ArticlePDF Available

A preliminary analysis of wound care and other-regarding behavior in wild chimpanzees at Ngogo, Kibale National Park, Uganda



Caring for others is a key feature of human behavior. Mothers, fathers, siblings, grandparents, and other group members provide care in the form of provisioning, protection, and first aid. To what extent is other-regarding behavior present in our primate relatives? Here we describe an unusual incident of other-regarding behavior toward an injured juvenile female chimpanzee (Pan troglodytes schweinfurthii) at Ngogo in Kibale National Park, Uganda. After the juvenile received a mild head wound from an adult female, several adolescent and juvenile chimpanzees gathered to touch, lick, and peer at the wound. One adolescent male wiped a leaf across the cut. Another adolescent male later groomed the injured female and briefly carried her. Across a 5-year period, we observed only three other instances of other-directed wound care in chimpanzees, occurring in 4% (4/100) of cases in which we observed individuals with fresh wounds, and 57 other instances of allomaternal carrying. Despite the infrequency of such behaviors, our study adds another chimpanzee field site to the list of those where other-directed wound care has been observed. Observations from wild chimpanzees provide insight into empathy and may inform our understanding of the evolution of other-regarding behavior in humans.
1 3
Primates (2021) 62:697–702
A preliminary analysis ofwound care andother‑regarding behavior
inwild chimpanzees atNgogo, Kibale National Park, Uganda
IsabelleR.Clark1 · AaronA.Sandel1· RachnaB.Reddy2,3· KevinE.Langergraber4,5
Received: 20 October 2020 / Accepted: 10 June 2021 / Published online: 1 July 2021
© Japan Monkey Centre 2021
Caring for others is a key feature of human behavior. Mothers, fathers, siblings, grandparents, and other group members
provide care in the form of provisioning, protection, and first aid. To what extent is other-regarding behavior present in our
primate relatives? Here we describe an unusual incident of other-regarding behavior toward an injured juvenile female chim-
panzee (Pan troglodytes schweinfurthii) at Ngogo in Kibale National Park, Uganda. After the juvenile received a mild head
wound from an adult female, several adolescent and juvenile chimpanzees gathered to touch, lick, and peer at the wound.
One adolescent male wiped a leaf across the cut. Another adolescent male later groomed the injured female and briefly
carried her. Across a 5-year period, we observed only three other instances of other-directed wound care in chimpanzees,
occurring in 4% (4/100) of cases in which we observed individuals with fresh wounds, and 57 other instances of allomaternal
carrying. Despite the infrequency of such behaviors, our study adds another chimpanzee field site to the list of those where
other-directed wound care has been observed. Observations from wild chimpanzees provide insight into empathy and may
inform our understanding of the evolution of other-regarding behavior in humans.
Keywords Pan troglodytes· Injury· Alloparenting· Infant carrying· Empathy
In humans, help from others in the form of care and provi-
sioning is key for recovering from illness and injury (Gurven
etal. 2000; Kaplan etal. 2000; Sugiyama 2004). Although
caregiving and other-regarding preferences may be most
extensive in humans, precursors of these behaviors can be
found in other animals (Hart 2011; Preston 2013). Caregiv-
ing behaviors such as carrying, provisioning, grooming, and
agonistic support have been observed in one of our closest
relatives, chimpanzees (Pan troglodytes), including toward
vulnerable young whose mothers are ill (Uehara and Nyundo
1983; Huffman and Seifu 1989), injured (Pruetz 2011), or
deceased (Hobaiter etal. 2014; Nakamura and Hosaka 2015;
Reddy and Mitani 2019; Samuni etal. 2019). Chimpanzees
occasionally attend to the wounds of groupmates, including
removing splinters in captivity (Köhler 1925; Yerkes 1943)
and grooming or licking wounds in the wild (Goodall 1983,
1986; Boesch 1991). Whether wound care behaviors actu-
ally benefit the wounded individual remains uncertain, but
licking may promote healing and seems to reflect an other-
regarding impulse (Dittus and Ratnayeke 1989; Boesch
1991). In rare instances, wound care involves tool use:
two juvenile male chimpanzees at Gombe, Tanzania, used
leaves to wipe the wounds of their infant sibling and mother,
respectively (Goodall 1986). Reports of wound care among
wild chimpanzees have been largely limited to maternal kin
(Goodall 1983, 1986), although wound care of genetically
unrelated individuals has been observed in western chim-
panzees at Taï, Côte D’Ivoire, where predation pressure and
social cohesion are elevated (Boesch 1991). Here we report
an unusual case of other-directed wound care involving sev-
eral chimpanzees and a juvenile female at Ngogo in Kibale
* Isabelle R. Clark
1 Department ofAnthropology, University ofTexas atAustin,
2201 Speedway Stop C3200, Austin, TX78712, USA
2 Department ofAnthropology, University ofMichigan,
AnnArbor, MI, USA
3 Department ofHuman Evolutionary Biology, Harvard
University, Cambridge, MA, USA
4 School ofHuman Evolution andSocial Change, Arizona
State University, Tempe, AZ, USA
5 Institute ofHuman Origins, Arizona State University, Tempe,
698 Primates (2021) 62:697–702
1 3
National Park, Uganda. We provide context by summarizing
wound care behaviors and instances of allomaternal carry-
ing at Ngogo.
