An abundance-occupancy time-lag during the decline of an arctiid tiger moth

The positive interspecific abundance-occupancy relationship is one of the most general patterns in ecology. Positive intraspecific relationships should also exist within species over time, and so a species should occupy more sites in years when it is more abundant. However, positive intraspecific relationships are not as ubiquitous as their interspecific counterparts. It has been hypothesized that low levels of temporal variation and time-lags between changes of abundance and occupancy within species make positive intraspecific relationships difficult to detect. We analyse 31 years of U.K.-wide data on the decline of an arctiid moth, Arctia caja, which provides the first empirical demonstration of an abundance-occupancy time-lag for any species. Such time-lags are probably common and we discuss their impact on the intraspecific abundance-occupancy relationship and their implications for conservation management. In A. caja, the time-lag indicates that the decline of the species is probably not driven by habitat loss.