Winter has been a critical period for traditional societies in Europe since times immemorial. People, of course, were aware that the turn of the seasons would eventually bring back spring, sun and food. They knew that the slow, imperceptible change would start when the days are short and cold, and the nights are long and bleak. Despite this, they would crave some reassurance that spring would indeed return, the snow would melt and the plants would thrive again.

Many historians and anthropologists think that this fear from eternal winter and the anticipation of spring are at the core of old and present-day religions, and of countless rites and rituals practised in the coldest months of the year. Christmas is the best known example: the birth of Jesus is celebrated on the date of an old pagan feast dedicated to the rebirth of the sun. The day is close to the actual date of the winter solstice, which marks the longest night in the year.

Bulgarians were not an exception. In winter and early spring they would celebrate several feasts with rites designed to ensure that the new cycle of life would start again. The dances of the kukeri, or mummers, are the most spectacular.

Dressed in animal skins, with faces hidden behind monstrous masks, the kukeri dance in the streets surrounded by the clang of sheep and cowbells hanging on their belts. The cacophony of noises and movements seem chaotic but is far from it. There is a clear concept behind the mummers' behaviour, a strong hierarchy and even a script.

The mummers organisation and costumes, the dates when they dance and even their names vary across the Bulgarian lands. For example, what is known as kukeri in eastern Bulgaria become babugeri west of Sofia. They can also be called survashkari, mechkari, dervishi, startsi and mechkari.

The group consists of masked unmarried men. They are led by a chief kuker who is usually a married man considered a pillar of the society. On this day, however, his behaviour can be less admonitory. Chasing the women in the streets, he aims to touch their legs with a long, red painted staff. The symbolism is clear: the rite ensures that more babies would be born in the community.

The chief kuker is usually joined by a man dressed as a hag carrying a ragdoll baby. This kuker's wife is the chief target of the villagers, who would try to abduct her or her baby. When this happens, the chief kuker would go into a mock rage and fight to bring back his wife and child. The couple would also perform a pantomime of sex.

Meanwhile file-and-rank kukeri would dance, go from home to home, dance more and collect food donated by the hosts. Their group can include other characters that openly mock the established social order. A fake priest would chastise people, a mock tax collector would "arrest" them in the streets and demand exorbitant sums of money, a barber would try to shave them with a grotesquely big wooden razor, a fake Gypsy musician would force a man clad as a bear to dance, and so on and so forth.

The chief kuker is not the only person of importance during the day. The rite would be impossible without a "king." Dressed in the villagers' idea of royal attire and accompanied by a group of bodyguards or ministers, he has an important task. When the day turns, the king and the whole village would gather for an outdoor feast. The king would not eat by himself, letting his bodyguards feed him. When he is finished, he would ritually plough the ground and sow some grain in it in a ritual that is supposed to provide fertility.

Kukeri costumes are meant to be scary. In different parts of the Bulgarian lands this is achieved through different means. In the west, fur, animal hides and birds' wings are the norm, while in the east there is a preference for colourful rags and sequins. The mummers in the west would dance immediately after Christmas and around New Year, while their brethren in the east would roam the streets in the days before Lent.

The tradition's pagan origins are evident. The established theory claims that the Bulgarian kukeri are the descendants of ancient Thracian Dionysian rites. Whatever the kukeri origins, their recent history has changed significantly.

Until the early 20th century, the kukeri dances were vital for rural communities. When the Bulgarian society started to urbanise itself and young people began to emigrate to the cities, the rite started to lose its base, meaning and significance. As it was slowly dying in the villages, nostalgia for the idealised rural life turned mummers into a symbol of "true Bulgarianness" despite the fact that the tradition is hardly unique for Bulgaria and is present in one form or another across Europe – and even as far as Japan. Their rowdy behaviour was tamed, anything resembling sex or mocking the established order was cleansed. The change took place under Communism, a time of rapid urbanisation and modernisation, but also of revived nationalism. By the 1960s, the government was eager to invent a new Bulgarian identity that was both nationalist and Communist. Kukeri, along with folk music, traditional costumes and crafts, were reinvented. Mummers became a modern festival, a spectacle for the eye emptied of its ancient spirit. The obscene antics disappeared and the dances were choreographed and sterilised. Kukeri were reduced to funny figures wearing impressive masks. They were promoted as bringers of health and good fortune to the guileless public, which was itself alienated from its own rural past and traditions.

The trend deepened after the collapse of Communism, when emigration from the villages continued, depopulation took over and nationalism rose, combined with consumerism. The two big festivals dedicated to kukeri dances, Surva in Pernik and Kukerlandia in Yambol, are both organised in towns, not in villages where the natural ground of the rite is. Both events feature troupes from all over Bulgaria and even abroad who compete on who can produce the most spectacular show and costumes. This has resulted in the creation of elaborate masks that would be unthinkable just 50 years ago. Participants also change – some mummer troupes include women and children, a grave disregard for the original essence of the rite, which is dedicated to the fertilising power of men. Some troupes have even monetised their experience – you can book them to put up dance for a wedding feast, regardless of the time in the year.

Of course, there are people who try to keep the tradition alive as close to the original – whatever original in folklore is.

Some of the best places to see kukeri and experience their magic are the villages around Pernik, Razlog and Yambol.

This article is illustrated with images of the mummers troupe in the village of Mogila, near Yambol