Study site andsubjects
We studied the Ngogo chimpanzees in Kibale National
Park, Uganda, from 2014 to 2019. The population fluctu-
ated between 181 and 219 individuals. Age classes were
defined as follows: infant (0–5 years, until weaning),
juvenile (5–9years), adolescent (nulliparous females of
9–14years; males of 9–15years, based on the size of exter-
nal genitals; Goodall 1983), and adult (parous females and
nulliparous females over 14years; males over 15years).
Non-natal females are estimated to be 13years old at the
time of immigration (Wood etal. 2017). Birth dates are
known to within one day to three months for individuals
born at Ngogo since 1995 and are estimated for older adults
based on physical features and genetic relationships (Wood
etal. 2017). Genealogies have been previously established
from genetic data (Langergraber etal. 2007). Individuals
are considered "unrelated" if they are not parent-offspring,
maternal/paternal siblings, or related through parents’ sib-
lings (e.g., "first cousins," "aunt-niece"), although they may
be more distantly related.
Behavioral observations
We recorded wound care behavior and allomaternal car-
rying adlibitum during one- to three-hour-long continu-
ous focal follows (Altmann 1974) of adolescent and adult
males or during general observations of individuals of all
ages and sexes outside of focal follows (N = 256 individuals,
mean ± SD = 222.67 ± 213.16 contact hours per individual).
AAS collected data during three field seasons (August 24,
2014 to August 30, 2015; October 16, 2017 to June 5, 2018;
June 1 to November 7, 2019). RBR collected data during
four field seasons (May 22 to August 19, 2015; June 24,
2016 to August 12, 2017; May 18 to June 8, 2018; July 17 to
July 28, 2019). IRC collected data during two field seasons
(February 24 to June 3, 2018; January 19 to June 3, 2019).
We recorded all occurrences of open wounds includ-
ing small cuts, lacerations, and puncture wounds. In many
cases, it was unclear how recently injury had occurred. We
report only wounds that appeared relatively fresh (open
and bloody) and count each wound once, regardless of the
total number of days the wound was observed. We excluded
healed scabs, scars, and other injuries that did not include
open wounds. We recorded self-directed and other-directed
wound care behaviors including touching/grooming, licking,
or wiping the wound with leaves ("leaf-dabbing": Whiten
etal. 1999). We defined allomaternal carrying as ventral or
dorsal carrying by a non-mother, considering only bouts that
lasted for two strides or more, including during travel as well
as play (Nishida 1983; Nishida etal. 1999).
Case study
On May 31, 2018, we observed an unusual case of other-
regarding behavior in which multiple chimpanzees pro-
vided care to a wounded juvenile female, Septima (5.5years
old). At 11:05, adult female Bacall (with a clinging infant)
grabbed and pulled Septima’s head, leaving a small but
bloody wound on her forehead (Fig. 1a). Adult male
Fig. 1 a Septima (5.5-year-old female) with minor forehead wound
inflicted by parous female, b Etta (7-year-old female; center) sniffs
and licks the leaves that Damien (12-year-old male; left) used to
wipe the forehead wound of Septima (right; lying down), c YoYo
(12.5-year-old male) carries Septima ventrally after hearing other
groupmates hunting nearby
699Primates (2021) 62:697–702
1 3
Garrison (Septima’s biological father) positioned him-
self between Septima and Bacall, who sat 2m from each
other. Bacall and Garrison moved out of view, while Sep-
tima moved a few meters before laying with her stomach
on the ground, still alert and responsive. Septima’s mother,
Dahlia, and infant sister, Hermione (1.5years old), were not
in visible range but were observed earlier and later in the
day, indicating that they may have been in the party, which
was large and spread out. Septima usually traveled with her
mother and maternal siblings.
