A single tree can produce more than 30,000 fruits (beechnuts) in one growing season. A real bonanza for hundreds of animal species, providing the fruits are able to ripen, something that occurs in just a few very special years. But in these years, it is in autumn that the forests are especially full of life. The tree branches are targeted by birds such as tits and finches, together with rodents, including dormice and squirrels that hoard the fruits. Ripe beechnuts fall to the ground by gravity, helped by the numerous visitors and gusts of autumn wind. The forest litter is covered with thousands of spiny leathery cupulas and crunches under the weight of wild boar and red and roe deer as they dig deep with their noses in search of food. But there is also turmoil below ground. Industrious voles transport the beechnuts to their burrows where they hoard them to guarantee a reserve of food for the winter and following spring. Bears are obviously not indifferent to this bonanza.

But beechnuts give bears genuine “power”. From 2004 to 2019, bears had to wait for a bumper crop for from two to as many as five years. In the years after a bumper year, technicians and researchers have confirmed that more females become mothers, as is also the case, for example, with black bears. But the rule does not always apply. Despite the scarce production of beechnuts observed from 2015 to 2018, the number of births in fact remained high, an indication that even in these years, the female bears found plenty of food, including acorns (turkey and downy oak) and other fruits that ripen in summer and autumn. For bears, the extraordinary nature of the Apennines is precisely this abundant supply of nuts and fleshy fruits and protecting them can help guarantee the survival of this adaptable animal.

In some years, each beech tree produces more flowers than in previous years and this is true for all, or almost all, the trees in the population, a phenomenon that usually occurs at intervals of from 2 to 10 years. The synchronisation enables the wind-pollinated plants to maximise the probability of regeneration. But this only happens in certain weather and climate conditions. If a cold, wet summer is followed by a hot, dry summer, the following year, the beech trees stop growing to reproduce, in other words, to flower, provided the spring has been mild. Plants over thirty years old usually produce the most fruits. After profuse flowering, the trees rarely have sufficient energy to flower abundantly again the following year. Hence the periodicity with which the flowers (and consequently the fruits) are produced. But what can cause a bumper year to fail? Heavy rainfall and spring frosts can inhibit pollen formation, pollination and thus the formation of fruits, just as severe summer drought can cause the fruits to abort, even if pollination has taken place. This sensitivity to drought makes the beech tree very susceptible to climate change, more so than oaks.

Especially in summer and autumn, bears can consume up to 20,000 kilocalories and when possible, they use every hour in the day to find food. Beech forests cover more than half the protected area in the heart of the Park and bears can find not only food there, but also safety and tranquillity. At lower altitudes of around 1,000 to 2,000 metres, the beech forests give way to oak woods: hundreds of square kilometres of turkey and downy oak woodland with highly nutritious acorns, very appetising for bears in autumn. For example, almost every year a turkey oak forest can produce an average of more than 500 kg of acorns in a thousand square metres. But in some years, acorn production may be more abundant than usual… even oaks have their bumper years and this inevitably attracts bears to less safe and less tranquil areas.

When temperatures rise about 20 degrees centigrade, turmoil breaks out, both above and below ground. Ants swarm on the top of boulders, among the tufts of grass and bushes, on the mounds of earth, through the dead leaves on the forest floor and over the roots and bark of the trees. In just a few square metres, millions of ants in columns explore the territory in search of caterpillars, spiders, seeds and fruits, while others tend and “milk” aphids, or fight and enlist allies to defend their colony. In the shelter of the nests, the workers of a single colony build and defend the nest and take care of the queen mothers, cleaning and feeding them, together with the eggs they lay, which will become larvae, then pupae and finally adults. The future of the colony in fact depends on the birth of new virgin queens and winged males. The life of the colony revolves around a single objective: to reproduce, defend and propagate itself. An ant colony can be considered as a self-sufficient macro-organism and its strength lies in the ants’ ability to create strong links and complex social arrangements. Each ant has its own role within a hierarchical structure organised into castes. Unity is strength and each colony has its own unique identifying odour that strengthens the bonds. When the breeding season arrives from late June onwards, swarms of virgin queens and winged males emerge from the nests and swarm in the air to mate. The queens that survive toads, spiders, birds and attack by other territorial ants tear off their wings and either look for a place to dig a new nest or return to their original nests. The males, on the other hand, die within hours, leaving behind thousands of descendants.

To the untrained eye, all ants look the same, but this is not the case. In recent years, detailed analysis of the ant remains found in bear droppings has revealed that bears feed on more than forty different species. The richness of the Park’s environments (grasslands, clearings, scrub and forests) provides an ideal environment for the life of these insects and it is home to well over eighty different species. Ants build below and above ground “skyscrapers” that can reach several metres in depth and width. The workers are formidable engineers, digging nests vertically and moving between the different levels, transporting the future generations to the best “apartments” This is a strategy to cope with possible variations in environmental conditions that could compromise the reproductive success of the colony, such as temperatures that are either too cold (below 10 degrees) or too hot (above 30 degrees). The nests are, in fact, conceived to ensure the right temperature and humidity conditions needed to raise the broods. The ants concentrate their nests under generally flat rocks, partly buried in the ground and well exposed to the sun. By warming up quickly, the stones create the right temperature to “wake up” the colony, while the warmth and food provided by the workers make the larvae grow faster. Other species construct mounds of earth known as anthills which may include leaves, grass stems and conifer needles. Reaching as much as a metre in height, the anthills are full of interconnecting galleries and chambers. Then there are other species that build their nests in pre-existing cavities in usually dead or dying trees or trunks.

Between June and July, more than 36% of a bear’s diet is provided by ants. During particularly hot and dry years, almost half the diet may consist of ants alone. These values are comparable with those of other populations of both brown and black bears, but are among the highest documented for brown bears in Europe. Consumption peaks between late June and mid-July, coinciding with the presence of the broods (eggs, pupae and larvae) in the nests, but bears may consume adult ants all year round. They rely on their claws to gain access to the nests, whether under a rock or inside a log or anthill. They lift rocks measuring as much as three square metres and weighing several quintals to scoop away the surface of the nests with quick paw strokes. If the ants are aggressive, the bears let them swarm over their legs, then lick them off, otherwise they lick the damaged surface directly. The workers usually take more than ten or so seconds to move the brood to safety in the depths of the nest, giving the bear the opportunity for a genuine raid. Along with the ants, however, bears also swallow soil debris and the leaves forming part of the nest, as is evident from close examination of bear droppings.

Why do bears eat ants? Ants are rich in proteins, fats and very rare amino acids that bears lack, all essential nutrients for building body mass, growing and storing fat. Each ant can provide about 0.004 kilocalories and bears can consume even millions of kilocalories of ants per day. A few hours digging out nests and tipping stones can meet a large part of their energy needs. During the spring, adult bears need to replenish the protein reserves they may have lost during hibernation (bears can lose 20 to 40% of the weight accumulated in autumn), while cubs as young as 5-6 months old (born in the den) need them to grow.

