Within mixed parties, mothers with young infants do not show any fear of, or distance
themselves from, adult males. Things are different in some communities, e.g. Gombe
(A. Pusey, pers. comm.) where females with new infants avoid adult males. A striking
case of the lack of avoidance of adult males by new mothers was seen in the case of the
birth of the infant female Katia to Kewaya, a resident nulliparous female, on
30 December 1998.^33 This birth was observed and recorded in detail by our senior field
assistant, Zephyr Kiwede (Kiwede 2000), and was described in Chapter 2. For present
purposes it is of interest to note the social situation at the time. The closest individuals
to Kewaya during the birth were Kigere, an experienced mother, and her two offspring,
Kadogo and Kato, who were approximately 1.5 m away from Kewaya. During the
course of the next hour, three further adult females (Nambi, Kutu and Kalema), all with
their offspring, joined Kewaya in the tree. At 10.30 two adult males, Muga and Andy,
joined the group. None of these chimpanzees, female or male, showed any particular
interest in the newborn infant. During the following week, while the Ficus mucusowas
in fruit, Kewaya continued to feed in it and all of the adult males of the community
joined in these feeding parties at one time or another; at no point did Kewaya avoid any
of the males, nor did any of them show any interest in the new baby. In this particular
case, therefore, the newborn daughter of a resident female who was with her mother was
entirely safe in the presence of adult males. Indeed, we have not seen any avoidance of
adult males by any of our resident females when they had new infants, but this relationship
has yet to be studied in detail at Sonso.
A second, and also interesting fact concerning Kewaya’s birth was that her own
mother, Zimba (as we know from genetic data), was not present either during the birth
or on the following days. Perhaps she disapproved?
Effects of oestrous females on party size and party type
Wallis and Reynolds (1999) and Newton-Fisher (1999d) found that in the Sonso
community, more males were found in parties when oestrous females were present.
The same has been reported for a number of other chimpanzee communities (Matsumoto-
Oda 1999 for Mahale; Anderson et al. 2002 for Taï; Hashimoto et al. 2001 for Kalinzu;
Wrangham 2000afor Kanyawara). It has also been suggested that females not in oestrus
may seek the company of oestrous females, an action shown to stimulate the resumption
of postpartum cycles (Wallis 1985, 1992b) and initiate the first full anogenital swelling
in adolescent females (Wallis 1994). Food abundance is not the cause of these larger
parties (Anderson et al. 2002: 96–7; Hashimoto et al. 2001: 953).
I analysed the 2001 sample to determine the effects of the presence of one or more
females in oestrus on the percentage of all community males present in the party. The
Effects of oestrous females on party size and party type 91(^33) In fact Kewaya is thought not to have immigrated but to have remained in her natal group, though this is
not certain. She was present from the start of our observations in 1991, at which time she was a juvenile; this
was seven years before she gave birth. Her name means ‘wire’ in Swahili, from the wire that was attached to
her right wrist.