A new study in the journal Frontiers in Ecology and the Environment shows leopards, the world’s most widespread but persecuted big cat, may be helping local residents in Mumbai by reducing dog bites and rabies risk. The joint lead author of this study, Alex Braczkowski explores his time in Mumbai working with Steve Winter on a National Geographic Magazine story, and the leopard which inspired this research.

It’s 23:35 p.m., 98 degrees and I can still feel the stickiness of the humid air on my skin. Mumbai’s underwater at this time of year, and the Sanjay Gandhi National park we’re working in has already seen over 300mm of rainfall in a week. I feel my smartphone vibrate in my pocket, and I almost topple over the small canvas tent I’m in to try read the SMS. It’s a message from Kunal Chaudhari, our fixer, and it reads: “Big daddy has crossed the bridge”. I can feel my stomach turn to knots; I’m excited because I may see Mumbai’s most famous (and largest) leopard (and on foot), but at the same time I’m fearful, because I’m crouched in a small piece of canvas, and leopards here have killed people in the past. I’m here assisting Steve Winter on a National Geographic Magazine assignment to document a population of leopards which lives perilously close to a population of about 300 000 people, and tonight I’m trying to get a glimpse of this leopard on a pair of military-grade thermal binoculars.

What followed that night was the most incredible sighting I’ve ever had of a leopard, an 80-kilogram plus male, a few meters from me on foot, barely acknowledging my presence. But it wasn’t the sight of the muscled cat that startled me that night. As I watched the leopard mark his territory near some small huts, eventually taking vantage on a small hill overlooking downtown Mumbai, I heard the howls and bellows of what seemed like at least 20 or 30 stray dogs….howling from the east, west and southern parts of the adjoining slum and bigger metropolis. After over four months in the field with Steve in India and Sri-Lanka, it was one of the most striking memories of the whole trip and one that I’d investigate further in the coming months.

Upon my return from the field I decided to pursue a PhD in environmental science at the University of Queensland, in Brisbane, Australia. Trying to decide a direction for my thesis, I always wanted to test the idea of trying to determine the economic and human-benefit of a large carnivore in a place where it lives closely alongside people. We’ve known for decades that carnivores are incredibly valuable to natural ecosystems — whether its wolves in Yellowstone or mountain lions in Yosemite, there’s been a ton of science (a big chunk done by Professor William “Bill” Ripple) showing their presence affects everything from the flow of rivers to the diversity of butterflies. If you lose them, you lose a critical link in an intricately tied chain — but almost all of the science until recently has been done in natural systems largely free of people (in national parks). I wanted to see if the rule held true when people and carnivores are thrown into the mix.

I teamed up with another fresh PhD student, Chris O’Bryan, an ecologist with an interest in carnivores from Tennessee. Together we roped in chief scientists, Professors Hugh Possingham and James Watson from the Nature Conservancy and Wildlife Conservation Society, and two of the universities top postdocs, Dr.’s Hawthorne Bayer and Martin Stringer. We brainstormed for hours, trying to isolate case studies and analytical approaches to tackle the question of how a large carnivore might live alongside and help people (Chris later led a paper with a broader team, collating studies across the globe — everything from frogs to vultures), and the most striking candidate that kept coming up in our talks was that same leopard I’d seen in Mumbai just a year earlier: “Big Daddy”.

During the time we were filming leopards in Sanjay Gandhi, we knew that Mumbai biologist, Nikit Surve had just found that the park had the highest density of leopards anywhere on earth, with an estimated 35 individuals roaming some 104 km2 of deciduous forest, bordered by at least 300 000 people living in informal settlements. We also knew that he, along with three studies before him showed leopards ate a ton of stray dogs inside and around the park, anything from 25-49 percent. We calculated that over a 15-year period this equated to 35 leopards eating between 800-2000 dogs (or 40 percent of their diet). But the most striking thing was the sheer number of dogs running around Mumbai and a study by Lex Hiby estimated nearly 100,000 of them roamed the city streets — moreover over a five-year period these dogs had bitten about 75,000 people per year. Our team spent nights in Brisbane sifting through Mumbai newspapers, trying to collate bite numbers, leopard sightings, estimates of people living around the park. The picture was getting clearer and our scientific question started to take shape: we wanted to know if Mumbai’s leopards could actually help their human neighbors? Could they be reducing dog bites, rabies risk and even be helping the Mumbai government with sterilization costs for dogs?

We focused on the area at the edge of the park, closest to where an estimated 350,000 people live. We tried to come up with a reasonable guess as to how far leopards venture outside of the park, and based on expert opinion and 10 confirmed photographic sightings we set this to be 500 meters. Based on dog bites, the 35 leopards living in the park and the low dog density in this immediate area, we modeled that dog bites in the area should number about 1,200 per year, but were closer to 140 (in other words leopards were saving a direct 1,000 bites per year in this area). We also calculated that dogs were saving the local government about $18,000 per year in sterilization costs. But the most interesting part of our work was looking at what Mumbai would look like without leopards — how bad could the dog problem be for residents?

Well under one set of assumptions, if leopards were to disappear from the park and dog densities were to reach those recorded in the center of the city, dog bites could swell to about 5,000 incidences. This would mean some $180,000 would be spent per year on treatment costs, but the most damning statistic is that this could lead to 90 human lives lost.

At a glance these results suggest Mumbai’s leopards are a good thing, acting kind of like a firewall against increases in dog numbers. At the time of our paper being put together and initially accepted (late 2016) there had been almost no attacks on people over a four year period. But in 2017 a spate of attacks on local villagers (and children) caused panic and fear. Vidya Athreya, a leader in leopard science in India found that the park had seen a rise in leopard attacks on people from 2001-2003 — a period when the government was actively translocating leopards from foreign forest patches. Understandably this caused strife in the local leopard population (leopards are territorial and don’t tolerate foreign intruders) but this was stopped shortly thereafter. But why the recent attacks? Some Mumbai residents believe it has to do with increasing pressure from developments and deforestation. For example the Maharashtra government has begun building stabling lines and a large shed for a large Metro project.

The trade-off is an incredibly difficult one — keeping leopards around (a sacred animal to many people living in the area) and live in fear when walking in the park or take a few bites from local dogs living around you. When it comes to human life — the question couldn’t be more serious, and a loss of human life is never acceptable no matter how sacred and attractive a wild animal may be.

Thinking about that night in the hide, staring at “Big Daddy” and hearing what seemed like every dog in Mumbai barking at the top of its lungs, I hope that this research will be the spark of an important conversation and maybe one which helps in Mumbai’s quest to live peacefully with its incredible dog-eating city leopards.

The article Leopards provide public health benefits in Mumbai, India appears in the March 2018 edition of Frontiers in Ecology and the Environment journal (DOI: 10.1002/fee.1776). All media enquiries can be forwarded to the joint lead authors of this study:

Alex Braczkowski: alexander.braczkowski@gmail.com

Christopher O’Bryan: obryancj@gmail.com