Rubbing behavior of European brown bears: factors affecting rub tree selectivity and density

Abstract

Scent-mediated communication is considered the principal communication channel in many mammal species. Compared with visual and vocal communication, odors persist for a longer time, enabling individuals to interact without being in the same place at the same time. The brown bear (Ursus arctos), like other mammals, carries out chemical communication, for example, by means of scents deposited on marking (or rub) trees. In this study, we assessed rub tree selectivity of the brown bear in the predominantly deciduous forests of the Cantabrian Mountains (NW Spain). We first compared the characteristics of 101 brown bear rub trees with 263 control trees. We then analyzed the potential factors affecting the density of rub trees along 35 survey routes along footpaths. We hypothesized that: (1) bears would select particular trees, or tree species, with characteristics that make them more conspicuous; and (2) that bears would select trees located in areas with the highest presence of conspecifics, depending on the population density or the position of the trees within the species’ range. We used linear models and generalized additive models to test these hypotheses. Our results showed that brown bears generally selected more conspicuous trees with a preference for birches (Betula spp.). This choice may facilitate the marking and/or detection of chemical signals and, therefore, the effectiveness of intraspecific communication. Conversely, the abundance of rub trees along footpaths did not seem to depend on the density of bear observations or their relative position within the population center or its border. Our results suggest that Cantabrian brown bears select trees based on their individual characteristics and their location, with no influence of characteristics of the bear population itself. Our findings can be used to locate target trees that could help in population monitoring.

Rub tree use and selection by American black bears and grizzly bears in northern Yellowstone National Park

“…We also note that grizzly bears rubbed on utility poles more often than did black bears. Thus, the selection of lodgepole pine, which are less common on the Northern Range compared with other tree species, and utility poles may reflect that both bear species select conspicuous objects for rubbing, which is a common behavior among bears and other mammals for scent communication (Karamanlidis et al 2007, Alberts 2011, Clapham et al 2013, González-Bernardo et al 2021.…”

Estimating abundance of a recovering transboundary brown bear population with capture-recapture models

“…We used a 4 × 4 km grid cell size based on known female range areas and a 8 × 8 km grid cell size for the remaining part of the study area, with one baited station placed in each grid cell. Hair traps were placed in the best predicted bear habitat, considering topography and accessibility by 4-wheel drive vehicles, a maximum of 10 min walk from the vehicle and bear expert opinion (tree types or tree species, with characteristics that make them more conspicuous for rubbing; González-Bernardo et al 2021; Proctor et al 2022). Sites were visited once every 15 days from May to September for sample collection and lure replacement. Systematic by camera traps (SCT), corresponding to cameras (Leaf river Outdoor, HCO Soutguard SG 550 and Uway Nicht Trakker until 2013, and Bushnell Trophy Cam or NatureView HD and Reconyx HC600 or XR6 after 2013) equipped with movement detection that were fixed on trees in areas with frequent animal passage away from the walked transects and that were associated nearby with hair traps similar to the ones used for the systematic by trails method (Burton et al 2015; Parres et al 2020; see Fig.…”

“…We used a 4 × 4 km grid cell size based on known female range areas and a 8 × 8 km grid cell size for the remaining part of the study area, with one baited station placed in each grid cell. Hair traps were placed in the best predicted bear habitat, considering topography and accessibility by 4-wheel drive vehicles, a maximum of 10 min walk from the vehicle and bear expert opinion (tree types or tree species, with characteristics that make them more conspicuous for rubbing; González-Bernardo et al 2021; Proctor et al 2022). Sites were visited once every 15 days from May to September for sample collection and lure replacement.…”

“…The average home range size (Kernel 85%) of brown bears in the Pyrenees (excluding recently translocated individuals) was 84 km² for adult females (N = 6) and 1,551 km² for adult males (N = 6) (Halotel 2022; similar to the average home range of radio-collared adult bears in similar Eurasian regions: Huber & Roth 1993;Mertzanis et al 2005;Gavrilov et al 2015).We used a 4 x 4 km grid cell size based on known female range areas and a 8 x 8 km grid cell size for the remaining part of the study area, with one baited station placed in each grid cell. Hair traps were placed in the best predicted bear habitat, considering topography and accessibility by 4-wheel drive vehicles, a maximum of 10 min walk from the vehicle and bear expert opinion (tree types or tree species, with characteristics that make them more conspicuous for rubbing; González-Bernardo et al 2021;Proctor et al 2022). Sites were visited once every 15 days from May to September for sample collection and lure replacement.…”

Estimating abundance of a recovering transboundary brown bear population with capture-recapture models

“…The average home range size (Kernel 85%) of brown bears in the Pyrenees (excluding recently translocated individuals) was 84 km² for adult females (N = 6) and 1,551 km² for adult males (N = 6) (Halotel 2022; similar to the average home range of radio-collared adult bears in similar Eurasian regions: Huber & Roth 1993;Mertzanis et al 2005;Gavrilov et al 2015).We used a 4 x 4 km grid cell size based on known female range areas and a 8 x 8 km grid cell size for the remaining part of the study area, with one baited station placed in each grid cell. Hair traps were placed in the best predicted bear habitat, considering topography and accessibility by 4-wheel drive vehicles, a maximum of 10 min walk from the vehicle and bear expert opinion (tree types or tree species, with characteristics that make them more conspicuous for rubbing; González-Bernardo et al 2021;Proctor et al 2022). Sites were visited once every 15 days from May to September for sample collection and lure replacement.…”