Why Animal Scavengers Protect Your Health

Summary

Podcast Summary: Short Wave – "Why Animal Scavengers Protect Your Health"

Date: October 1, 2025
Host: Regina Barber
Guest: Jonathan Lambert, NPR Science Reporter
Notable Contributors: Anant Sudarshan (University of Warwick), Chinmay Sonawane (Stanford), Christopher O’Brien (Maastricht University)

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Episode Overview

In this episode, Regina Barber and Jonathan Lambert discuss the critical role animal scavengers—like vultures, hyenas, and civets—play in protecting human health by cleaning up carcasses and preventing the spread of disease. Using India’s “vulture crisis” as a launching point, they explore why conserving apex scavengers is vital, highlight cascading effects of their decline, and consider conservation solutions that tie animal well-being directly to public health.

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Key Discussion Points & Insights

The Essential Role of Scavengers: India’s Vulture Crisis

[01:09]

• Jonathan Lambert recounts the rapid, catastrophic decline of vultures in India during the 1990s due to the use of a livestock painkiller (diclofenac) toxic to vultures.
  • “Way back in the early 1990s, there were some 50 million vultures across India. But… their numbers plummeted by like, 95%.” – Jonathan Lambert, [01:11]
• Regina Barber, astonished: “95%? That is huge.” [01:26]
• The result: researchers link the vulture collapse to hundreds of thousands of additional human deaths over five years.

How Vultures (and Other Scavengers) Protect Human Health

[03:38]

• Vultures are extremely efficient at consuming carcasses:
  • “They can pick a cow carcass clean in under 40 minutes.” – Jonathan Lambert, [03:51]
• Rotting flesh hosts harmful bacteria and pathogens; by rapidly removing carcasses, vultures prevent outbreaks.
• Their incredibly acidic stomachs protect them from diseases:
  • “Their stomach is like 10 times more acidic than ours.” [04:05]

The Domino Effect of Vulture Loss

[04:25]

• Anant Sudarshan explains that without vultures, carcasses are dumped in water bodies, leading to spikes in waterborne diseases:
  • “A lot of them will end up in water bodies, because that’s one easy way to dispose of them.” – Anant Sudarshan, [04:25]
• Mortality data showed a 4% annual increase—about 100,000 extra deaths—attributed to vulture decline.
• Carcasses fuel population booms of feral dogs, increasing rabies deaths:
  • “Something like 50,000 additional people were dying from rabies as a result of these cascading interactions.” – Chinmay Sonawane, [05:12]

Other Scavengers and Ecosystem Health

[06:03]

• Hyenas in Ethiopia: Prevent roughly five cases of anthrax and bovine TB per year by scavenging cattle.
• Civets in Malaysia: By consuming carrion quickly, they reduce bacteria on flies, potentially lowering incidence of diarrheal diseases.
  • “Flies are a big vector for these kinds of diseases, so reducing the bacteria load on them could lead to fewer people getting sick.” – Jonathan Lambert, [06:20]
• Australian Turtles: Scavenging improves wetland water quality.

Scavengers in Decline

[06:57]

• Global review: Of 1,300+ scavenger species, up to 36% are declining or threatened.
  • “The biggest, most specialized scavengers… were more likely to be threatened.” – Jonathan Lambert, [07:22]
• Why? Habitat loss, hunting, and wildlife trade.

Apex vs. Smaller Scavengers

[07:46]

• When apex scavengers (like vultures or hyenas) vanish, smaller scavengers (rats, feral dogs) fill the gap, but poorly.
• Smaller scavengers are less efficient and can themselves transmit diseases to humans.
  • “When we lose these large wildlife, smaller wildlife tend to replace them.” – Chinmay Sonawane, [07:38]
  • “Smaller scavengers… just aren't as good at scavenging as what they call apex scavengers.” – Jonathan Lambert, [08:03]

Public Health Implications

[09:03]

• Christopher O’Brien’s Takeaway:
  • “We need to be always factoring in nature into the equation of human health, human suffering, human well being in general, and we can't ignore it.” – Christopher O’Brien, [09:03]

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Conservation Solutions

What’s Being Done and What Can Be Done?

