Teeth constitute a bridge between an organism and its environment. Dental wear is a good proxy for (paleo) ecologists to better comprehend the ecology and habitat of modern and extinct species. In this study, we showed Dental Microwear Texture Analysis to be a useful tool, integrating not only specific plant selection but also dietary quality and digestibility in order to understand resource use. Resource-partitioning, seasonal and sexual variations in the diet of two deer species on a Spanish game estate are explored here through Dental Microwear Texture Analysis. This Mediterranean area is on the fringes of the average European environments in terms of constraints and diet for extant red and fallow deer, resulting in an opportunity to understand their ability to live in harsh conditions and the feeding strategies they developed. These two taxa already experienced harsh living conditions during the Pleistocene. Dental microwear texture shows both deer feeding differently on the herbaceous layer in a context where it is the main resource consumed annually. These differences are linked to body mass. With its smaller incisor arcade, Dama dama is able to be more selective, hence focusing on less fibrous parts of forages. Cervus elaphus is more plastic, with dietary variations corresponding to seasonal plant availability and the physiological requirements of stags and does. In general, C. elaphus consumes a more fibrous and less digestible vegetable material than D. dama. This study brings light on the feeding behavior of the two game species under constraint conditions. The results of this study are discussed in terms of realized vs potential ecological niches.