Ecological Modelling 108 (1998) 145 – 153 Modelling the population dynamics of red deer (Cerus elaphus L.) with regard to forest development Vlado Stankovski a,b , Marko Debeljak c, *, Ivan Bratko a , Miha Adamic  c a Faculty of Computer and Information Science, Trz  as  ka 25, 1000 Ljubljana, Sloenia b Clinical Department of Traumatology, Uniersity Clinical Centre, Zaloska 2, SI -1000 Ljubljana, Sloenia c Biotechnical Faculty, Department of Forestry, Uniersity of Ljubljana, Vec  na pot 83, 1000 Ljubljana, Sloenia Accepted 17 March 1997 Abstract Recent advances in artificial intelligence in general, and in machine learning in particular, enable scientists to apply new machine learning technics to their specific areas. In our work we apply such a machine learning technique to the modelling of population dynamics of red deer for the 40000 hectares co-natural manage forest area on high Karst of Notranjska in Slovenia. We used the RETIS program, a machine learning tool developed by A. Karalie ` at the Institute Joz  ef Stefan in Ljubljana. This program induces regression trees from data, and has already been applied to several ecological problems. RETIS was applied on data, collected in the period 1976 – 1994, which included several meteorological parameters, parameters about the state of the forest, and parameters about the population of the red deer. Given these data about the observed system, the system RETIS automatically induces a model which has the form of a regression tree. We evaluate our induced models qualitatively and quantitatively. For the qualitative evaluation, we present an expert interpretation of the models. We show that quantitatively, using the models (we use a relative prediction error) and given the meteorological parameters during winter and summer and an estimate of the number of red deer in the area, it is possible to predict the state of the forest in the near future. This is very important for maintaining the balance between red deer population and other parameters of the forest, which will allow sustainable development of the complex forest ecosystem. © 1998 Elsevier Science B.V. All rights reserved. Keywords: Models; Artificial intelligence; Population dynamics; Red deer; Forest ecosystem; Sustainable management 1. Introduction The survival of any species in any ecosystem depends on many inter- and intra-specific rela- tions and their interactions with the environment * Corresponding author. Tel.: +386 611231161 ext. 536; fax: +386 61271169; e-mail: marko.debeljak@uni-lj.si 0304-3800/98/$19.00 © 1998 Elsevier Science B.V. All rights reserved. PII S0304-3800(98)00025-8