A systematic review and meta-analysis of the proportion of dogs surrendered for dog-related and owner-related reasons

- We summarized results across studies reporting the proportion of dogs surrendered for various reasons.
- Results were combined in an attempt to provide a more precise result.
- Sources of heterogeneity were explored to explain variation in results among studies.
- Owner health/illness as a reason for dog surrender had an overall estimate of 4.6% (95% CI: 4.1%, 5.2%).
- Country was a significant source of variation (p < 0.01) among studies reporting behavioural problems as a reason for dog euthanasia. Further research and standardization of data collection are needed.

Companion-animal relinquishment is a worldwide phenomenon that leaves companion animals homeless. Knowing why humans make the decision to end their relationship with a companion-animal can help in our understanding of this complex societal issue and can help to develop preventive strategies. A systematic review and meta-analysis was conducted to summarize reasons why dogs are surrendered, and determine if certain study characteristics were associated with the reported proportions of reasons for surrender.Articles investigating one or more reasons for dog surrender were selected from the references of a published scoping review. Two reviewers assessed the titles and abstracts of these articles, identifying 39 relevant articles. From these, 21 articles were further excluded because of ineligible study design, insufficient data available for calculating a proportion, or no data available for dogs. Data were extracted from 18 articles and meta-analysis was conducted on articles investigating reasons for dog surrender to a shelter (n = 9) or dog surrender for euthanasia (n = 5). Three studies were excluded from meta-analysis because they were duplicate populations. Other reasons for excluding studies from meta-analysis were, (1) the study only investigated reasons for dog re-relinquishment (n = 2) and (2) the study sample size was <10 (n = 1). Two articles investigated reasons for both dog surrender to a shelter and dog surrender for euthanasia. Results of meta-analysis found owner health/illness as a reason for dog surrender to a shelter had an overall estimate of 4.6% (95% CI: 4.1%, 5.2%). For all other identified reasons for surrender there was significant variation in methodology among studies preventing further meta-analysis. Univariable meta-regression was conducted to explore sources of variation among these studies. Country was identified as a significant source of variation (p < 0.01) among studies reporting behavioural problems as a reason for dog surrender for euthanasia. The overall estimate for studies from Australia was 10% (95% CI: 8.0%, 12.0%; I2 = 15.5%), compared to 16% (95% CI: 15.0%, 18.0%; I2 = 20.2%) for studies from other countries.The present systematic review and meta-analysis highlights the need for further research and standardization of data collection to improve understanding of the reasons for dog relinquishment.