Let’s start by examining how the snake approaches its aerial task. In ordinary circumstances, the Paradise tree snake has a circular cross section. When it leaps into the unknown, however, it flattens its body forming a kind of triangular cross-section that is flat along the bottom and arched across the top.

It’s not hard to see how this approximates to the cross-section of an ordinary aerofoil. In fact, Krishnan and co says is better described as a lifting bluff body.

The Paradise tree snake begins its glide by launching itself from a tree branch with a small horizontal velocity. It then falls ballistically at an angle of up to 60° from the horizontal.

During this fall, it forms its body into an undulating S-like shape. This ensures that significant parts of its body travel perpendicular to the airflow, like a wing.

Ophiologists (those who study snakes) assume that it is this that creates the snake’s lift and indeed as the snake picks up speed, the trajectory becomes shallower. So the lift must increase.

The Paradise tree snake can end its flight flying at angles as shallow as just 13 degrees. And it can travel significant distances. “In field observations, the snakes cover a horizontal distance of about 10 meters, on average, when jumping from a height of about 9 meters,” say Krishnan and co.

In the last two or three years, ophiologists have become curious about how the snakes perform this trick and have carried out a number of wind tunnel and water flow experiments to find out. These have shown conclusively that the Paradise tree snake’s cross-section does indeed generate lift.

But these experiments have also revealed puzzle. It turns out that the lift peaks when the snake body’s angle of attack is precisely 35 degrees to the incoming airflow. But why this should be the case is not clear.

This is the question that Krishnan and co set out to answer by studying the flow of air using a computer simulation.

These guys created a two-dimensional model in which an aerofoil that matches the cross-section of the Paradise tree snake in-flight could be put through its paces. The advantage of a computer model is that it is possible to vary all kinds of features such as the speed, density and viscosity of the fluid flow (factors that are together known as the Reynolds number). And to study the resulting air flow in detail.

One thing the model did not capture was the three-dimensional shape of the snake. Most experts in this field think that three-dimensional effects become important in this kind of flight, so Krishnan and co had limited expectations for the outcome of their simulation.

So their results were something of a surprise. These guys say they were clearly able to observe the spike in lift. “Significant enhancement in lift appears at an angle of attack of 35 degrees,“ they say.

And because this is a computer simulation they could see exactly how this list was generated. It turns out that at this angle of attack, the smooth flow of air over the snake’s body suddenly becomes more complex. It separates from the surface and forms two pairs of vortices above and behind the snake, one at the top of the triangular arch and one at the trailing edge.