Zubair Khalid

Virologist/Molecular Biologist | Veterinarian | Bioinformatician

Conventional & Molecular Virology • Vaccine Development • Computational Biology

Dr. Zubair Khalid is a veterinarian and virologist specializing in conventional and molecular virology, vaccine development, and computational biology. Dedicated to advancing animal health through innovative research and multi-omics approaches.

Dr. Zubair Khalid - Veterinarian, Virologist, and Vaccine Development Researcher specializing in Computational Biology, Multi-omics, Animal Health, and Infectious Disease Research

Category: Blog

How Do Snakes Move? The Four Main Locomotion Methods

Snakes move through four primary locomotion methods: serpentine undulation, concertina locomotion, sidewinding, and rectilinear movement. Each method uses different muscle groups, body-substrate interactions, and environmental conditions. Understanding these methods matters for students, researchers, and life-science professionals who study animal biomechanics, design bio-inspired robots, or manage human-snake conflict situations. This article explains the mechanics of each method, the conditions where each is used, and how researchers study snake movement using both biological observation and robotic models.

At a Glance: The Four Locomotion Methods

Locomotion Method Primary Mechanism Typical Substrate Example Species Energy Considerations
Serpentine undulation Lateral body waves push against surface irregularities Open ground, grass, sand Rat snakes, garter snakes Efficient on surfaces with push points
Concertina Alternating anchor and pull phases with accordion-like body bends Narrow tunnels, branches, pipes Boas, pythons, tree snakes Higher energy cost per distance
Sidewinding Sequential body lifts and contacts at an angle to travel direction Loose sand, hot desert surfaces Sidewinder rattlesnakes, desert vipers Reduces contact with hot surfaces
Rectilinear Belly scales grip and pull the body forward in a straight line Flat ground, inside burrows Boas, pythons, large vipers Slow but steady and quiet

Serpentine Undulation: The Most Common Method

Serpentine undulation, also called lateral undulation, is the movement pattern most people picture when they think of snakes. The snake forms a series of S-shaped curves along its body and pushes backward against surface irregularities, rocks, grass stems, or small bumps. The body waves travel from head to tail, and each curve provides a push point that drives the snake forward.

The effectiveness of serpentine undulation depends on friction anisotropy, meaning the snake's skin resists movement differently depending on direction. The ventral scales grip the substrate more effectively when sliding backward than forward, which converts lateral body waves into forward propulsion. Research on snake-inspired robots has shown that body undulation and the physical architecture of a snake body offer significant benefits over legged or wheeled designs in certain scenarios, which is why many research groups have developed snake-inspired robots to exploit these advantages [6].

Serpentine undulation works best on surfaces with enough irregularities to push against. On perfectly smooth glass or polished metal, a snake using this method will struggle because there are no push points. The snake can still move, but the efficiency drops considerably. Studies of optimal snake locomotion on flat surfaces have derived analytical solutions for kinematics that minimize energy cost or maximize velocity under varying friction anisotropy conditions, assuming uniform weight distribution and negligible body rigidity [17].

Muscle Coordination in Serpentine Movement

The snake's axial musculature contracts in sequence along the body. Electromyography studies in snakes have revealed how muscle contraction dynamics relate to body motion kinematics. Researchers have developed methods for chronic subdermal implantation of up to eight bipolar electrodes above target muscles, allowing reliable recording of muscle activity over multiple days in species such as Amazon tree boas and Western diamondback rattlesnakes [8]. These recordings show that muscle activation waves travel along the body in coordination with the visible undulation pattern.

The neural control of this movement involves central pattern generators, which are neural circuits that produce rhythmic motor patterns without requiring sensory feedback for each cycle. Snake robots have been built using cyclic inhibitory central pattern generator models to reproduce serpentine locomotion, demonstrating that this neural architecture can generate the traveling waves seen in biological snakes [30].

Concertina Locomotion: Anchoring and Pulling

Concertina locomotion is used when a snake needs to move through narrow spaces such as burrows, tunnels, pipes, or dense vegetation. The snake anchors the rear portion of its body against the tunnel walls, then extends the front portion forward. After the front section finds a grip, the snake pulls the rear section forward, creating an accordion-like pattern of alternating anchor and pull phases.

