wake just after dawn at 7 a.m., yet no successful copulations were observed prior to
7.30 a.m. Instead, the chimpanzees were most likely to spend their earliest hours
feeding, concentrating their copulations in the mid-morning hours.
As can be seen from Table 6.2, few data were collected for the first period
(6.00–7.00 a.m.) when light was poor and most chimpanzees were not yet moving.
Copulations were seen with increasing frequency up to the 9.00–10.00 period. There is
no evidence that copulations were concentrated at first waking, indeed they are concen-
trated around the mid-morning time. There were only five observations of parties in the
first hour with oestrous females present, but no copulations took place.
To explore the effects of male status on copulation rates, rates were calculated for each
of the males over the day. The results are shown in Fig. 6.3 which distinguishes three high
status males, Duane (DN), Maani (MA) and Black (BK), from those of lower status.
Interestingly, the three highest status males copulated less frequently than the lower
ranking males and this was consistent throughout the day. Also, the pattern of copula-
tions differs for these two groups. When the high ranking males are reaching their peak
rate in the late morning, the lower ranking males’ rate declines, and then it picks up at
midday and into the early afternoon when the rate of the dominant males declines. This
is consistent with the idea that the high ranking males take the earlier opportunity to
inseminate the females who are in full oestrus, leaving lower ranking males to rely on
sperm competition to achieve reproductive success.
We also investigated the relationship between copulation and feeding. Do males
copulate more when they are less busy feeding, and vice versa? The situation turned out
to be a little more complicated than this. The study was confined to groups with oestrous
120 Social behaviour and relationships
Table 6.2:Copulations by time of day, September 2001–December 2003. Based
on approx. 2000 hours of observation, 600 hours with oestrous females present
(data compiled by M. Emery Thompson).
Time of No. of No. of No. of No. of scans No. of
day copulations copulations copulations e-scans*
observed by high status by low
males status males
0600–0700 0 0 0 29 5
0700–0800 11 2 9 411 91
0800–0900 62 21 41 1455 432
0900–1000 76 17 59 1524 490
1000–1100 65 23 42 1374 479
1100–1200 47 18 29 1019 339
1200–1300 36 5 31 676 241
1300–1400 10 2 8 320 88
1400–1500 12 0 12 336 65
1500–1600 8 2 6 421 91
1600–1700 5 1 4 362 75
1700–1800 3 0 3 179 40
1800–1900 0 0 0 55 11
Total 335 91 244 8161 2447* e-scansscans with one or more oestrous female present.