Socio-geographic and demographic analysis of the official national registry data of dogs’ population in Portugal in 2023. Data from SIAC

National data on dog populations has been historically scarce, hindering effective policy and welfare efforts. The SIAC (Information System for Companion Animals) registry now provides a robust dataset for analyzing dog demographics in Portugal. This study examines SIAC data (2004-2023), analyzing breed, sex, reproductive status, age, and geographic distribution. Chi-square tests with post-hoc residual analysis identified significant demographic and breed variations across districts, while clustering based on standardized residuals grouped districts by distinct profiles. Geographic and socioeconomic distributions were assessed using the European Deprivation Index and urbanicity classification, with spatial visualizations generated in R and QGIS. The dataset includes 2,581,870 dogs, with a predominance of younger dogs (ages 2-3 years), a slight male majority (51.6 %), and 54.4 % neutered. Mixed-breed dogs were most common (39.6 %), followed by Portuguese Podengo (10.9 %) and Labrador Retriever (6.1 %). Age distributions varied geographically, with younger dogs in rural areas and older dogs in urban settings. Rural regions had higher dog-to-household ratios, while urban and economically deprived areas had higher absolute dog numbers but lower ratios. The findings establish baseline data for canine studies and highlight social patterns in the dog population. They underscore the role of rural areas in preserving native Portuguese breeds and the need for targeted public health and veterinary initiatives. By integrating demographic, geographic, and socioeconomic factors, this study provides key insights to inform public health and animal welfare policies, advocating for tailored strategies to meet the diverse needs of urban and rural canine populations.