[This was written for the Cause Exploration Prize]
Epistemic Status (how confident I am)
Slightly confident. I make a lot of educated guesses/extrapolations on numbers due to the limited data but they seem to be fairly consistent with the literature. I'm less confident on the validity of the DogPopDy model used to assess the tractability section as I couldn't play around with the model myself and it may have contain a mistake.
- I estimated the free-ranging dog population in India to be 46 million, of which 12 million are adult females who give birth to 24 million pups every year.
- Using Welfare-Adjusted Life Years (WALYs) and an early-stage mortality of 81%, 180 million WALYs are incurred from pups alone. Using the number of cortical neurons as a comparative ratio, one WALY is equal to 1/30 DALYs.
- The WHO reports that 36% of all rabies cases occur in India. This translates to 1.3 million DALYS every year and 3 billion USD of economic losses every year from rabies and rabies prevention programs.
- Taken together, an uncontrolled free-ranging dog population leads to 8 million DALYs every year in India.
- Using the Dog Population Dynamic model (DogPopDy), I estimate keeping a 35k FRD population in-check in the 'best-case' scenario requires 1.2mil USD, and this is unlikely to work in real-world conditions.
Summary of the Problem
Free-ranging dogs (FRD) are dogs not confined to any physical space. Global estimates of the FRD population range from 500-700 million . FRD dogs often lead lives filled with neglect, abuse and suffering, with the only solace being that they often die young.
Anyone living in India can attest to the ubiquity of FRD dogs and their often pitiful existence is a flaring source for heated debate between animal activists and residents who wish for their removal from neighbourhoods, with the former motivated by human-induced canine suffering and the latter by canine-induced human suffering. The sheer magnitude of both types of suffering provides strong motivation for intervention.
We can break FRD associated suffering/costs into three categories -
- FRD Suffering
- Human suffering from dog bites
- Human suffering from rabies + Economic cost of rabies
Free-Ranging Dog population in India
The exact FRD population size in India is unavailable due to the feasibility of conducting such a national census. A 2012 government report estimates a size of ~17 million, however, this is quite unreliable as it was based on a crude methodology relying on passive surveillance by veterinary personnel.  A more reliable estimate can be found by extrapolating a large, rigorous study done in Punjab done between 2016-17 that estimated a mean population of "944,000 (extrapolated using human population data)—1,569,000 (extrapolated from km2)" using the SuperDuplicates method. The SuperDuplicates method was found to be the most accurate to real populations in a separate 2018 comparative study of different survey methods conducted in a village in India.  Using these numbers and collapsing over the rural vs urban difference in population, we arrive at a 20:1 human:dog ratio.Since FRD's are primarily dependent on humans for food (handouts or scavenging) , it seems fair to extrapolate numbers based on human population and not land area. To be conservative and consistent with a ratio used in another paper , I will use a ratio of 1:30 (one FRD dog for every human). Given India's population of 1.38 billion, we arrive at a FRD population of 46 million.
Two aspects of the FRD population are important w.r.t any population intervention - the male:female ratio and the young:adult ratio. Using the same estimates from the punjab study, the FRD population was skewed male and adult — sex ratio of 1.23 males for every female and age ratio of 0.32 pups/juveniles for every adult dog. This leads to an breakdown of -
31 million adults and 15 million juveniles/pups
19 million male adults and 12 million females
A 2008 study in Jaipur found that 50% of adult females got pregnant in a year  and the median litter size was found to be 4 in a separate study by the Dog Lab in Kolkata.  Hence, an estimate for the number of pups born every year is 24 million. This is potentially a conservative estimate as other studies have found a significantly greater rate of pregnancy, larger litter sizes, and more than one breeding cycle per year.  
Welfare-Adjusted Life Years (WALYs)
Researchers in 2018 proposed adapting the Disability-Adjusted Life Year approach for animals resulting in Welfare-Adjusted Life Years (WALYs) . The WALY is the sum of a) the years lived with impaired welfare due to a particular cause and b) the years of life lost due to the premature death from the same cause. Since no data exists on the average healthy lifespan of FRD's, I will assume a healthy free-ranging dog lives on average for 10 years (a conservative estimate given the average dog lifespan seems to be 11.2yrs and the majority of FRD's are mixed breeds that tend to live longer).
Equating Human and Dog Suffering
It is not straightforward to compare the suffering of humans and dogs. A crude method to compare human and non-human suffering is to use the number of cortical neurons to assess how many animals equals one human [Scott Alexander does precisely this in a 2019 post ] A 2017 study estimated the number of cortical neurons in a golden retriever and a dog of unspecified breed, finding 627 million neurons and 429 million neurons respectively.  Taking the approximate middle ground leaves the average FRD with 500 million cortical neurons. The estimate for the number of human cortical neurons is around 15 billion , which leaves us with the same (!) 30:1 ratio, i.e. one DALY equals 30 WALYs. 
