Pan Africa News, 28(2):17–20 (2022)

Note

First observation of fellatio by a wild non-estrus adultfemale chimpanzee on an adult male, and subsequent meat
sharing in Mahale
Kenichiro Hikida✉

Graduate School of Science, Kyoto University, Japan(✉ E-mail: hikida.kenichirou.54e@st.kyoto-u.ac.jp)

ABSTRACT

Sociosexual behaviors such as mounting and genital touch have been extensively reported in chimpanzees.
However, there are a small number of reported cases of fellatio, with only a few cases between captive juveniles or adultmales. In this study, fellatio from a non-estrus adult female to an adult male holding bushpig meat were observed forthe first time. After a series of sociosexual behaviors including fellatio, the meat was shared through begging behavior
from the female to the male, suggesting that the series of displayed sociosexual behaviors may have occurred to reduce
tension, so that the female could then make a smooth transition to begging behaviors. In addition, the fact that fellatio
displayed between male and female in a context similar to previously reported cases of fellatio between adult males
suggests that the social bond-strengthening effect of fellatio can also function between an adult male and female.

Keywords: Pan troglodytes schweinfurthii, Mahale Mountains National Park, sociosexual behaviors, fellatio, meat
sharing

INTRODUCTION

In primates, sociosexual behaviors without mating
have been observed in both opposite-sex and same-sex
partners. Some of these examples include mounting without penile penetration in the olive baboon (Papio anubis)(Owens 1976) and in the Japanese macaque (Macacafuscata) (Takahata 1982), and anal penetration between
males in the Geoffroy’s spider monkey (Ateles geoffroyi) (Busia et al. 2018) and in the snub-nosed monkey(Rhinopithecus roxellana) (Fang et al. 2018).
Although the forms and frequencies of sociosexual
behaviors may vary among taxa, they appear to serve social functions. Such behaviors can appear in a variety ofcontexts, such as mating practices (the Japanese macaque:
Gunst et al. 2013), negotiation of dominance relations (thesnub-nosed monkey: Huang et al. 2017), and reducing
social tension after aggression or during food sharing (thebonobo [Pan paniscus]: de Waal 1990; Hohmann & Fruth,2000).
Although chimpanzees (Pan troglodytes) engage insociosexual behavior less frequently than bonobos (Woods& Hare 2011; Gruber & Clay 2016), it has been extensively reported (Crawford 1942; Kutsukake & Castles
2004; also see a review by Sandel & Reddy 2021). The
frequently reported behavioral types in chimpanzees
are mounting and touching of genitals (including mutualtouching). However, there are few reported cases of fellatio, or mouthing of the male penis by another individual.
Some acts of fellatio are directed to still immature males
as reported by Malick & Savage (1977) and SavageRumbaugh & Wilkerson (1978) who noted oral-genital
contacts among captive juvenile chimpanzees in the con-text of play. Nishida (1981) reported that an adult femaleat Mahale mouthed her weaning male offspring’s penis
as means of appeasing his frustration. Only two reported
cases of fellatio were performed on adult males, and bothwere by other males to reduce tension, one among captive chimpanzees in Primate Foundation of Arizona inthe USA (Shefferly & Fritz 1992) and the other among
sanctuary-living chimpanzees in Chimfunshi Wildlife
Orphanage in Zambia (Brooker et al. 2020). To the best of
my knowledge, there have been no reports of fellatio byan adult female chimpanzee on an adult male.
This study reports the first such case and describes
other accompanying sociosexual behaviors, the context,
and subsequent meat sharing.

METHODSThis case was observed between chimpanzees ofthe M group in the Mahale Mountains National Park,Tanzania, on September 20, 2019 (see Nakamura et al.
2015 for details of the study site). The case was recorded
first on a field note and subsequently with a video camera(Panasonic HC-W585M). An adult male named Darwin(DW) and an adult female named Fawn (FW) were theparticipants in this event. FW had borne an infant thatyear and thus was non-estrous.

OBSERVATIONS

At 08:35 h on September 20, 2019, a large party of
the M-group chimpanzees ranged southeast of the area
called K1, less than 1 km from the researchers’ camp, andDW was followed. At 08:53 h, DW was holding a freshcarcass of a bushpig (Potamochoerus larvatus) piglet. At17

Pan Africa News, 28(2):17–20 (2022)

