The Neighbourhood Bat Watch project reveals that rapid declines of bats after white-nose syndrome are exacerbated by a high rate of colony exclusion

Long-term and large-scale monitoring of wildlife populations is fundamental to answer questions relevant to conservation. Participatory (or "citizen") science has become a popular tool to collect additional data and for monitoring trends across larger scales. As white-nose syndrome (WNS), a disease caused by a fungal pathogen, spreads throughout North American bat populations, a participatory science project was initiated in 2012, asking the public to help monitor bat maternity colonies in Quebec, Canada. Using historical data from 1997 to 2011 and the Neighbourhood Bat Watch database from 2012 to 2022, we examined variation in the distribution and size of maternity colonies in relation to WNS invasion and maternity colony exclusions from buildings in Qu & eacute;bec. Based on 580 emergence counts from 144 colonies, colony size of little brown bats (Myotis lucifugus (LeConte, 1831)) declined from 77% to 85% during the WNS invasion period, while trends during the epidemic and established periods varied depending on the species and geographical region. Out of the 287 colonies with long-term monitoring, 102 (36%) have subsequently been excluded from buildings. The probability of exclusion was higher in the north than the south, and in houses than in outbuildings. The Neighbourhood Bat Watch allowed us to estimate trends in bat populations and rate of colony exclusions, therefore informing where conservation efforts are most needed.