young females from other troops, and 
so this practice has little effect on troop 
size and composition. 
Young males also leave their natal 
troop, but the process is not voluntary 
and it can be unsuccessful. As young 
males matured in the study troop, they 
were basically ignored by the resident 
adult males but harassed by a three- 
year-old native male. After much ha- 
rassment by this male, all three juvenile 
males left the study troop and began to 
travel on their own, generally avoiding 
their natal troop. One young male that 
returned for a day was continually 
threatened by the three-year-old male 
and virtually ignored by most of the 
other troop members, except for his 
mother, who spent the entire day and 
probably most of her energy trying to 
defend him from the harassment of the 
three-year-old native. This is in direct 
contrast to a young female that re- 
turned for a day. She was enthusiasti- 
cally greeted, groomed, and invited to 
play. 
Two unsuccessful male transfers 
took place during the study. In one 
case, an adult male joined the troop for 
one month. During this time he avoid- 
ed the resident males, threatened the ju- 
veniles, and frequently ran into the 
center of a resting group, mounted a fe- 
male, then ran off. After one month of 
avoidance, bullying, and “sneaking” 
copulations, he was attacked and killed 
by two of the resident females and one 
of the resident males. In the other case, 
a large subadult male shadowed the 
study troop for a few days and then 
walked into the center of the troop 
where he was groomed by the juvenile 
females. After an hour of what ap- 
peared to be acceptance, he was vi- 
ciously attacked by at least seven of the 
resident females and one of the resident 
males. When my proximity to the inci- 
dent brought the attack to an end, the 
male had severe wounds on his body 
and was bleeding profusely. Barely able 
to move away, he had lost one eye and 
probably died shortly after. In both of 
these attacks, the victim was pinned to 
the ground and the attackers bit furi- 
ously. In another case, I heard a loud 
uproar from a neighboring troop, and 
when I reached its territory', found a 
dead, twenty-three-month-old male 
that had been expelled from the local 
troop. The severe bites on his body 
looked as though they were inflicted by 
colobus canines. W'hile it is not uncom- 
mon for a subgroup of lone females to 
41 