Bears feed mainly on five genera of ants. The Formica and Lasius genera occur in more than 70% of the droppings containing these hymenopterans. These are followed by Tetramorium (about 40%), Camponotus (about 24%) and Myrmica (about 20%), also the most abundant genera in the Park. Among the Lasius genus, bears are especially fond of the small honey-coloured yellow species. When bears find their nests, they feed on these alone. The ants form very large colonies, both above and below ground and very close together. The workers also produce a secretion, a sweet strong-smelling pheromone which seems to attract bears. When disturbed, these ants are also among the slowest to save their brood. Most ants of the Formica genus build visible mounds housing very large colonies, excellent pickings for bears, as they can thus eat for a long time without moving around too much, saving a great deal of energy. Species such as Formica pratensis and Formica sanguinea belonging to the Serviformica group dominate. The other genera, found everywhere in the Park, form smaller, or at least less “conspicuous”, colonies. The presence in the bear’s diet of ants of the Myrmica genus is curious, as they are very aggressive, bellicose insects with a sting and generally shunned by many mammals, including insectivores. But this does not seem to be the case with the Marsican bear. Bears in the Apennines prefer to feed mainly on ants living in open grasslands or in areas of transition with forests. On the other hand, they consume very few species (in practice only two) of the ants that inhabit the beech forests and dig their nests in the wood. These are Lasius fuliginosus and Aphaenogaster subterranea. From one to six different ant species have been found in bear droppings, depending on the bears’ feeding strategy.

Each year, regardless of age and gender, bears in the Apennines consume ants on a constant basis. A staple in the bears’ diet, ants are essential for the growth and survival of the cubs. Females and cubs are smaller than adult males and can therefore put on weight more quickly for the same number of ants consumed. Ants can also be found everywhere, so they do not attract several bears to the same spot, as for example a deer carcass might. This means that females with young can find quiet, safe places away from adult males, which in the spring can be very dangerous for newborn cubs.

Small clusters of dark red, fleshy, spherical fruits emerge from their leaves; the bear sniffs them insistently, then moves on to the next bush. These are alpine buckthorn bushes and we are in an area of buckthorn scrub. There is a sense of industrious anticipation in the air ahead of the coming months. Depending on the season and slope, in a few days or weeks the berries will turn black and become appetising for bears. Around the same time and in much the same way year after year, the bears in the Park come to these sunny rocky areas from all directions. For the bears, it’s buckthorn time.

For more than 10 years, PNALM researchers and technicians have been spending their summers observing bears feeding in the buckthorn scrub. The first bears start to arrive as early as the first week of August, but the peak of the gatherings occurs between mid-August and the first week of September. Every year, males and females of all ages and females with cubs or juveniles in tow have between thirty and sixty days to feed on these fruits, depending on the weather (rain and temperature) which influences their ripeness and persistence. As the weeks pass, the bears move from one amphitheatre to another following the ripening of the berries, staying for almost a month in some particularly buckthorn-rich sites. From mid-September, sightings become very rare and the bears move down to lower altitudes in search of pears, apples, acorns or beechnuts, depending on the year.

This berry, just a few millimetres in diameter and weighing just 0.26 grams, seems to have all the characteristics needed to enable bears to fatten up and prepare for winter. In late summer, bears can choose from more than nineteen different species of fruit, but most of the nourishment and energy comes from eating this one berry. In some years, it contributes more than 70% of their energy intake and even in years when there is an abundance of sugar and fat rich nuts such as beech nuts, buckthorn alone contributes almost half the summer diet. A study carried out between 2006 and 2008 using various techniques (direct observations and genetic and radiotelemetric monitoring) found that more than half the Park’s bears regularly visit these areas each year between August and September. A diet consisting only of fruit could have high metabolic costs for a bear, but with their reduced requirements, Apennine bears are less constrained by an essentially frugivorous diet than larger bears. Young bears and in particular females, sometimes weighing considerably less than half the weight of an adult male bear, can easily accumulate fat and lean mass by eating mainly fruits.

The ease with which bears find, handle and assimilate nutrients from the buckthorn makes this fruit an ideal food during the period of hyperphagia. The bushes are distributed in groups throughout the territory, making this resource easy to look for and locally abundant. Bears concentrate more than half their feeding and resting activities in an area of just a few hundred metres around the buckthorn scrub. In practice, bears sleep and eat in the same place. The bushes are just a few tens of centimetres high and the berries are clearly visible grouped in clusters at the tip of the branches, so they can be easily grasped and manipulated. Often in a sitting position, the bears bend the branches apparently effortlessly and grasp the fruit with their lips. They do not waste even a single bite and, in fact, only berry residues (skin and seeds) are found in the excrement, with no leaves or twigs.

Buckthorn acts as a magnet and bears move the centre of their activity to these areas between August and September. During this season between 2006 and 2010, twelve male and female bears were monitored with tracking collars. As the buckthorn ripens, the females in particular restrict their movements to an area of a few tens of square kilometres (around 30 km2) and the buckthorn scrub can occupy up to 40% of the territory used by the bears during this period. But each bear obtains energy and nourishment from its environment in a different way. There is no single recipe for all bears. Age, gender, individual history, the proximity of the buckthorn scrub to the bear’s habitual territory and the availability of other natural foods, not to mention competition with other bears or animals, are all factors that can influence a bear’s daily choice of how and where to feed. Some bears spend no more than three days in the buckthorn scrub, while others remain there for more than a month. But most animals move between the bushes for an average of at least eighteen days, with no difference between males and females.

In summer, neither males nor females have exclusively nocturnal rhythms. Females limit their movements between seven in the morning and three in the afternoon, while males are more twilight animals and only start moving again after five in the afternoon. However, during the long years of research and monitoring carried out to date, it has not been uncommon to see young bears and females with cubs moving through the bushes even in the middle of the day, perhaps taking advantage of a cloudy sky. The bears’ hours of inactivity coincide with the times when those areas are most heavily frequented by tourists and also the hottest hours of the day. In the Park, the choice of when and for how long to feed therefore seems to represent a balance between the costs of feeding at high temperatures and the risk of encountering humans. The number of hours/day available for feeding can, on the other hand, significantly limit the amount of berries a bear is able to ingest. Females with cubs and juveniles, the groups with special needs and able to benefit most from a strictly frugivorous diet, also face the most risks. Going out during the day can not only ensure an optimal meal, it also lets you enjoy the peace of mind of eating away from potentially aggressive adult males. And, in fact, the infanticide of two cubs by a male bear was documented for the first time in 2007 right in an area of buckthorn scrub.