Most members of the party began to travel at 11:15,
but Septima remained with several chimpanzees including
Damien (12-year-old male), Etta (7years, Damiens mater-
nal sister), Joya (7-year-old female), and Bach (9.5-year-old
male); notably, all four of these individuals are orphans and
genetically unrelated to Septima. Adolescent male Damien
approached Septima and brushed an overhanging cluster
of leaves across her wound, sniffing and licking the leaves.
Juvenile female Etta sniffed and licked the same leaves
(Fig.1b), touched the wound with her fingers, licked her
fingers, and licked the wound directly (see Online Resource
1 for video). Juvenile female Joya peered, her face within
10cm of Septima’s head. Adolescent male Bach approached
to sniff and possibly lick the wound. When they all began to
travel, Septima followed Damien and embraced him ventro-
ventrally. Septima did not appear to have trouble walking.
We lost sight of Septima until 12:00, when she was
observed following Buckner (18.5-year-old male) and his
maternal brother, Holland (8years)—also orphans and
unrelated to Septima. Around 12:30, YoYo (12.5years,
paternal brother of Septima and maternal brother of Joya)
groomed Septima, including her wound. Joya and Sanger
(10years, Septima’s maternal sister) approached to peer
at the wound. As they peered, Septima touched the wound
herself and licked her fingers repeatedly. Septima followed
YoYo when he began to travel, but both stopped after only
several meters while the rest of the group, including Sep-
tima’s sister, moved on. Septima reached both arms toward
YoYo and he embraced her ventro-ventrally, thrust briefly,
then continued to intermittently embrace, groom, and play
with her while lying down. At 12:52, YoYo moved as if to
travel but sat back down less than a meter from Septima,
who remained lying on the ground, and gently poked her
twice. She whimpered and did not move, and YoYo returned
to grooming her.
At 13:00, following a total of 30 minutes of grooming and
resting in close proximity, YoYo and Septima sat up as other
group members began hunting a duiker within audible range.
YoYo began to move toward their vocalizations, Septima
whimpered, and YoYo repeatedly turned back to reach for
her. When the duiker began to make alarm calls, they both
became alert and YoYo picked up Septima, stood bipedally,
and held her briefly as she clung to him ventrally (Fig.1c;
see Online Resource 2 for video). She fell off when YoYo
returned to all fours. YoYo attempted to move past Septima
but, when she began screaming, reached back and pulled her
to him. They embraced for three seconds, but Septima fell
off again when YoYo began to run. He paused to look over
his shoulder when she began screaming again while follow-
ing him. They ran out of view, and Septima was not seen for
the remainder of the day. In the following days, Septima was
back with her mother without signs of injury.
Other cases ofwound care
During a 5-year period, we observed chimpanzees with
fresh wounds on 100 occasions (Table1). In 29% of these
instances, we observed self-directed wound care. Almost
half (13/29) of these cases included tool-assisted wiping
of wounds using leaves, or "leaf-dabbing" (Whiten etal.
1999). At least four of these 13 tool-assisted cases also
involved self-grooming and licking. The other 16 cases
were not tool-assisted and involved only self-grooming or
licking. Wounded individuals received care from others for
4% (4/100) of the wounds we observed, including the case
study reported above. We describe the three other cases of
other-directed wound care in brief.
On March 9, 2017, RBR found adolescent male PeeWee
(11years) grooming the wounds of an older, genetically unre-
lated male, Barron (16years). Barron’s ear was bleeding and
split into two pieces, the inside of his elbow was wounded and
bleeding, and he avoided putting weight on his hand, which
hung limp from his wrist. We did not observe how Barron
acquired these injuries. PeeWee groomed the bloody spots on
Barron’s elbow and ear, holding one piece of the ear in each of
his own hands as he peered down the center of the split. While
this pair is not genetically related, they exhibited a strong
social bond (Reddy and Mitani 2019; Sandel etal. 2020). Later
in the day, Barron was observed to alternate between touching
his own ear wound and licking his fingers repeatedly.
