Artificial night light helps account for observer bias in citizen science monitoring of an expanding large mammal population

1. The integration of citizen scientists into ecological research is
transforming how, where, and when data are collected, and expanding the
potential scales of ecological studies. Citizen-science projects can
provide numerous benefits for participants, while educating and connecting
professionals with lay audiences, potentially increasing acceptance of
conservation and management actions. However, for all the benefits,
collection of citizen-science data is often biased towards areas that are
easily accessible (e.g. developments and roadways), and thus data are
usually affected by issues typical of opportunistic surveys (e.g. uneven
sampling effort). These areas are usually illuminated by artificial light
at night (ALAN), a dynamic sensory stimulus that alters the perceptual
world for both humans and wildlife. 2. Our goal was to test whether
satellite-based measures of ALAN could improve our understanding of the
detection process of citizen scientist-reported sightings of a large
mammal. 3. We collected observations of American black bears (Ursus
americanus; n = 1,315) outside their primary range in Minnesota, USA, as
part of a study to gauge population expansion. Participants from the
public provided sighting locations of bears on a website. We used an
occupancy modelling framework to determine how well ALAN accounted for
observer metrics when compared to other commonly used metrics (e.g.
housing density). 4. Citizen scientists reported 17% of bear sightings
were under artificially-lit conditions and monthly ALAN estimates did the
best job accounting for spatial bias in detection of all observations,
based on AIC values and effect sizes (β ^ = 0.81, 0.71 – 0.90 95% CI).
Bear detection increased with elevated illuminance; relative abundance was
positively associated with natural cover, closer proximity to primary bear
range and lower road density. Although the highest counts of bear
sightings occurred in the highly illuminated suburbs of the
Minneapolis-St. Paul metropolitan region, we estimated substantially
higher bear abundance in another region with plentiful natural cover and
low ALAN (up to 275% increased predicted relative abundance) where
observations were sparse. 5. We demonstrate the importance of considering
ALAN radiance when analyzing citizen scientist-collected data, and we
highlight the ways that ALAN data provides a dynamic snapshot of human
activity. 31-Jul-2020