Life in the buckthorn scrub is a big change for bears in the Park. Bears move from being alone to all-out gatherings and therefore have to deal with the tensions that can arise from a life that is a little too social. But they do not come unprepared and show great ability in overcoming the problems of coexistence that may arise from this forced sociability. All this is the result of a long process of mutual understanding established over the years. In more than 14 hours of observation between 2006 and 2007, bears were seen to spend more than 70% of their available time feeding almost exclusively on buckthorn (and more rarely on ants, grass and roots), moving around the area from bush to bush. Bears spend no more than 5% of their time on the alert and only 1% in social interaction, mostly involving states of vigilance or alertness towards other bears or parental interactions in the case of females with yearling cubs.

But life in the buckthorn scrub has many more twists and turns than you might think. Bears provide a vital link in the transport of nutrients from high altitudes to the valley floor. Because of their mobility and relatively long intestinal retention time (over 5 hours in the case of the berries), bears can play a key role in seed dispersal between distant environments. Droppings with buckthorn have also been found at low altitudes (~3-5 km away and 1000 m below the feeding grounds). The seeds may then be dispersed again by small mammals and birds, which in turn derive a source of nourishment. In practice, bears are like farmers, planting seeds everywhere and growing a plant community that feeds both themselves and other animals, while at the same time providing food to meet the energy needs of many species.

All the information gathered underlines the exclusive importance for bears of buckthorn bushes and scrub within the Park. Any factor adversely affecting the level of berry productivity or the times available for the bears to feed can significantly reduce the energy provided by this food. The worse affected are mainly females with cubs and juveniles. However, although remote, these areas are today a destination for hikers and enthusiasts, a phenomenon in expansion in recent years, especially associated with the possibility of seeing bears. The high incidence of both wild and domestic ungulates observed feeding in the buckthorn scrub could also have some effect on the future productivity of the various populations.

At dusk, bears make their appearance in the clearings at the bottom of the valley in search of fresh vegetation, but that’s not all. A bear is quietly grazing downwind, browsing on leaves and shoots. Hidden in the tall grass no more than 150 metres from the bear, an alert doe concentrates on the potential predator. As soon as the wind veers in its favour, the bear stops, sniffs the air and rises up a little on its hind legs. It starts moving again like a bloodhound in search of its prey. It zigzags with its nose to the ground, sniffs the air, then retraces its steps again and again. The distance between the doe and the bear gets shorter and shorter. After about twenty minutes, when the bear is just a few dozen metres away, the doe leaps sideways, but does not flee. Then surprisingly, she starts jumping about in all directions in front of the predator. Drawing attention to herself would seem suicidal or desperate. The bear ignores the doe and goes back to sniffing determinedly in the direction the doe sprung out from. When it reaches its target, the bear plunges its head down into the grass, then walks away into the woods, clutching in its jaws the inert corpse of a fawn just a few weeks old. So this is what the doe wanted to protect: her newborn infant.

But when the opportunity arises, bears may also feed on hares, dormice, squirrels and voles. In the 1970s, bears rarely ate meat (only 2% of excrement) and exclusively of domestic ungulates (sheep and goats). However, since the 1980s, following reintroduction of red and roe deer to the central Apennines, Marsican bears eat meat ever more frequently. Among the various species bears prey on, red deer appear most often in their diet. The red deer is the most widespread and numerous wild species in the Park and also the most vulnerable, especially in certain seasons. 

Male bears generally consume almost twice as much meat as females, in line with their different life strategies. A female needs to accumulate mainly fat to carry a pregnancy to term, whereas for males, having a more powerful muscle mass enables them to compete in strength with other males. It is also true that males move around in much larger territories and are therefore more likely to come across available carcasses.

Consumption of wild ungulates peaks between April and June, during the first few months after the bears leave their den. Before the snow has completely melted, the bears go in search of animals that have died during the winter, been buried by avalanches or preyed on by wolves. A bear can sniff out the remains of a dead deer, even after dozens of days, especially if well preserved under snow. But during these months, the bears mainly prey on newborn deer and wild boar. Bears locate their prey by following the scent of the young or its mother, or by bursting into the herds in an attempt to flush out the mothers and make them flee so they can then locate the fawns.

As the season progresses, the young wild animals become less and less vulnerable, but sheep, goats, cows and horses make their appearance in the pastures, even high up in the mountains, and from July to September, these become the main source of animal protein for the bears. From October onwards, meat consumption drops to an annual low and bears eat almost exclusively wild prey. This season coincides with the mating season and the stags, worn out by fasting and exhausting fights to defend their harem of females, fall easy prey to bears and wolves. Many also die of starvation.

This may seem a paradox when you think, for example, that only one or two species of wild ungulate live in the boreal forests, whereas there may be as many as seven in southern Europe. Actually though, it’s not so surprising if you consider three factors: temperature, snow conditions and the availability of food. In northern latitudes, bears have very short summers and very long winters and they have very little time indeed to fatten up by eating mainly fruits and herbaceous plants. The hibernation period can last over six months and bears lose much more weight than do their southern counterparts. The trees in those forests do not produce nutritious energy-rich seeds, such as pine nuts, beechnuts, acorns or chestnuts. But the harsh, snowy winters debilitate the elk, making them an easy meal in the first few months after the snow melts. Its smaller size and physiological and morphological adaptations for a strictly vegetarian diet make the Marsican bear one of the brown bears most able to gain weight by feeding mainly on plants.

Brown bears are basically necrophages (in other words, they eat animals that are already dead), but they can also prey on red and roe deer, elk and even bison, albeit with less agility than wolves. It’s the opportunity that makes the bear a predator. The more a prey is vulnerable, available (present in large numbers) and accessible (non-aggressive and easy to isolate), the more likely it is to be chosen for an attack. The general rule is to avoid large, aggressive animals that could put the predator’s own life at risk. But even eating only carcasses is not such an obvious choice, because you can only benefit if you’re the only one eating them. The larger the carcass, the more likely it is to attract other competitors, but the smaller it is, the less likely it is to be found before being eaten by other scavengers. Bears have specialised in usurping carcasses killed by other predators such as wolves and lynxes, a phenomenon known as kleptoparasitism. So for bears, the best strategy is to prey on the young of a species, then to only attack the adults when they are at their weakest, or to feed on the carcasses of medium and large animals whenever possible.

A study carried out in the Park s in this area between 2006 and 2010, showed that domestic livestock accounts for an average of 63% of the biomass ingested by wolves, followed by wild prey (mainly wild boar and red and roe deer). However, a targeted study carried out in winter, when it is possible to follow the wolf tracks in the snow and interpret their behaviour, found that both solitary wolves and packs feed for 73% on pre-existing carcasses, with 76% of these being the carcasses of domestic animals that have died for reasons other than predation (such as disease and malnutrition). This suggests that the great availability of domestic animal carcasses in the Park may reduce the need, attitude and behaviour of a true predator such as the wolf. Bears are certainly among the first to take advantage of this situation, obviously in summer, when there are more domestic animals, and therefore also carcasses, available at high altitudes.

