following her, staying near her and feeding in her company. When she moved, they
moved. Black, Maani and Nkojo had all mated with her. The alpha male, Duane, how-
ever, had not been with them. He had come visiting a few times and examined Nambi’s
swelling, its size and its odour, but he had not been seen to copulate with her. On day 3
he sat on the ground, observing Nambi who was in the canopy. On day 4, however, he
climbed up into the tree with the other males and Nambi. The three males gave way to
him as he moved towards her. Once or twice they came close; he chased them away
fiercely, threatening to attack if they didn’t flee even if it meant hair-raising acrobatics
in the treetops. They fled screaming and eventually took to sitting on the ground beneath
the tree, eyeing Nambi from below.
Duane was now clearly interested in Nambi but not yet copulating with her. He
sniffed her swelling from time to time but still they did not copulate. She for her part was
not just passive. During the previous days she had been making life hard for the three
adult males by resting up a lot of the time on small branches at the periphery of feeding
trees, so each time they moved towards her the branch swayed and made things difficult.
But she couldn’t do this all the time, she had to feed and move around in the treetops, so
they succeeded in mating with her. She now moved to a sturdier branch with Duane and
positioned herself making it easy for him to mate with her and eventually he did.
After staying with her for two hours, Duane needed to feed. He moved away from
Nambi and immediately there was a scramble from below as Black, Maani and Nkojo
climbed up into the treetops to attempt to mate with Nambi; Maani succeeded first as
she was receptive, Black succeeded next after a chase, and finally it was Nkojo’s chance
but he had left it too late. Duane returned, having fed, and monopolized Nambi again.
He stayed with her for most of the day, moving with her on the forest floor and some-
times waving saplings to draw her attention when he wanted to move on or to mate. The
two stayed together in this way the next day as well, but the day following she was
already showing the first signs of detumescence and he left her; the other males could
now mate with her and they did so from time to time when she made herself accessible.
Over the next three days her swelling declined further and she ceased to be of sexual
interest to the males, or to show any interest in them.
Copulation can take place on the ground, in the understorey or up in the treetops
where we see it most often. On rare occasions the pre-copulatory stage is noisy, when a
female emits screams loud and long as if she were terrified, while a male postures close
to her demanding sex; this can be the end of a long period during which the male has
been showing an erection and eyeing a female with a full swelling. O’Hara (in progress)
is looking at the ways in which female sexuality influences male behaviour and is
exploring the consequences of male aggression.
Often a female will give small high-pitched squeaky screams during copulation, and
sometimes break off after mating with a scream and run a short distance away rapidly.
But on other occasions this does not happen, she just remains with her male until they
copulate again.
Males often mount a female several times but, unless the male is interrupted or the
female runs away, after one or more mounts with pelvic thrusts he ejaculates. Hasegawa
Sex and reproduction 117