Combining data from 43 standardized surveys to estimate densities of female American black bears by spatially explicit capture–recapture

Abstract

Spatially explicit capture-recapture (SECR) models are gaining popularity for estimating densities of mammalian carnivores. They use spatially explicit encounter histories of individual animals to estimate a detection probability function described by two parameters: magnitude (g 0 ), and spatial scale (r). Carnivores exhibit heterogeneous detection probabilities and home range sizes, and exist at low densities, so g 0 and r likely vary, but field surveys often yield inadequate data to detect and model the variation. We sampled American black bears (Ursus americanus) on 43 study areas in ON, Canada, 2006Canada, -2009. We detected 713 animals 1810 times; however, study area-specific samples were sometimes small (6-34 individuals detected 13-93 times). We compared AIC c values from SECR models fit to the complete data set to evaluate support for various forms of variation in g 0 and r, and to identify a parsimonious model for aggregating data among study areas to estimate detection parameters more precisely. Models that aggregated data within broad habitat classes and years were supported over those with study area-specific g 0 and r (DAIC c C 30), and precision was enhanced. Several other forms of variation in g 0 and r, including individual heterogeneity, were also supported and affected density estimates. If study design cannot eliminate detection heterogeneity, it should ensure that samples are sufficient to detect and model it. Where this is not feasible, combing sparse data across multiple surveys could allow for improved inference.

Relationships among food availability, harvest, and human–bear conflict at landscape scales in Ontario, Canada

“…Most of Ontario's human population lived in SR (Statistics Canada 2007, 2012. Human populations in SR increased from 2001 to 2006 and again from 2006 to 2011, with some of the largest increases occurring in areas with the highest bear densities (Statistics Canada 2007, 2012Howe et al 2013). Black bear harvest densities in SR ( À x 2004-2011 5 2.6/100 km 2 ) were .4 times those in NER or NWR (Dix-Gibson 2012).…”

“…However, both harvest metrics and measures of HBC vary among years in response to changes in the availability of natural foods (Gilbert et al 1978;Garshelis 1989;McDonald et al 1994;Noyce and Garshelis 1997;Ryan et al 2004Ryan et al , 2007Howe et al 2010). This variation obscures trends and may also confound tests for relationships among bear population size, hunting pressure, harvest, and HBC, which makes it difficult for managers to assess whether management actions are having the desired effect unless concurrent data on food availability are available to provide insights (Garshelis 1991, Gore et al 2006, Garshelis and Noyce 2008, Treves et al 2010.…”

“…Controversy surrounding the effects of the 1999 cancellation of the spring hunting season on the frequency of HBC spurred the Ontario Ministry of Natural Resources (OMNR) to appoint an independent Nuisance Bear Review Committee in 2002 (Howe et al 2010). That committee recommended standardizing collection of data on HBC, and the expansion of food availability surveys to the entire province (Poulin et al 2003).…”

“…Since then, minimizing conflicts with humans has become an increasingly important aspect of black bear management (Hristienko andMcDonald 2007, Spencer et al 2007). Most management agencies have initiated programs to educate the public about how to minimize human-bear conflict (HBC), but their effectiveness is difficult to measure because of multiple influences on the frequency of, and reporting rate for, human-bear interactions (Garshelis 1989, Gore et al 2006, Spencer et al 2007, Howe et al 2010. Sport harvest can be a cost-effective means of removing animals from the population, so it is intuitive and convenient for managers to assume that harvest could be used to limit or reduce HBC by reducing bear density and distribution.…”

Assessing and comparing population densities and indices of skinks under three predator management regimes

“…Positive responses to particular baited detection devices have been observed in wolverines returning repeatedly to camera traps (Royle et al 2011) and black bears returning to barbedwire hair-collection corrals (Howe et al 2013). As far as we know, similar responses to particular live-capture traps have not been published.…”