Can Snakes Climb Trees? How Snakes Climb Bark and Walls

How snakes grip a tree trunk

A snake has no claws or suction pads, so climbing depends on friction and shape. Most snakes have a row of wide, overlapping belly scales called ventral scales. Each scale has a free back edge, a little like a roof tile. When a snake presses its body against bark, those edges catch on cracks, ridges and bumps.

Good climbers improve this grip in two ways. Many, including rat snakes, have a belly that is flat with sharp angled edges along each side, so the body in cross-section looks a little like a loaf of bread. These “corners” can be pressed into grooves in the bark. Climbers can also stiffen and bend their bodies to push sideways against the trunk, wedging themselves between rough points.

Concertina climbing: the main technique

On a tree trunk or branch, most snakes use a version of concertina locomotion, named after the folding musical instrument:

1. The snake grips the trunk firmly with the back half of its body, bending it into tight curves.
2. It stretches the front of its body upward.
3. It then grips with the front, often by curling it around the trunk or wedging it against the bark.
4. Finally it pulls the back half up and grips again.

This stop-and-go movement is slow and costs a lot of energy, but it is reliable. A 2007 study by Henry Astley and Bruce Jayne on corn snakes on cylinders of different sizes and slopes found that the snakes switched to concertina movements on steep and upward perches, and that steep, wide cylinders were the hardest to climb.

On rough bark with plenty of grip points, snakes can use smoother lateral undulation, the side-to-side wave they use on the ground. The different ways snakes get around are described in How do snakes move without legs?.

Lasso locomotion: a discovery from Guam

In 2021, researchers working in Guam described a completely new way of climbing. The brown tree snake, an invasive species there, had been seen getting past smooth metal baffles placed on poles to protect bird nest boxes. Video showed how.

The snake formed a loop of its body around the pole, like a lasso, with a small wiggling bend inside the loop. By moving those bends, it could slowly inch the whole loop upward and climb a smooth cylinder that was too wide to grip with ordinary concertina movements. The researchers named it lasso locomotion. It was slow and tiring, with frequent rests, but it worked.

Which snakes climb best?

Snakes vary hugely in climbing ability. Body shape is the main reason.

The boa constrictor shows how weight matters. Young boas are light and regularly climb into trees, but big adults, which can weigh more than 10 kg (22 lb), spend most of their time on the ground. Slim, light snakes with long tails are almost always the best climbers.

Why do snakes climb?

Snakes climb for several practical reasons:

• Food. Bird eggs, nestlings, tree frogs, lizards and roosting bats live off the ground. Rat snakes are well known for raiding nests and birdhouses.
• Safety. Branches, tree holes and loose bark offer hiding places away from many ground predators.
• Warmth. Climbing into sunny branches helps a snake warm up after a cool night.
• Travel. In forests and flooded areas, moving through trees can be easier than moving across the ground.

Snakes in attics, walls and birdhouses

The same skills that let a snake climb a tree let it climb a building. Rat snakes can go up rough brick and stone walls, wooden siding, vines and downspouts, and they slip into attics through gaps near the roof. They are usually following mice, rats, bats or nesting birds. Many people in the eastern United States first discover how well snakes climb when they find one in a birdhouse or under the eaves.

Most snakes found this way are harmless rat snakes. If one is in a place where it might be dangerous or unwanted, it is best to keep a respectful distance and contact local wildlife authorities rather than try to handle it.

Can snakes climb down head first?

Yes. On the way down, snakes usually move head first and use their coils as brakes, gripping and releasing in turn. Experiments with corn snakes showed they slide more on steep downward slopes and have to squeeze harder to control their speed. Some snakes simply let go and drop the last part of the way.