This is why bears prefer attacking domestic livestock. According to compensation reports, more than half of the bear damage reported is attributable to large domestic animals, followed by poultry, orchards and crops. Compensation reports compiled over the last twenty years show that sheep and goats represent the most preyed on category, followed by cows and horses. In the case of cows and horses, more than 90% of the animals preyed on are usually only a few weeks or months old, the most vulnerable category. The high frequency of attacks on sheep and goats can be explained partly by the lack of prevention systems, partly by particular environmental conditions (such as foggy or stormy days) and partly by the simple fact of their abundance in the Park. Attacks on cows and horses, on the other hand, are due to the habit of leaving livestock grazing unattended in high altitude meadows.

Getting to a carcass first is certainly an advantage for any animal. Bears can eat up to 40 kg of meat per day. If they find an intact carcass, they first gut it in search of the lungs, liver and heart, the most nutritious and digestible parts. The bear never touches the contents of the stomach or intestines and rarely eats the skin. The carcasses look as though they’ve been skinned. After the viscera, the preferred morsels are the rump and the parts nearest to the hind limbs. In the case of a stag, bears do not disdain the antlers, especially if still covered in velvet, or they may feed on the bony tips, rich in calcium and minerals. As skilful usurpers, bears try to secure exclusivity by partially burying the carcass with earth, leaf litter and branches, or where possible, by dragging it into the bushes or woods where they can eat it in peace, safe from danger or competitors. Some researchers have observed that bears do not consume the carcass immediately, but may wait up to three days before eating it. This would slow down decomposition and at the same time allow the meat to mature and thus become more palatable. Other bears use a more effective strategy to avoid theft, sleeping on the carcass, or guarding it at close range.

Anecdotal evidence suggests that in the Park it is rare for one bear alone to eat a cow or deer carcass. An average of at least three bears have been observed feeding on the same carcass on the same day, rarely together, as well as wolves, foxes and griffon vultures. The links between predators are very complex. Researchers have shown that bears generally prevail over other predators such as wolves, even when these are in groups, while other predators act as facilitators for the bear, in other words, they provide them with free carcasses. It is surprising how even the simple act of eating or preying on another animal can affect the lives of numerous other animals, including birds, reptiles, amphibians and insects… even plants. But bears can be very aggressive towards other scavengers, even when these are other bears. Females with cubs tend to avoid carcasses if they can, as the presence of males in the vicinity can compromise the safety of their young. In Yellowstone National Park, one of the main causes of cub death is the simultaneous presence of males and females on the same carcass.

The great availability of domestic animal carcasses and their extensive use by bears confirm the importance of this resource in the diet of this species in the Apennines. What to do with livestock carcasses has always been a problem in the mountains, where it is often difficult or impossible to reach them with appropriate means of transport and tools to dispose of them. On one hand, these carcasses represent a very important source of nutrition. On the other, through a mechanism of food habituation, they may expose bears to increased risks of poaching, conflict, accidents and disease transmission.

Bears are always on the lookout for the most abundant and nutritious foods and this is why their diet is so diverse from season to season. In terms of energy, 65% of a bear’s diet consists of fruits and nuts, followed by herbaceous plants and insects (25%), domestic and wild ungulates (8%) and finally roots (2%). The diet of a bear in the Apennines is amazingly nourishing. In every season, it includes proteins, sugars and fats… an “explosive” mixture that ensures efficient digestion and rapid weight gain. All foods are not, however, the same and some play a really key role that a bear just can’t do without. But these animals are also very adaptable and if there is a shortage of a particularly important resource, they find a way to replace it.

Spring is when plants start to grow again. As the trees burst into bud, the meadows begin to turn green again, starting from the valley floor, then moving ever higher up the mountains as summer progresses. From late March to May, almost 40% of a bear’s diet is made up of herbaceous plants. Bears feed mainly on grasses, taking advantage of the more digestible and nutritious first clumps, but they also eat tree buds. From June and throughout July, bears prefer to eat the roots, leaves and flowers of other herbaceous plants, three times more nutritious than grasses. But consumption of plants during the spring is minimal following a year with a bumper crop of beechnuts, when the nuts that fell to the ground the previous autumn make up more than 30% of the bears’ diet. They continue eating these beechnuts until the end of July, although to a lesser extent. Red and roe deer and wild boar make up an important part of the bears’ diet in both spring (13%) and early summer (5%). From June, with the start of the grazing season, domestic ungulates also make an appearance in the diet (4%). Bears can nevertheless meet their animal protein and fat requirements by feeding mainly on insects (such as ants) which represent between 32% and 48% of the diet, depending on the year. From March to July, bears also get their fill of the highly digestible sugars contained in rosehips in spring and both wild and domestic cherries in early summer.

As the summer progresses, the bears’ appetite increases, as does their weight. From August onwards, they in fact enter the period of so-called “hyperphagia”, peaking in autumn, when bears require three times as much energy as in the spring. From the end of September, brown bears can consume up to 20,000 kilocalories, even putting on more than a kilo per day. But during this period, putting on weight means above all accumulating fat reserves, and bears achieve this by feeding on sugar-rich fruits easily converted into adipose reserves. Between August and September, a bear’s diet is essentially frugivorous, with fruit contributing more than 70% of their energy intake. They consume around twenty different species of berries and larger fruits, but the key resource is the alpine buckthorn, a berry just a few millimetres in size that ripens on high-altitude scree and can contribute from 30% to 70% of the diet, depending on the year. Although very high in proteins and lipids, nuts contribute little during the summer, except in years of abundant beechnuts, when their consumption quadruples. Bears also feed on insects, herbaceous plants, livestock, wild ungulates and roots. Each of these resources contributes from 2% to 8%. As early as July, the insects they feed on include bees, bumblebees and the larvae of flies and other insects, the latter probably associated with the consumption of carcasses.

But it is in autumn that the diet of a bear gets really “fatty”. During this season, as well as eating fruit, especially apples and pears, bears also consume nuts, rich not only in sugars, but also in oils and proteins. Nut consumption peaks during this season and can account for from 49% to over 90% of the diet. The predominant nuts in a bear’s autumn diet are acorns (the fruits of turkey, downy and other species of oak) and beechnuts. Acorns are produced in roughly the same quantity year after year, but every 2 to 5 years or so, there is a bumper crop of beechnuts. Years with massive beechnut production, well above the long-term average, are known in Italian as “pasciona”. In these years, bears feed almost exclusively on beechnuts. In all other years, bears compensate for the scarcity of beechnuts by feeding on at least fifteen other species of berry and fruit, in addition to pears, apples and acorns. The rest of their diet consists of herbaceous plants, coinciding with the second phase of vegetative growth at higher altitudes, deer and insects. Autumn coincides with the deer’s breeding season and males in particular, undernourished and weakened by their “amorous” battles, become easy prey for wolves and bears.

