernation.

A noticeable decline in activity occurs during the hottest part of summer. This reduction is thought to result from two main factors. First, because of their large body size, bears avoid prolonged movement during periods of extreme heat. Second, summer brings increased human presence to forests through tourism, recreation, and other outdoor activities, creating additional disturbance that bears generally seek to avoid.

For thousands of years, Greece’s mountains and lowlands have been shaped by human presence and activity, and wildlife has evolved alongside these changing landscapes. The interactions between people and wildlife are numerous and inevitable, as both depend on the same landscapes and natural resources. Even in Greece, where humans and large carnivores have historically coexisted, traditional patterns of coexistence have been disrupted by shifting social, political, and economic conditions, profoundly affecting rural communities.

Over recent decades, rapid technological development has transformed the way natural resources are used, bringing significant changes to rural economies and societies. At the same time, widespread rural depopulation driven by urbanisation has weakened the social fabric of the countryside, reshaped long-established value systems, and left many areas rich in natural and cultural heritage increasingly marginalised.

Meanwhile, across both Greece and Europe, populations of large carnivores have been recovering. A combination of conservation measures and favourable ecological conditions has enabled species such as the brown bear and the wolf to expand into parts of their former range. As a result, encounters between wildlife and people are becoming increasingly common in rural areas.

Despite these changes, what must be preserved is the long-standing framework of coexistence between wildlife and rural communities. Such coexistence is not always conflict-free; tensions and challenges are inevitable where people and wildlife share the same landscapes. Callisto works to improve the conditions that make peaceful coexistence possible by implementing projects, initiatives, and practical interventions that address the complex interaction between ecological processes and human activities.

Farmers, livestock breeders, beekeepers, and other rural producers should not be expected to bear alone the economic costs resulting from damage caused by large carnivores. The conservation of wildlife cannot come at the expense of already vulnerable rural livelihoods.

The greatest challenge is to ensure conditions that allow wildlife and the people who live and work alongside it to coexist sustainably. For this reason, Callisto systematically promotes effective preventive measures that reduce or prevent damage to livestock, crops, and other agricultural assets caused by wild animals.

At the same time, Callisto advocates for a fair, efficient, publicly funded compensation system that distributes the costs of wildlife damage across society rather than placing the burden solely on producers. Fair compensation is an essential prerequisite for successful human–wildlife coexistence.

The organisation also works to minimise the impacts of major infrastructure projects and other human interventions on the natural environment. Since 2009, Callisto’s Rapid Response Team has provided practical support to local communities and public authorities in responding to incidents involving large mammals approaching human settlements.

Through research, conservation, and environmental management, Callisto promotes sustainable coexistence between people and wildlife while working to safeguard nature and natural resources as public goods. The organisation studies and protects populations and habitats of large carnivores and other threatened wildlife species, recognising that conserving wildlife is inseparable from maintaining the ecological balance on which both nature and people depend.

The principal international legal instruments protecting the brown bear are:

1. The Bern Convention

(Law 1335/1983 – Convention on the Conservation of European Wildlife and Natural Habitats)

The brown bear is listed as a strictly protected species. The Convention prohibits:

-the capture, possession, or killing of individuals;
-the destruction or degradation of breeding sites;
-the possession, transport, trade, or commercial use of live or dead animals, taxidermied specimens, or parts of the animal.

2. The EU Habitats Directive (92/43/EEC)

The brown bear is listed:

-in Annex II, as a species whose conservation requires the designation of Special Areas of Conservation (SACs); and
-in Annex IV, as a species requiring strict protection throughout its natural range.

3. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)

CITES has been implemented in Greece since 1 January 1984.

The brown bear is included among the species for which international trade, including trade in parts or derivatives, is strictly regulated or prohibited. The Convention is implemented across the European Union through the relevant EU Wildlife Trade Regulations.

4. Other European Union Environmental Legislation

A range of additional EU environmental directives also contribute indirectly to the protection of the brown bear and its habitat.

Among the most important is the Environmental Impact Assessment (EIA) Directive, which requires environmental assessments for projects likely to affect ecologically sensitive areas or threatened species. These assessments evaluate potential impacts and establish the environmental conditions that must be met before a project can proceed. Approval is granted only after the competent public authorities formally determine that the conservation status of protected species and habitats will not be compromised.

Under Greek legislation, the killing, capture, possession, or public exhibition of brown bears is prohibited under Article 258 (paragraphs 2e and 2f) of the Greek Forest Code (Legislative Decree 86/1969).

According to the Red Data Book of Threatened Animals of Greece (2009), the brown bear is classified as Endangered in Greece and Vulnerable at the international level.

The principal threats facing the brown bear in Greece include:

-Habitat degradation, destruction, and fragmentation resulting from large infrastructure projects—including motorways, wind farms, dams, and other developments—as well as forest fires, intensive logging, and other forms of habitat disturbance.
-Illegal killing by poachers.
-Mortality caused by the widespread use of poisoned baits.
-Road mortality resulting from collisions with vehicles.

Callisto works to reduce these threats through scientific research, environmental monitoring, and interventions aimed at improving the environmental planning of infrastructure projects. Where necessary, the organisation advocates for mitigation measures that reduce wildlife-vehicle collisions, minimise habitat destruction, and maintain ecological connectivity between bear populations.

Callisto also promotes the widespread use of preventive measures to reduce conflicts between people and large carnivores, including electric fencing and Livestock Guardian Dogs. In parallel, its Rapid Response Team intervenes whenever incidents occur involving interactions between people and bears.

Finally, Callisto carries out extensive public awareness and environmental education campaigns while promoting participatory decision-making processes in matters relating to wildlife conservation and management.