Urban free-roaming cat populations (or community cats, according to the Spanish legislation) present complex challenges, including public health risks, coexistence conflicts with residents, animal welfare, and threats to biodiversity conservation. In 2020, Córdoba, Spain, initiated one of the most extensive citywide trap–neuter–return (TNR) programs, incorporating 225 groups of cats (usually named colonies) into a meticulously structured management framework. Over four years, the program stabilized cat populations, achieving 95% sterilization coverage and effectively limiting population growth despite external challenges, including abandonment, influxes from unmanaged areas, and compensatory effects. Although the overall population showed a modest decline of 2.68%, this outcome reflects not only the recent inclusion of numerous colonies still undergoing stabilization but also the prevention of an estimated 70% population growth without intervention, as projected by our population viability analysis (PVA). Key results highlight the program’s cost-effectiveness, with an average annual cost of EUR 0.62 per person. The long-term projections from a population viability analysis (PVA) using demographic modeling suggest a potential 55% population reduction by 2028, contingent on sustained efforts. The program’s integration of citizen science, systematic data collection, and adaptive management demonstrates its scalability and replicability as a model for urban and peri-urban feline management globally. Its significance lies not only in its scope and scale but also in demonstrating the ethical and practical feasibility of large-scale TNR initiatives in urban contexts. Córdoba’s program, which predates Spain’s Animal Welfare Law 7/2023 mandating structured feline colony management plans, demonstrates a pioneering framework for compliance and innovation in urban animal management. These findings underscore the critical role of sustained interventions, community collaboration, and legal frameworks in ensuring long-term success and addressing global challenges in urban animal welfare and biodiversity conservation.

La Graciosa, a Natura 2000 site in the Canary Islands, faces substantial conservation challenges, including a large free-roaming cat population that threatens the island’s native biodiversity. In July 2024, a Trap–Neuter–Return (TNR) campaign achieved an 81.4% sterilization rate within urban areas, highlighting TNR’s short-term effectiveness in reducing reproductive potential and, consequently, mitigating predation pressures primarily through the prevention of new litters and reduced reproductive activity in cats. The campaign’s success relied heavily on the active involvement of the local community, who assisted with identifying, trapping, and monitoring free-roaming cats, thereby facilitating a high sterilization rate. However, administrative restrictions hindered access to peri-urban zones, leaving essential population clusters unsterilized and limiting the campaign’s overall scope. Additionally, strong opposition from conservation groups, amplified by extensive media coverage, halted the project prematurely, reducing the effective sterilization rate to 69.3% within three months. Population Viability Analysis (PVA) suggests that achieving high sterilization rates could lead to population reduction over time; however, the inability to access all population segments and to reach the ideal 93–95% sterilization threshold limits TNR’s potential as a long-term standalone solution. Our findings underscore the need for adaptive, context-specific management frameworks in ecologically sensitive areas that integrate TNR with complementary measures, consider regulatory barriers, and value community involvement. This case study provides crucial insights for policymakers and conservationists seeking to balance biodiversity conservation with humane management practices in protected areas.