Data on bears’ diets would seem to confirm the richness of Apennine ecosystems. There has never been evidence of nutritional stress among the bears captured and monitored during the years of study, indicating that years when all kinds of food resource are scarce are very rare indeed, at least within the Park. These conclusions are further reinforced by a study conducted in 2013 and 2014 in which the diet of eight bears was reconstructed using an alternative technique (analysis of the stable isotopes contained in hair samples). The study found that the diet of each bear both overlaps and differs from that of other bears, again highlighting the fact that these animals have many different types of food available. Since the birth and survival of the cubs is closely linked to the health of their mother, and since average birth rates have remained high over the past 15 years, it can also be assumed that the bears have always found enough food to eat.

According to research, bears in the Park appear to have a very “wild” diet and eat mainly natural foods, in other words, no notable dependence on human-derived foods has been documented. Bears may, however, sometimes eat domestic animals and fruit from cultivated plants (such as damsons, plums, cherries, apples and pears), a phenomenon favoured by the overlap between the bears’ territories and cultivated land or pastures. In the entire park area, including the external protection zone, there are generally just a few dozen cases per year of damage to crops (mainly involving pear, apple and cherry trees), while damage to livestock is no more than double this, most commonly involving livestock, farmyard animals and beehives.

Some bears may, however, become bolder and even go in search of food in populated areas. Studies demonstrate that this phenomenon may be caused by a multitude of often interacting factors (age, sex, the animal’s temperament, social hierarchy, the seasonal and annual fluctuation of natural food sources and the availability and accessibility of human-derived food sources). For a bear that needs to gain tens of kilograms in a few months, any food of human origin is equivalent to “fast food”… nutritious, appetising, plentiful and easy to acquire. Under these conditions and especially in a protected area where they feel safe, some bears give in to temptation and may get used to frequenting built-up areas where there is little competition with other bears. This phenomenon could also be triggered by human carelessness. Research has shown widespread consumption of roots, which are nothing but the carrots left in vast quantities for cows and horses out to pasture. As well as creating dependency (tons of carrots are available throughout the summer), this resource has also been associated with the onset of confident (loss of mistrust of humans and frequentation of populated areas) and problematic (chronic damage to human activities) behaviour.

As can be expected, the resources bears feed on naturally fluctuate from year to year and this will be ever more the case in the light of current and future climate change. Prudent and proactive “bear-proof” management should aim to maintain abundant and mature populations of beech and oak trees, in order to preserve the long-term availability of all the other key resources. All this, in parallel with the adoption of a series of good practices aimed at reducing the sources of attraction for bears in populated areas and their dependence on human-derived resources, the origin of conflicts more social than economic.

Bear tracks lead up the valley floor and disappear into the beech forest, from where the bear will not emerge again until at least the end of March.
With the onset of winter, bears find themselves facing unfavourable conditions, with freezing temperatures and food shortages. They are, however, true strategists and spend all winter resting safely in a den. But their rest is more than just immobility.
Between the fourth and second week before the long winter sleep, bears in the Apennines gradually become lazier and more nocturnal. They limit their movements to no more than a kilometre from their future winter shelter and lose their appetite, until they enter a genuine state of dormancy, known more correctly as hibernation. In this state, bears do not feed, defecate or urinate. Their breathing slow down at 1 to 2 breaths per minute, white their heart rate at 8-10 beats per minute. Their metabolism “takes a break”. They literally “cool down” and their body temperature may drop as low as four to five degrees Celsius. And something amazing happens… it is precisely during this period that the pregnant females are about to give birth.

Bears manage to counteract all the problems associated with months of immobility, fasting and urine retention. Something that smacks of magic even to the experts. To begin with, they don’t suffer from uraemia or dehydration. During hibernation, kidney function is drastically reduced and all urea is reabsorbed in the bladder. The volume of plasma flow decreases by 90%, as does oxygen consumption (up to 70% less) and filtration rate. Despite this, urea levels in the blood do not increase, quite the opposite, paradoxically they decrease.

How is that possible? Urea is a product of protein metabolism and during hibernation bears consume mainly fats. So urea production in bears is two to ten times slower in winter than in summer. In addition, the urea reabsorbed by the bladder passes into the intestinal lumen, where it is hydrolysed into ammonia by certain symbiotic bacteria. Once transported to the liver, the ammonia reacts with the glycerol released during lipolysis of the fat to produce amino acids, ideal to prevent loss of muscle mass. Incredibly, during hibernation the bears’ muscles do not, in fact, atrophy or lose strength. Bears lose just ten to fifteen percent of their muscle proteins and keep their muscles active and toned by shivering, with very short (about 0.2 seconds) muscle contractions repeated every three to ten seconds. Neither do bears suffer from osteoporosis, meaning their bone tissue doesn’t degenerate and lose density. They can therefore tolerate the high levels of fat in circulation without risking atherosclerosis or heart disease.

How long do bears hibernate? This depends on the interaction of numerous factors: environmental conditions, physical needs and the nutritional status of the animals. The first snowfall, a drop in outside temperatures, the hours of light and amount of food available in the wild are all decisive in triggering the beginning of the long sleep. At southern latitudes, for example, brown bears enter the den later and spend less time in hibernation than bears living at colder, snowier northern latitudes. But to determine the duration of hibernation, an optimal ratio between weight and accumulated fat is decisive. Where the energy balance of feeding during winter is more favourable than hibernation, it may be advantageous for some bears to remain active for all or part of the winter. In fact, in temperate climates where food sources are accessible even during winter, individuals with a delicate energy balance, such as young bears just a few years old, or females accompanied by cubs born during the summer, remain more alert than other bears. In the Apennines, most of the bears monitored spend the winter in the den, but in years with little snow and preceded by an autumn with abundant production of beech nuts or acorns, a juvenile and a female in the company of her two cubs spent the entire winter eating nuts.

In the Apennines, bears generally enter the den with the season’s first snowfall. Females are the first to retire around the end of November, but some may already be in their den as early as the first week of November. The latest generally wait at most until mid-December. Males wait longer. They usually make up their minds around 8 December, but may put hibernation off until the end of the year. Due to their size and weight, males consume energy more slowly and so can stay active longer. The reawakening of bears is as gradual as their entry into the den. They first go through a phase of “walking hibernation” and do not resume their normal pace until a week after leaving the den. At the end of March, males and females abandon their den, although females may wait until mid-April when the temperatures are rising the fastest and the snows are melting. The “sleepiest” are the pregnant females who usually enter the den first and may remain nearby until as late as the end of May, given that they need to take care of the still relatively immobile cubs.

More than half the bears studied generally used just one winter den throughout the entire hibernation period, while the remaining animals changed dens at least once between January and March, finding a second den within a few kilometres of the first. Although a den may be abandoned for natural reasons (floods, earthquakes), man is the main cause. During research, it was demonstrated that the abandonment of a den between January and February coincided with the passage of hikers. But the changes occurring between late February and March generally coincided with an increase in average seasonal temperatures, perhaps suggesting an early attempt to explore or move nearer to the spring feeding grounds. In fact, excrement was found in more than half the second dens, indicating that the bears had fed in the meantime.

