A dangerous well-controlled jump | Polarjournal
Foxes move their heads to listen for prey moving under the snow and assess their depth. Once they’ve located prey underneath the snow, polar foxes can dive at up to 14 km/h into what appears to be a soft surface. Photo: Michael Wenger

Polar foxes hunt lemmings in powder snow without hurting their noses.

Headfirst dives into the snow are not recommended. Although powder has physical properties similar to those of liquids, once compacted, its properties are those of a solid. A study published in the Proceedings of the National Academy of Sciences on April 29 describes the advantage that polar foxes have over felines when it comes to catching small mammals under the snow: a long, slender snout. “The fox’s sharp snout doesn’t compress the snow significantly, it penetrates it without much resistance,” explains Sunghwan Jung, Cornell University researcher in charge of the research project, in a press release.

To reach these conclusions, PhD student Jisoo Yuk scanned not only red and arctic fox skulls, but also those of pumas and lynxes from the American Museum of Natural History in Manhattan. The early-career researcher then 3D printed them, before dropping them in different materials, such as snow and water. His findings prove that thin muzzles minimize tissue damage when foxes dive head first, unlike felines with shorter muzzles. Canids evolved in packs, wounding their prey repeatedly with their long, slender jaws. Felines, on the other hand, are more solitary, killing prey in one fell swoop with a wider, more powerful jaw.

“Some foxes also seek out eggs and carcasses left behind by polar bears,” explains Aude Lalis, senior lecturer in genetics and evolutionary genomics at the Muséum national d’histoire naturelle in Paris. Image: Michael Wenger

“Polar foxes feed on lemmings digging galleries under the snow,” explains Aude Lalis, Senior Lecturer in Genetics and Evolutionary Genomics at the Muséum National d’Histoire Naturelle in Paris. “It hears them or and smells them. Some fox populations depend on lemmings even in winter, because this small mammal doesn’t overwinter; it stays warm, under the snow.”

Jumping maneuvers present risks, as they reach speeds of up to 14 km/h as they dive into the snow. However, the research team explains that they have not received any reports of skull injuries in animals following such jumps.

Camille Lin, Polar Journal AG

Link to the article: Yuk, J., Pandey, A., Park, L., Bemis, W.E., Jung, S., 2024. Effect of skull morphology on fox snow diving. Proceedings of the National Academy of Sciences 121, e2321179121. https://doi.org/10.1073/pnas.2321179121.

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