1 Department of Wildlife Conservation, Institute of Nature Conservation of Polish Academy of Sciences, Mickiewicza 33, 31-120 Krakow, Poland
2 Department of Epizootiology with Clinic of Birds and Exotic Animals, Faculty of Veterinary Medicine, Grunwaldzki Square 45, 50-366 Wroclaw, University of Environmental and Life Sciences, Wroclaw, Poland
3 Department of Evolutionary Biology and Conservation of Vertebrates, Institute of Environmental Biology, University of Wroclaw, Sienkiewicza 21, 50-335 Wroclaw, Poland
4 Department of Biology, Faculty of Veterinary Medicine, University of Zagreb, Heinzelova 55, 10000 Zagreb, Croatia
Bears undergo some significant changes reflected in blood values during winter season. The most significant are reduced urea and increased creatinine, by some authors considered to be physiological indicators of hibernation. Studied group of six captive brown bears (Ursus arctos) showed decreased activity in winter but were accepting food and walked outdoors. Blood parameters assessed in February 2011 revealed mean values of leucocytes and neutrophils as significantly lower, and creatinine significantly increased compared to captive and free living bears sampled during other seasons when bears are active.
Chang G, Mao FC, Yang C, Chan F (2006) Hematological profiles of the Formosan black bear (Ursus thibetanus formosanus). Zool Stud 45: 93-97.
Evans A, Sahlen V, Stzen O, Fahlman D, Brunberg S, Madslien K, Frobert O, Swenson JE, Arnemo JM (2012) Capture, anesthesia and disturbance of free-ranging brown bears (Ursus arctos) during hibernation. PLoS One 7: e40520.
Fröbert O, Christensen K, Fahlman Å, Brunberg S, Josefsson J, Särndahl E, Swenson JE, Arnemo JM (2010) Platelet function in brown bear (Ursus arctos) compared to man. Thromb J 8: 11.
Hellgren EC (1998) Physiology of hibernation in bears. Ursus 10: 467-477.
Hissa R (1997) Physiology of the European brown bear (Ursus arctos arctos). Ann Zool Fenn 34: 267-287.
Hissa R, Siekkinen J, Hohtola E, Saarela S, Hakala A, Pudas J (1994) Seasonal patterns in the physiology of the European brown bear (Ursus arctos arctos) in Finland. Comp Biochem Physiol A Physiol 109: 781-791.
Huber D, Kusak J, Zvorc Z, Baric Rafaj R (1997) Effects of sex, age, capturing method, and season on serum chemistry values of brown bears in Croatia. J Wild Dis 33: 790-794.
Kusak J, Baric Rafaj R, Zvorc Z, Huber D, Forsek J, Bedrica L, Mrljak V (2005) Effects of sex, age, body mass, and capturing method on hematologic values of brown bears in Croatia. J Wildlife Dis 41: 843-847.
Nelson RA, Beck TD, Steiger DL (1984) Ratio of serum urea to serum creatinine in wild black bears. Science 226: 841-842.
Nelson RA, Wahner HW, Jones JD, Ellefson RD, Zollman PE (1973) Metabolism of bears before, during, and after winter sleep. Am J Physiol 224: 491-496.
Noyce KV, Garshelis DL (1994) Body size and blood characteristics as indicators of condition and reproductive performance in black bears. Int Conf Bear Res and Manage 9: 481-496.
Partridge J (1992) Management Guidelines for Bears and Raccoons. The Association of British Wild Animal Keepers, Bristol.
Spady TJ, Harlow HJ, Butterstein G, Durrant B (2009) Leptin as a surrogate indicator of body fat in the American black bear. Ursus 20: 120-130.
Stenvinkel P, Fröbert O, Anderstam B, Palm F, Eriksson M, Bragfors-Helin AC, Qureshi AR, Larsson T, Friebe A, Zedrosser A, Josefsson J, Svensson M, Sahdo B, Bankir L, Johnson RJ (2013a) Metabolic changes in summer active and anuric hibernating free-ranging brown bears (Ursus arctos). PLoS One 8: e72934
Stenvinkel P, Jani AH, Johnson RJ (2013b) Hibernating bears (Ursidae): metabolic magicians of definite interest for the nephrologist. Kidney Int 83: 207-212.