This study presents the scientific and methodological foundation of Spain’s first national framework for the ethical management of community cat populations: the Action Plan for the Management of Community Cat Colonies (PACF), launched in 2025 under the mandate of Law 7/2023. This pioneering legislation introduces a standardized, nationwide obligation for trap–neuter–return (TNR)-based management of free-roaming cats, defined as animals living freely, territorially attached, and with limited socialization toward humans. The PACF aims to support municipalities in implementing this mandate through evidence-based strategies that integrate animal welfare, biodiversity protection, and public health objectives. Using standardized data submitted by 1128 municipalities (13.9% of Spain’s total), we estimated a baseline population of 1.81 million community cats distributed across 125,000 colonies. These data were stratified by municipal population size and applied to national census figures to generate a model-ready demographic structure. We then implemented a stochastic simulation using Vortex software to project long-term population dynamics over a 25-year horizon. The model integrated eight demographic–environmental scenarios defined by a combination of urban–rural classification and ecological reproductive potential based on photoperiod and winter temperature. Parameters included reproductive output, mortality, sterilization coverage, abandonment and adoption rates, stochastic catastrophic events, and territorial carrying capacity. Under current sterilization rates (~20%), our projections indicate that Spain’s community cat population could surpass 5 million individuals by 2050, saturating ecological and social thresholds within a decade. In contrast, a differentiated sterilization strategy aligned with territorial reproductive intensity (50% in most areas, 60–70% in high-pressure zones) achieves population stabilization by 2030 at approximately 1.5 million cats, followed by a gradual long-term decline. This scenario prioritizes feasibility while substantially reducing reproductive output, particularly in rural and high-intensity contexts. The PACF combines stratified demographic modeling with spatial sensitivity, offering a flexible framework adaptable to local conditions. It incorporates One Health principles and introduces tools for adaptive management, including digital monitoring platforms and standardized welfare protocols. While ecological impacts were not directly assessed, the proposed demographic stabilization is designed to mitigate population-driven risks to biodiversity and public health without relying on lethal control. By integrating legal mandates, stratified modeling, and realistic intervention goals, this study outlines a replicable and scalable framework for coordinated action across administrative levels. It exemplifies how national policy can be operationalized through data-driven, territorially sensitive planning tools. The findings support the strategic deployment of TNR-based programs across diverse municipal contexts, providing a model for other countries seeking to align animal welfare policy with ecological planning under a multi-level governance perspective.

Free-roaming cats may contribute to zoonotic risk via parasites and other eukaryotic taxa, yet surveillance in protected island settings is limited and conventional coprology can miss low-intensity or degraded signals. We conducted a cross-sectional 18S rRNA metabarcoding survey to establish a baseline profile of potentially pathogenic eukaryotes in community cats from La Graciosa (Natura 2000, Canary Islands, Spain) prior to large-scale antiparasitic interventions. We analysed 152 faecal samples, including fresh samples collected during a high-throughput TNR campaign (n = 37) and dry environmental deposits (n = 115). Host amplification was reduced using a feline 18S blocking primer; libraries were sequenced with Oxford Nanopore technology; and taxonomy was assigned using SILVA-based classifiers with downstream filtering for veterinary/zoonotic relevance. After quality control, 72 eukaryotic taxa were retained and DNA from at least 24 potentially pathogenic taxa was detected. Dipylidium caninum was most frequent (74.3%; 113/152), and opportunistic fungi/yeasts were common (e.g., Pichia kudriavzevii 42.4%, Diutina catenulata 31.5%). Zoonotic protozoa showed low-to-moderate detection frequency (Acanthamoeba castellanii 13.3%, Toxoplasma gondii 7.9%, Balamuthia mandrillaris 4.6%). Overall richness did not differ between fresh and dry samples (p > 0.05), but fresh samples contained higher richness of potentially pathogenic taxa (p < 0.01).

Managing community cats on islands requires reconciling animal-welfare mandates with biodiversity protection under real operational constraints. In the Canary Islands (Spain), national Law 7/2023 endorses ethical, non-lethal colony management, while subsequent regional resolutions restrict TNR in and around protected areas, narrowing municipal room for action. We combine a multilevel governance assessment with stochastic demographic simulations parameterized from official records to compare three sterilization regimes over 20 years. The intensive regime (≈60–70%/year) reflects the coverage threshold previously identified by Spain-based modelling and field evaluations and adopted in national program guidance; the 20%/year regime represents the pre-resolution baseline widely observed across the archipelago up to December 2024; and the 4%/year regime reflects the post-resolution reality, with abrupt declines in sterilizations, operations largely confined to urban cores, and program suspensions in multiple municipalities. Minimal (4%) and low (20%) efforts produce rapid population growth, bringing numbers close to the assumed carrying capacity under our deliberately high-K configuration and sustaining high densities and associated welfare and ecological risks; only sustained high-coverage TNR prevents saturation and produces progressive declines across island contexts. Under insular constraints, outcomes are determined by achievable coverage rather than regulatory intent; aligning policy and implementation to secure continuous, high-coverage TNR—particularly in risk-sensitive areas with appropriate safeguards—offers a feasible pathway to meet animal-welfare obligations while limiting ecological pressure.