They drop a pretty neat resource called 'Bio Toxin' when killed. It can be use as a steonger alternative to the Narcotic. It can also be used for a new 'Shocking Tranq Dart' which can shock the target and add a substantial amount of torpor. Perfect for knocking out Quetzal's.
Using a quetzal, kill the ones on the surface for easy bio toxin, then use it to make shocking darts, which are better than tranq darts, or use the bio toxin as a better narcotic for being Dino's torpor up