摘要：Faecal pellet count is an indirect census method used to estimate the density of an animal population. Factors that affect the accuracy and precision of this method are the defecation rate, the decay time and the detectability of the droppings. In this study, we analysed the influence of some variables on the detectability of droppings: (i) environmental variables, EV (vegetation type, grass height, meteorological conditions); (ii) subjective variables, SV (operator, subjective visibility); (iii) faeces–species related variables, SRV (Capreolus capreolus Linnaeus, 1758; Cervus elaphus Linnaeus, 1758 and Lepus europaeus Pallas, 1778). The average values of dropping detectability, expressed as percentage of observations from the minimum detectability (0) to the maximum (1), were: 0.99 (SD = 0.07) for red deer faeces; 0.93 (SD = 0.16) for roe deer faeces; 0.89 (SD = 0.21) for European brown hare faeces. The red deer detectability value was statistically higher than the roe deer and European brown hare values (X2 = 26.61, df = 2, p < 0.01). A generalised linear model (GLM) analysis shows that the variables which negatively affect the dropping detectability are different for the three species: (i) vegetation type, especially deciduous forest, for the red deer; (ii) grass height for the European brown hare; (iii) subjective visibility, especially the category “none”, for the roe deer. These results suggest that the characteristics of both the study area and the species considered could affect the detectability of droppings, and therefore also the entire estimation density. So, faecal pellet count monitoring programmes should carefully take into account the environmental characteristics and should be performed when detectability is maximised (e.g. short grass, fewer leaves, less undergrowth).
关键词：Faecal pellet count; visibility; dropping detectability; percentage of observation; GLM