Indian FRD WALYs
Free-ranging dogs face an overwhelming mortality rate, especially when young. Researchers at the Dog Lab followed 364 pups in a five-year period and found only 19% surviving till the reproductive age (7 months) . Given the previous estimate of 24 million pups born per year, this implies around 20 million pups die every year. Assuming 9 WALYs for each pup death and omitting the loss due to their impaired welfare, this results in 180 million WALYs.
High quality data on the average lifespan of a FRD does not seem available. The same 2008 Jaipur study estimated a female FRD living on average 3.8 yrs if she survived the first year. I'll assume the average FRD lifespan to be 5 years. If we take the simple picture that the FRD population remains stable every year at holding capacity, 4 million adult dogs die every year leading to 20 million WALYS.
Hence, the loss from premature deaths is 200 million WALYs, or, using our 30:1 ratio, 6.67 million DALYs every year.
This does not include the WALYs lost from disease which seem difficult to calculate given the lack of data.
Human DALYs and Economic Costs
The Integrated Disease Surveillance Programme (IDSP) reported 7.4 million dog bites occurring in 2018 in India. According to a 2021 systematic review, FRD-induced bites accounted for ~60% of all animal bites, i.e 4.5 million, and were mainly reported in male individuals belonging to lower socio-economic status. 
A 2015 paper estimating the global burden of endemic rabies found that 
canine rabies causes approximately 59,000 (95% Confidence Intervals: 25-159,000) human deaths, over 3.7 million (95% CIs: 1.6-10.4 million) disability-adjusted life years (DALYs) and 8.6 billion USD (95% CIs: 2.9-21.5 billion) economic losses annually. The largest component of the economic burden is due to premature death (55%), followed by direct costs of post-exposure prophylaxis (PEP, 20%) and lost income whilst seeking PEP (15.5%), with only limited costs to the veterinary sector due to dog vaccination (1.5%), and additional costs to communities from livestock losses (6%).
The WHO reports that 36% of all rabies cases occur in India. This translates to 1.3 million DALYS every year and 3 billion USD of economic losses every year from rabies and rabies prevention programs. These figures do not include the costs of dog bites that do not translate into rabies.
Hence, attempting to take consistently take conservative estimates and only considering FRD mortality and human rabies mortality/costs, the total DALYs incurred by FRD's every year is around 8 million DALYs.
Animal Birth Control and Vaccination (ABCV)
Animal Birth Control and Vaccination (ABCV) is the most common intervention proposed for mitigating welfare/economics costs associated with FRDs. It involves catching adult FRDs, spaying/neutering, vaccinating and marking each dog, and releasing them back to the street. Cities across India launch ABCV campaigns, such as Nashik (human popl 1.5mil, estimated dog popl 50k) allotting $141,000  and Belagavi (human popl 750k, estimated dog popl 25k) planning to allot $75,000 . Previous attempts appear to be somewhat successful at reducing FRD population, with a study in Jodhpur seeing a "decrease in our dog population size ranging from 27.7% (Area 6) to 51.2% (Area 3) between 2005 and 2007." 
A useful paper published in 2020 - Modelling the challenges of managing free-ranging dog populations - outlines a "agent-based dog population dynamics model to examine the time, effort, financial resources, and conditions needed to successfully control FRD in a typical urban setting." The authors highlight that only in the “best-case” and high intensity scenario, ABCV resulted in a significant and lasting reduction in FRD population sizes. 
Specifically, for a city with 35k dogs, it requires 42k surgeries and $500k over a 5yr period to reduce the population to 1.5k dogs after 20 years. Here, best-case means that all dogs are equally catchable (i.e no dogs go uncaught) and no dog immigration occurs. Assuming a real-world scenario with a 5% uncatchable rate and 1% immigration, the models do not show population control.
[Best case, high intensity scenario]
I sadly wasn't able to get NetLogo to work and run the Dog Population Dynamics (DogPopDy) myself (available here - https://www.comses.net/codebases/33e71fe5-2d11-42ec-bb1e-9f725196d567/releases/1.0.0/ )
I noted a factor that may enable a more optimistic interpretation of the model's results. The model caps monthly surgeries at each ABC center at 250, stating these were regulations set out by the Animal Welfare Board of India. However, looking at the guidelines , the number 250 only crops up as an example for how many kennels should be built (pg.59). If such regulations do not exist (and it's difficult to see why they would), the number of surgeries at each center are constrained mainly by operating theatres and veterinary staff.
A more pessimistic update is that the model uses a surgery cost of 700 INR (8.8USD). The AWBI has mandated a minimum rate of 1650 INR (21 USD), a 2.4x increase.
Accounting for this price increase, keeping a 35k FRD population in-check in the 'best-case' scenario requires 1.2mil USD. Even then, DogPopDy indicates this would not work in real-world conditions.
