Simulating the effort necessary to detect changes in northern spotted owl (Strix occidentalis caurina) populations using passive acoustic monitoring

Passive acoustic monitoring is a promising method for monitoring rare and nocturnal species, and for tracking changes in forest wildlife biodiversity. We conducted simulations to compare and evaluate various passive acoustic sampling designs effectiveness for monitoring spotted owl (Strix occidentalis caurina) population trends. We found that each design was effective for detecting a decline (or stability) in spotted own populations within 10 years with even a moderate amount of sampling. There are however, important considerations and tradeoffs among the various design options. Often, estimated changes in use of the landscape were biased with a consistently lower magnitude of change compared to simulated changes in the population. Although this method has challenges, passive acoustic monitoring can be used to effectively monitor northern spotted owls in the Pacific Northwest.