Indexing small mammalian carnivores in the southern Kalahari, South Africa

Abstract

Monitoring animal populations in changing environments is crucial to wildlife conservation and management, but restrictions in resources are a recurring problem for wildlife managers and researchers throughout Africa. Land-useinduced shrub encroachment in Kalahari savannah rangelands has led to fragmentation of the landscape. Mammalian carnivores are particularly vulnerable to local extinction in fragmented landscapes, but their low numbers and their often nocturnal and secretive habits make them difficult to monitor. In this study, we tested the applicability of a passive tracking method and compared two measurement methods and index calculations for monitoring small carnivores across a grazing gradient in the southern Kalahari. During the four years of monitoring in a five-year period, we used the knowledge of indigenous Khoisan Bushmen for the identification of carnivore tracks on 640 sand transects (5 m × 250 m). Our results showed that this simple and inexpensive observation method enabled detailed monitoring of 10 small carnivore species across the grazing gradient. A binary index calculated an index based on presence/absence of a species' tracks on each transect, whereas the track intrusion index used the number of track intrusions to each transect for each species in its calculations. For less common species, the two indices were similar in trend and magnitude, because the number of intrusions to each transect was typically 1 or 0. Usually, the two indices showed relatively strong correlations. However, species with patchy distributions of higher numbers presented difficulties for the binary index to monitor trends, but not for the track intrusion index.

Guiding the management of an agricultural pest: Indexing abundance of California meadow voles in artichoke fields

“…Binary data were only weakly or even negatively correlated with trap results (Table 1). This latter result was not entirely unexpected, since the reduction of continuous data to binary data represents a loss of information (Allen A. et al, 1996, Allen B. et al, 2011Baldwin et al, 2014;Blaum et al, 2008;Engeman, 2005;Engeman et al, 1989).…”

Monitoring wild pig populations: a review of methods

“…For example, tracking plots are easier to record as showing activity or not, without accurately recording the intensity of activity at each station. Nevertheless, reduction of potentially continuous data to binary observations is easily demonstrated to have less descriptive ability and result in a greater opportunity for erroneous inferences (Engeman et al 1989), and this principle has been especially well-demonstrated for tracking plot data (e.g., Allen et al 1996Allen et al , 2011Blaum et al 2008;Engeman 2005;Engeman et al , 2002.…”

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