Radiolab: "Argentine Invasion"

Original Air Date: July 31, 2012
Hosts: Jad Abumrad & Robert Krulwich
Special Guests: David Holway, Neil Tsutsui, Mark Moffett, Melissa Thomas, Jill Shanahan

Overview:

This episode of Radiolab explores the fascinating—and unsettling—story of the Argentine ant, an invasive species that has quietly conquered vast stretches of the globe. Through investigative fieldwork, jaw-dropping ant battles, and cutting-edge evolutionary biology, the hosts unravel how a tiny, violent, and hyper-loyal species can become an empire-building superorganism, raising questions about biology, competition, and the parallels (and perils) for human society.

Key Discussion Points & Insights

1. A Seemingly Ordinary Neighborhood—Hiding an Ant Empire

• [01:45–05:15]
  • The hosts meet Dr. David Holway, ecologist at UC San Diego, in a quiet California suburb.
  • Holway demonstrates the ant "border" using a curious vial device—collecting ants from either side of a driveway ([03:20]).
  • Hosts are stunned as two ants from opposite sides are placed in a container and immediately get into a deadly fight ([04:20]).
    • Quote (Robert): "They lock antenna. And soon they're in a ball. This isn't good. That is heavy duty fighting." ([04:26])

2. Origin Story: The Floodplains of Argentina

• [05:16–07:23]
  • Guests Neil Tsutsui and Mark Moffett describe the birthplace of the Argentine ant, a harsh, flooded plain between two rivers.
  • Constant flooding forces ant groups into repeated conflict with each other, breeding extreme aggression and purity within colonies.
    • Quote (Mark Moffett): "Over time, eons of this, they simply do not know how to stop killing each other." ([06:21])

3. A Global Stowaway—How the Ants Conquered the World

• [07:23–10:44]
  • In the late 19th century, some ants escape on ships, first spotted in New Orleans (1891), then California (1907).
  • Their unique strategy: absolute in-group loyalty, total out-group aggression, and a refusal to mix with other ant lines.
    • Quote (Jad): "Their survival strategy was pretty simple. Kill everything. If it’s not one of us, kill it no matter what." ([08:06])
  • Unlike other ants, Argentine ants do not take slaves or capture outsiders, maintaining genetic "purity."
  • This facilitates huge, unified populations—so-called "supercolonies."
  • Their spread is aided by human-altered habitats—lawns, sprinklers, and transport networks.

4. Scientific Road Trip—Mapping the Supercolony

• [11:42–13:10]
  • Neil Tsutsui and Andy Suarez travel up California, performing the "ant fight test" at intervals (i.e., mixing ants from different areas to see if they fight).
    • Quote (Neil Tsutsui): "Tap, tap, tap, sniff, sniff, sniff, sniff. And they recognize San Diego ants as being members of the same colony." ([12:29])
  • They find that across 600 miles, from San Diego to north of San Francisco, ants never fight—they are part of one, immense colony.

5. Supercolonies Around the World

• [13:11–15:10]
  • Melissa Thomas and other scientists discover related supercolonies across Europe, Japan, Australia, New Zealand, South Africa, and more.
  • Experiments reveal ants from places like Japan and Italy still recognize each other as kin after thousands of miles and generations.
    • Quote (Jad): "Just think about that for a second... Imagine one of those [ant mounds] 600 miles wide… with trillions and trillions of ants in it." ([13:10])
    • Quote (Neil Tsutsui): "At some point in the past, one colony in Argentina got picked up and moved around and spread... The descendants of those ants we have now, across all continents except Antarctica." ([14:53])

6. Biological Allegiance & Uncomfortable Parallels to Human Society

• [15:10–16:10]
  • The hosts press Neil on whether this loyalty and in-group aggression parallel aspects of human behavior.
    • Quote (Neil Tsutsui): "For our Argentine ant research, we’ve had people say, 'look, the lesson… is that we should all be like Argentine ants and get along.' But then, on the other hand, I’ve had white supremacist websites cite my research and say… 'the key to success is not mixing the races.'" ([15:32])
    • He cautions against drawing too neat a moral lesson from ants.

7. A New Challenger Appears—The Empire Fractures

• [16:10–18:32]
  • Jill Shanahan discovers that a new family of Argentine ants (a rival supercolony) has established itself in California.
  • Fieldwork locates the border between two warring ant empires—a hellish "channel of death" in the middle of a leafy suburb, with "hundreds of thousands" of dead ants ([18:09]).
    • Quote (Melissa Thomas): "Live ants were pouring into this area and fighting to the death. Masses and masses of them fighting." ([18:18])
    • Quote (David Holway): "There were times when we didn’t even need to get out of the car to find the super colony boundary because you'd see the dead workers spilling over the curb." ([18:34])

8. The Price of Empire

• [19:03–19:18]
  • The conquests come at a devastating cost; these ants may be numberless, but they are locked in endless war at the borders of their empires.
    • Quote (Robert Krulwich): "This, then, is the price of empire... every day, they pay the price in bodies. At the border, this guy has lost all... he’s only got limbs on one side now." ([19:03])

9. Cycle of Violence and Expansion

• [19:18–19:48]
  • Violence and intolerance is a successful strategy—until it meets itself, or something even more dangerous.
    • Quote (Jad): "So in the end, this strategy of violence and intolerance seems to be pretty good. Until it meets itself." ([19:18])

Memorable Quotes

• “These are Genghis Khan in an ant.”
  — Robert Krulwich ([10:30])

• "They simply, simply do not know how to stop killing each other."
  — Mark Moffett ([06:21])

• "The smell that bonds them together hasn’t changed."
  — Neil Tsutsui ([14:50])

• "Every day, they pay the price in bodies."
  — Robert Krulwich ([19:03])

Timestamps for Critical Segments

• [01:45–05:15] — Field demonstration of Argentine ant aggression and boundaries
• [05:16–07:23] — Description of ancestral home and behavior origins
• [11:42–13:10] — Road trip experiment showing a 600-mile-wide ant supercolony
• [13:11–15:10] — How one colony has gone global, spanning continents
• [15:10–16:10] — Parallels to human society, interpreted (and misinterpreted)
• [16:10–18:32] — Discovery of a new colony, the border war, and the massacre zone
• [19:03–19:18] — Reflections on the cost and sustainability of empire

Tone & Style

Radiolab’s characteristic sense of awe, playful curiosity, and occasional dark humor run through the episode, with vivid sound design and scene work. Scientific guests describe their work with excitement and gravitas, while the hosts probe for big-picture meaning—and unresolvable social analogies—lurking beneath the surface of ant warfare.

Summary Takeaways

In “Argentine Invasion,” Radiolab unearths the mind-boggling invasion of Argentine ants—a species whose blend of rigid loyalty, relentless violence, and uncanny adaptability has allowed it to forge supercolonies spanning continents. Yet, beneath their empire’s surface lies an endless cycle of war, death, and the paradox of unity through exclusion. The show closes with the sobering observation that even the most successful empires pay a fearsome price—and may eventually collide with rivals just as ruthless as themselves.