To consume hard-shelled food such as mussels or clams, sea otters utilize rocks as tools to break them open. They have specific rocks that they repeatedly use for this purpose.

Art and fact by Kristina Leslie, Instagram @tinaleslie_

[Edited by Nicole Rodrigues]

Reference:

Haslam, M., Fujii, J., Espinosa, S., Mayer, K., Ralls, K., Tinker, M. T., & Uomini, N. (2019). Wild sea otter mussel pounding leaves archaeological traces. Scientific reports, 9(1), 4417. https://doi.org/10.1038/s41598-019-39902-y