Researchers have discovered a previously unknown method of locomotion that snakes use to climb large, smooth trees. For a century, there have only been four observed methods of snake locomotion: rectilinear, lateral undulation, sidewinding, and concertina. Researchers from Colorado State and University of Cincinnati identified this new category of "lasso locomotion" in the climbing repertoire when studying how to protect the nests of endangered Micronesia starlings on Guam from the highly invasive species of brown treesnakes. From Colorado State University/Eurekalert!:
CSU's Tom Seibert, co-author and emeritus faculty, said the team was attempting to use a three-foot long metal baffle to keep the brown tree snakes from climbing up to bird boxes. These same baffles have been used to keep other snakes and raccoons away from nest boxes in the yards of bird-watchers. But this new study suggests these might pose little obstacle to brown tree snakes.
"We didn't expect that the brown tree snake would be able to find a way around the baffle," he said. "Initially, the baffle did work, for the most part. We had watched about four hours of video and then all of a sudden, we saw this snake form what looked like a lasso around the cylinder and wiggle its body up."
Seibert said that he and CSU biologist Martin Kastner almost fell out of their chairs when they first observed this new form of locomotion.
"We watched that part of the video about 15 times" Seibert said. "It was a shocker. Nothing I'd ever seen compares to it."
To confirm the discovery, the team subsequently reached out to University of Cincinnati's Bruce Jayne, an expert on different aspects of locomotion and muscle function, especially in snakes.
Brown tree snakes, in particular, are champion climbers, said Jayne, study co-author and professor of biological sciences.
"Brown tree snakes are especially good at getting almost anywhere," Jayne said. "It's impressive. They can climb vertically using even the tiniest projections on a surface, and they can bridge enormous gaps in the tree canopy. They can push themselves up vertically more than two-thirds of their body length."
Jayne said 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.
"Lasso locomotion expands the climbing repertoire of snakes" (Current Biology)