Pan Africa News, 26(1): 4–6 (2019)Note

A five-year-old chimpanzee ranged alone: Reconsidering
independence in ranging
Michio Nakamura1 & Hitonaru Nishie1,2
1 Graduate School of Science, Kyoto University, Japan
2 JSPS Research Fellow, Japan(E-mail: nakamura@jinrui.zool.kyoto-u.ac.jp)

INTRODUCTION

Chimpanzees (Pan troglodytes) have a long period of
dependency when they are immature. Dependence on themother may have various aspects. Infants are dependent
for almost every aspect: nutrition, transportation, hygiene,
and thermoregulation. Nutritional independence seems tobe achieved at around their third year but infants continue
to suckle the nipple to around fourth to fifth year of age(Matsumoto 2017). After weaning, offspring is considered
to enter juvenility. He/she is no more carried by the mother and eats by himself/herself. Still, juveniles are thought
to be dependent in ranging as they are almost always
together with their mothers (Pusey 1983; Hayaki 1988).
Thus, in many studies about chimpanzee ranging behavior or party size, infants and juveniles are “not counted as
independent animals” (Doran 1997).
Even if not the mother, a juvenile still needs somebody to be near. When a juvenile is away from its mother,he/she follows other adults or stays in a larger party(Pusey 1983). In a rare case when a five-year-old juvenile
male was left behind by his mother who emigrated to aneighboring group for ten months, he was almost always
observed to be together with a particular adult male
(Hiraiwa-Hasegawa & Hasegawa 1988). Thus, even when
juveniles are away from mothers, they are still with somebody else and are “virtually never alone” (Pusey 1990).
Orphans are of special interest in terms of dependency on adults (Nakamura et al. 2014). At Mahale, threeyear-old orphans may survive (Nakamura & Hosaka
2015). Such infant orphans are often “adopted” by somenon-mothers (Boesch et al. 2010; Nakamura & Hosaka
2015). Orphans are also dependent on their “adoptive
mothers” to be carried, groomed, or shared the beds with.
Although juvenile orphans are not “adopted” in such away, they usually need to follow someone. Hayaki (1988)
noted that “young orphans seem to need an attachment toa particular individual.” Although such particular partners
were sometimes less obvious (Nakamura & Hosaka 2015),
juvenile orphans had been always observed in a ranging
party containing at least one adult.
Here we report two cases of a five-year-old orphan
female at Mahale who seemed to have ranged completely
alone. These cases may provide us information to reconsider what independence in chimpanzees’ ranging is.

Figure 1. Close-up of Quinoko, a five-year-old orphan
female in 2018zees at the Mahale Mountains National Park, Tanzania
in August and September 2018. The orphaned juvenile inquestion, Quinoko (Figure 1), was born in January 2013,
thus 5 years and 7–8 months old (onset of juvenility) at thetime of the observations. Her mother had died in January
2018 (7–8 months earlier). Her elder sister (born in 2006)
also used to take care of Quinoko in her infancy but had
disappeared (probably emigrated) one month prior to themother’s death. Thus, Quinoko no more had maternal kin
in the M group.

OBSERVATIONS

Case 1
On August 20, 2018, HN and a research assistantwere searching for chimpanzees in the flatter area within
the M group’s home range since morning. They could nothear any vocalizations. At 9:47 h they split into two parties to look for chimpanzees in different locations. Soon,the assistant found Quinoko on a tree. He followed her
for a while as she moved eastward on trees. The assistantgave up following Quinoko when she went off the trail tothe east.
At 10:29 h, H N and the assistant reunited andsearched for other chimpanzees. They could only find two
adult females at 14:39 h at a different place about 1.5 km
from where Quinoko had been witnessed. Judging fromcircumstantial evidence, it seemed that the majority ofchimpanzees were high up in the mountain.

METHODS

Case 2On September 13, 2018, the majority of M-group

The study was conducted on the M group chimpan-

4Pan Africa News, 26(1): 4–6 (2019)

Figure 2. Ranging of Quinoko on September 14, 2018 relative to other chimpanzees’ movement
Quinoko’s travel route is shown in thick black arrow. White circles indicate the locations where she crossed
observation trails. Other chimpanzees’ estimated routes (on 13th and 14th) are shown in dotted grey arrows.
Grey dotted circles indicate estimated locations of vocalizations heard while following Quinoko on 14th. One gridcorresponds to 0.5 km by 0.5 km.

termittently heard, mostly from west. It seems the large
nomadic party was spreading widely and approaching.
Quinoko still moving through trees, headed north to thenorthwest while she replied four times to the vocalizations. At 12:56 h, she was high up in a tree looking at thedirection of the voices. By 13:19 h she was completely
within the range of widespread chimpanzees but still did
not physically meet any.
At 13:26 h, she finally descended to the ground, ran
on the trail, and pant-grunted to an adult male Carter whocame from the west. After this reunion, Quinoko continued to move in this nomadic party until the evening.