This method is slower and more energy-intensive than serpentine undulation because the snake must repeatedly establish and release anchors. However, it allows movement in confined spaces where lateral undulation is impossible. The body bends are tighter and more pronounced than in serpentine movement, with the snake forming sharp curves that press against opposite sides of the tunnel.

Research on snake robots climbing in crowded pipes has demonstrated the practical application of concertina-like movement. A sinusoidal curve control method combined with a hybrid force-position controller allowed a snake robot to move faster and more stably through crowded pipe environments compared to previous control methods [4]. This work shows how understanding the mechanics of confined-space movement translates into engineering solutions.

When Snakes Choose Concertina Movement

Snakes switch to concertina locomotion when the environment demands it. In a narrow burrow, the walls provide the anchor points needed for this method. On open ground, a snake might use concertina movement when it needs to move slowly and carefully, such as when stalking prey or moving through thick leaf litter where push points are unpredictable.

Tree-dwelling snakes use a variation of concertina movement when climbing branches. The body wraps around the branch, anchors with the rear section, extends forward, then pulls the rear section up. This allows movement along branches of varying thickness and orientation.

Sidewinding: Movement for Loose Substrates

Sidewinding is a specialized locomotion method used primarily on loose substrates like sand, where serpentine undulation would fail because the substrate cannot provide stable push points. The snake moves at an angle to its body orientation, lifting portions of the body off the ground while other portions maintain contact.

The characteristic sidewinding track shows a series of parallel J-shaped marks instead of the continuous wavy trail of serpentine movement. The snake's body makes contact with the ground in a series of short segments, and the lifting of body sections reduces the surface area in contact with hot desert sand. This has a thermoregulatory benefit because it minimizes heat absorption from the substrate.

Sidewinding also allows movement across surfaces that would be difficult for other methods. The reduced contact area means the snake can move across loose sand without sinking, and the lifting motion prevents the body from dragging through the substrate. The sidewinder rattlesnake of North American deserts and several African and Asian desert vipers use this method as their primary form of locomotion.

Biomechanics of Sidewinding

The sidewinding gait involves a traveling wave of body lift that moves from head to tail while the snake's overall direction of travel is at an angle to the body axis. The head moves forward and to the side, the body follows in a rolling wave, and the tail lifts and moves to a new position. The result is a diagonal movement path with the body oriented roughly perpendicular to the direction of travel.

The frictional anisotropy of snake skin plays a role in sidewinding as well. Research on anisotropic origami feet for burrowing robots has noted that biological systems exploit anisotropic body forces for locomotion, including the frictional anisotropy of a snake's skin [7]. This principle allows the snake to generate directed movement from the interaction between body waves and substrate resistance.

Rectilinear Locomotion: The Straight-Line Method

Rectilinear locomotion is the slowest of the four methods but allows snakes to move in a straight line without visible body bending. This method is used by heavy-bodied snakes such as boas, pythons, and large vipers, particularly when moving across open ground or through burrows where lateral undulation would be conspicuous or inefficient.

The movement is produced by the belly scales and the associated musculature. The snake's ventral scales alternately grip the substrate and release, pulling the body forward in a smooth, gliding motion. The skin stretches and contracts as the scales move, creating a rippling effect along the belly. From above, the snake appears to glide without any lateral movement.

Rectilinear locomotion is quiet and allows a snake to move without the side-to-side motion that might alert prey or predators. It is also effective on flat, smooth surfaces where serpentine undulation would lack push points. The method is energy-intensive for the muscle work involved, but it provides precise, controlled movement.

Muscular Basis of Rectilinear Movement

The rectilinear method relies on the complex arrangement of muscles connecting the ribs to the ventral scales. These muscles contract in sequence, lifting and advancing small sections of the belly scales while other sections maintain grip. The result is a continuous wave of scale movement along the belly.

This method requires significant muscular coordination because the snake must maintain grip with some scales while advancing others. The movement is slower than serpentine undulation but provides greater control and stability, which is advantageous for heavy-bodied snakes that cannot easily perform the rapid lateral bending of serpentine movement.

