Information about local population densities is essential to manage ungulates and is often obtained by pellet group counts. Estimating the rate of pellet group disappearance is critical for the reliability of this method. However, no studies have been performed an pellet group disappearance rates in Mediterranean climate, and no quantitative information is available on loss of pellet groups of wild boar (Sus scrofa) and fallow deer (Dama dama). We investigated disappearance rate of wild boar and fellow deer pellet groups in a coastal Mediterranean area and assessed the influence of possible correlates. Every season, 30 fresh pellet groups per species were deposited in each of 4 habitat types, and their disappearance rate was recorded the first week after placement and every 3 weeks thereafter. Pellet group loss varied more in relation to season than to habitat and followed a similar pattern in both ungulates. Pellet groups persisted longest in winter: at least 99% of fallow deer and 100% of wild bo ar pellet groups were still present 1 month after deposition, and 78% of pellet groups of both species had remained 3 months after deposition. Conversely. The disappearance rate increased dramatically in autumn, particularly for fallow deer: 88% of fallow deer and 5% of wild boar pellet groups disappeared 1 month after deposition. Dung beetles (Geotrupes: Aphodius) and rooting activity of wild boar influenced disappearance rate of pellet groups. In Mediterranean regions, pellet group counts should be performed during winter, and pellet groups should be counted in a 1-month period to optimize the reliability of the method.