08:54 h, after climbing a nearby tree, he started eating
meat from the bushpig. At 08:58 h, FW with the infant attached to her belly appeared from an unknown location,
climbed the same tree, and sat on a lower branch in frontof DW. No other individuals were observed in the vicinity. Because a clear view of the subjects was not possible,
at 08:58 h the observation location was changed and video
recording begun at 09:01 h (Video 1 available online at
http://mahale.main.jp/PAN/2021/005.html; hereinafter,times in descriptions from video footage are given inhours:minutes:seconds).
At 09:02:04 h, FW touched the erect penis of DW
with her left hand for 3 s. Her face was not visible as herback was turned to the camera, but judging from the direction of the head, it is assumed that her gaze was not on
DW’s penis but on his hand holding the piglet. DW continued to eat without any significant reaction. At 09:02:07 h,FW mouthed DW’s penis for 3 s (Figure 1). She touched
DW’s penis again for 3 s, this time pinching it with herleft thumb and index finger. At 09:02:22 h, FW presented
her rump to DW and pressed her non-swollen sexual skinagainst DW’s erect penis for 4 s (Figure 2). No penile penetration occurred. FW reached toward DW’s hand holding
the piglet at 09:02:27 h, but he moved it away from her. At
09:02:31 h, DW turned his back completely on FW. Then,
at 09:02:40 h, FW moved to face DW, and at 09:02:51 h,
she reached for his mouth and hand holding the meat
while peering into his face. At 09:03:22 h, FW loosely
grabbed DW’s hand holding the meat. At 09:03:34 h,FW grinned, pant-screamed slightly, and then reached
for the meat. FW eventually obtained a small amount ofmeat which DW had removed from his mouth. DW thenclimbed further up the tree and left FW, ending the interaction, at 09:03:51 h.

DISCUSSION

In the present case, a non-estrus female, FW, after
several types of sociosexual behaviors, such as touching
the penis, fellatio, and genito-genital contact without penile insertion, begged DW for bushpig meat by extending
her hand to the mouth of DW. This is the first such reportof fellatio between opposite-sex adult chimpanzees andis also the first report of fellatio in the context of foodsharing.
Sociosexual behaviors during food sharing have beenreported in wild chimpanzees and have been interpreted
as actions performed to reduce social tension (Sandel &Reddy 2021). Thus, it can be assumed that the series ofsociosexual behaviors in this report also served to reduce
tension. Alternatively, such behavior may function as begging, because typical begging behaviors, such as peering
into the face and reaching for the mouth, also occurred.
Gilby (2006), who studied begging behaviors during
meat sharing, classified them according to their intensity,from milder to more intense: (1) sitting close to the meat
holder and peering at him, (2) reaching out to the meat
holder (no contact), (3) touching the meat holder, and (4)reaching a hand near to the meat holder’s mouth and mak-Figure 1. Fellatio between FW (right) and DW (left)

Figure 2. FW (right) pressing her sexual skin to DW’s (left) erect penis

18Pan Africa News, 28(2):17–20 (2022)

ing contact with it. The series of sociosexual behaviors
observed in this study, if they were considered beggingbehaviors, would be classified as category (3). However,
several behavioral elements observed in this study were
not reported in Gilby’s behavioral repertoire of begging.
In addition, according to Gilby’s definition of harassment
during meat-eating, the observed behaviors were not considered harassment, because there was no contact withDW’s mouth or hands, nor was his behavior restricted.
Although it is difficult to conclude from just one case, theseries of displayed sociosexual behaviors may have occurred to reduce tension, so that FW could then make asmooth transition to begging behaviors.
The connection between meat sharing and sexual
behavior in these observations may seem relevant to themeat-for-sex hypothesis (Stanford 1996), especially regarding reciprocation on a long-term basis (Gomes andBoesch 2009). In this case, however, it is unlikely that
there was an immediate reciprocal exchange of meat sharing and mating opportunities for two reasons. The firstis that the female was non-estrous and lactating, whichmeans copulating with her would not lead to pregnancy.
The second is the negative responses of DW, such as turning away after a series of sociosexual behaviors. In thiscase, even though meat sharing occurred after the begging behaviors, it appeared unlikely that DW gave meat in
immediate return for the sociosexual behaviors of FW.
Fellatio is considered rare because males are at highrisk of exposing their vital organs to other chimpanzees’
mouths. It has been proposed that such high-risk behaviors can be used to test and strengthen alliances between
same-sex partners (Kirkpatrick 2000). For chimpanzee
males, forming alliances with other males is crucial.
Thus, for a rare case of male–male fellatio, such a function of strengthening male–male relationships was emphasized (Brooker et al. 2020). However, as reported inthis study, fellatio can occur between a female and a malein the probable context of tension reduction. Thus, thefunction that is used to test social bonds may also apply to
opposite-sex partners.
This report describes a very rare case of heterosexualfellatio observed in the wild. However, it is difficult toknow why such behaviors are rare and why this case occurred in this context. More such observations are needed
to gain a deeper understanding of sociosexual behaviors
as well as the function of fellatio in chimpanzees.

sent study was financially supported by JSPS KAKENHI#2019J23191 and #4903 (JP17H06381).

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ACKNOWLEDGEMENTS

https://doi.org/10.1163/156853977X00324

I would like to thank the Tanzania Wildlife ResearchInstitute (TAWIRI), Tanzania Commission for Scienceand Technology (COSTECH), and Tanzania National
Parks (TANAPA) for permission to conduct this research. I am grateful to the Mahale Mountains National
Park (MMNP) and Mahale-Gombe Wildlife ResearchCentre (MGWRC) for their logistic support. I thank allcolleagues and local assistants of the Mahale Mountains
Chimpanzee Research Project (MMCRP) for their continuous help and support. I would like to thank Editage(www.editage.com) for English language editing. The pre-Nakamura M, Hosaka K, Itoh N, Zamma K (eds) 2015.
Mahale Chimpanzees: 50 Years of Research. Cambridge
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Received: 21 January 2022
Accepted: 28 February 2022

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