How Snakes Switch Between Locomotion Methods

Snakes are not limited to a single locomotion method. They switch between methods based on substrate conditions, speed requirements, and the immediate environment. A snake moving across open ground might use serpentine undulation, then switch to concertina movement when entering a burrow, then use rectilinear movement when stalking prey on flat ground.

The ability to switch methods reflects the flexibility of the snake's musculoskeletal system. The same muscles that produce rapid lateral undulation can produce slow, controlled rectilinear movement. The neural control systems can generate different gait patterns and transition between them as conditions demand.

Research on snake robots has explored how control systems can generate multiple locomotion patterns. Genetic algorithms have been used to generate snake robot locomotion patterns, demonstrating that different gaits can be optimized for different conditions [28]. Environment-adaptable locomotion in snake-like robots has also been studied, showing how robots can adjust their movement patterns based on terrain [26].

The Role of Body Compliance in Complex Terrain

Snakes can traverse almost any terrain, including large obstacles like boulders and fallen trees that lack obvious anchor points. Research on the variable kingsnake has shown that this generalist species combines lateral oscillation with cantilevering to traverse large, smooth obstacles. The overall gait is preserved regardless of step height and surface friction [9].

Analysis of three-dimensional body kinematics during obstacle traversal revealed that the snake maintains perfect stability even on challenging low-friction, high-step surfaces. When this gait was applied to a snake robot, the robot rapidly and stably traversed steps nearly as high as a third of its body length. However, as step height increased, the robot rolled more frequently and sometimes flipped over, reducing traversal probability [9].

The absence of such failure in the biological snake inspired researchers to add body compliance to the robot. With better surface contact, the compliant body robot suffered less roll instability and traversed high steps at higher probability [9]. This finding demonstrates that body compliance is a critical factor in snake locomotion on complex terrain, allowing the body to conform to surfaces and maintain stability.

Snake Locomotion in Water

Snakes are also capable swimmers, using modified forms of undulation for aquatic movement. Underwater snake robots have been developed to study the efficiency of different swimming gaits, including lateral undulation and eel-like motion patterns. Research has investigated the relationship between gait parameters, forward velocity, and energy consumption for different motion patterns [5].

The long, slender structure of snakes provides superior capabilities for access through narrow openings and confined areas, which is interesting for inspection and monitoring operations in subsea industries and marine archaeology [5]. Bioinspired locomotion through oscillatory gaits is interesting from an energy efficiency perspective, and increasing motion efficiency in terms of achieved forward speed is a key issue for underwater robots [5].

Energy efficiency is one of the main challenges for long-term autonomy of underwater robots. Studies have considered both velocity and power consumption of underwater snake robots for lateral undulation and eel-like motion patterns, with simulation and experimental results supporting theoretical findings [5]. Path tracking control and locomotion efficiency optimization have also been studied, with improved pigeon-inspired algorithms used to dynamically select gait parameters that maximize energy efficiency [21].

Climbing and Vertical Movement

Some snakes are accomplished climbers, and the mechanics of vertical movement differ from horizontal locomotion. Research on the Pacific lamprey, which uses a scansorial gait similar to snake climbing, has demonstrated dynamic climbing on flat, near-vertical surfaces. The lamprey-inspired robot Trident achieved a peak net vertical stride displacement of 4.1 cm per step and a vertical climbing speed of 4.8 cm per second when actuating at 1.3 Hz [3].

The reduced-order model developed in this research explored the relationship between body actuation and vertical and lateral motions of the robot. The computational and experimental results demonstrated that a lamprey-inspired climbing gait coupled with appropriate attachment is a useful climbing strategy for snake robots climbing near-vertical surfaces with limited push points [3].

For biological snakes, climbing involves concertina-like movements with the body wrapping around branches or pressing against surfaces. The scales provide friction that prevents slipping, and the body's flexibility allows the snake to conform to irregular surfaces. Tree-dwelling species have evolved body shapes and scale patterns that enhance climbing ability.

Air-to-Land Transitions and Self-Righting

Snakes sometimes fall from trees or other elevated positions, and their ability to control landing and self-right is important for survival. Recent observations of wingless animals, including snakes, have shown that adaptations and body morphing are essential for rapid self-righting and controlled landing [10]. These skills reduce the risk of physical damage during collision, minimize recoil during landing, and allow for a quick escape response to minimize predation risk.

