Purple Faced Langeus need a male to become an established breeding group, wolves seemed very depressed.
Last time I was there the Purple faced Langurs were a breeding pair + male offspring, and then 2.0 living seperately. So they need more females, rather than a male.
Agree the wolf setup isn't entirely ideal- its a female(?) only group so socially not a natural pack- I think they don't like people looking at them from above that much either.