Too few data and not enough time: Approaches to detecting Allee effects in threatened species

Abstract

The detection of Allee effects is critical in assessing extinction risk, but is extremely difficult when sampling small, low-density populations. Failure to detect true Allee effects could lead to overoptimistic assessments of threat status, as well as the development of inappropriate species recovery plans. We outline a broadly applicable approach for evaluating Allee effect likelihood in analyses of sparse demographic data, explicitly acknowledging the uncertainties associated with detecting subtle Allee effects among the suite of factors that can influence demographic variability. Detailed information on the probability of Allee effects will empower conservation decision makers to balance extinction risks against the political and economic costs associated with management action. We use an illustrative case study involving demographic analyses of the endangered Cape Sable seaside sparrow, highlighting the value of information on Allee effect likelihood for the development of restoration measures within species recovery plans.