The size, mass distribution, and speed of an animal determine its self-righting method, with larger animals depending on the conservation of angular momentum and smaller animals primarily using aerodynamic forces [10]. Many animals falling through the air adopt a skydiving posture while descending, which allows for controlled landing and effective settling.

Studying Snake Locomotion: Methods and Tools

Researchers study snake locomotion using a variety of methods, including high-speed video analysis, force plate measurements, electromyography, and robotic models. Each method provides different information about the mechanics of movement.

High-speed video allows researchers to track the movement of specific body points over time, revealing the kinematics of different gaits. Force plates measure the forces exerted by the snake on the substrate, providing information about propulsion and weight distribution. Electromyography records muscle activity, revealing the neural control of movement.

Robotic models serve as physical simulations of snake locomotion, allowing researchers to test hypotheses about movement mechanics in controlled conditions. Snake robots have been developed to study everything from basic undulation to complex obstacle traversal. A survey of snake-inspired robot designs categorized different types of robots based on their main characteristics and discussed their relative advantages and disadvantages [6].

Kinematic Analysis Methods

To quantify static stability of snakes during complex movements, researchers developed methods to interpolate continuous body position and orientation in three dimensions between discrete tracked markers [9]. This allows analysis of the base of support and stability during obstacle traversal.

The analytical framework for optimal snake locomotion on flat surfaces provides a theoretical basis for understanding movement efficiency. This framework derives analytical solutions for optimal kinematics that minimize cost of transport or maximize velocity under varying friction anisotropy conditions [17]. While the framework assumes uniform weight distribution and negligible body rigidity, it can be extended to more complex scenarios.

Snake Locomotion and Robotics Applications

The study of snake locomotion has direct applications in robotics. Snake-inspired robots are being developed for search and rescue operations, inspection of confined spaces, and exploration of complex environments. The body undulation used by snakes and the physical architecture of a snake body may offer significant benefits over typical legged or wheeled locomotion designs in certain types of scenarios [6].

Snake robots have been developed for climbing in crowded pipes, traversing large obstacles, swimming underwater, and burrowing through granular media. Each application requires different locomotion strategies, and researchers continue to develop new control methods to improve performance.

Control Methods for Snake Robots

Deep reinforcement learning has been used to enable adaptive locomotion of snake-like robots in dynamically changing viscous environments. This approach overcomes the inherent performance limitations of classical predefined control methods by allowing the robot to learn adaptive gaits based on sensory feedback [18]. Simulation results across a wide range of dynamic viscosity changes revealed that the reinforcement learning agent autonomously acquires non-sinusoidal adaptive gaits that improve propulsion velocity and transport efficiency [18].

Reinforcement learning has also been combined with central pattern generators for soft snake robot control. The controller is composed of a reinforcement learning module for learning goal-tracking behaviors and a central pattern generator with Matsuoka oscillators for generating stable and diverse locomotion patterns [19]. This bioinspired design allows the robot to naturally learn to entrain desired locomotion patterns.

Distributed coach-based reinforcement learning has been proposed to expedite training speed for snake robot control. This method uses a completely distributed graphical formulation and explicit stochastic density propagation rules for each robot link [23]. Preliminary results from simulation and real-world experiments demonstrated promising performance compared to state-of-the-art methods.

Energy Efficiency in Snake Robots

Energy efficiency is a major concern for untethered snake robots. Multi-objective optimization algorithms have been used to find optimum gait parameters that minimize average power consumption while maximizing forward velocity [22]. The fast non-dominated sorting multi-objective symbiotic organism search algorithm provides advantages in obtaining a uniformly distributed solution set with good diversity in a single run [22].

Dynamic modeling for locomotion-manipulation of snake-like robots using geometric methods has been studied to understand the relationship between body movements and energy expenditure [27]. These models help researchers design more efficient control strategies.

Common Misconceptions About Snake Movement

Several misconceptions about snake locomotion persist in popular understanding. One is that snakes move by pushing against the ground with their scales in a rowing motion. In reality, most snake movement involves lateral body waves that push against surface irregularities, not a rowing action of the scales.

Another misconception is that snakes can move faster than a running human. In fact, most snakes move at speeds well below human running speed. The fastest snake movements are strike responses, which are quick but cover short distances.

