and needs the introduction of unrelated animals for "blood refreshment". In the long term, authorities hope to establish a population of about 1,000 animals in the area. One of the northernmost current populations of the European bison lives in Vologodskaya Oblast in the Northern Dvina valley at about 60°N. It survives without supplementary winter feeding. Another Russian population lives in the forests around the Desna River on the border between Russia and Ukraine. The north-easternmost population lives in Pleistocene Park south of Chersky in Siberia, a project to recreate the steppe ecosystem which began to be altered 10,000 years ago. Five wisents were introduced on 24 April 2011. The wisents were brought to the park from the Prioksko-Terrasny Nature Reserve near Moscow. Winter temperatures often drop below −50 °C. Four of the five bison have subsequently died due to problems acclimatizing to the low winter temperature. Plans are being made to reintroduce two herds in Germany and in the Netherlands in Oostvaardersplassen Nature Reserve in Flevoland as well as the Veluwe. In 2007, a bison pilot project in a fenced area was begun in Zuid-Kennemerland National Park in the Netherlands. Because of their limited genetic pool, they are considered highly vulnerable to illnesses such as foot-and-mouth disease. In March 2016, a herd was released in the Maashorst Nature Reserve in North Brabant. Zoos in 30 countries also have quite a few bison involved in captive-breeding programs. Cultural significance Representations of the European bison from different ages, across millennia of human society's existence, can be found throughout Eurasia in the form of drawings and rock carvings; one of the oldest and most famous instances of the latter can be found in the Cave of Altamira, present-day Spain, where cave art featuring the wisent from the Upper Paleolithic was discovered. The bison has also been represented in a wide range of art in human history, such as sculptures, paintings, photographs, glass art, and more. Sculptures of the wisent constructed in the 19th and 20th centuries continue to stand in a number of European cities; arguably the most notable of these are the zubr statue in Spała from 1862 designed by Mihály Zichy and the two bison sculptures in Kiel sculpted by August Gaul in 1910–1913. However, a number of other monuments to the animal also exist, such as those in Hajnówka and Pszczyna or at the Kyiv Zoo entrance. Mikołaj Hussowczyk, a