Table 1 Number of wounds (N = 100) for which individuals engaged
in self-directed care in the form of (1) leaf-dabbing, which was some-
times accompanied by grooming/licking, and (2) only grooming/lick-
ing, and for which wounded individuals received these forms of care
from other groupmates
In three of the of the four wound cases in which we observed other-
directed care, we also observed the wounded individual licking their
own wounds
Self-directed Other-directed
Maternal kin
Leaf-dab 13 1 0
Groom/lick 13 1 2
Total 26 2 2
700 Primates (2021) 62:697–702
1 3
On July 5, 2017, RBR observed adult female Bacall
inspect and groom a cut on the hand of her adolescent son,
Williams (10years). Williams may have received the injury
in an aggressive interaction with another adult female, as he
was lunging toward this female and screaming when Bacall
ran toward him. Bacall’s first action was toward the injury,
rather than toward the other female or reassuring Williams.
Bacall picked up Williams’ arm by the wrist, pulled it toward
her, and peered at the wound before grooming it with her
fingers and mouth.
On January 25, 2018, AAS observed juvenile male Hol-
land (7.5years) groom and lick a puncture wound on the
arm of his older, young adult maternal brother, Buckner
(18years). Buckner likely received this injury during an
aggressive encounter with conspecifics the previous day
(Sandel and Watts 2021). He was observed to self-groom
and lick his wound immediately prior to Holland’s care.
Although there is a large age gap between this maternal sib-
ling pair, and Buckner had already traveled independently
from their mother for much of Holland’s life, the pair’s rates
of association, proximity, grooming, reassurance, and travel
vigilance increased dramatically after their mother died in
2017, prior to this incident (Reddy and Mitani 2019).
Other cases ofallomaternal carrying
We observed 58 cases of allomaternal carrying of 26 infants
and only one young juvenile (Septima, described above) by
34 individuals. Fourteen of the 26 infants were carried only
once, and the other 12 were carried multiple times, some by
multiple individuals. Half of our observations involved close
maternal kin (29/58, all siblings except for two instances in
which a juvenile male carried his maternal sister’s infant),
and the rest involved individuals that were not maternally
related, though one case involved paternal siblings and
several cases involved individuals that were more distantly
related on the paternal side. The majority of carrying epi-
sodes were brief and not repeated, often occurring in the
context of play or travel. Carrying occasionally occurred
in response to the distress of the individual carried, as in
Septima’s case. In another instance, we observed an immi-
grant female retrieve and carry an infant back to his mother,
after he cried as researchers approached the sapling he was
playing in alone. We also observed a young adult male twice
carry his infant brother, whose mother’s ability to travel was
hindered by a missing foot from a past snare injury.
We observed an unusual case of other-regarding behavior
toward an injured juvenile female chimpanzee. An adoles-
cent male wiped her wound with leaves, a juvenile female
touched and licked the wound, and another adolescent male
groomed and briefly carried her. Wound care of others
appears to be rare among chimpanzees at Ngogo (Table1).
We observed only three additional instances of other-
directed wound care, representing 4% of observed wounds
during this period. In contrast, we observed self-directed
wound care for 29% of wounds. Given that we did not
observe the infliction of wounds in most cases and did not
continuously follow wounded individuals, these results may
underestimate the prevalence of both self- and other-directed
wound care. We also observed 57 additional instances of
allomaternal carrying, but unlike the carrying that occurred
during the case study, no other instance was associated with
an injured group member.
The case of Septima was a rare example of tool-assisted,
other-directed wound care. Self-directed "leaf-dabbing" of
wounds has previously been reported at Ngogo and other
chimpanzee sites (Goodall 1983; Whiten etal. 1999; Sanz
and Morgan 2007; Watts 2008). The extension of this behav-
ior to others has only been reported among two pairs of
maternally related chimpanzees in the wild (Goodall 1986).
More broadly, previous reports of wound care have either
been limited to mothers and offspring (Goodall 1983, 1986)
or occurred among genetically unrelated chimpanzees
in West Africa, where heightened predation pressure and
social cohesion may facilitate cooperation among non-kin
(Boesch 1991). There is no leopard predation at Ngogo.
While the three other cases of wound care we observed
occurred between mother and son, maternal brothers, and a
pair of genetically unrelated adolescent males with a strong
social bond (Reddy and Mitani 2019; Sandel etal. 2020),
Septima’s caretakers were not maternal relatives nor close
social affiliates of hers. Their other-regarding behaviors may
have been activated by her distress (Preston 2013; de Waal
and Preston 2017), which was made apparent by her lying
prostrate on the ground, whimpering, and screaming.
