#  Researchers Discover New Snake Locomotion in Young Anacondas 

 





April 10, 2025

 

 

     ![S-start of juvenile anaconda (E. notaeus) on a red synthetic turf. Credit: Nature Physics (2025). DOI: 10.1038/s41567-025-02835-7](/sites/g/files/omnuum6811/files/styles/hwp_16_9__480x270/public/2025-07/S-start%20of%20juvenile%20anaconda_LMahadevan.jpg?h=15e1a914&itok=YD8B9Nie) 

*S-start of juvenile anaconda (E. notaeus) on a red synthetic turf. The starting point of locomotion is an S shape including three co-linear regions, connected by two curved regions that are elevated from the contact surface (as observable from the shadow cast on the substrate) as the middle, straight segment pushes down against the surface. Series of overlaid time-lapse images separated by 0.1 s show the S-start—the snake moves rightwards as a localized pulse of non-planar bends propagates through the snake. Credit: Nature Physics (2025). DOI: 10.1038/s41567-025-02835-7*



 



 

Researchers led by L. Mahadevan, a professor of applied mathematics and organismic and evolutionary biology at Harvard's School of Engineering and Applied Sciences, have identified a previously undocumented form of snake locomotion in young anacondas, revealing a surprising twist—literally—in how these reptiles move. The new movement, dubbed the “S-start,” resembles a gliding, S-shaped launch that enables juvenile snakes to escape danger quickly. It appears to be a unique startle reflex, different from the well-known slow, lumbering movement observed in adult snakes.

The team described the motion of the snakes as appearing to launch themselves backwards in a smooth, swift curve. "This movement is the serpentine analog of the moonwalk—a fast, graceful glide that seems to defy common sense," Mahadevan said. "We used observations to create a mathematical framework, in order to understand under what conditions movements like this are possible, and why they are lost as the snake gets older, heavier, and relatively less strong."

The combination of computational analysis with experiment and observation showed the S-start is present only in the "Goldilocks" zone of an anaconda's weight and strength. The behavior occurs specifically in young snakes that are past the newborn and super-strong stage, but are not yet a too heavy adult. Young anacondas are at physical peak to perform the S-start, neither flying off the ground or being overwhelmed by ground friction. The team's findings also correct misconceptions about the continuous, sideways motion, known as sidewinding.  They found that the S-starts are "non-planar," meaning that some segments of the snake are off the ground, almost like walking.

"We realized that the sidewinding motion is very similar to this S-motion, in that it consists of S-starts that are repeated again and again," Mahadevan said. "Perhaps, from an evolutionary point of view, this transient movement was taken up and then repeated, and this became the origin of sidewinding,"

The initial observation came from co-author Bruce Young, a herpetologist in Missouri, who noticed the movement in juvenile anacondas and reached out to Mahadevan’s team. What began as a curious observation evolved into a multidisciplinary investigation involving high-speed video analysis, force measurement, and mathematical modeling. The discovery is published in [*Nature Physics.*](https://www.nature.com/articles/s41567-025-02835-7)

Researchers believe the findings could have implications beyond herpetology. Understanding the biomechanics of this movement could help improve the design of bio-inspired robots, particularly those meant to navigate tight or unstable environments. The study also highlights the importance of exploring animal movement at all life stages, as juveniles may hold keys to understanding the evolution of complex locomotive behaviors.



 

 

 



 

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