How Wild Predators Can Improve Human Health

Dingoes Increase Cattle Profits by Eating Kangaroos

Australia

The dingo has long had a bad rap in western culture, even before Azaria Chamberlain’s death prompted the pop-culture punchline “The dingo got my baby!”. When livestock goes missing in the Australian bush, ranchers blame dingoes, which do on occasion prey on sheep and cattle. And like coyotes and wolves in North America, the canids are often killed in retaliation.

Counterintuitively, research shows that dingoes can actually increase livestock productivity, despite snacking on the occasional lamb. In many areas of Australia, wild kangaroos compete with livestock for food. Using a computer model, scientists discovered that pasture biomass increases when dingoes help control populations of red kangaroo, which are Australia’s largest native herbivore. More grass equals fatter, healthier cattle, which in turn produce more meat and milk per animal and increases profit margins.

Dingoes have a major conservation benefit, too. Non-native cats and foxes are decimating dozens of unique Australian species, like the adorable bilby or the Instagram-famous quokka. But research shows that when dingoes are around, cats spend more time hiding and less time hunting. (They also sometimes end up as dingo dinner.) So reinstating dingoes as the top predator is a cheap way to tackle invasive species and help farmers get more out of their grazing lands.

Urban Leopards Prevent Rabies by Eating Feral Dogs

India

It’s not every day that you see a leopard prowling through city streets, but it’s a common occurrence in Mumbai, India. Sanjay Gandhi National Park sits in the middle of the rapidly expanding city, and it’s also home to a population of 35 leopards. While living check-to-jowl with a big cat does have its risks, these leopards are actually saving thousands of lives each year but removing a far more dangerous animal — feral dogs.

Feral dogs are a major health issue in India, where they cause the majority of the 20,000 rabies deaths each year. And with an estimated 30 million stray dogs across the country, it’s exceedingly difficult and expensive to control dog populations. Enter the leopards.

Scientists recently estimated that Mumbai’s leopards consume about 1,500 dogs per year — about 40 percent of their diet — preventing around 1,000 bite incidents and 90 potential rabies cases. They also calculated that having leopards around saves the city an estimated $18,000 USD in dog-management costs. You can read more about this research in our story on Cool Green Science.

Cougars Reduce Deer-Vehicle Collisions

United States

For unlucky drivers in the eastern United States, Bambi can be deadly. An estimated 1.2 million deer-vehicle collisions occur every year, causing 200 human deaths (plus a whopping 29,000 injuries) and costing $1.6 billion USD in damages. Accident rates continue to rise despite expensive efforts to control deer populations by hunting and even birth control.

Humans eradicated the carnivore species that once kept deer populations in check — like cougars, bobcat, and lynx — from eastern forests several centuries ago through a combination of hunting and habitat destruction. But in recent decades, the predators are making a comeback. Cougars are slowly expanding their range into the midwestern states, chowing down on deer as they go.

In South Dakota, where cougars are already established, the cats prevent $1.1 million in collision costs annually. Scientists wondered just how much of a benefit cougars might provide if they recolonized all of their original range. Models suggest that within 30 years of re-establishment, cougars could reduce deer densities and collisions by 22 percent in the eastern US, preventing 21,400 human injuries, 155 fatalities, and $2.13 billion in avoided costs.

Who knew having big cats around could save so many human lives?

Falcons Protect Vineyard Crops from Hungry Songbirds

New Zealand

Nothing compliments a good Marlborough sauvignon blanc like a falcon disemboweling a songbird. But then again, I’m a birder.

New Zealand wineries work hard to protect their precious (and tasty) grapes from hungry wildlife, particularly insects and songbirds. Three species of non-native songbirds, introduced by settlers from Europe, are particularly pesky for the country’s vintners. Meanwhile, native bird species are under great threat from mammalian predators that — you guessed it — were also introduced during colonization.

But there’s a potential solution that could reduce crop-raiding birds, improve grape harvests, and help a threatened species: stocking vineyards with New Zealand falcons. Research from a group of Kiwi scientists shows that the presence of falcons reduced the number of non-native pest birds and decreased the amount of bird-eaten grapes by 95 percent. They calculated that reintroducing falcons could potentially save the vineyard between $234 and $326 USD per hectare, depending on the grape variety. Early research from California suggests that barn owls might play a similar role, where in agricultural landscapes 99.5 of their of prey are agricultural pest species.

It’s a win-win for oenophiles, vintners, and conservationists. Cheers to that.

Vultures, Hyenas & Jackals Clean Up Dangerous Human Waste

Europe, Africa & Asia

Waste management is key when it comes to improving lives and health of people living in the developing world. As it turns out, local scavengers are already lending a helping paw (or wing), scoring a meal and protecting human health in one go.

In Serbia, golden jackals reduce more than 3,700 tonnes of domestic animal waste each year, including road-killed animals and waste dumps, with a savings of more than €500,000 annually. They also consume an estimated 13.2 million rodents that would otherwise eat important food crops. When scaled up across the species’ range, this amounts to more than 13,000 tonnes of organic waste across urban landscapes in Europe.

Spotted hyena play a similar role in sub-Saharan Africa. Scientists studying Ethiopian hyenas reported that nearly 90 percent of animals they studied frequently scavenged at human waste dumps, consuming waste and livestock carcasses.

And canids aren’t the only species helping out with waste removal: a study on vultures in Yemen found that the birds dispose of up to 22.4 percent of the local villages’ organic waste each year. Other research suggests that vultures, like Mumbai’s leopards, help control feral dog numbers, thus preventing rabies deaths.

More science is needed to establish a direct link between the waste-removal services that these species provide and improved human well-being.  But it’s easy to see how less waste can benefit human health. By removing waste and carcasses, predators likely reduce groundwater contamination and the risk of disease. And this keeps livestock herds healthier, too, protecting valuable assets for rural people.