Ageing of ungulate pellets in semi-arid landscapes: how the shade of colour can refine pellet-group counts

Pellet-group counts can be useful in monitoring ungulate population trends, particularly in elusive species. In semi-arid areas, ambient conditions conserve the pellets during the dry season. Thus, dating of accumulated pellet groups should be helpful in approximating the numbers of ungulates present during any chosen part of the dry season. The aims of this study were to confirm that the decay rate of pellet groups was low during the dry season, to identify the major causes of decay and to test the usefulness of criteria, easily measurable in the field, in dating pellets. Every month during the dry season pellet groups of five African savanna ungulates were collected fresh and deposited on bare ground at an experimental site. The levels of hardness, cracking, scattering, attack by insects and shade of colour of the pellets were monitored until the rainy season started. As expected, only a few pellet groups decayed completely during the dry season. The pellets’ shade of colour was the best criterion to date them. We discuss pellet colour as an original tool for monitoring the trends in ungulate use of target areas in semi-arid environments.