A study on the functionality, variability and selective preferences of the Transmontano Livestock Guardian Dog, carried out in the Baixo Sabor region, was presented at the X Iberian Congress on Animal Genetic Resources, held at the Escola Agrária de Castelo Branco, from 15 to 17 September. The results confirmed the importance of the dog nucleus placed in that region since 2012, within the scope of the Livestock Guardian Dog Programme, with the support of EDP (Compensatory Measure MC8, Baixo‑Sabor Hydroelectric Project). This nucleus has great genetic and phenotypic diversity and high functionality. Indeed, it has the potential to increase the breed's population, represents a great diversity of lineages, and reflects the variability in livestock farmers' preferences regarding phenotype, ensuring greater breed diversity.