Persistence of roe (Capreolus capreolus) and red (Cervus elaphus) deer pellet-groups in a Mediterranean mosaic landscape

The need to assess population size is central to any population monitoring program. Reliable estimations of the disappearance time of pellet groups are essential for converting pellet density into deer density. The disappearance time of pellet groups is highly variable and is considered to be habitat specific. Due to the increase of roe and red deer populations in Portugal, Forestry Authorities are requiring estimates of those species densities hence disappearance time is crucial to achieve this goal. In a Mediterranean ecosystem, roe and red deer pellet groups disappearance time was determined within six habitat types, over a 10-month period. The disappearance time (days) of pellet groups significantly differed between the habitats in each species. For both species, pellets persisted longer in coniferous and open areas, probably due to low levels of moisture. Pellet decomposition was faster in deciduous habitats for both species; in such habitats, the role of dung beetles and other saprophagus invertebrates is preponderant. In Portugal, deer surveys have been using decay rates from elsewhere in Europe. Consequently, we recommend the use of our results for future deer monitoring programs as more accurate for the Portuguese context.