Distance-based Criteria to Identify Minimum Number of Brown Bear Females with Cubs in Europe

Distance-based Criteria to Identify Minimum Number of Brown Bear Females with Cubs in Europe. Ordiz, A., Rodríguez, C., Naves, J., Fernández, A., Huber, D., Kaczensky, P., Mertens, A., Mertzanis, G., Mustoni, A., Palazón, S., Quenette, P. Y., Rauer, G., & Swenson, J. E. Ursus, 18:158–167, 2007.

Pdf doi abstract bibtex

Counts of females with cubs-of-the-year (FWC) have been used as an index for monitoring brown bear (Ursus arctos) populations or estimating a minimum number of adult females in several small and medium-sized populations. Because discriminating among family groups is crucial to this procedure, we sought to improve criteria used to differentiate among FWC using spatial and temporal distances between sightings. We used telemetry data from 11 FWC from southern and central Europe and 15 FWC from Sweden to determine the likelihood that observations were of the same FWC based on the distance moved and elapsed time period. Euclidean distances traveled by each FWC were estimated daily. We then calculated straightline distances traveled by each FWC using intervals of 1-180 days, or the maximum available. We obtained the maximum values (highest percentiles) of distances over time for each FWC. We considered 2 periods of bear activity: early spring, from first observations after denning until 30 June, and the remaining active season from 1 July until the onset of denning. Native FWC living in the boreal forest of Scandinavia moved farther than those living in the temperate forests of southern and central Europe. Differences among FWC in southern and central Europe may be related to habitat characteristics and to the origin (native or released) of the bears we studied. For example, based on the upper 95% prediction interval of the curve fitted of the 80 percentile in the early spring-June period, 2 observations 30 days apart are unlikely to be of the same individual if \textgreater13 km apart for FWC in the boreal forest, \textgreater15 km and \textgreater7 km, respectively, for released and native FWC in southern and central Europe. Our findings may be useful for biologists and managers to help differentiate FWC and thereby estimate the minimum number of family groups present, particularly in areas with low densities of FWC.

@Article{Ordiz2007,
  author   = {Ordiz, Andr{\'{e}}s and Rodr{\'{i}}guez, Carlos and Naves, Javier and Fern{\'{a}}ndez, Alberto and Huber, Djuro and Kaczensky, Petra and Mertens, Annette and Mertzanis, Georgios and Mustoni, Andrea and Palaz{\'{o}}n, Santiago and Quenette, Pierre Y. and Rauer, Georg and Swenson, Jon E.},
  title    = {{Distance-based Criteria to Identify Minimum Number of Brown Bear Females with Cubs in Europe}},
  journal  = {Ursus},
  year     = {2007},
  volume   = {18},
  pages    = {158--167},
  issn     = {1537-6176},
  url_pdf  = {http://uni-goettingen.de/de/document/download/ab42507a6315e034304d480142c8185a.pdf/Ordiz_et_al_(2007)_URSUS_criteria_to_identify_number_of_brown_bear.pdf},
  abstract = {Counts of females with cubs-of-the-year (FWC) have been used as an index for monitoring brown bear (Ursus arctos) populations or estimating a minimum number of adult females in several small and medium-sized populations. Because discriminating among family groups is crucial to this procedure, we sought to improve criteria used to differentiate among FWC using spatial and temporal distances between sightings. We used telemetry data from 11 FWC from southern and central Europe and 15 FWC from Sweden to determine the likelihood that observations were of the same FWC based on the distance moved and elapsed time period. Euclidean distances traveled by each FWC were estimated daily. We then calculated straightline distances traveled by each FWC using intervals of 1-180 days, or the maximum available. We obtained the maximum values (highest percentiles) of distances over time for each FWC. We considered 2 periods of bear activity: early spring, from first observations after denning until 30 June, and the remaining active season from 1 July until the onset of denning. Native FWC living in the boreal forest of Scandinavia moved farther than those living in the temperate forests of southern and central Europe. Differences among FWC in southern and central Europe may be related to habitat characteristics and to the origin (native or released) of the bears we studied. For example, based on the upper 95{\%} prediction interval of the curve fitted of the 80 percentile in the early spring-June period, 2 observations 30 days apart are unlikely to be of the same individual if {\textgreater}13 km apart for FWC in the boreal forest, {\textgreater}15 km and {\textgreater}7 km, respectively, for released and native FWC in southern and central Europe. Our findings may be useful for biologists and managers to help differentiate FWC and thereby estimate the minimum number of family groups present, particularly in areas with low densities of FWC.},
  comment  = {public},
  doi      = {10.2192/1537-6176(2007)18[158:DCTIMN]2.0.CO;2},
  isbn     = {1537-6176},
  pmid     = {9312},
}

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Because discriminating among family groups is crucial to this procedure, we sought to improve criteria used to differentiate among FWC using spatial and temporal distances between sightings. We used telemetry data from 11 FWC from southern and central Europe and 15 FWC from Sweden to determine the likelihood that observations were of the same FWC based on the distance moved and elapsed time period. Euclidean distances traveled by each FWC were estimated daily. We then calculated straightline distances traveled by each FWC using intervals of 1-180 days, or the maximum available. We obtained the maximum values (highest percentiles) of distances over time for each FWC. We considered 2 periods of bear activity: early spring, from first observations after denning until 30 June, and the remaining active season from 1 July until the onset of denning. Native FWC living in the boreal forest of Scandinavia moved farther than those living in the temperate forests of southern and central Europe. 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