The brown tree snake’s movements seemed strange, but the time-lapse footage did not make it entirely obvious if the movements marked a new mode of locomotion. So in 2019, Dr. Seibert returned to Guam to replicate the experiment, this time with a 4K-resolution camera and two baffles stacked on top of each other.
The new video showed that a brown tree snake could climb the baffle by forming a loop with its body, crossing over itself at least once, and forming small bends in its body to inch its way up. The motion seemed to exhaust the snakes, which paused frequently, breathed heavily and sometimes slipped down the pole. After viewing the video, Dr. Jayne tried and failed to get the brown tree snakes in his lab to climb a pole using lasso locomotion. “Maybe they’ve gotten fat, old and lazy,” he said.
Dr. Jayne believes lasso locomotion is an entirely new type of slithering. “Lasso locomotion is in outer space,” he said. “It’s different enough that it doesn’t fit into any of the four categories.” When a snake climbs a tree using concertina, the distance between its head and tail shrinks and swells as it alternates between gripping uphill and gripping downhill on the tree, sometimes at the same time. In contrast, in lasso locomotion, the looping region of the body the snake uses to grip does not change, and the animal moves itself upward with little sideways bends around the circumference of its cylinder.
“Given the right circumstances, it’s clear that snakes can find a way, and this new form of locomotion is an example of that,” said Gregory Byrnes, a biologist at Siena College who was not involved with the research.
It’s possible that other snakes in the same genus as the brown tree snake are also capable of lasso locomotion, Dr. Jayne said. But one cannot simply walk into the woods and expect to observe a nocturnal snake using an exhausting and specific type of locomotion. “One of the problems of studying snakes is their secretive nature,” he said. “We may not have observed the behavior in the wild because we’re barely observing the animals in the wild.”
Although Dr. Savidge and Dr. Seibert were also amazed by lasso locomotion, their awe was tempered with the realization that they would need to take down all the nest boxes they had installed on narrow metal poles. Fruit-eating Micronesian starlings are one of two remaining native forest birds on Guam. “This bird is all there is,” Dr. Savidge said. “There’s nothing else to disperse those native fruits in the forest anymore.”
The researchers also tested a new baffle design shaped like an ice cream cone, wider at the top and narrower at the bottom. “Snakes cannot climb that,” Dr. Seibert said, and so far, he’s been right.
[Like the Science Times page on Facebook. | Sign up for the Science Times newsletter.]