Although the wound itself appeared to be relatively
minor, multiple unrelated individuals tended to Septima,
including two adolescent males. Male chimpanzees do not
typically provide parental care, as females mate with multi-
ple males and paternity is uncertain. However, male chim-
panzees have been observed to carry infants for extended
periods (Notman and Munn 2003; Pruetz 2011; Cibot
etal. 2019), provide care to their orphaned younger sib-
lings (Hobaiter etal. 2014; Reddy and Mitani 2019), and
adopt related as well as unrelated orphaned infants (Boesch
etal. 2010; Samuni etal. 2019). Given that both adolescent
males described here were among those observed to care for
their younger siblings following maternal death (Reddy and
Mitani 2019), they may have been predisposed to providing
care to Septima, as prior experience seems to augment the
empathic response (reviewed by Preston and de Waal 2002).
Most of the individuals who attended to her were orphans,
701Primates (2021) 62:697–702
1 3
suggesting that maternal loss itself may have enhanced their
perspective-taking ability toward Septimas distress in the
absence of her mother.
The benefits of wound care behaviors in nonhuman pri-
mates remain to be studied. Grooming may remove dirt
particles, and licking is thought to facilitate wound healing
given the antibacterial properties of saliva (Dittus and Rat-
nayeke 1989; Hart and Powell 1990; Boesch 1991). Leaf-
dabbing of wounds may reduce infection risk compared to
direct contact, or it may be more akin to the exploratory
touching and probing of novel objects such as carcasses
(e.g., Cronin etal. 2011). Experimental evidence shows that
chimpanzees are attuned to images of wounded conspecifics
and experience negative arousal in response to prosthetic
wounds on a familiar human experimenter, suggesting that
they empathize with injured others (Sato etal. 2019). This
attention to and curiosity about wounds may lead to wound
care of others under certain conditions, such as signs of dis-
tress or the presence of a strong social bond. Thus, regard-
less of how beneficial wound care is, attention to wounds
may represent an empathetic precursor of human-like proso-
ciality, for which there is increasing evidence of in social
mammals like apes (Warneken etal. 2007; Yamamoto etal.
2009; Melis etal. 2011). While allomaternal care is rare
among chimpanzees, we found that wound care and car-
rying sometimes occur even among non-kin. The question
should no longer be whether chimpanzees have the capacity
for other-regarding preferences, but how socio-ecological
and demographic factors drive variation in the expression
of prosocial behaviors across individuals and populations.
Supplementary Information The online version contains supplemen-
tary material available at https:// doi. org/ 10. 1007/ s10329- 021- 00925-7.
Acknowledgements We thank the Uganda Wildlife Authority, the
Uganda National Council for Science and Technology, and the Mak-
erere University Biological Field Station for permission to conduct
research. For support in the field, we are grateful to John Mitani, David
Watts, Samuel Angedakin, Alfred Tumusiime, Ambrose Twineomu-
juni, Brian Kamugyisha, Charles Birungi, Chris Aliganyira, Diana
Kanweri, Godfrey Mbabazi, and Lawrence Ndangizi. Funding was
provided by the Leakey Foundation, the University of Michigan, the
Nacey-Maggioncalda Foundation, the National Science Foundation
(1540259, F031543, BCS-1613392, DGE-1256260), and the National
Geographic Society (CRE-9742-15).
Conflict of Interest The authors declare that they have no conflicts of
Altmann J (1974) Observational study of behavior: sampling methods.
Behaviour 49:227–267
Boesch C (1991) The effects of leopard predation on grouping pat-
terns in forest chimpanzees. Behaviour 117:220–241
Boesch C, Bolé C, Eckhardt N, Boesch H (2010) Altruism in forest
chimpanzees: the case of adoption. PLoS ONE 5:1–6
Cibot M, Mccarthy MS, Lester JD etal (2019) Infant carrying
by a wild chimpanzee father at Bulindi, Uganda. Primates
Cronin KA, van Leeuwen EJC, Mulenga IC, Bodamer MD (2011)
Behavioral response of a chimpanzee mother toward her dead
infant. Am J Primatol 73:415–421
De Waal FBM, Preston SD (2017) Mammalian empathy: behavioural
manifestations and neural basis. Nat Rev Neurosci 18:498–509
Dittus WPJ, Ratnayeke SM (1989) Individual and social behavioral
responses to injury in wild toque macaques (Macaca sinica). Int
J Primatol 10:215–234
Goodall J (1983) Population dynamics during a 15 year period in one
community of free-living chimpanzees in the Gombe National
Park, Tanzania. Z Tierpsychol 61:1–60
Goodall J (1986) The chimpanzees of Gombe: patterns of behavior.
