Kamal Ghorui
People usually assume that all snakes move with serpentine locomotion, using S-shaped movements to propel themselves. However, not all snakes move in such a way. There is another type of locomotion peculiar to many snake species, including such snakes as boas, pythons, and vipers, which are known for their large body mass. Rectilinear locomotion is an interesting type of movement that snakes use to propel themselves forward without curving their bodies sideways. As scientists explain, this form of locomotion involves specialised scales on the belly of the snake, muscular action, and control of friction. Serpentine locomotion and sidewinding are the only two types of movement in which snakes do not remain silent.
What is rectilinear locomotion in snakes
Linear progression is the technical term used to refer to rectilinear locomotion in certain types of snakes. The movement of the snake takes place in a straight-line motion instead of moving in a loop or any type of curvature. The snake holds its body upright during rectilinear locomotion as it moves slowly. This process of locomotion has been mentioned in an article called ‘Snakes mimic earthworms: propulsion using rectilinear travelling waves‘ as being achieved through “sequential lifting, anchoring, and pushing against individual ventral scales”.Rectilinear locomotion can be seen in heavier snakes such as the boa or python. These types of snakes have large scales on their bellies that act as anchors when the snakes move their ribs in waves within their skin.The process of rectilinear locomotion is similar to “caterpillar locomotion” since it involves creeping movements.Rectilinear locomotion is ideal for snakes when they want to move silently and gradually. Instead of making dramatic side-to-side movements, rectilinear movement causes minimal disturbance, which helps snakes stay undetected from potential predators.
Why do some snakes move in a straight line
The linear locomotion of a snake is primarily related to its size and predatory nature. The larger snakes are usually very bulky and cannot use the fast serpentine movement while stalking their prey.According to scientific research, rectilinear locomotion makes it possible for them to move with minimal energy consumption. This mode of movement ensures that the belly of the snake stays in contact with the ground, giving them stability as they advance. Their ventral scales serve as tiny gripping pads. More research has been done into snake locomotion, and it has been found that friction plays a very significant role in it.The scales of snakes have been investigated by biologists who found out that the scales can produce different levels of friction depending on the direction. This gives snakes the ability to progress in a certain direction successfully without the need for any limbs.
Snake muscles and scales as the means of locomotion
The secret of such a peculiar form of locomotion lies beneath the skin of the snake. The snakes consist of hundreds of ribs that connect to well-developed muscles. During rectilinear movement, the muscles of the snake move in a wavy manner.The muscles connected to several ribs at an angle activate the movement of a belly scale. With the help of contraction and relaxation, scales slide upwards while pulling backwards, thus pushing the body forward.This whole process is very complicated, and everything must happen according to the plan in order to make the snake’s movement comfortable.As stated by biologists studying snake locomotion, this is one of the most interesting examples of limbless locomotion in nature. Moreover, this form of locomotion inspired scientists working on snake robots.
Snakes use more than one type of movement
Not all snakes move using only straight-line locomotion at all times. Almost all snakes can switch between several different types of locomotion according to their environment.Four main types recognised are:
- Serpentine locomotion – the standard form of slithering
- Rectilinear locomotion – the straight-line crawling form
- Concertina locomotion – an accordion-like climb
- Sidewinding – a unique form used when moving on loose sand
Sidewinding is mainly seen in desert snakes, whereas rectilinear locomotion is mostly seen in large snakes. There have been many discoveries of novel ways of locomotion, too. The latest discovery from researchers in 2021 was “lasso locomotion” observed in brown tree snakes while climbing vertical posts. “This wasn’t something a snake was supposed to be able to do,” the researcher. Snakes turn out to be more mechanical than we thought.