At this point, I'll admit to being left pretty stumped as I'd expected ABCV interventions to be more effective and tractable than they are. Alternate approaches include straight-up culling - which is evidently bad from a moral standpoint, not effective unless thoroughly implemented, and not tractable given cultural/social norms (thankfully!) and mass shelter-building and adoption - which doesn't seem to be tractable given the massive population and the fact that all dogs need to be sheltered/adopted for this to work.
Interventions that reduce the holding capacity of neighbourhoods, specifically reducing garbage spillovers and direct feeding, may be somewhat more effective and tractable. However, this essentially entails starving millions of dogs and barring people from feeding starving dogs as well as increasing the likelihood of dog bites (since aggressiveness is linked to hunger), all while having no tangible way of knowing if this is actually working.
A final important point - controlling FRD populations can only occur if there is dedicated multi-decade monetary support, widespread implementation, and continuous monitoring coupled with sophisticated research, modelling and target-setting. These are things governments tend to be woefully unable to deliver and programs that have been going on for years can be abruptly cut short by funding pauses, wiping out any benefits within a few years (e.g. Guwahati). These are also things EA is much better positioned to being able to carry out.
Free-ranging dog populations in India are associated with at least 8 million DALYS (6.67 from dog WALYS, 1.3 from human rabies DALYs) and an economic cost of 3 Billion USD every year. The economic cost of Animal Birth Control to contain a FRD population in a city of 1 million people is around 1 million USD spread over 5 years of intervention, assumes a closed and perfectly catchable dog scenario, and requires continuous monitoring and intervention over decades. Alternative interventions that are effective and tractable are not obvious.
The main actionable intervention at this point is to hit pause on the millions of dollars being spent/planning to be spent on ABC measures across cities in India before further research/modelling is done as it's likely they're a complete sink of money and human resources with little to no benefit.
 Stray Dogs and Public Health: Population Estimation in Punjab, India, 2022, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8878280/pdf/vetsci-09-00075.pdf
 A Comparative Study of Enumeration Techniques for Free-Roaming Dogs in Rural Baramati, District Pune, India, 2018, https://www.frontiersin.org/articles/10.3389/fvets.2018.00104/full
 Scavengers can be choosers: A study on food preference in free-ranging dogs, 2019, https://doi.org/10.1016/j.applanim.2019.04.012
 Modelling the challenges of managing free-ranging dog populations, 2020, https://www.nature.com/articles/s41598-020-75828-6
 Fecundity and longevity of roaming dogs in Jaipur, India, 2008, https://bmcvetres.biomedcentral.com/articles/10.1186/1746-6148-4-6
 High early life mortality in free-ranging dogs is largely influenced by humans, 2016, https://www.nature.com/articles/srep19641
 Population ecology of free-ranging urban dogs in West Bengal, India, 2001, https://www.researchgate.net/publication/279928804_Population_ecology_of_free-ranging_urban_dogs_in_West_Bengal_India
 To be or not to be social: foraging associations of free-ranging dogs in an urban ecosystem, 2014, https://link.springer.com/article/10.1007/s10211-013-0158-0
 Welfare-Adjusted Life Years (WALY): A novel metric of animal welfare that combines the impacts of impaired welfare and abbreviated lifespan, 2018, https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0202580&type=printable
 [PARTIALLY RETRACTED] CORTICAL NEURON NUMBER MATCHES INTUITIVE PERCEPTIONS OF MORAL VALUE ACROSS ANIMALS, 2019, https://slatestarcodex.com/2019/03/26/cortical-neuron-number-matches-intuitive-perceptions-of-moral-value-across-animals/
 Dogs Have the Most Neurons, Though Not the Largest Brain: Trade-Off between Body Mass and Number of Neurons in the Cerebral Cortex of Large Carnivoran Species, 2017, https://www.frontiersin.org/articles/10.3389/fnana.2017.00118
 Wikipedia, https://en.wikipedia.org/wiki/Cerebral_cortex
 Burden of illness of dog-mediated rabies in India: A systematic review, 2021, https://cegh.net/article/S2213-3984(21)00112-3/fulltext
 Estimating the Global Burden of Endemic Canine Rabies, 2015, https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0003709
 Stray dog population demographics in Jodhpur, India following a population control/rabies vaccination program, 2010, https://www.sciencedirect.com/science/article/pii/S0167587710002084
 DogPopDy model - https://www.comses.net/codebases/33e71fe5-2d11-42ec-bb1e-9f725196d567/releases/1.0.0/
 Animal Welfare Board India ABC guidelines - http://awbi.in/awbi-pdf/revised_abc_module.pdf
The authors of the paper note that "We estimated a human to stray dog ratio of 28:1 and 32:1 in rural and urban areas, respectively." But, the numbers in table 3 don't map onto these ratios. Not sure of what's happening here which is why I play it safe and use a 30:1 ratio to estimate population size.
Such gross equivalences leave me feeling...gross but I'm unaware of better ways of doing such comparisons.