Harvard University Press, Cambridge
Gurven M, Allen-Arave W, Hill K, Hurtado M (2000) ‘It’s a Wonder-
ful Life’: signaling generosity among the Ache of Paraguay. Evol
Hum Behav 21:263–282
Hart BL (2011) Behavioural defences in animals against pathogens and
parasites: parallels with the pillars of medicine in humans. Philos
Trans R Soc B 366:3406–3417
Hart BL, Powell KL (1990) Antibacterial properties of saliva: role in
maternal periparturient grooming and in licking wounds. Physiol
Behav 48:383–386
Hobaiter C, Schel AM, Langergraber K, Zuberbühler K (2014) ‘Adop-
tion’ by maternal siblings in wild chimpanzees. PLoS ONE
Huffman MA, Seifu M (1989) Observations on the illness and con-
sumption of a possibly medicinal plant Vernonia amygdalina
(Del.), by a wild chimpanzee in the Mahale Mountains National
Park. Tanzania Primates 30:51–63
Kaplan H, Hill K, Lancaster J, Hurtado M (2000) A theory of human
life history evolution: diet, intelligence, and longevity. Evol
Anthropol 9:156–185
Köhler W (1925) The mentality of apes. Routledge, Trench, Trubner
& Co, London
Langergraber KE, Mitani JC, Vigilant L (2007) The limited impact of
kinship on cooperation in wild chimpanzees. Proc Natl Acad Sci
Melis AP, Warneken F, Jensen K etal (2011) Chimpanzees help con-
specifics obtain food and non-food items. Proc R Soc B Biol Sci
Nakamura M, Hosaka K (2015) Orphans and allomothering. In: Naka-
mura M, Hosaka K, Itoh N, Zamma K (eds) Mahale chimpanzees:
50 years of research. Cambridge University Press, Cambridge
Nishida T (1983) Alloparental behavior in wild chimpanzees of the
Mahale Mountains, Tanzania. Folia Primatol 41:1–33
Nishida T, Kano T, Goodall J etal (1999) Ethogram and ethnography
of Mahale chimpanzees. Anthropol Sci 107:141–188
Notman H, Munn J (2003) A case of infant carrying by an adult male
chimpanzee in the Budongo Forest. Pan Africa News 10:7–9
Preston SD (2013) The origins of altruism in offspring care. Psychol
Bull 139:1305–1341
Preston SD, de Waal FBM (2002) Empathy: its ultimate and proximate
bases. Behav Brain Sci 25:1–71
Pruetz JD (2011) Targeted helping by a wild adolescent male chim-
panzee (Pan troglodytes verus): evidence for empathy? J Ethol
Reddy RB, Mitani JC (2019) Social relationships and caregiving
behavior between recently orphaned chimpanzee siblings. Pri-
mates 60:389–400
702 Primates (2021) 62:697–702
1 3
Samuni L, Wittig R, Crockford C (2019) Adoption in the Taï chimpan-
zees: costs, benefits and strong social relationships. In: Boesch C,
Wittig RM (eds) The chimpanzees of the Taï Forest: 40 years of
research. Cambridge University Press, Cambridge, pp 141–158
Sandel AA, Watts DP (2021) Lethal coalitionary aggression associated
with a community fission in chimpanzees (Pan troglodytes) at
Ngogo, Kibale National Park, Uganda. Int J Primatol 42:26–48
Sandel AA, Langergraber KE, Mitani JC (2020) Adolescent male chim-
panzees (Pan troglodytes) form social bonds with their brothers
and others during the transition to adulthood. Am J Primatol
Sanz CM, Morgan DB (2007) Chimpanzee tool technology in the
Goualougo Triangle, Republic of Congo. J Hum Evol 52:420–433
Sato Y, Hirata S, Kano F (2019) Spontaneous attention and psycho-
physiological responses to others’ injury in chimpanzees. Anim
Cogn 22:807–823
Sugiyama LS (2004) Illness, injury, and disability among Shiwiar
forager-horticulturalists: implications of health-risk buffering
for the evolution of human life history. Am J Phys Anthropol
Uehara S, Nyundo R (1983) One observed case of temporary adop-
tion of an infant by unrelated nulliparous females among wild
chimpanzees in the Mahale Mountains, Tanzania. Primates
Warneken F, Hare B, Melis AP etal (2007) Spontaneous altruism by
chimpanzees and young children. PLoS Biol 5:1414–1420
Watts DP (2008) Tool use by chimpanzees at Ngogo, Kibale National
Park, Uganda. Int J Primatol 29:83–94
Whiten A, Goodall J, Mcgrew WC etal (1999) Cultures in chimpan-
zees. Nature 399:682–685
Wood BM, Watts DP, Mitani JC, Langergraber KE (2017) Favorable
ecological circumstances promote life expectancy in chimpanzees
similar to that of human hunter-gatherers. J Hum Evol 105:41–56
Yamamoto S, Humle T, Tanaka M (2009) Chimpanzees help each other
upon request. PLoS ONE 4:1–7
Yerkes RM (1943) Chimpanzees: a laboratory colony. Yale University
Press, New Haven
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