A third misconception is that snakes cannot move on smooth surfaces. While serpentine undulation is inefficient on perfectly smooth surfaces, snakes can use rectilinear locomotion or concertina movement to make progress. The speed and efficiency may be reduced, but movement is still possible.

Snake Locomotion and Human-Snake Conflict

Understanding snake locomotion has practical applications for reducing human-snake conflict. Snakebite envenoming is classified as a Neglected Tropical Disease and causes mortality, morbidity, and economic impacts for hundreds of thousands of people per year, particularly in tropical, low- and middle-income countries [16]. Most research on snakebite interventions focuses on improving clinical management instead of bite prevention, but prevention may provide a better mechanism to minimize snakebite impacts [16].

Community engagement approaches that discuss snake behavior and biology have been shown to reduce human-snake conflict. A participatory workshop intervention in rural Uganda found that a fearful attitude toward snakes often led to human-snake conflict, with snake killings occurring commonly and some bites occurring during attempted killings [16]. Workshops appeared to challenge negative attitudes, as understanding snake behavior seemed to build compassion toward snakes and therefore has the potential to reduce human-snake conflict [16].

Those who attended workshops were more likely to suggest giving snakes space instead of attempting to kill them, and were more likely to suggest hospital treatment if bitten [16]. This emphasizes that appropriate knowledge about snake behavior, including locomotion, can lead to safer human-snake interactions.

Snake Distribution and Climate Change

Climate change is expected to cause complex shifts in snake distributions, which will affect both human exposure to snakebite and biodiversity conservation. Approximately 138,000 deaths and 400,000 disabilities result from snakebite annually, and the World Health Organization has pledged to reduce the resulting health burden by 50% by 2030 [15].

Research has modeled the effects of climate change on snake distributions, predicting substantial short- and long-term shifts including range contractions for many threatened species and increased human exposure to species of major public health concern [15]. Understanding snake locomotion helps predict how snakes will move through changing landscapes and where human-snake encounters are likely to increase.

Snake Locomotion in Different Species

Different snake species have evolved specialized locomotion methods suited to their habitats and lifestyles. Arboreal species tend to be slender and use concertina movement for climbing. Burrowing species may use rectilinear movement or specialized burrowing techniques. Aquatic species use modified undulation for swimming.

The Northern pine snake provides an example of a species with specific habitat requirements. Research on ophidiomycosis in Northern pine snakes in New Jersey has tracked known-aged individuals over multiple years, finding that approximately 85% were positive for the fungal pathogen in at least one year and overall positivity was 65% [14]. This research demonstrates the importance of long-term monitoring for understanding snake populations and their movements.

Species-Specific Locomotion Adaptations

The Bitis genus of African vipers includes heavy-bodied species that primarily use rectilinear locomotion. These snakes are ambush predators that move slowly and rely on camouflage. The trade dynamics of Bitis within the exotic pet market have been investigated, with conservation status ranging from Least Concern to Endangered [11].

The trade of Bitis species, despite being largely legal, often involves grey and illegal activities due to regulatory ambiguity and inconsistency [11]. Understanding the locomotion and behavior of these species is relevant for both conservation and public safety.

Practical Assessment of Snake Locomotion

For researchers and professionals working with snakes, assessing locomotion can provide valuable information about an animal's health and behavior. Observing which locomotion method a snake uses in different conditions can indicate its species, size, and physical condition.

When observing snake locomotion, consider the following factors:

  1. Substrate type and condition, including surface texture, moisture, and temperature
  2. The snake's speed and whether it changes speed during movement
  3. Whether the snake uses a single method or switches between methods
  4. The presence of obstacles or confined spaces that might trigger method switching
  5. The snake's body condition, including any visible injuries or abnormalities

Recording Locomotion Observations

For research purposes, locomotion observations should be recorded systematically. Video recordings allow frame-by-frame analysis of movement patterns. Measurements of speed, stride length, and body wave frequency provide quantitative data for comparison across individuals and species.

When recording observations, note the date, time, location, environmental conditions, and the snake's behavior before and after the observed movement. This context helps interpret the locomotion data and identify patterns related to temperature, time of day, or other factors.

