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Robust abundance estimates of wild animal populations are needed to inform management policies and are often obtained through mark–recapture (MR) studies. Visual methods are commonly used, which limits data collection to daylight hours and good weather conditions. Passive acoustic monitoring offers an alternative, particularly if acoustic cues are naturally produced and individually distinctive. Here we investigate the potential of using individually distinctive signature whistles in a MR framework and evaluate different components of study design.

Knowledge of the occurrence and distribution of cetaceans is particularly important for conservation and management, but is still limited within Namibian waters. We collated 3211 cetacean records from the Namibian Exclusive Economic Zone (EEZ) for the period 2008 to 2016 and applied the principle of minimum cross entropy (MinxEnt) to predict habitat suitability. MinxEnt is a generalised form of maximum entropy modelling that allows incorporation of additional information such as sampling bias.

Take a close look at the image above. Each black dot is a Cape Cormorant (see below) as seen from a light aircraft. Can you count the cormorants? This aerial view of a colony of Cape Cormorants is a composite of several of the thousands of images taken during a 2017 survey of Ilha dos Tigres, an island off the coast of Angola. The purpose of this survey was to document all visible animals using this island, so every dot counts!

Human and, increasingly, elephant pressure on Namibia's wetlands and riparian belts are a major cause of conservation concern. Many wetland birds are listed in Namibia's Red Data Book (Simmons & Brown in prep) because of population declines caused by the degradation and destruction of wetland habitats, and because of high levels of disturbance. Good information on the status of major wetlands and their avifauna is important for their conservation management. Birds provide one of the best indicators of wetland health.

This study has provided baseline data on crocodile numbers from aerial and spotlight counts. These data can be used with the results of future counts to determine population trends. The census has also provided information on their distribution of crocodiles in the Kavango and Caprivi regions. And third, it has resulted in the first population estimate for crocodiles in the north-east wetlands of Namibia.