Probably some form of derived hair. Probably something they can trim, but just as likely it'd be very painful to lose one out of its socket.
We have seen Predators with flattened off dreadlocks. Now of course Cleopatra might have the tips in the beads, but the implication is that they're short.
As to why it might appear on the Predalien? The Requiem Predalien was a one in a million mutant. The Predator skull also features sockets for the dreadlocks and so it could've manifested in an odd manner. It's a feature of their biology and it happened to appear on the hybrid. And given they've never had a consistent Predalien whose to say the next one has it or not? It's just an odd quirk of Chet.