1. The development of camera-traps has provided an opportunity to study ecological relationships and population
dynamics of species that are rare, difficult to observe or capture.Their use has seenamajor increase recently,
particularly with the recent progress inmethods adaptedtospecies for which individuals cannotbe identified.
2. We took advantage of extensive camera-trap data sets from large spatiotemporal-scale studies of a diverse
assemblage of avian and mammalian scavengers in subarctic/arctic tundra to determine sampling designs that
minimize detection errors (false-negative) and to evaluate the influence of sampling design on estimation of site
occupancy.
3. Results showed that raw error rates in daily presence varied between 5 and 30% among species when using
time-triggered cameras with a 5-min interval. Using movement-triggered cameras resulted in larger raw error
rates, between 30 and 70%, as well as a lower number of daily presences detected. Increasing the time interval
from 5 to 20 min greatly increased the raw error rate in daily presence, but it had negligible impacts on estimates
and precision of occupancy and detection probability.
4. Occupancy estimates weremostly influenced by variation in the number of days included during the sampling
period. Formost species, a threshold of between 20 and 30 problem-free days (i.e. without camera-related technical
problems) was required to stabilize occupancy and detection probability, as well as to maximize their precision.
5. Based on the results, we discuss guidelines for establishing sampling designs according to the different ecological
questions researchers might want to answer. To our knowledge, our study is the first to directly test the influence
of sampling design in camera-trap studies, providing guidelines that are likely to be directly applicable to a
large range of species and ecosystems.
