# Ant Rafting (DD-662)

> Red imported fire ants (Solenopsis invicta) come from the flood-prone wetlands of Brazil. When water rises, a colony can link itself into a floating raft that carries workers, brood and the queen. In a 2011 PNAS study, Mlot, Tovey and Hu of Georgia Tech filmed raft-building and measured how it works. Ants grip each other jaw-to-leg and leg-to-leg. A single ant's cuticle is only mildly water-repellent, but linking together boosts the colony's water repellency, much like weaving a waterproof fabric. Air trapped around and between the ants cut the raft's average density by about 75%, to about 0.2 g/mL. That trapped air also lets the ants on the bottom breathe, so they rarely drown. About half the ants form the bottom layer. Ants on top walk to the edge and get trapped there by their neighbors, which is how the raft grows. The paper describes rafts floating for days, and Hu's group told reporters they can last up to about three weeks, though most begin to fall apart after a week. Ants also build bridges, ladders and chains in the same way.

- Department: Nature (also Science)
- First published: 2025-10-16
- Last updated: 2025-10-16
- Permalink: https://detailenjoyer.com/case/ant-rafting/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-662-F01**: Trapped air cuts a fire-ant raft's average density by about 75%. _(Write-up · Exhibit C (Air does the floating))_
- **DD-662-F02**: Fire ants grip each other jaw-to-leg and leg-to-leg to form rafts. _(Write-up · Exhibit B (How they link))_

## Write-up

A colony that floats. Fire ants link legs and jaws into waterproof rafts.

1. **Built for floods**: Fire ants (Solenopsis invicta) come from flood-prone Brazilian wetlands and raft whole colonies, including the queen and brood.
2. **How they link**: Ants grip each other jaw-to-leg and leg-to-leg, weaving a sheet that's far more water-repellent than any single ant.
3. **Air does the floating**: Trapped air cut a raft's average density by about 75%, and it lets the bottom ants breathe underwater.
4. **How it grows**: Ants on top walk to the edge and get pinned there by their neighbors, which adds to the raft.
5. **How long**: The study describes rafts floating for days. Researchers say up to about three weeks, though most start breaking up after a week.

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## Reel vs. record

- **Duration**: the 2011 study describes rafts floating 'for days'. Researchers have said they can last up to about three weeks, but most start falling apart after about a week.
- **Air pockets**: trapped air isn't only between the bottom ants. Each ant holds a thin film of air (a plastron), which also lets the bottom layer breathe.
- **Missing**: about half the ants form the bottom layer. Rafts grow because ants on top walk to the edge and get trapped there, not through deliberate 'repair'.
- **Species**: the studied raft-builder is the red imported fire ant (Solenopsis invicta), native to Brazil and invasive in the US and elsewhere.
- **Grip**: they link with their jaws (mandibles) and claws on their feet (tarsi), and those links let the raft flex rather than break.

## Video: Ant Rafting: A Colony That Floats

- Duration: 25.7 s · Published: 2025-10-16
- File: https://detailenjoyer.com/assets/videos/DP4qffwEvKZ.mp4

### Transcript

DID YOU KNOW? When floods threaten their colonies, fire ants perform one of nature's most remarkable survival feats. They build living bridges and rafts out of their own bodies! By linking their legs and jaws together, thousands of ants form a buoyant, interlocking structure that can float for weeks on water. The ants on the bottom grip tightly while trapping air pockets between them, creating a waterproof layer that keeps the colony afloat. Others move freely across the surface to stabilize or repair the raft as it drifts. NOW YOU KNOW!

## Questions & answers

**Q: Which ant was studied building rafts?**  
A: The red imported fire ant, Solenopsis invicta. _(Source: Write-up · Exhibit A (Built for floods) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; Science News: Teamwork keeps fire ants high and dry)_

**Q: Where are fire ants originally from?**  
A: Flood-prone wetlands of Brazil. _(Source: Write-up · Exhibit A (Built for floods) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; Science News: Teamwork keeps fire ants high and dry)_

**Q: About how much does trapped air cut a raft's density?**  
A: About 75%, to roughly 0.2 g/mL. _(Source: Write-up · Exhibit C (Air does the floating) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS)_

**Q: How do the ants link together?**  
A: Mandibles and tarsi. _(Source: Write-up · Exhibit B (How they link) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; National Geographic Education (2017): Floating fire ants mess with Texas)_

**Q: How long did the 2011 study say rafts float?**  
A: For days. Other accounts say up to about three weeks. _(Source: Write-up · Exhibit E (How long) · Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS; National Geographic Education (2017): Floating fire ants mess with Texas)_

## Sources

- [Mlot, Tovey and Hu (2011), Fire ants self-assemble into waterproof rafts to survive floods, PNAS](https://www.pnas.org/doi/10.1073/pnas.1016658108)
- [Science News: Teamwork keeps fire ants high and dry](https://www.sciencenews.org/article/teamwork-keeps-fire-ants-high-and-dry)
- [National Geographic Education (2017): Floating fire ants mess with Texas](https://blog.education.nationalgeographic.org/2017/08/31/floating-fire-ants-mess-with-texas/)

## Cite this case file

Easterling, Marcus. "Ant Rafting." The Detail Department (DetailEnjoyer), case file DD-662, last updated Oct 16, 2025. https://detailenjoyer.com/case/ant-rafting/