The relevance of herbivores for ecosystem function is generally recognized (Milchunas et al. 1998; McNaughton et al. 1998). Through their effects on vegetation large mammalian herbivores may affect the structure, productivity and species composition of plant communities (van Wieren, 1989; Bugalho, 1994).

Effects on vegetation may lead to changes in habitat features on which other animal species are dependent making large mammalian herbivores an important group to consider in nature conservation issues (Putman, 1988). Use of plant resources and effects on vegetation may differ between species of herbivores due to different foraging strategies (Gordon and Iason, 1988; Hoffman, 1989; Bugalho, 1996).

Concerning wild herbivores, of particular relevance are their potential effects on tree regeneration and adult trees, by direct consumption or marking (Massei, 1998) during reproductive behaviour, respectively. 

Deer numbers have recently increased throughout their geographical range (Geist, 1998) including Portugal (Bugalho, 1986). The effects of deer on plant communities have been investigated at northern latitudes (Putman, 1988) but there is a dearth of information for habitats in southern Europe. In particularly no attempts have been made to distinguish between effects of different deer species on tree regeneration.

In thi study we aimed to investigate the effects 3 species of deer: red (Cervus elaphus), roe (Capreolus capreolus) and fallow (Dama dama) deer on tree regeneration, in relation to their foraging strategies, in 3 study areas located from South to North of Portugal.

To quantify the effects of deer in the regeneration of trees, fenced plots were established in the study areas, and tree seedlings will be counted seasonally inside and outside the plots.