Many animals engage in aggression, but chimpanzees stand out in terms of fatal attacks against adults of their own species. Most lethal aggression occurs between groups, where coalitions of male chimpanzees occasionally kill members of neighboring communities that are strangers. However, the first observed cases of lethal violence in chimpanzees, which occurred at Gombe, Tanzania in the 1970s, involved chimpanzees that once knew each other. They followed the only observed case of a permanent community fission in chimpanzees. A second permanent fission recently transpired at Ngogo, Kibale National Park, Uganda. Members of a large western subgroup gradually ceased associating peacefully with the rest of the community and started behaving antagonistically toward them. Affiliation effectively ended by 2017. Here, we describe two subsequent lethal coalitionary attacks by chimpanzees of the new western community on males of the now separate central community, one in 2018 and the second in 2019. The first victim was a young adult male that never had strong social ties with his attackers. The second was a high-ranking male that had often associated with the western subgroup before 2017; he groomed regularly with males there and formed coalitions with several. Other central males present at the start of the second attack fled, and others nearby did not come to the scene. Several western females joined in the second attack; we suggest that female–female competition contributed to the fission. This event highlighted the limits on protection afforded by long-term familiarity and the constraints on costly cooperation among male chimpanzees.
Full-text available
Social relationships play an important role in animal behavior. Bonds with kin provide indirect fitness benefits, and those with nonkin may furnish direct benefits. Adult male chimpanzees (Pan troglodytes) exhibit social bonds with maternal brothers as well as unrelated adult males, facilitating cooperative behavior, but it is unclear when these bonds develop. Prior studies suggest that social bonds emerge during adolescence. Alternatively, bonds may develop during adulthood when male chimpanzees can gain fitness benefits through alliances used to compete for dominance status. To investigate these possibilities and to determine who formed bonds, we studied the social relationships of adolescent and young adult male chimpanzees (N = 18) at Ngogo in Kibale National Park, Uganda. Adolescent male chimpanzees displayed social bonds with other males, and they did so as often as did young adult males. Adolescent and young adult males frequently joined subgroups with old males. They spent time in proximity to and grooming with old males, although they also did so with their age peers. Controlling for age and age difference, males formed strong association and proximity relationships with their maternal brothers and grooming relationships with their fathers. Grooming bonds between chimpanzee fathers and their adolescent and young adult sons have not been documented before and are unexpected because female chimpanzees mate with multiple males. How fathers recognize their sons and vice versa remains unclear but may be due to familiarity created by relationships earlier in development.
Full-text available
Previous studies have shown that humans experience negative emotions when seeing contextual cues of others’ pain, such as injury (i.e., empathic pain), even without observing behavioral expressions of distress. However, this phenomenon has not been examined in nonhuman primates. We tested six chimpanzees (Pan troglodytes) to experimentally examine their reactions to others’ injury. First, we measured viewing responses using eye-tracking. Chimpanzees spontaneously attended to injured conspecifics more than non-injured conspecifics, but did not do so in a control condition in which images of injuries were scrambled while maintaining color information. Chimpanzees did not avoid viewing injuries at any point during stimulus presentation. Second, we used thermal imaging to investigate chimpanzees’ physiological responses to others’ injury. Previous studies reported that reduced nasal temperature is a characteristic of arousal, particularly arousal associated with negative valence. We presented chimpanzees with a realistic injury: a familiar human experimenter with a prosthetic wound and artificial running blood. Chimpanzees exhibited a greater nasal temperature reduction in response to injury compared with the control stimulus. Finally, chimpanzees were presented with a familiar experimenter who stabbed their (fake) thumb with a needle, with no running blood, a situation that may be more challenging in terms of understanding the cause of distress. Chimpanzees did not physiologically distinguish this condition from the control condition. These results suggest that chimpanzees inspect others’ injuries and become aroused by seeing injuries even without observing behavioral cues, but have difficulty doing so without explicit (or familiar) cues (i.e., open wound and blood).
