The wonderful babirusa sequences in Attenborough's Life Of Mammals series were filmed here at Nantu from the same hides I was in. I was re-watching the series a short while ago, and when the babirusa came on screen I had a total deja vu moment! Unfortunately I never saw any of the babirusa engaged in their "boxing matches".
Truly a sight I would have loved to have seen - at least one Mammalwatching trip report from last year suggests that the babirusa have now become completely extinct in Nantu, along with the Sulawesi warty pigs. Anoa may be just about hanging on.