Direct comparative assessment of radial and transect surveys to document wild mammal activity across diverse habitat types

Abstract

Wild mammals are often difficult to directly observe, especially in woodland and forest habitats with dense vegetation, so surveys of largely indirect signs of their activities (e.g. tracks and spoor) are often a more practical option for monitoring populations. This study compared two different approaches to surveying largely indirect indicators of activity by a range of wild mammals across a gradient of ecosystem integrity in southern Tanzania. Surveys of all such signs of wild mammal activity detected around all identifiable surface water bodies within a 2 km radius of 32 convenient camping locations with perennial surface water were complemented on alternative days with similar surveys along transects between each camp and the next camp that required similar time and effort. For most of the wild mammal species detected, radial surveys around water bodies proved more sensitive than those along transects between them, because the former approach samples distinct and convenient locations that attract most animal species. Transect surveys were found to be more sensitive for only sable (Hippotragus niger) and spotted hyaena (Crocuta crocuta), which are known to routinely commute considerable distances across their home ranges, and for greater kudu (Tragelaphus strepsiceros) that seldom drink surface water.