The Chimpanzees of the Taï Forest - edited by Christophe Boesch November 2019
When their mothers die, chimpanzees often adopt younger vulnerable siblings who survive with their care. This phenomenon has been widely reported, but few studies provide details regarding how sibling relationships change immediately following the deaths of their mothers. A disease outbreak that killed several females at Ngogo in Kibale National Park, Uganda, furnished an opportunity to document how maternal death influenced the social relationships of siblings. We describe social interactions between four adolescent and young adult males and their younger immature maternal siblings 9 months before and 8 months after their mothers died. We also show how the behavior of individuals in the four recently orphaned sibling pairs contrasts to the behavior displayed by chimpanzees in 30 sibling pairs whose mothers were alive. Following the death of their mothers, siblings increased the amount of time they associated, maintained spatial proximity, groomed, reassured, and consoled each other. During travel, younger orphans followed their older siblings, who frequently looked back and waited for them. Both siblings showed distress when separated, and older siblings demonstrated heightened vigilance in dangerous situations. Chimpanzees who were recently orphaned interacted in the preceding ways considerably more than did siblings whose mothers were alive. These findings suggest that siblings provide each other support after maternal loss. Further research is needed to determine whether this support buffers grief and trauma in the immediate aftermath of maternal loss and whether sibling support decreases the probability that orphans will suffer long-term consequences of losing a mother if they survive.
Although infanticide by wild adult male chimpanzees has been reported from multiple sites, affiliative infant carrying by males is rare. We observed infant carrying by an alpha male chimpanzee at Bulindi (Uganda) on two consecutive mornings and collected faecal samples from the newborn infant female, her mother and all candidate fathers to determine whether the alpha male was the infant’s father using a likelihood-based method of paternity assignment. In contrast to previous observations of male care of orphans, in this case the mother was present during observations. Further, unlike reports of male aggression towards infants, the infant was reunited with her mother on the third morning, and survived. Neither mother nor infant presented visible injuries. The alpha male never directed aggression towards the infant. Rather, he displayed attentive behaviours, for example by holding the infant to his chest, supporting her while moving, grooming her, and ‘cuddling’ and ‘rocking’ her. Paternity results revealed with a high degree of certainty that the alpha male was the infant’s father. There are several alternative explanations for the male’s behaviour, but this unusual case also highlights the need for further studies to determine under what circumstances adult male chimpanzees can recognise their own offspring.
Recent research on empathy in humans and other mammals seeks to dissociate emotional and cognitive empathy. These forms, however, remain interconnected in evolution, across species and at the level of neural mechanisms. New data have facilitated the development of empathy models such as the perception-action model (PAM) and mirror-neuron theories. According to the PAM, the emotional states of others are understood through personal, embodied representations that allow empathy and accuracy to increase based on the observer's past experiences. In this Review, we discuss the latest evidence from studies carried out across a wide range of species, including studies on yawn contagion, consolation, aid-giving and contagious physiological affect, and we summarize neuroscientific data on representations related to another's state.
Demographic data on wild chimpanzees are crucial for understanding the evolution of chimpanzee and hominin life histories, but most data come from populations affected by disease outbreaks and anthropogenic disturbance. We present survivorship data from a relatively undisturbed and exceptionally large community of eastern chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda. We monitored births, deaths, immigrations, and emigrations in the community between 1995 and 2016. Using known and estimated ages, we calculated survivorship curves for the whole community, for males and females separately, and for individuals ≤2 years old when identified. We used a novel method to address age estimation error by calculating stochastic survivorship curves. We compared Ngogo life expectancy, survivorship, and mortality rates to those from other chimpanzee communities and human hunter-gatherers. Life expectancy at birth for both sexes combined was 32.8 years, far exceeding estimates of chimpanzee life expectancy in other communities, and falling within the range of human hunter-gatherers (i.e., 27–37 years). Overall, the pattern of survivorship at Ngogo was more similar to that of human hunter-gatherers than to other chimpanzee communities. Maximum lifespan for the Ngogo chimpanzees, however, was similar to that reported at other chimpanzee research sites and was less than that of human-hunter gatherers. The absence of predation by large carnivores may contribute to some of the higher survivorship at Ngogo, but this cannot explain the much higher survivorship at Ngogo than at Kanyawara, another chimpanzee community in the same forest, which also lacks large carnivores. Higher survivorship at Ngogo appears to be an adaptive response to a food supply that is more abundant and varies less than that of Kanyawara. Future analyses of hominin life history evolution should take these results into account.