During MIS 3 a group of Neanderthals transported at least 15 marine fossils collected from the surrounding area, to Prado Vargas cave. Why?

Were Neanderthals the First Collectors?
First Evidence Recovered in Level 4 of the Prado Vargas Cave, Cornejo, Burgos and Spain 🏺🧪
https://www.mdpi.com/2571-550X/7/4/49