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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.

This year's game count results showed the drastic decrease in game numbers, with gemsbok numbers being down 86% compared to 2019 and plains zebra and wildebeest down 93% and 97% respectively. Red hartebeest have all disappeared from the park as most of them died, a few were harvested, and a few got onto neighbouring properties. Only giraffe managed to increase, as 4 more calves were born over the last year, bringing the total to 22. Naturally, successful reproduction in the other game species over the past season has been very low.

The year’s results show a significant decrease in animals counted (-37%) and overall population estimate (-19%). The game harvesting operations done in the preceding year would have contributed to the lower game numbers. The northern sections of the park (zone 6, 7, 8 and 9) received the most rain and thus an overwhelming majority (53%) of the animals were counted in this area. For the first time in 8 years the park’s modelled carrying capacity is higher than the total grazer biomass (stocking rate).

Knowledge of a population’s abundance is of primary importance for conservation management. However, robust estimates of abundance are often difficult to obtain, especially for cetaceans which spend most of their lives submerged. Cetacean abundance is commonly estimated using aerial or vessel-based line transect surveys and distance sampling methods. During 2012–2014, the first line transect surveys to estimate cetacean abundance were conducted in Namibian waters.

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.

The coastal population of common bottlenose dolphins Tursiops truncatus found in Namibia is regionally isolated and unique. This population faces several potential anthropogenic threats, especially in Walvis Bay, including boat-based tourism, a commercial harbour undergoing expansion, and aquaculture for oysters and mussels. Between 2008 and 2012, 238 boat-based surveys were conducted, resulting in 170 encounters with bottlenose dolphins. Overall, group sizes varied from 1 to 45 individuals (mean 10.7).

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!

Numbers of most species dropped during 2015 due to the effects of the drought & the lack of grazing. Although there were a few mortalities, many animals have moved to areas outside the park where conditions are more favourable. This is to be expected in an open system.

Mountain Zebra numbers were up in 2013 due to movement into the park from the west to take advantage of the artificial waters and better grazing.

Springbok numbers were down during 2012 due to dispersal into broken hilly country to the west of the park. Where they were present, they were only found in small groups which could have resulted in under counting.

Numbers of some species were up in 2011 due to the effect of good rains. This also caused a decrease in Mountain Zebra numbers as they moved westwards out of the park.

A vehicle-based road count method is used. This method works well for common plains game but will not give good results for all species; especially smaller secretive animals, nocturnal animals, and animals in mountainous areas. Other monitoring methods (e.g. aerial census, foot patrols, specialist species monitoring) and local knowledge are also important. This means that the road counts will provide part of the information rather than replace these other methods - i.e. the methods all work together each providing a piece of the 'pie'.