Limitations of Current Knowledge

While significant progress has been made in understanding snake locomotion, several limitations remain. The analytical framework for optimal snake locomotion assumes uniform weight distribution and negligible body rigidity, which may not hold for all species [17]. The framework can be extended to more complex scenarios, but this work has not yet been completed.

Electromyography studies in snakes face challenges because electrodes attached to or implanted beneath the skin may unintentionally be removed by force or friction caused from undulatory motion [8]. While chronic recording techniques have been developed, they require careful surgical implantation and animal care.

Robotic models provide valuable insights but cannot fully replicate the complexity of biological snake locomotion. The compliance, sensory feedback, and neural control of biological snakes exceed current robotic capabilities. Research continues to bridge this gap through improved materials, sensors, and control algorithms.

Professional Escalation Criteria

When working with snakes in research or management contexts, certain observations warrant professional consultation:

  1. A snake that cannot move normally or shows signs of locomotion impairment may require veterinary assessment
  2. Unusual locomotion patterns in a known species may indicate injury, illness, or environmental stress
  3. Snake movements that create unexpected human-snake conflict situations may require consultation with wildlife management professionals
  4. Observations of snake locomotion in areas where snake distributions are shifting due to climate change may be relevant to public health authorities

For snakebite prevention, community engagement approaches that discuss snake behavior and biology have been shown to reduce human-snake conflict [16]. If you encounter a snake, giving it space instead of attempting to kill it reduces the risk of being bitten [16].

Frequently Asked Questions

How does a snake move without legs?

Snakes move using their axial musculature, belly scales, and body flexibility. The four main methods are serpentine undulation, which uses lateral body waves against surface irregularities, concertina locomotion, which alternates anchoring and pulling in confined spaces, sidewinding, which lifts body segments on loose substrates, and rectilinear movement, which uses belly scales to pull the body forward in a straight line. The frictional anisotropy of snake skin, meaning the skin resists movement differently depending on direction, is essential for converting body movements into propulsion [7].

How does the snake move on smooth surfaces?

On smooth surfaces, snakes switch from serpentine undulation to rectilinear locomotion or concertina movement. Rectilinear locomotion uses the belly scales to grip and pull the body forward without lateral bending. Concertina movement anchors part of the body and pulls the rest forward. Both methods are slower than serpentine undulation but allow progress on surfaces without push points.

How do the snake move in sand?

Snakes move in sand using sidewinding, which lifts portions of the body off the ground while other portions maintain contact. This reduces the surface area in contact with the substrate, preventing the snake from sinking into loose sand. Sidewinding also minimizes heat absorption from hot desert surfaces, providing a thermoregulatory benefit.

Why do snakes move in an S pattern?

The S pattern, or serpentine undulation, is the most common snake locomotion method. The snake forms lateral body waves that push backward against surface irregularities, converting the waves into forward propulsion. This method is efficient on surfaces with enough push points, such as grass, soil, or rocky ground.

Can all snakes use all four locomotion methods?

Most snakes can use multiple locomotion methods, but they may specialize in certain methods based on their body shape and habitat. Heavy-bodied snakes like boas and pythons commonly use rectilinear movement. Desert species like sidewinder rattlesnakes specialize in sidewinding. Arboreal species use concertina movement for climbing. The ability to switch methods provides flexibility across different environments.

How fast can a snake move?

Snake speed varies by species, size, and locomotion method. Most snakes move at speeds well below human running speed. The fastest movements are strike responses, which are quick but cover short distances. Serpentine undulation is generally faster than rectilinear or concertina movement, but speed depends on substrate conditions and the snake's physical condition.

How do snakes climb trees?

Snakes climb trees using concertina locomotion, wrapping their bodies around branches and alternating anchor and pull phases. The scales provide friction that prevents slipping, and the body's flexibility allows the snake to conform to irregular surfaces. Some arboreal species have evolved body shapes and scale patterns that enhance climbing ability.

Why do snakes move differently in water?

Snakes swimming in water use modified forms of undulation, including lateral undulation and eel-like motion patterns. The body waves push against the water instead of surface irregularities. Underwater snake robots have been developed to study the efficiency of different swimming gaits, with research investigating the relationship between gait parameters, forward velocity, and energy consumption [5].

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References and Further Reading

This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.