For nearly 100 years, all snake locomotion has been traditionally categorized into four modes: rectilinear, lateral undulation, sidewinding, and concertina.
Recently, US researchers have identified a fifth mode of snake locomotion on the island territory of Guam. The findings were published in the journal Current Biology on January 11.
The US island of Guam has been dealing with the spread of the so-called "brown tree snakes," which caused a decline in bird populations in local forests, except for a relatively small number of Micronesian starlings.
This bird serves an important ecological function by dispersing fruit and seeds which can help maintain Guam's forests.
As part of a joint research project by the universities of Colorado State and Cincinnati aimed at addressing this problem and protecting starlings' nests, the researchers used a three-foot long metal baffle to keep the brown tree snakes from climbing up to bird boxes, assuming that the baffle would hinder the four popular locomotion of snakes.
However, the snake surprised them with a fifth locomotion that helped it overcome the metal baffle. It managed to form what looked like a lasso around the cylinder and wiggle its body up.
"Initially, we thought the baffle did work, then we observed the snake surprise us with this locomotion for the first time," Tom Seibert from the Colorado State University said in a report published on the university's website.
"We watched that part of the video about 15 times. It was a shocker. Nothing I'd ever seen compares to it," he added.
Snakes typically climb steep, smooth branches or pipes using a movement called concertina locomotion in which the snake bends sideways to grip at least two regions. But with lasso locomotion, the snake uses the loop of the lasso to form a single gripping region, which is more physically demanding than other climbing methods.
"Even though they can climb using this mode, it is pushing them to the limits. The snakes pause for prolonged periods to rest," Seibert said.