Estimating population size and trends of the Swedish brown bear Ursus arctos population

Abstract

Estimating population size and trends are key issues in the conservation and management of large carnivores. The rebounding brown bear Ursus arctos population in Sweden is monitored by two different systems, both relying on voluntary resources. Population estimates have been calculated using Capture-Mark-Recapture methods, based on DNA-based scat surveys in five of the six Swedish counties with established bear populations. A total of 1,358 genotypes were identified using DNA extracted from collected scats. An independent ongoing programme, the Large Carnivore Observation Index (LCOI), was initiated in 1998. The LCOI uses effort-corrected observations of bears by moose Alces alces hunters during the moose hunt (. 2 million observation hours/year) and has shown a good correlation with relative population density of bears using the DNA-based method. From this, we have calculated population trends during the period 1998-2007. Using an exponential model, we estimated the yearly increase in the bear population to be 4.5% at the national level, varying between 0 and 10.2% in different counties. We used the regional population estimates and the trends from the LCOI, taking the variation from both systems into account using parametric bootstrapping, to calculate the regional as well as the national population size in Sweden in fall 2008. In one case (the northernmost county; Norrbotten) a DNA-scat survey was lacking, so we used assumptions based on data from the neighbouring county to estimate population size. We estimated the Swedish brown bear population to be 3,298 individuals (2,968-3,667; 95% confidence intervals) in 2008. Our results suggest that reliable information, necessary for the management of the brown bear population can be obtained from volunteers using standardised methods.

Counts of unique females with cubs in the Apennine brown bear population, 2006–2014

“…On the contrary, the closure-corrected density we reported for the core Apennine brown bear population lays in the upper tail of brown reported bear densities (e.g., Proctor et al 2010, Kindberg et al 2011). This supports the contention that habitat productivity in the PNALM ecosystem is currently adequate for bears ) and underlines the role of the PNALM ecosystem as a last, critical stronghold of brown bears in the Apennines.…”

Wolves, people, and brown bears influence the expansion of the recolonizing wolf population in Scandinavia

“…Wolves were functionally extinct in the 1960s, but wolf recovery accelerated during the 1990s (Wabakken et al 2001), with ;11 packs in 2001 (Vilà et al 2003), 31 packs in 2010 (Liberg et al 2012), and 43 packs (;400 wolves) in 2014 (Svensson et al 2014). Regarding brown bears, as few as ;130 were left in Sweden by 1930 (Swenson et al 1995), but legislation changed and the population increased steadily, reaching ;1000 bears in the 1990s (Zedrosser et al 2001) and ;3,300 by 2008 (Kindberg et al 2011). Presently most wolves and bears are in Sweden; few inhabit Norway.…”

The potential impacts of changes in bear hunting policy for hunting organisations in Croatia

“…Accurate population estimates of a cryptic species such as the brown bear are exceedingly difficult to obtain; however, new technologies have been used to produce more accurate estimates in the Scandinavian and Slovenian bear populations. Genetic techniques use capture-mark-recapture analysis with DNA extracted from non-invasive samples of faeces and hair (Kindberg et al 2011;Swenson et al 2011;Skrbinšek et al 2012). This technique also reduces error through double counting, which can be a problem with transboundary populations.…”

“…Some countries like Norway have small populations recovering from over-hunting, and hunting is strictly controlled by the government with population targets closely monitored through genetic analysis of hair and scats (Swenson 2012). Sweden, an EU member state, holds the majority of the Scandinavian trans-boundary population, estimated to be 3,298 bears in 2008, with an annual harvest quota, culled in order to reduce human-wildlife conflict, of 233 bears in the same year (7 % of the population; Kindberg et al 2011). Finland, also an EU member state which uses culling as a last resort to reduce conflict between people and bears, has an estimated population of 920 bears ) and an annual harvest quota regulated by the government (which Croatia's current bear hunting policy is based upon both the biological sustainability of the quotas and the economic sustainability of the hunting organisations (Fig.…”