# Slithering Locomotion

> How does a snake move forward with no legs and nothing to push against? Using corn snakes and milk snakes, a computer model and some slippery table tops, the authors show that belly scales grip sideways better than forwards, and that slithering snakes lift parts of their body to press harder where it counts. On a smooth surface, a snake can slither all it likes and go nowhere.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2012-hu-shelley-slithering-locomotion/

## Citation and access

- **Authors:** David L. Hu and Michael J. Shelley
- **Year published:** 2012
- **Journal or source:** Natural Locomotion in Fluids and on Surfaces: Swimming, Flying, and Sliding (The IMA Volumes in Mathematics and its Applications, vol. 155), Springer
- **Full citation:** Hu, D. L. and Shelley, M. J. 2012. Slithering locomotion. In: Childress, S., Hosoi, A., Schultz, W. W. and Wang, Z. J. (eds.) Natural Locomotion in Fluids and on Surfaces: Swimming, Flying, and Sliding. The IMA Volumes in Mathematics and its Applications 155. Springer, New York. pp. 117-135.
- **DOI:** 10.1007/978-1-4614-3997-4_8
- **Access status:** Publisher link only
- **Where to find it:** https://doi.org/10.1007/978-1-4614-3997-4_8

## Tags

- **Species:** Reptiles > Boa constrictor; Reptiles > Corn snake; Reptiles > Milk snake
- **Behaviour and ecology:** Behaviour; Energy budget; Movement
- **Methods and technology:** Literature review; Simulation
- **Data type:** Existing data; Modelling or theoretical; Review
- **Observer qualification:** Not needed
- **Discipline:** Behaviour and ecology
- **Year published:** 2012

## Detailed keywords

- **Species:** Studied: snakes (suborder Serpentes); laboratory experiments with juvenile corn snakes and milk snakes (no scientific names given). Skin thickness measured from the shed skin of a 30 cm corn snake and a 2 m red-tailed boa. Speed and mass data compiled from earlier studies for 140 snakes (the text says 140 species, the figure caption says 140 specimens). Mentioned for comparison: red racer (60 to 135 cm long, up to 130 cm per second), threadsnakes, anacondas, worms, snails, insects, horses, cockroaches and human infants.
- **Location and habitat:** Laboratory study, no field site. Test surfaces: stretched cloth (roughness about 0.2 mm), smooth fiberboard table top (roughness about 20 micrometres), a cloth-covered incline (0 to 12 degrees) and photoelastic gelatin. Authors based at the Georgia Institute of Technology, Atlanta, and the Courant Institute, New York University, USA.
- **Topics:** limbless locomotion; snake gaits (lateral undulation or slithering, sidewinding, concertina, rectilinear); friction and frictional anisotropy of belly scales; body lifting and weight redistribution while slithering; energetic cost of transport; speed and body size scaling; gait choice by body size; skin wear and shedding; microscopic push points; snake-like robots.
- **Statistics or models:** Kinematic model of the snake as a one-dimensional curve with a travelling wave of curvature; Newton’s second law with an anisotropic sliding friction law; numerical solution (second-order Adams-Bashforth scheme, trapezoidal rule); dimensionless ratios (Froude number, frictional anisotropy); scaling arguments (speed with mass to the one-third power; maximum travel before skin wear inversely proportional to length); mechanical efficiency. Inconsistencies in the paper: (1) “140 species” in the text versus “140 specimens” in the Figure 2 caption; (2) body lifting raises speed by “35%” in Section 4.3 but “up to 30%” in the Discussion; (3) efficiency is said to rise “nearly up to 50%” from 0.3 to 0.55, which is a rise of over 80%; (4) the milk snake on cloth is given an efficiency of 0.25 in Section 4.2 but 0.3 with no lifting in Section 4.3; (5) the observed body shape is given as amplitude 7.0 in one place and (2, 8) in another.
- **Data type:** Review of the authors’ earlier work (Hu et al. 2009, Proceedings of the National Academy of Sciences) and of other snake locomotion studies, with laboratory observations of snakes, existing data compiled from the literature, and modelling. No dates of data collection given.

## Synopsis

### 1. What they did

Animals without legs, such as worms, snails and snakes, move over land by sliding their bellies along the ground. Swimming, flying and walking have been studied much more than sliding. In this book chapter, the authors review and expand their own earlier work on how snakes slither across flat surfaces, using dry friction between belly and ground.