The choice of an ideal shelter is critical as it must provide protection from adverse weather conditions and predators, especially in the case of nursing mothers. Bears may use their den as a simple bed, or they may even excavate a genuine underground “mini-apartment”. All depends on the local climate and geomorphology, together with, last but not least, the animal’s sex, age and, in the case of a female, whether or not she will be giving birth. But brown bears usually dig out a tunnel or look for natural caves. In the Apennines, the karst geomorphology provides them with a wide choice of cavities and natural caves. And in fact, a natural cavity offers not only physical protection, but also a relatively stable, dry and thermally and acoustically insulated environment. These characteristics are ideal in humid temperate environments where temperatures rarely fall below -10°C and where winter precipitation may sometimes be in the form of rain.

What is a bear’s den like in the Apennines? A den generally consists of an entrance, a tunnel or “antechamber” and a main “room”. The entrance is usually low and wide to encourage accumulation of snow in front, providing thermal insulation and reducing heat loss. The height and width of the chamber are proportional to the size of the bear and in most cases (80% of the dens examined) it contains a bed made of earth, leaves and twigs, ideal for insulating the animal from the ground. The small size of the den compared to the dimensions of the bear guarantees better thermal stability.

Bears generally do not use the same dens from one year to the next. However, one or more individuals may choose to hibernate in the same areas. What are the ideal requirements of a hibernation site? A stable temperature, security, tranquillity and proximity to spring foods. In the Apennines, bears select inaccessible, undisturbed locations. Most of the dens are situated at high altitudes (about 1600 m), below the limit of the trees in beech forests, on very steep slopes (with gradients of about 35°) and one to three kilometres away from roads or inhabited areas. Steep slopes at high altitudes also help keep the den thermally insulated. On one hand, the more abundant snow cover closes the entrance, on the other, these slopes are the first to be freed from the snow in the spring. Bears do not have a preferred exposure, but take into account the local microclimate deriving from the physical structure and vegetation in the area immediately surrounding the den (presence of rocks, trees and vegetation). Proximity to spring feeding areas would seem to be a factor, especially for females. In the first weeks after leaving the den, the females, in fact, tend to move around and feed in a limited area of about three to four kilometres around the location of the den.

The body temperature of bears decreases in the den, but only slightly, so they can still react to external stimuli. But what are a bear’s reactions if disturbed while sleeping? In the best of situations, the bears stay in their dens, but their heart rate and temperature increase and do not return to hibernation rhythms until two or three weeks later, with considerable consumption of energy reserves. On the other hand, as documented by a number of studies, the presence of human activities (forestry, hunting, the passage of people and research activities) even as far away as a kilometre (200 m at drastic levels) from a winter den can induce bears to move away. This is especially so if the disturbance occurs in the first few months after entry. When this happens, bears may experience significant weight loss (over 25%). In Sweden, a study of 90 bears fitted with tracking collars showed that 22% of bears leave or change dens during the winter. In the case of pregnant females in particular, this change led to the abandonment or death of the young. Under extreme conditions (for example, if the bears were captured and handled in their den), the abandonment rate rose to 92%. Some bears were able to find a new den, but only after several weeks and by travelling long distances, while others interrupted their winter sleep definitively. All this in extreme temperatures and with no opportunity to feed.

In the Apennines, almost half the known dens fall outside the protected area of the Abruzzo, Lazio and Molise National Park. The dates of den entry and exit coincide with the start of numerous human activities (hunting, forestry, dog training, sports and recreational activities, truffle hunting and the search for deer antlers) which could interfere with the bear’s dormancy.

With their massive build, these animals usually move at a slow pace. Their weight is greatly influenced by age and the season. They reach maximum weight in autumn, when they continue accumulating excess body fat until they become practically obese. Carrying this amount of weight greatly limits their speed of movement and modifies their posture, but it allows the bears to survive in a state of dormancy known as hibernation for up to six months without eating or drinking.

An adult Apennine male weighs an average of about 144 kg (between 66 and 205 kg), while females are lighter, with an average weight of 93 kg (68-151 kg). Each year, the weight of a bear can increase by as much as 30-40 kg before hibernation. Males are a total of 133-181 cm long with a shoulder height of from 71-100 cm, while females measure 122-150 cm and 62-87 cm respectively. When standing upright on its hind legs, a bear can therefore reach as much as a couple of metres in height. Bears are among the mammals with the greatest weight difference between birth and adulthood. The cubs are born prematurely and are defined as altricial. When newly born, they are blind and hairless and weigh no more than 500 grams. The growth of bears is concentrated during the first five years of life, but they may also continue growing as adults, especially the males, as size is an important factor in competition for females.

The limbs of bears have adapted to withstand the load of their “excess” weight. The muscles are well developed along the entire length of the limb. Their shoulder blades have become stronger and “disproportionately” large compared with other carnivores to provide a strong anchor point for the mighty “oversized” shoulder muscles. But the other bones of the forelimb are also characteristic. The humerus is more robust and the radius is slightly curved, while the morphology of the olecranon process has adapted to support the bicep muscles more effectively. The elbow and wrist joints have become more mobile, enabling the feet in particular to assume both supine and prone positions. Most carnivores walk on the tips of their feet, but like man, bears place their weight on the soles of their feet, a plantigrade posture providing support and stability. As a result, bears generally amble rather than run, but when they do run they can reach speeds of as much as 45-50 km/h, although over very short distances. Their strong and specifically structured limbs also give bears many other “powers”. They can climb anywhere to eat or escape danger, dig for food, build a winter shelter and manipulate objects with dexterity.

A bear’s tracks are unmistakable for their size, shape and the presence of five claws. The palms of the front and back feet consist of a thick adipose membrane covered by a thickened epidermis. Known as the plantar cushion, this is kidney-shaped and extends transversely in the front foot and pyriform and longitudinal in the back foot. The front foot of an adult bear is 9-15 cm long and 9-14 cm wide, while the back foot measures 14-23 cm and 8-19 cm respectively. The five strong, curved, non-retractile claws can be as much as 10 cm long. Being a plantigrade enables bears to stand upright on two legs, a posture they assume when uncertain or curious.

Bears have 36-42 teeth and complete their dentition at an age of about 15 months. The vestigial premolars are often deciduous, few in number, small, or even missing altogether in some individuals. Bears use their incisors and canines to seize and cut and molars to grind and crush. Their dentition has several characteristic features, including the presence of a diastema (toothless space behind the canines), also found in herbivores and ideal for tearing grass. A bear’s molars have a long, large surface and are particularly flat with a tubular appearance (bunodont teeth), ideal for grinding various kinds of food.

