Estimation of Abundance from a Correlated Binary Time Series

In the face of increasing extinction rates, it is vital to have estimates of relative and absolute species abundance and their relationship to important factors. For species that live in the oceans or large lakes, this can be a difficult task. Here, we present a method for estimating absolute abundance from a single binary acoustic time series. The dependence in the series is exploited to allow the estimation of abundance when some animals remain hidden, and in the face of uncertainty about the range over which sounds carry. Simulations show that the method works well, even when some assumptions are violated. The method is illustrated using data on sperm whales in the Sargasso Sea.