# Tree Scaling (DD-650)

> Climbing a vertical trunk is hard for an animal with no limbs, and biologists have studied how snakes do it in detail. In a 2020 review, Bruce Jayne of the University of Cincinnati described arboreal concertina locomotion. The snake grips a cylinder with alternating left and right bends, and keeps a grip with the uphill part of its body before letting go with the downhill part. It then stretches forward and pulls the rest of its body up. Concertina is reliable, but slow and energetically costly. On rough bark or among twigs and branches, snakes can also use lateral undulation, pushing against bumps and side branches with a wave that passes along the body. This needs something to push against; it doesn't work on smooth surfaces. In 2021, a team including Thomas Seibert, Julie Savidge and Jayne described a new mode in Current Biology called lasso locomotion. Brown tree snakes (Boiga irregularis) on Guam wrapped a single loop around smooth poles too wide for concertina, then inched upward by small bends moving within the loop. The discovery came from efforts to keep the invasive snakes away from nests of endangered birds. The footage shows a snake gripping a pale, smooth trunk at night with tight coils and moving up in stages. The source doesn't identify the species.

- Department: Nature (also Science)
- First published: 2025-09-12
- Last updated: 2025-09-12
- Permalink: https://detailenjoyer.com/case/tree-scaling/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-650-F01**: Concertina climbers grip before letting go. _(Write-up · Exhibit A (Grip before you let go))_
- **DD-650-F02**: Brown tree snakes can climb poles using lasso locomotion. _(Write-up · Exhibit D (The lasso))_

## Write-up

Snakes that climb straight up. Concertina climbers grip, stretch and pull.

1. **Grip before you let go**: In arboreal concertina, the snake grips with its uphill section before releasing its downhill section.
2. **Slow but safe**: Concertina climbing is reliable but slow and energetically costly.
3. **Pushing on bumps**: Lateral undulation needs bumps or branches to push against, so it fails on smooth surfaces.
4. **The lasso**: In 2021, brown tree snakes were seen climbing wide, smooth poles by forming a single loop.
5. **Why it was found**: The work came from efforts to keep invasive brown tree snakes on Guam away from bird nests.

## Related case files

- [insularis blue (DD-628)](https://detailenjoyer.com/case/insularis-blue/): A tree-dwelling snake
- [Snake Supreme (DD-694)](https://detailenjoyer.com/case/snake-supreme/): Another snake case
- [The Baobab Tree (DD-268)](https://detailenjoyer.com/case/the-baobab-tree/): I linked more on trees
- [The Hills Have Lungs (DD-321)](https://detailenjoyer.com/case/the-hills-have-lungs/): I linked more on trees

## Reel vs. record

- **Note**: 'Pressing their scales against rough bark': in lateral undulation, snakes push sideways against bumps, twigs and branches. On a smooth trunk it doesn't work, which is why concertina is used there.
- **Note**: 'Muscular strength... specialized movement patterns': true, and well studied. Biologists define concertina by gripping with the uphill part before releasing the downhill part.
- **Missing**: concertina climbing is slow and costly in energy, which limits how fast snakes can go up trunks.
- **Missing**: a third climbing mode, lasso locomotion, was described in 2021 in brown tree snakes climbing smooth poles too wide for concertina.
- **Note**: 'Many employ a concertina motion': on vertical cylinders like trunks and poles, concertina is the standard mode. On branches with plenty of footholds, undulation is more common.

## Video: Tree Scaling: Snakes That Climb Straight Up

- Duration: 24.4 s · Published: 2025-09-12
- File: https://detailenjoyer.com/assets/videos/DOhdnx-kVwj.mp4

### Transcript

DID YOU KNOW? Snakes climb trees by using a combination of muscular strength, flexibility, and specialized movement patterns that allow them to grip and push against the bark. Many employ a concertina motion where parts of the body anchor tightly against the surface while other sections extend forward, then pull the rest along. Some species use lateral undulation, pressing their scales against rough bark or branches in wave-like movements to gain traction. NOW YOU KNOW!

## Questions & answers

**Q: What climbing mode uses alternating grips and stretches?**  
A: Grip uphill, release downhill, stretch forward. _(Source: Write-up · Exhibit A (Grip before you let go) · Jayne (2020): What defines different modes of snake locomotion?, Integrative and Comparative Biology (PMC))_

**Q: What is the main drawback of concertina climbing?**  
A: Reliable but energetically expensive. _(Source: Write-up · Exhibit B (Slow but safe) · Jayne (2020): What defines different modes of snake locomotion?, Integrative and Comparative Biology (PMC); Savidge, Seibert, Kastner & Jayne (2021): Lasso locomotion expands the climbing repertoire of snakes, Current Biology)_

**Q: What does lateral undulation need to work?**  
A: It fails on smooth surfaces. _(Source: Write-up · Exhibit C (Pushing on bumps) · Jayne (2020): What defines different modes of snake locomotion?, Integrative and Comparative Biology (PMC))_

**Q: Which snake was seen using lasso locomotion?**  
A: On Guam, in 2021. _(Source: Write-up · Exhibit D (The lasso) · Savidge, Seibert, Kastner & Jayne (2021): Lasso locomotion expands the climbing repertoire of snakes, Current Biology; Colorado State University: Scientists discover bizarre new mode of snake locomotion)_

**Q: Where were the lasso-climbing snakes studied?**  
A: Where they're invasive. _(Source: Write-up · Exhibit E (Why it was found) · Colorado State University: Scientists discover bizarre new mode of snake locomotion)_

## Sources

- [Jayne (2020): What defines different modes of snake locomotion?, Integrative and Comparative Biology (PMC)](https://pmc.ncbi.nlm.nih.gov/articles/PMC7391877/)
- [Savidge, Seibert, Kastner & Jayne (2021): Lasso locomotion expands the climbing repertoire of snakes, Current Biology](https://www.cell.com/current-biology/fulltext/S0960-9822(20)31763-2)
- [Colorado State University: Scientists discover bizarre new mode of snake locomotion](https://warnercnr.source.colostate.edu/scientists-discover-bizarre-new-mode-of-snake-locomotion/)

## Cite this case file

Easterling, Marcus. "Tree Scaling." The Detail Department (DetailEnjoyer), case file DD-650, last updated Sep 12, 2025. https://detailenjoyer.com/case/tree-scaling/