- Background. They compiled published speed and size data for 140 snakes, described the four main snake “gaits” (lateral undulation or slithering, sidewinding, concertina and rectilinear movement), and summarised earlier studies of the energy cost of each gait.

- Friction measurements. Using juvenile corn snakes and milk snakes (about 30 cm long), they measured how easily the snakes slide forwards, backwards and sideways on cloth and on smooth fiberboard.

- A computer model. They built a model of a slithering snake that uses these friction values and the snake’s wave-like body shape to predict speed and efficiency.

- Body lifting. They filmed snakes from the side and added to the model the way snakes lift parts of their body off the ground while slithering.

### 2. What they found

Snake gaits, size and speed

- Over 2,900 snake species range from 10 cm threadsnakes to 10 m anacondas, and their body proportions stay about the same at every size.

- Speed in the undulating gaits rises in step with body length, unlike birds and fish, where speed rises more slowly with size.

- Snakes lighter than about 1 kg mostly use undulating gaits; heavier snakes mostly use concertina or rectilinear movement. The authors explain this by strength: a large snake cannot pull its whole body against friction at once, so it moves one part at a time.

- From earlier treadmill studies: slithering costs about as much energy per kilogram per metre (23 joules) as running does for a mammal or bird of similar size. Sidewinding is the cheapest gait (8 joules) and concertina the most costly (170 joules).

- Because snakes shed their skin rather than healing it, the authors estimate that the distance a snake can travel before wearing through its belly skin gets shorter as the snake gets longer, so avoiding wear matters most for large snakes.

Friction and the belly scales

- The overlapping belly scales catch on tiny bumps in the ground. On cloth, the snakes slid most easily forwards (friction 0.11), less easily backwards (0.14) and least easily sideways (0.19).

- The key to speed is how much harder it is to slide sideways than forwards. On cloth this was about twice as hard for milk snakes; on smooth fiberboard it was about the same, and a milk snake “slithered in place”, hardly moving forward. The model matched this.

- Inertia hardly matters: friction is far stronger, so a snake stops almost as soon as it stops slithering.

- The snakes slithered as fast on cloth as on boards with pegs, because the tiny bumps in the cloth act as “microscopic push points”.

- On a cloth incline, a milk snake slithered in place at 7 degrees and slid backwards on steeper slopes (supplementary video).

Body lifting

- Slithering snakes lifted the peaks and troughs of their body wave off the ground, pressing down harder with the parts in between.

- In the model, moderate lifting made the snake 35% faster and raised its efficiency from 0.3 to 0.55, not counting the effort of lifting.

### 3. What they concluded

- Snakes use two main mechanisms to slither on flat surfaces: belly scales that give more grip sideways than forwards, and lifting parts of the body to reduce drag and press harder where the body pushes forward.

- How well a snake slithers depends heavily on the surface. On surfaces too smooth for the scales to grip, snakes switch to other gaits or lift their bodies.

- Microscopic push points are a new idea that should be considered in models of snakes on all surfaces.

- The model is crude: it does not include the snake’s ability to change the angle of its scales or the energy spent lifting the body, which may be large for big snakes. Pressure sensors might help measure how snakes shift their weight.

- Body lifting shows that limbless movement has things in common with walking, where animals lift rather than drag their limbs. This matters for designing efficient snake-like robots.

### 6. Other technologies, skills or innovations

- Friction measured on unconscious snakes laid out straight, on cloth and fiberboard.

- Time-lapse and side-view video of slithering snakes, with four supplementary videos on YouTube.

- Photoelastic gelatin, which glows where force is applied, was tried but was too sticky for snakes to move naturally.

### 8. Implications for tracking (Original Wisdom's observations)

_These are Original Wisdom's observations, not the authors'._

- The chapter does not discuss trails, but its findings may help trackers read snake trails: a snake’s gait depends on its size and on the surface, and a slithering snake presses down hardest between the bends of its body wave and lifts at the bends. Whether this shows in a trail on sand or soil was not tested.

## Cite this summary

Lawrence, K. 2026. Summary of: Slithering Locomotion (Hu and Shelley, 2012). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2012-hu-shelley-slithering-locomotion/