Group Structure and Behaviour of Babirusa (Babyrousa babyrussa) in Northern Sulawesi

Abstract

Studies were carried out at two ‘salt-licks’ in lowland tropical forest on North Sulawesi, Indonesia. During 60 days of observation 586 sightings of babirusa were made comprising 161 of adult males, 155 of adult females, 11 adults of unknown sex, 78 of subadult males, 53 of subadult females and 34 subadults of indeterminate sex; juveniles were observed 94 times, 19 males, 12 females and 63 of unknown sex. We saw 226 groups ranging in size from one to eight animals (median = 2). Almost half the sightings were of solitary animals, usually adult males. Bachelor groups of four or more babirusa were never seen. Adult females were rarely seen without company, often both juveniles and subadults being sighted together with them. There were never more than three adult females in a group. There were about twice as many family groups without adult males as there were with males. Agonistic behaviour between males was confined to ‘threat at a distance’, ‘nose in the air’, ‘head under jaw submission’ and ‘front half supported’ behaviours. There were fewer incidents of female-female agonistic behaviour, but in two, the dominant female chased her inferior off the ‘salt-lick’.