[09:23]

• Conservation efforts—protecting habitats, restricting hunting—are crucial.
• Banning of toxic drugs (like diclofenac in India) is a step, but recovery is slow.
• “The Indian government banned the use of that toxic painkiller… but the vultures are still struggling to get back to anything close to their old numbers.” – Jonathan Lambert, [09:41]

Broad Lesson

[09:56]

• Human health is tightly linked to the health of natural scavenger populations.
• “This all just shows how dependent our collective health is on the natural world and parts of it that we often ignore. …Protecting animals that are really good at eating dead stuff could lead to a healthier planet for everyone, us included.” – Jonathan Lambert, [09:56]

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Notable Quotes & Memorable Moments

• “Their stomach is like 10 times more acidic than ours.” – Jonathan Lambert, [04:05]
• “Millions more feral dogs, millions more people being bitten by these dogs.” – Chinmay Sonawane, [05:12]
• “A world with fewer apex scavengers is one that could make humans sicker.” – Jonathan Lambert, [08:50]
• “We need to be always factoring in nature into the equation of human health…” – Christopher O’Brien, [09:03]
• “It shows how widening our sense of what we can do to improve health… could lead to a healthier planet for everyone, us included.” – Jonathan Lambert, [09:56]

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Important Timestamps

• 01:09 – The story of India’s vulture crisis and its human health aftermath
• 04:25 – How vulture loss leads to waterborne diseases and rabies surge
• 06:03 – Hyenas, civets, and turtles as other key scavengers
• 06:57 – Global decline: 36% of scavenger species threatened
• 07:38 – Replacement by smaller scavengers and shortcomings
• 09:03 – Nature’s role in public health (Christopher O’Brien)
• 09:41 – Vulture conservation challenges in India
• 09:56 – Final reflections on health, scavengers, and conservation

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Tone and Style Notes

The episode balances a conversational and lively tone (“Hyenas… they get a bad rap in Lion King, but maybe they’re awesome” [06:14]) with rigorously presented research and impactful stories. Humor and vivid imagery are interwoven with sobering statistics, engaging the listener while emphasizing the vital—if often overlooked—connection between animal scavengers and human health.

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Summary prepared for listeners seeking clear insights, key moments, and actionable lessons from NPR’s Short Wave episode: "Why Animal Scavengers Protect Your Health."

Transcript

[A]

This message comes from Memorial Sloan Kettering Cancer center this October. For a short time, your gift to MSK will be triple matched to help support breast cancer research, treatment, and care. Donate [e-mail] match.

[B]

You'Re listening to Shortwave from NPR. Hey, Shortwavers. Regina Barber here, and today I'm joined by NPR science reporter Jonathan Lambert. Hey, John.

[C]

Hey, Gina. Hey.

[B]

Okay, so you're here today to make a case for scavengers like vultures and hyenas that they're good for human health. I mean, honestly, I believe it. They're usually smart. They clean up dead stuff.

[C]

Yeah, totally. To me, though, health isn't the first thing that comes to mind when I picture a vulture hunched over the rancid, rotting flesh of a dead cow, tearing strings of lifeless meat from bone till there's nothing left.

[B]

I really love this visual you're giving me. Yeah, it's that rotting stuff laying around. That's not good for us humans, right?

[C]

And scavengers taste for that. Rotting stuff actually has major benefits for human health, which is maybe best conveyed by a little story.

[B]

Excellent. I love stories. Let's do this.

[C]

Okay, so we're going to India. Way back in the early 1990s, there were some 50 million vultures across India. But in the mid-90s, they started vanishing. And over the course of several years, their numbers plummeted by like, 95%.

[B]

95%? That is huge. So why was that happening?

[C]

A painkiller for livestock that just happens to be toxic to vultures. Its patent ran out in 1993, and usage spiked. Once cheaper generics came onto the market, vultures started eating dead cows that had the drug in their system, which led to a mass die off.

