How foxes dive into snow

Some mammals plunge-dive or dig out snow to catch prey hidden beneath the snow. Among them, arctic foxes and red foxes are known to be great hunters that catch small animals by snow diving. Here, we investigate the morphological characteristics of snow-diving foxes and the dynamics of snow diving to understand how they penetrate snow. First, we scanned dry skulls of a series of species in Felidae (cats and allies) and Canidae (dogs and allies, including foxes) to analyze key geometrical features such as snout length and width. In comparison with the bobcat and puma in the Felidae, the fox's snout is noticeably longer and narrower, thereby having a higher curvature. Next, we evaluated the benefits and dynamics of the structural differences between cats and foxes when diving into snow. To measure the impact force, we dropped 3D-printed skulls of cats and foxes into a container filled with snow. We also tested artificially snout-shortened 3D-printed models of foxes. When the snout is reduced in length by 25%, it generates twice the impulse compared to the original fox snout. Similarly, the bobcat generates a greater force during the impact phase. These results imply that the fox’s sharp and long snout helps to quickly approach prey when diving through snow with less impact force.