Abstract Population size and trends of large carnivores are difficult to determine, but are often needed to inform conservation actions. Direct counts maintained over long time periods are extremely difficult to achieve. Indices of population sizes can be used to estimate large carnivore abundances, but are often case-, species- and sitespecific. Here, we test the general applicability of track-based indices to estimate large carnivore abundance. We surveyed 15 306.4km of roads associated with 339 transects across a wide geographical scale, large range of densities and variable substrates for tracks of African large carnivores. A combined model for all carnivore species on sandy soils serves as a robust approach to predict large carnivore densities. Thus, indices based on track counts can provide useful estimates of carnivore abundance. We found consistent relationships between track densities and the actual carnivore densities, having taken account of substrate.

Population estimation is an important task in all wildlife conservation. Such estimations are often difficult in low-density species such as big carnivores. The painted dog (Lycaon pictus) is an endangered species and the first aim of IUCNs action plan is to assess the size and the distribution of the remaining population. This study is the first step towards a quantitative method to distinguish painted dog footprints from footprints of feral domestic dogs and hyaenas. Footprint photographs were collected and digitally processed and total pad area and angles between the digits and backpad of the paw were measured. Both the pad area and the angles show a statistically significant difference between the species. However, further analysis shows that there is no significant difference in pad area between painted dog females and domestic dog males. Size of the pads alone is therefore not suitable as a measure to determine the species from an unknown footprint. The angles between backpad and digits seem to be more suitable to distinguish between species. Therefore, a combination of pad size and the angle between backpad and digits might be useful to estimate the species from an unknown footprint in the field.

Indirect signs of species presence (e.g., tracks, scats, hairs) are frequently used to detect target species in occupancy, presence/absence, and other wildlife studies. Indirect signs are often more efficient than direct observation of elusive animals, making such signs well suited for long-term and broad-scale monitoring programs. However, error associated with misidentification of indirect signs can be high, and should be measured if meaningful inferences about population parameters are to be made. This study addressed the need for systematic approaches to estimate and minimize variation due to observer error in identifying indirect signs. I reanalyzed data from 4 replicates of a presence/absence survey of northern river otters (Lontra canadensis) that had been conducted by Texas Parks and Wildlife Department (1996-2003). Sixteen observers had recorded tracks at sample points under bridges (n = 250) distributed throughout 27 counties in the Piney-Woods ecoregion of east Texas. My objectives were to 1) determine if observers were a source of bias in the survey, 2) estimate the proportion of error associated with track identification skill, and 3) evaluate the use of an international certification procedure that measured observer tracking skill. The null hypothesis that observers had no effect on the variation in reported sign was rejected. Indeed, binary logistic regression tests indicated that observers were significantly associated with variation in reported track presence. Observers were not randomly distributed among bridge sites, and therefore were significantly correlated with 4 habitat variables that may have influenced heterogeneity in otter occupancy and probability of detection (watershed, vegetation-type, water-type, bridge-area). On average, experienced observers (n = 7) misidentified 44% of otter tracks, with a range of 0% to 100% correct detection. Also, 13% of the tracks of species determined to be 'otter-like' were misidentified as belonging to an otter. During the certification procedure, participants misidentified the tracks of 12 species as otter. Inaccurate identification of indirect signs is a likely source of error in wildlife studies. I recommend that observer skill in identification of indirect signs be measured in order to detect and control for observer bias in wildlife monitoring.