[B]

Ooh, that is terrible. Okay, how did this mass die off affect the area, though?

[C]

Well, some researchers estimate that the absence of vultures led to hundreds of thousands of additional deaths in the five years after the crash.

[B]

Human deaths?

[C]

Yes, humans.

[B]

And you said hundreds of thousands?

[D]

Yeah. Yeah.

[C]

It's one of the clearest examples of how scavengers are connected to human health. But it's far from the only one. And a new analysis suggests that many other scavengers are declining worldwide.

[B]

So today on the show, how human health is intertwined with scavenging animals, why.

[C]

Their decline could lead to more human disease, and how conservation could help.

[B]

You're listening to Shortwave, the science podcast from npr.

[E]

Support for npr, and the following message come from Edward Jones. What does it mean to live a rich life? It means brave first Leaps, tearful goodbyes and everything in between. With over a hundred years of experience navigating the ups and downs of the market and of life, your Edward Jones financial advisor will be there to help you move ahead with confidence. Because with all you've done to find your rich, they'll do all they can to help you keep enjoying it. Edward Jones Member, SIPC this message comes from Schwab. Everyone has moments when they could have done better. Same goes for where you invest. Level up and invest smarter with Schwab. Get market insights, education and human help when you need it. This message comes from dell technologies. Dell AI PCs are newly designed to help you do more faster. That's the power of Dell AI. Powered by Intel Core Ultra processors. Upgrade today by visiting Dell.com deals okay.

[B]

John, so back to these vultures. How exactly did their disappearance lead to hundreds of thousands of people dying?

[C]

The answer lies in the fact that vultures are really, really good at cleaning up dead bodies.

[B]

I knew it. I knew it.

[C]

Like, they can pick a cow carcass clean in under 40 minutes.

[B]

That is super fast.

[C]

Yeah, and rotting flesh is host to all sorts of bacteria, many of which can cause human diseases.

[B]

And these vultures, they're not getting sick. So what's going on there?

[C]

They're super well adapted to eating dead meat. One fun fact, their stomach is like 10 times more acidic than ours.

[B]

This is making my acid reflux look like nothing.

[D]

Yeah, yeah.

[C]

I spoke to Anant Sudarshan, an environmental economist at the University of Warwick who studied the fallout of this mass die off. Here's what he had to say.

[F]

What happens to these carcasses if vultures are not removing them? And at least in India, a lot of them will end up in water bodies because that's one easy way to dispose of them.

[C]

As a result, waterborne pathogens like coliform bacteria can become a bigger problem. Anant and his colleagues analyzed mortality data from the country and found it ticked up 4% because vultures disappeared. That's a lot. And translates to about 100,000 additional deaths a year.

[B]

I mean, it does sound like these vultures are essential for, like, sanitizing the environment.

[C]

Yeah, and their absence had another crucial effect. All that extra meat ended up becoming food for feral dogs, which spiked in number.

[B]

Oh, wow.

[C]

Here's Chinmay Sonawane, a biology grad student at Stanford.

[G]

Millions more feral dogs, millions of more people being bitten by these dogs. And it's estimated something like 50,000 additional people were dying from rabies as a result of these cascading Interactions.

[B]

Rabies. I mean, that's very, very scary. Okay, so this decline of vultures sets off these series of dominoes that, like, ultimately results in more people dying.

[D]

Yeah.

[C]

And to Chinmay, the story of these vultures really exemplifies the huge but often hidden benefits that scavengers provide.

[B]

So I'm guessing other scavengers are doing maybe the same thing.

[C]

For sure. Chinmay told me there's been a burst of studies looking at the relationship between human health and scavengers in the past few years.

[B]

So what other scavengers have actually been studied?

[C]

So one study estimates that hyenas scarfing up cattle carcasses outside of one of the largest cities in Ethiopia prevents five cases of anthrax and bovine tuberculosis each year.

[B]

Oh, wow. Okay. Hyenas, I mean, they get a bad rap in Lion King, but maybe they're awesome.

[D]

Yeah. Yeah.

