Key Findings
The researchers reviewed 39 papers and theses on the effectiveness of dog population management.
Despite limited comparisons due to inconsistencies in study design, the authors concluded that fertility control methods, such as CNR, are the most effective for managing free-roaming dog populations. While culling can reduce population size, it fails to maintain these reductions over time.
Summary
Free-roaming dogs, making up about 75% of the global dog population, are a significant topic of academic research due to their impact on public health, animal welfare, and wildlife conservation. Managing their population is a critical focus, but studies on this topic vary widely, examining different aspects such as effectiveness, dog welfare outcomes, and public health implications.
The authors of “The Effectiveness of Dog Population Management: A Systematic Review,” Lauren M. Smith et al., aimed to synthesize existing evidence on the effectiveness of different dog population management methods. Their objectives included determining where and when these studies were conducted, what methods were used, and the effects on dog population size, health and welfare, public health risk, public attitude, and wildlife. They also evaluated the quality of reporting in these studies to aid future decision-making.
The authors began with a pre-filtered list of 4,863 papers and narrowed it down to 36 peer-reviewed papers and three theses, with 82% of them published between 2008 and 2018. Most studies were conducted in a single country (87%) and they covered 15 countries across Africa, Asia, Central America, Europe, North America, and South America. The primary mechanisms investigated for dog population management were neutering, culling, and sheltering, though some studies explored using a mix of these methods.
The reviewed studies were primarily classified into two approaches: observational/intervention and modeling. Observational studies focused on real-world data collection and analysis, while intervention studies evaluated the impact of specific imposed actions. Modeling studies used simulations to predict the outcomes of different management strategies.
Observational / Intervention-based Studies
In reviewing the observational / intervention-based studies, the authors identified the following key points:
Population Size and Demographics
The reviewed literature concentrated on fertility control and the combination of birth control and sheltering. All studies implemented fertility control in both male and female dogs at varying intensities and consistently reported a reduction in dog population size. One study noted a significant 34% decrease in population size when fertility control and sheltering over nine months. However, the author cautioned that this reduction might primarily be attributed to the sheltering effect due to its short-term nature.
Health and Welfare
Fertility control was found to improve body condition scores and reduce the prevalence of injuries in dogs. However, it also led to an increase in the prevalence of certain pathogens and ectoparasites. Post-operative complications from fertility control were generally low. One study on sheltering indicated no significant differences in behavioral problems post-adoption for previously free-roaming dogs.
Public Health
The studies reviewed showed that culling reduced the prevalence of visceral leishmaniasis in dogs in the short term, but long-term effects were not significant. A significant reduction in visceral leishmaniasis cases in children following culling was also noted. Fertility control was also found to reduce public health risks, including a decrease in human bite cases and human rabies cases. The combination of fertility control and culling or sheltering was associated with reduced prevalence of Echinococcus granulosus in humans and livestock.
Public Attitude
The evidence on public perception was mixed. One study found no significant change in public perception regarding dog population management methods after three years of fertility control. In contrast, another study reported a positive shift in public attitude towards free-roaming dogs following fertility control and sheltering campaigns.
Modelling Studies
The authors also reviewed several studies that modeled the impact of dog population management interventions:
Population Size and Demographics
Modeling studies examined the effects of culling, fertility control, sheltering, movement restrictions, and combined effects on dog population demographics. One study found that fertility control could reduce the population by 75%, compared to just 13% with culling, given the same capture probability and intervention intensity. Another study reported that fertility control could lead to a population decrease ranging from 14% to 78% over 20 years, depending on neutering coverage. Sheltering alone had minimal impact on population size, but when combined with movement restriction, it could result in a 5% decrease over 30 years to a 73% decrease over 20 years.
Public Health
Both culling and fertility controls were effective methods in reducing dog rabies prevalence and the rabies basic reproductive number (R0). One study on fertility control estimated a 92% decrease in human rabies cases over five years with 25% to 50% intervention coverage. Another study found that both culling and fertility control were effective at various intensities, but fertility control proved more effective than culling when combined with rabies vaccination.
Wildlife Impact
One study showed that sterilization controls reduced the risk of diseases to the Indian fox.
The authors concluded that fertility control methods, such as CNR, are the most effective for managing free-roaming dog populations. While culling can quickly reduce population numbers, it often fails to maintain these reductions over time and is frequently criticized for this shortcoming. That said, comparisons between different dog population management techniques are limited due to variations in measurement time scales, application rates, and dog subpopulations targeted.
In addition, the authors also recommend that future studies adopt common metrics, improve reporting quality, and enhance study design and modeling approaches to better evaluate the true impact of dog population management. Additionally, control groups should be utilized to accurately attribute observed effects to the management interventions.
Miscellaneous
Data From Study:
–
Year of Publication:
2019
External Link:
Smith, L.M.; Hartmann, S.; Munteanu, A.M.; Dalla Villa, P.; Quinnell, R.J.; Collins, L.M. The Effectiveness of Dog Population Management: A Systematic Review. Animals 2019, 9, 1020.
https://doi.org/10.3390/ani9121020