Marsican bears have a unique skull, shorter, wider, taller and with a much shorter rostrum than any other European brown bear. It is characterised by the expansion of the two supraorbital apophyses and greater distance between the two zygomatic arches, with consequent enlargement of the facial profile. From an evolutionary point of view, experts believe the enlarged temporal fossa to be a consequence of the expansion of the masseter-pterygoid and temporal muscles used in mastication, making for a stronger bite. This modification would appear to be associated with a higher content of fibrous plant material and nuts in the bears’ diet. The modified shape of the first molar would seem to confirm this hypothesis. Variations in the shape of the teeth, zygomatic arch and temporal fossa have also been observed in the exclusively vegetarian panda. Considered together with the exclusive presence of certain digestive enzymes specifically for herbaceous plants, the Marsican bear is one of the most specialised brown bears for a vegetarian diet.

Smell plays an important role in the lives of bears. When a bear moves through its territory, it uses its sense of smell to locate all the thousands of smells it encounters, whether food, water, mates, competitors or dangers. Recent studies have shown that these animals are able to communicate with each other by releasing and laying odorous chemical “trails”. The bear’s sense of smell is over two thousand times better than that of man, although comparable with other carnivores. The area of the brain responsible for the sense of smell (known as the olfactory bulb) is at least five times larger than the same area in the human brain and much more innervated than in other carnivores. The nasal epithelium of bears has hundreds of times more receptors than that of man. Some studies conducted on polar bears have shown that bears use air currents, positioning themselves downwind to pinpoint dead animal carcasses as much as several kilometres away. But bears are also very adept at locating food underground, including rodents, bulbs or insects.

Bears have very small eyes compared to the size of their brains and are to all intents and purposes short-sighted. Sight is used by bears in coordination with smell, for example, to identify the most palatable parts of a specific plant. Bears communicate by vocalising with other bears, but also with other competitive carnivores. For example, some studies have shown that bears and lynxes compete for carcasses by vocalising, using their calls to signal their presence and reduce competition. But their hearing also allows bears to locate small prey underground, or find carcasses of wild ungulates by following the sound of hunters’ gunfire. This shows that although their hearing is less acute and well-developed than in other carnivores, it nevertheless plays an important role in the life of bears.

A bear’s whole life revolves around finding food. They must put on weight to hibernate and breed. So it is not surprising that their morphology has evolved to enhance their ability to find food and compete, or that they use mainly the sense of smell to “define” their ecological and social world.

The phylogenesis of bears has been traced through palaeontology (the study of fossil remains) and genetics (the study of mitochondrial DNA and genetic makeup or genome). The bears alive today have relatively recent progenitors, but to reconstruct their history we have to go back several millions of years, to the subfamily Hemicyoninae and genus Cephalogale in particular. This group appeared for the first time in Eurasia during the mid-Oligocene, about 30 million years ago, from a branch that split off from the line that originated today’s canids. The first representatives of this genus were mostly very tiny, smaller than a fox, although some species could reach almost the size of modern bears. The first bears are thought to have derived from this genus during the Miocene, namely about 20 million years ago. These animals belonging to the Ursavus genus spread progressively through the Asian continent, North America and Europe, originating all today’s bears and their countless predecessors. The first line to break away was the Ailuropodidae subfamily (about 15 million years ago), that of today’s giant panda (Ailuropoda melanoleuca). Subsequently, between six to thirteen million years ago, a second split occurred, originating two other subfamilies: the Tremarctinae and the Ursinae. The former originated several species of bear that proliferated in North America, but the only one still surviving today is the spectacled bear (Tremarctos ornatus), widespread in South America.

As for the Ursinae subfamily, starting from Ursus minimus, a common progenitor that appeared about 4-5 million years ago, a first branch split off to originate three species of bear living in the Asian continent today: the Asian black bear (Ursus thibetanus), the sloth bear (Ursus ursinus) and the sun bear (Ursus malayanus). About 3.5 million years ago, a second line then split off in Asia and North America, originating the American black bear (Ursus americanus). About one to two million years ago, two branches then split off from a common progenitor known as Ursus etruscus: the  “dead” branch of cave bears including the well-known Ursus spelaeus and the branch that originated the polar bear (Ursus maritimus) and brown bear (Ursus arctos). The oldest brown bear fossil dating back to about half a million years ago was found in China, from where it then spread to Asia, Europe and North Africa. Brown bear fossils have also been found in Britain. Brown bears made their appearance in Alaska about 100,000 years ago, then spread further south no earlier than 13,000 years ago. Since their separation from the polar bear, brown bears have diversified into at least six groups, or clades, many of which have survived to the present day, thanks to their isolation in refuge areas formed during the Ice Age.

During their evolution, bears became specialised for a diet of herbaceous plants and fruits. Exceptions with a strictly carnivorous diet are the polar bear and a number of extinct species. In bears, the evolution from carnivore to omnivore with a particular predilection for plant food involved elongation of the molars and the transition from transverse to sagittal mastication, giving them greater strength and the ability to shred. The first evidence of an omnivorous diet in the evolutionary line of bears dates back to the Miocene (about 15-12.5 million years ago), with the discovery in North America of bone remains of Aurorarctos tirawa, one of the  “original” bears and a contemporary of Ursavus.

In carnivorous mammals, such as canids, the larger the species, the greater the consumption of meat. Some experts believe the anatomical transition in mastication coincided with the bears’ particular ability to hibernate. This characteristic adaptation allows bears to overcome the ecological limits imposed by their large body size, namely, the need to ingest a considerable quantity of food, enabling them to cope with seasonal fluctuations in the availability of resources or the drastic climate changes that accompanied their evolution. The adaptation of hibernation seems to have appeared in the Miocene as an optional choice, depending on the latitudes where the bears lived and the presence or absence of snowy winters. The two bear species alive today that do not hibernate originated during the Pliocene in the climates of the lower-middle temperate zone of the American continent (spectacled bear) and Indian subcontinent (sloth bear), with the appearance of colder, drier climates and markedly seasonal rainfall patterns. But it was in the cold Arctic climates of the temperate zones during the Pleistocene glaciations that the pronounced seasonality made it obligatory to spend the winter in a state of dormancy, as is still the case today for most living bear species.

Analysis of mitochondrial DNA (transmitted exclusively through the maternal line) has enabled the main phylogenetic lines of brown bears in Europe to be reconstructed, allowing the bears to be classified into genetically distinct population groups. This produced a very complex tree of clades and sub-clades. To put it simply, three main lines can be distinguished in Europe: an eastern line present in Romania, Slovakia, Estonia, Finland and northern Sweden; a north-western line present in the Pyrenees, Norway and southern Sweden; a south-western line distributed over the Alps, Apennines, Balkans, Greece, Bulgaria and Romania. The first brown bear fossils found in Italy date from about 7000-5500 years ago, when bears were probably distributed continuously over the whole peninsula. Recent studies have highlighted the uniqueness of the mitochondrial DNA of Apennine bears, although an affinity with the south-western Alpine-Balkan line has been identified. This apparent contradiction is resolved by research carried out on the whole genome, showing that the Marsican brown bear population has been completely isolated from this line for more than 3000-4000 years..