[C]

Another study found that civets and other scavengers in Malaysia actually reduce the amount of diarrhea causing bacteria that build up on flies by quickly eating carrion. So flies have less time to multiply. Flies are a big vector for these kinds of diseases, so reducing the bacteria load on them could lead to fewer people getting sick.

[B]

Okay, let's back up for a second. What's a civet?

[C]

They're kind of cat like, but also like a long legged weasel. Google them after this.

[B]

Okay.

[C]

And turtles. In Australia, eating carrion was associated with improvements in water quality in wetlands. The list really goes on and on. But there's one big problem.

[B]

Oh yeah, what's that?

[C]

Yeah, like I mentioned, many of these species are declining. Chinmay and his colleagues published a big analysis of all this work in the journal PNAS in June, looking for broader patterns on how scavenging species influence health and also how those scavenging species are doing. They looked at over 1300 species and found that up to 36% are declining or threatened with extinction.

[B]

Ooh, that is a lot. Why?

[C]

Yeah, it's a combination of habitat loss, hunting, and the wildlife trade. Yeah, but they found that not all scavengers were equally at risk. The biggest, most specialized scavengers, things like vultures or hyenas, were more likely to be threatened.

[B]

Wow.

[G]

When we lose these large wildlife, smaller wildlife tend to replace them.

[B]

Okay, what kind of smaller wildlife is he talking about?

[C]

Smaller or less specialized scavengers who sometimes eat carrion, but can eat other things, too. Think things like rats or mice or in India, feral dogs.

[B]

Okay, but if those, like, smaller scavengers are still eating carcasses, wouldn't they maybe sub in for these other scavengers?

[C]

Chinmay actually thought that going into his study. But he and his colleagues ended up finding that these smaller scavengers just aren't, aren't as good at scavenging as what they call apex scavengers.

[B]

Okay, apex scavengers, this is like the great white sharks of eating dead stuff. And these smaller ones just can't keep up.

[C]

Yeah, exactly. Here's Chinmay again.

[G]

Therefore, there's more carcass waste, therefore more pathogens in the environment. And then therefore, people are more likely to pick up disease from these sources.

[B]

Right. I mean, that logic makes sense.

[C]

Yeah. And smaller scavengers like rats or dogs are more likely to carry pathogens themselves. Plus humans are a lot more likely to come into close contact with those than, say, a vulture.

[B]

So in the end, what does this all add up to?

[C]

Chinmay says basically that a world with fewer apex scavengers is one that could make humans sicker. Other researchers I spoke to agreed. Here's Christopher o', Brien, a biologist at Maastricht University.

[H]

The take home message is that we need to be always factoring in nature into the equation of human health, human suffering, human well being in general, and we can't ignore it.

[B]

So what's being done and like, what can be done to help these scavengers?

[C]

Conservation, basically. Chinmay and his colleagues argue that taking steps to conserve top scavengers by protecting their habitat or restricting their hunting could help preserve some of the benefits they provide. But what happened to India's vultures offers a cautionary tale of sorts.

[B]

What's going on right now with those vultures?

[C]

Yeah. So the Indian government banned the use of that toxic painkiller by veterinarians in 2006, but the vultures are still struggling to get back to anything close to their old numbers.

[B]

That is very devastating.

[D]

Yeah.

[C]

And this all just shows how dependent our collective health is on the natural world and parts of it that we often ignore. And it shows how widening our sense of what we can do to improve health, to include something as seemingly random as protecting animals that are really good at eating dead stuff, could lead to a healthier planet for everyone, us included.

[B]

John, thank you for, you know, reinforcing my love for scavengers.

[C]

Actually, happy to do it.

[B]

Short wavers. If you like our show, do us a favor and share it with one, one friend. It helps us grow and sustain our show. We appreciate you. This episode was Produced by Burleigh McCoy and edited by our showrunner, Rebecca Ramirez. Tyler Jones checked the facts, Jimmy Keeley was the audio engineer, Beth Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber.

[C]

And I'm Jonathan Lambert.

[B]

Thank you for listening to Short Wave from N.

[I]

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