chimpanzees went up to the east in the morning. Judging
from the vocalizations, they continued to move southward
in the high mountain on the day (Figure 2, a dotted line to
the right).
On September 14th, MN was heading to where he
can hear vocalizations assuming large party was still on
the mountain. Along the way, at 8:25 h, he found Quinoko
alone on a tree eating Saba comorensis fruits (Figure 2).
As MN followed her, Quinoko moved northward throughtrees, sometimes eating Saba and Pycnanthus angolensis
fruits. At 9:37 h she made a humble bed on a high Cordia
tree and lay down on it (Figure 3). At 9:48 h, chimpanzee
vocalizations were heard from far southeast (still high inthe mountain). Quinoko did not show any response. At
10:00 h she started to move again and ate Saba. She again
rested at 10:39 h. At 11:01 h, chimpanzee calls were heard
again, this time from far south but it seems they climbed
down to flatter area. Soon afterward at 11:03 h, vocalizations came from west-northwest (someone may have preceded the main party). Still, Quinoko did not respond. At
11:13 h, she started to move and ate Saba and Pycnanthus
on the way.
At 12:27 h, many vocalizations came from the west.
This time they were much closer. Quinoko finally vocalized at 12:29 h: a whimper-like “hu hu” then a pant-hootwithout a climax. The other chimpanzees’ calls were in-

DISCUSSION

It is unusual for a five-year-old juvenile to range
alone, even considering that Quinoko was an orphan. In
Case 1, although the observation time was short, it is likely that Quinoko had long been alone because we did notsee other chimpanzees nearby despite a deliberate search.
In Case 2, Quinoko was alone at least for five hours.
Because most chimpanzees had been in the higher area
since the day before, and we found her in the morning, we
believe that she had stayed alone since the day before.
Pusey (1983) noted that one of the reasons why juveniles follow mothers is a need to learn how to find andprocess numerous seasonal and widely dispersed foods.

5Pan Africa News, 26(1): 4–6 (2019)

Figure 3. Quinoko resting
on a high tree

This means juveniles are still dependent because theylack sufficient knowledge for foraging. However, as we
observed in Case 2, Quinoko ate fruits several times anddid not seem to have difficulty in finding and eating fruits.
At this time, Saba and Pycnanthus, both Mahale chimpanzees’ major foods, were beginning to fruit in many
places. Thus in such a season, the demerit of being alone
on foraging may not be so obvious.
Still, Quinoko’s ranging behavior was not completely
same as usual. Notably, she never descended on the
ground while she was alone. In Case 2, she moved around
2 km only through trees. This is unlikely when we follow
an adult chimpanzee ranging alone. Because at Mahale,
tree canopies are often sparse, there seems to be a certain
cost to move a long distance without descending on the
ground. Quinoko actually seemed to incur extra costs todetour to the place where a branch is close to branch of thenext tree or to jump from a tree to the next. It is possiblethat presence of the human observers may be the reason
that she did not descend on ground. However, Quinoko is
not usually so shy and did not show any nervous attitude
toward us or try to flee. Thus, she might rather have hadsome unspecified anxiety.
Despite such possible anxiety, Quinoko never whimpered or made distress calls when she was far from others. This is contrasting to the situation when a similaraged non-orphan gets lost. He/she would loudly whimperand scream and deliberately search for the mother (Hayaki
1988; Matsusaka 2003). An orphan also whimpers when
he/she temporarily loses sight of the chimpanzee whomhe/she is following. This may mean that juvenile chimpanzees do call only when there is somebody close enoughto hear them. It is understandable that a chimpanzee does
not call when he/she is completely alone not to attract
predators.
Although juvenile chimpanzees almost always range
with others, our observations suggest that they can be
independent in some situations. It is unknown whether
Quinoko chose to be alone (because she was harassed byothers, for example) or was accidentally alone (i.e., got
lost) for some reason. She ranged for a long time and did
not seem to have difficulty in finding food. Still, as she
never descended on the ground and kept moving on trees,
it is suggested that ranging alone may cause some anxiety.
This may be a proximate reason that juveniles are virtu-

ally never alone.

ACKNOWLEDGMENTS

We would like to thank the Tanzania Commission for
Science and Technology, the Tanzania Wildlife ResearchInstitute, and the Tanzania National Parks for the permissions
to conduct field research at Mahale. We thank Dr. T. Matsusaka
for comments on the manuscript. The study was supported by
the MEXT/JSPS kakenhi JP15H04429, #4903 JP17H06381,
JP26284138 (to MN), and 17J40059 (to HN).

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Received: 23 October 2018
Accepted: 12 March 20196