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Detection of pregnancy in a hibernator based on activity data

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Abstract

Pregnancy and parturition are often difficult to detect in wild-living animals, especially in species that give birth to altricial young in burrows or caves. Current methods to detect pregnancy and birth in hibernating animals often entail disturbances that can affect the animals' reproductive success. We developed a new method to confirm pregnancy and parturition in hibernating brown bears (Ursus arctos) using activity data recorded in dual-axis motion sensors mounted on GPS–GSM neck collars on 30 brown bears during 52 hibernation seasons in Sweden. We adjusted recorded activity to the individual basal activity level for each bear. Pregnant females showed characteristic activity patterns during the period of pregnancy, with significantly higher daily activity levels and frequency of active periods during pregnancy than nonpregnant bears. Pregnant females were active on average 2.20 times more often during the pregnancy period than during the postpartum period, compared with 0.97 times for nonpregnant females. A pregnancy index was defined as the average of the proportion of mean daily activity levels and the proportion of activity events during the pregnancy period compared with the postpartum period. It averaged 2.61 ± 1.73 (SD) for pregnant females and 0.94 ± 0.24 for nonpregnant females. Using this method, we evaluated a group of adult females that had an unverified reproductive status but were classified as not pregnant because no cubs had been observed after den emergence. The results suggested that 35 % of those females had, in fact, been pregnant.

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Acknowledgments

We thank the Swedish Environmental Protection Agency, the Norwegian Directorate for Nature Management, the Swedish Association for Hunting and Wildlife Management, the Research Council of Norway, and the Austrian Science Foundation (project P20182) for funding the Scandinavian Brown Bear Research Project. We also thank the Vereinigung von Freunden und Förderern der Goethe-Universität Frankfurt in Germany for their financial support. This is scientific paper no. 151 from the Scandinavian Brown Bear Research Project.

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Authors and Affiliations

  1. Department of Biological Sciences, Goethe University Frankfurt, BioCampus—Niederursel, Max-von-Laue-Straße 9, 60438, Frankfurt am Main, Germany

    Andrea Friebe

  2. Faculty of Arts and Science, Department of Environmental and Health Studies, Telemark University College, No-3800 Bø i, Telemark, Norway

    Andreas Zedrosser

  3. Institute for Wildlife Biology and Game Management, University for Natural Resources and Life Sciences, Vienna, Gregor Mendel Str. 33, 1180, Vienna, Austria

    Andreas Zedrosser

  4. Department of Ecology and Natural Resources Management, Norwegian University of Life Sciences, Post Box 5003, NO-1432, Ås, Norway

    Jon E. Swenson

  5. Norwegian Institute of Nature Research, Post Box 5685, Sluppen, NO-7485, Trondheim, Norway

    Jon E. Swenson

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  1. Andrea Friebe
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Correspondence to Andrea Friebe.

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Communicated by C. Gortázar

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Friebe, A., Zedrosser, A. & Swenson, J.E. Detection of pregnancy in a hibernator based on activity data. Eur J Wildl Res 59, 731–741 (2013). https://doi.org/10.1007/s10344-013-0728-5

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