The isolation, associated with a progressive reduction in numbers, would seem to have begun as early as 8000 years ago and accelerated drastically from 600 years ago until more recent times. The increase in the numbers of humans, deforestation associated with the development of farming and direct mortality at the hand of man were undoubtedly decisive factors in bringing about the decline in numbers and reduction in the distribution area of the bear population. Reproductive and genetic isolation in numerically small populations, intensified by phenomena associated with adaptation to local environmental conditions, can lead to profound genetic, but also morphological and behavioural, changes in individuals. And that is what happened to the bear in the Apennines. Apennine bears, in fact, have a completely different skull structure from other brown bears, greater physiological adaptations to a vegetarian diet and a much more peaceful disposition. Confirming the intuition of naturalist and zoologist Giuseppe Altobello in the early 1920s, the differences observed have led many experts to consider the Apennine bear as a unique subspecies, known as Ursus arctos marsicanus.

The Apennine population has low genetic diversity, high levels of inbreeding and a considerable decrease in effective population size (the number capable of breeding and thus able to produce new individuals). All this can contribute to reducing the capacity of these bears to survive, breed and adapt.

Bears are physiologically adapted to overeat and to convert any excess calories efficiently into body mass. To survive, bears need eight to nine times more energy than other carnivores. Their only goal is to become obese, with the advantage over us that they can do so while remaining healthy. If we ate like a bear, we would suffer from diabetes, heart problems and high blood pressure. In less than seven to eight months, a bear may put on as much as 30-40 kg of weight. But in nature, nothing happens by chance.

In the Apennines, bears may spend up to five months in the den, a strategy developed to save energy in a season when food is scarce. Between November and December, both males and females enter a lethargic state known as hibernation, not eating, drinking, defecating or urinating . Their breathing and heart rate slow down and the energy costs of an active life are decreased by more than 70%. In order to survive this fast, bears therefore have nothing but the fat reserves accumulated during the rest of the year to rely on. When a bear wakes up, it may have lost up to 20% of its weight before entering the den. So for a bear, it’s better to put on a few extra kilos before the long sleep. But not all bears can spend the winter “in economy mode”. If a female has mated in the spring, when she enters the den, the embryo starts developing again after a period of “quiescence” known as diapause. This culminates between January and February when she gives birth. While the mother is still “sleeping”, the cubs are awake and active. They must be fed and kept clean and warm. So when she wakes, a mother may have already lost almost 50% of her accumulated fat reserves. To successfully survive this delicate phase, a female therefore needs to focus on gaining as much weight as possible during the year.

Some researchers have shown that implantation of the embryo and subsequent development of the foetus only occur in females that have managed to accumulate 20% to 30% of body fat. Cubs are born weighing less than 500 g, but when they leave the den at three to four months old after being nourished exclusively on milk, they can weigh as much as 5-9 kg. Nursing females therefore need to produce milk with a very high fat (about 18%) and protein (about 6%) content and before winter they need to supplement their diet with abundant protein. This enables their offspring to put on weight rapidly, not only in the den, but also during the first few months after birth when the female will have to think not only of feeding her young, but also herself.

Although classified as carnivores, bears eat far less protein than this definition suggests. To gain weight, their diet needs to be a well-balanced mix of proteins, fats and carbohydrates. An unbalanced diet, for example, lacking in protein with respect to the other macronutrients, would double the maintenance requirement and make it more difficult to gain weight. When protein is lacking, instead of putting on weight, bears lose it rapidly. On the other hand, the same would happen with a high-protein diet, albeit with much more gradual effects over a longer period of time. Several studies in captivity have shown that if bears are able to select their food each day, they choose a mixed diet, with proteins accounting for about 17% of the assimilated energy and the addition of foods rich in fats, or if not available, carbohydrates. In nature, it’s harder to eat an optimum meal every day, not least because the availability of resources varies with the seasons. So the bears balance their diet over a much longer time scale of months rather than days.

They accumulate lean mass mainly in spring and early summer and body fat in midsummer and autumn. This diet coincides with the seasonal availability of food. In the first few months after leaving the den, the bears eat foods richer in proteins than energy (herbaceous plants for example), then when fruits ripen in summer and autumn, they have much higher calorie foods at their disposal, providing fats and carbohydrates to help balance the protein excess in spring. This rule is followed by all species of temperate zone bears, from the more “vegetarian” black bears to the more “carnivorous” species such as the grizzly. Due to their smaller size and therefore lower energy requirements, black bears are also able to maintain their body mass during the spring months, or even to gain weight. Considering that a Marsican bear is on average even smaller than a black bear, an animal in the Apennines can probably put on weight throughout the entire year. But that’s not all. Apennine bears have access to a mixed diet rich in high energy foods throughout the year, undoubtedly making it easier for them to stay fit and healthy.

Bears plan their life around what they can find to eat. This means that during the year, their physiology and behaviour may change many times. The timing of these animals is amazing, but evolution is not to be taken lightly! Bears have, in fact, evolved specifically to enable them to optimise resources, time and energy.

In the early summer months, when calorie-rich foods are scarce, bears invest their energy in reproducing, in other words, mating or raising their offspring. During this period, a high-protein diet is beneficial to both males who have to compete with each other and females who have to nurse their young. In this period of “hypophagia”, bears have less appetite and need less energy. In females, after fertilisation, foetal development stops at a few cells. When the season of plenty comes, the bears can therefore concentrate exclusively on feeding, minimising any further expenditure of energy. Summer, in fact, ushers in the period of “hyperphagia”, when the bears’ appetite increases exponentially, as does their energy requirement. With the arrival of winter when food supplies begin to run out, the bears finally stop feeding and leading an active life. Mothers in particular devote themselves solely to caring for their young.

Bears have a very simple digestive system, consisting of an oesophagus, stomach and small and large intestines. Unlike herbivores such as deer or horses, they therefore lack a specialised chamber (caecum or rumen) where, thanks to symbiosis with bacteria, complex carbohydrates such as herbaceous plant fibres can be digested. Bears in general, and Marsican bears in particular, have few adaptations for a vegetarian diet. These consist of their dentition and skull structure, allowing them to fragment the plant matter in their diet more efficiently, and specific enzymes to digest plants. A bear’s digestion times are therefore very rapid and sufficient to efficiently assimilate proteins, lipids and simple carbohydrates only. So for a bear, meat is 90% digestible, fruits 60% digestible, and grass just 30% digestible. But on the other hand, herbaceous plants are the most common and rich in proteins, although with a lower calorie content. Insects, particularly ants, contain fewer calories than meat, but are easy prey and very high in protein and rare amino acids. Bears know how to exploit the qualities of each food. For example, in the case of herbaceous plants, the limiting factors are poor digestibility and low nutrient content. The bears therefore go in search of the first shoots, or the most nutritious vegetative parts (buds, leaves and roots) which they eat in large quantities. In the case of berries, the limiting factors are mainly size and weight. So in order to obtain a satisfying mouthful, bears have to seek out the richest bushes, or fruits growing in clusters. In either case, having time to feed is a factor in their favour.