I think that they are most definetely solitary, and usually only get together in the case of romace and raising children.
they are probably Cunning, Patient, Ambitious and extreamly Agressive and very territorial
territorial,cunning and agressive would make for a very dangerous combination and would explain why the one Nick's ancestor encountered killed his competetor to get rid of his rival , both to increase his buisness and so expand his territory.
patience because they probably prefer to ambush their prey, and much like tigers they probably pounce on their prey, they would need to have alot of patience so they could wait for the perfect moment to Attack and Kill their prey.
they probably have many natural enemies in the wesen world, such as Jagerbar, Abartige Aasfresser, and Lowen.
they are also probably a common problem for Grimms, since Grimms have made many ways to kill them, which may say something about their agression or maybe they would have a certain blood lust which makes them more prone to kill.