Shelter Dog Census Changes Track Intakes but Resolve Slowly via Outcomes and Especially Adoptions

In animal shelters, the census (in-care population) changes when monthly intakes and outcomes are not balanced, and census changes may in turn affect subsequent intakes and outcomes. This observational, retrospective study examined these relationships using monthly dog statistics from the Shelter Animals Count database for United States government-related (GRO) and non-government (NGO) sheltering organizations over 2022-2024. Two linear regression models were applied: a concurrent model that decomposes single-month imbalances by intake and outcome type, and a cumulative model that estimates the effect of past census changes on subsequent monthly intakes and outcomes. Concurrent imbalances involved larger contributions from intakes than outcomes for both organization types. Accumulated past census increments dissipated predominantly through increased outcomes rather than reduced intakes, with adoptions making the largest absolute contribution; noncommunity live outcomes and nonlive outcomes were markedly overrepresented relative to their average shares. The implied time for 95% census recovery averaged approximately 7.6 months for GRO and 5.2 months for NGO. The marginal live release rate fell below the bulk average for GRO (85.8% vs. 90.1%) but not for NGO (96.8% vs. 96.6%). These findings argue against assumptions of fixed adoption or transfer capacity and support a view in which census perturbations are dampened (through shelter efforts) rather than permanent or unbounded.