Data from: One-stage spatial mark-resight analysis reveals an increasing grizzly bear population with declining density near roads

Wildlife ecologists throughout the world strive to monitor trends in
population abundance to help manage wildlife populations and conserve
species at risk. Spatial capture-recapture studies are the gold standard
for monitoring density, yet they can be difficult to apply because
researchers must be able to distinguish all detected individuals. Spatial
mark-resight (SMR) models only require a subset of the population to be
marked and identifiable. Recent advances in SMR models with radio-collared
animals required a two-staged analysis. We developed a one-stage
generalized SMR (gSMR) model that used detection histories of marked and
unmarked animals in a single analysis. We used simulations to assess the
performance of one- and two-stage gSMR models. We then applied the
one-stage gSMR with telemetry and remote camera data to estimate grizzly
bear (Ursus arctos) abundance from 2012 to 2023 within the Canadian Rocky
Mountains. We estimated abundance trends for the population and
reproductive females (females with cubs of the year). Simulations suggest
one- and two-stage models performed equally well. One-stage models are
more dependable as they use exact likelihoods whereas two-stage models
have shorter computation times for large datasets. Both methods had
> 95% credible interval coverage and minimal bias. Increasing the
number of marked animals increased the accuracy and precision of abundance
estimates and > 10 marked animals were required to obtain
coefficients of variation < 20% in most scenarios. The grizzly bear
population increased slightly (growth rate λmean = 1.02) to a 2023 density
of 10.4 grizzly bears/1000 km2. Reproductive female abundance had high
interannual variability and increased to 1.0 bears/1000 km2. Population
density was highest within protected areas, within high quality habitat
and far from paved roads. The density of activity centers declined near
paved roads over time. Mechanisms of decline may have included direct
mortality and shifting activity centers to avoid human activity. Our study
demonstrates the influence of human activity on localized density and
importance of protected areas for carnivore conservation. Finally, our
study highlights the widespread utility of remote camera and
telemetry-based spatial mark-resight models for monitoring spatiotemporal
trends in abundance.