Abstract: Background Genetic research in companion animals has been dominated by dogs, while cats remain comparatively understudied. To address this gap, Darwin’s Ark, an open-data community science nonprofit engaging pets and their people in scientific discovery, launched Darwin’s Cats in 2025 with the goal of enrolling 100,000 cats. Objectives To develop a scalable community-science platform for collecting feline phenotypes and DNA to enable investigation of genetic and environmental determinants of cat health Animals A community-science cohort of 20,636 pet cats. To date, 995 cats have been sequenced, with 1,504 additional samples in process. Methods We built an interactive website that encourages survey completion through immediate feedback and engagement, including scientifically-informed personality results. To facilitate DNA collection in cats, we developed a fur-based sampling method using a small comb, and a scalable fur-to-genotype workflow using low-pass whole genome sequencing that generates ~99 million data points per cat. Results The pet cat population differs markedly from dogs, with geographic stratification and less influence of breed ancestry. Genome-wide association studies replicate known associations for fur length, white coat, tabby pattern, and colorpoint, and identify new associations for polydactyly, ear tufts, and body weight. We detect tentative signals for disease-relevant phenotypes including respiratory infection frequency, inflammatory bowel disease, and urinary disease. Conclusions Darwin’s Cats is a powerful new resource for accelerating veterinary research. These results demonstrate that it can achieve the scale needed to discover factors underlying common, complex diseases, including cardiac, renal, gastrointestinal, urinary, and inflammatory disorders, and to investigate gene–environment interactions shaping health.
