Dynamic Occupancy Models for Explicit Colonization Processes

The occupancy model has become increasingly popular in ecology as a means to account for imperfect detection of a species when predicting where it is likely to occur. The dynamic, multi-season occupancy model extends the framework to account for open populations with occupancies that change over time through local colonizations and extinctions. However, few versions of the model relate these probabilities to the occupancies of neighboring sites or patches. I will present a version that does incorporate this information, where a site is more likely to be colonized if more of its neighbors were previously occupied and if it provides more appealing environmental characteristics than its neighboring sites. Additionally, a site without occupied neighbors may become colonized through long-distance dispersal. In my presentation, I will describe the concept and mathematics of the occupancy model, how we incorporate the spatial and temporal processes, and use the model to obtain inference for the ongoing Common Myna (Acridotheres tristis) invasion in South Africa. The results suggest that the Common Myna continues to enlarge its distribution and its spread via short-distance movement, rather than long-distance dispersal. Overall, the new modeling framework provides a powerful tool for managers examining the drivers of colonization, including short- vs. long-distance dispersal, habitat quality, and distance from source populations.