Sea otters and other animals leave evidence of their tool use that can be studied using the same archaeological techniques as for ancient humans
Source: https://www.newscientist.com/article/2196595-sea-otter-archaeology-could-tell-us-about-their-2-million-year-history/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home