Data from: Camera-based occupancy monitoring at large scales: power to detect trends in grizzly bears across the Canadian Rockies

Monitoring carnivores is critical for conservation, yet challenging
because they are rare and elusive. Few methods exist for monitoring
wide-ranging species over large spatial and sufficiently long temporal
scales to detect trends. Remote cameras are an emerging technology for
monitoring large carnivores around the world because of their low cost,
non-invasive methodology, and their ability to capture pictures of species
of concern that are difficult to monitor. For species without uniquely
identifiable spots, stripes, or other markings, cameras collect
detection/non-detection data that are well suited for monitoring trends in
occupancy as its own independent useful metric of species distribution, as
well as an index for abundance. As with any new monitoring method,
prospective power analysis is essential to ensure meaningful trends can be
detected. Here we test camera-based occupancy models as a method to
monitor changes in occupancy of a threatened species, grizzly bears (Ursus
arctos), at large landscape scales, across 5 Canadian national parks
(~21,000 km2). With n = 183 cameras, the top occupancy model estimated
regional occupancy to be 0.79 across all 5 parks. We evaluate the
statistical power to detect simulated 5–40% declines in occupancy between
two sampling years and test applied questions of how power is affected by
the spatial scale of interest (park level vs. regional level), the number
of cameras deployed, and duration of camera deployment. We also explore
several ecological mechanisms (i.e., spatial patterns) of decline in
occupancy, and examine how power changes when focusing only on grizzly
bears family groups. As hypothesized, statistical power increased with the
number of cameras and with the number of days deployed. Power was
unaffected, however, by the ecological mechanisms of decline, indicating
that our systematic sampling design can detect a decline regardless of
whether occupancy declined due to range edge attrition, ecological trap or
other mechanisms. Despite their lower occupancy, power was similarly high
for grizzly bear family groups compared to grizzly bears in general. We
highlight which study design attributes contributed to high power and we
provide advice for establishing cost-effective camera-based programs for
monitoring large carnivore occupancy at large spatial scales.