in this period, was a rather calm individual. He, and the other middle ranking males during this period,
Nkojo, Kikunku and Magosi, were able to sire offspring. These facts show that while rank is important
it is not essential to be a top-ranking male to achieve reproductive success.
Indeed, some males fail. Vernon, Duane’s close ally and the beta male until he disappeared in
June 1999, sired no offspring. Nor did the high-middle ranking male Jambo who allied with Black
until his death in May 2003. Bwoya, who lived from 1965 to 2001, died without offspring. Tinka,
the omega male, born in 1965 and still alive at the time of writing in 2004, has had no offspring.
Zesta, the male who was killed by his fellows as a young adult male, likewise did not produce an
offspring with Janie (see Chapter 8); her daughter Janet, born 11 months after his death, was sired
by Duane.
Can we link births with specific copulations?
In five recent Sonso births where conception cycles were identified with endocrine data and
pregnancy test strips, gestation length averaged 229 days (range 210–241; Emery Thompson,
unpublished data). This is the first such estimate for wild chimpanzees and is remarkably consistent
with previous reports for captive chimpanzees (229.4 days,N8, Martin et al. 1978; 233.3 days,
N3, Shimizu et al. 2003).^103 The actual fathers of these five infants have not been identified at
the time of writing.
Offspring not sired by Sonso males
As seen in Table C.1, five of the individuals whose genetic sequences we have studied in the Sonso
population have fathers who are not among the Sonso males. That is to say, their nuclear genetic
sequences cannot be assigned to (or derived from) any of the Sonso males sampled. This includes
Genetics of the Sonso community 251Table C.2: Reproductive success for the periods
before and after mid-1995: (a) while Magosi was
alpha male, (b) while Duane was alpha male.
Name of father No of offspring
(a)While Magosi was alpha male (prior to mid-1995)
Magosi 4
Nkojo 2
Black 1
Muga 1
Duane 1
Kikunku 1
(b)While Duane was alpha male (after mid-1995)
Duane 4
Black 3
Nkojo 2
Kikunku 1
Maani 1
Magosi 1(^103) I am grateful to Melissa Emery Thompson for permission to use these findings.