From the Field

Having a leopard in the neighborhood may seem a terrifying prospect, but the reality is that large predator may save your life.

A new study published in the journal Frontiers in Ecology and the Environment suggests that leopards in Mumbai, the world’s sixth most-populated city, may save human lives by feeding on feral dogs. Feral dogs are a major health issue in India, where they are the leading cause of rabies deaths.

The study was led by researchers from the University of Queensland School of Earth and Environmental Sciences.

Sanjay Gandhi National Park, with a population of 35 leopards, has the densest population of these big cats in the world. The park is also in the middle of the burgeoning city of Mumbai, with more than 20 million people. Approximately 350,000 people, many of them in poverty, live all along the periphery of the small national park. Leopards can be seen strolling the city streets, and hunting in parking garages.

“While leopards are often in conflict with people over livestock like cattle and sheep and are frequently persecuted throughout their range, we show that these unique predators can also be beneficial to human society,” says Christopher O’Bryan, one of the joint lead authors on the study, and a PhD student at the University of Queensland.

That’s because 40 percent of the average leopard’s diet consists of feral or stray dogs, the researchers found. The density of feral dogs in and around the national park is an average of 17 dogs per square kilometer compared to other parts of Mumbai away from the park boundary that can have upwards of 680 dogs per square kilometer.

India’s rising feral dog population causes a major health crisis in the country. While exact population figures are difficult to verify, many sources estimate 30 million stray dogs live in India. Approximately 20,000 people per year die of rabies, most of them due to dog bites.

The study found that the small population of leopards “may consume about 1,500 dogs per year, saving around 1,000 bite incidents and 90 potential rabies cases.” The presence of leopards was also estimated to save $18,000 in dog management costs.

“Dog bites in these slums are very costly to people,” O’Bryan told me in a Skype interview. “There are the costs for medical treatments and hospitalization, as well as the costs associated with lost work time.”

O’Bryan is quick to point out that living with leopards has its own risks and costs. In 2017, there were seven leopard attacks in the area. “A lot of the news coverage focuses solely on the negatives of the leopards,” says O’Bryan. “The leopards can certainly be a health hazard. We are suggesting that they may also be a health benefit. We believe it’s important to assess both the costs and benefits associated with living in close proximity to predators.”

This study is a notable departure from usual studies on the benefits of large carnivores, which usually focus on predator effects in large national parks and protected areas. The classic example is research on the ecological benefits of wolves in Yellowstone National Park, which has shown that reintroducing these predators has had a host of cascading effects, including causing changes in elk behavior that leads to revegetation of native plants along streams.

That study, and others like it, focus on the benefits to the park’s ecosystem. “This leopard study may be the first research that looks at a large predator’s effect on human health and well-being,” O’Bryan says.

Around the globe, expanding human populations encroach on predator habitat. This is often portrayed solely in terms of conflict. Many predators are forced to adapt to what is essentially a new ecosystem. Instead of preying on just native Indian mammal species, the urban leopards hunt feral dogs.

Leopards are widespread and adaptable, but they have disappeared from nearly 80 percent of their global historic distribution. They remain in conflict with people in much of their range. Understanding their benefits to people – and the benefits provided by other predator and scavenger species – may help shape a future where people and predators can better coexist.

“There are so many questions that arise from this study, and that’s a good thing,” says O’Bryan. “We see this as a call for more research on the costs and benefits of predators in human-dominated landscapes.”

The article Leopards provide public health benefits in Mumbai, India appears in the March 2018 edition of Frontiers in Ecology and the Environment journal.