Using the distal portion of the trunk to check or test uneven, loose, slippery, deep or other potentially dangerous substrate before stepping on it. Elephants may use the trunk to check for loose rocks or particularly, when walking through a river, to test whether the river bed is firm, the substrate is rocky or whether there might be a sudden drop-off. The trunk is seen to reach out and tap or touch the ground before each step is taken.
An adult female stretches her trunk down to the bottom of the river to check the substrate to make sure it is safe to walk across. We can see that there is a deep spot and her Test-Subtrate technique has helped her navigate. (Maasai Mara, Kenya)
