Pan Africa News, 27(1): 2–5 (2020)

Note

Nkala Forest: Introduction of a forest-savanna mosaic field siteof wild bonobos and its future prospects
Ena Onishi1 , James Brooks1, Innocent Leti2, Claude Monghiemo2, JeanChristophe Bokika2, Yuta Shintaku3, 4, Gen’ichi Idani1, 3 & Shinya Yamamoto1, 5✉✉✉

1 Wildlife Research Center, Kyoto University, Japan
2 Mbou-Mon-Tour, Democratic Republic of the Congo
3 Japan Monkey Centre, Japan
4 Primate Research Institute, Kyoto University, Japan
5 Institute for Advanced Study, Kyoto University, Japan(✉E-mail: enaonishi@gmail.com, gidani@wrc.kyoto-u.ac.jp, shinyayamamoto1981@gmail.com)

INTRODUCTION

environments (Inogwabini et al. 2013; Narat et al. 2015a,b, c; Pennec et al. 2016; Serckx et al. 2014, 2015, 2016).
Wild bonobos in Mbali thus present a promising and novel
research opportunity for understanding bonobo behavior
from a broader species level.
Studies in forest-savanna mosaic environment arealso important for theories of human evolution. Many researchers suggest that much of human evolution occurredin forest-savanna mosaic environments after divergencefrom a forest-dwelling ancestor, and it is therefore essential to study how savanna environments inf luence
great apes’ behavior and society. Such an approach has
been taken to some extent with chimpanzees (e.g., Pruetz& Bertolani 2009), however there are few studies withwild bonobos. Some research in forest-savanna mosaicenvironments has been conducted on local ecology (e.g.,Serckx et al. 2015; Trolliet et al. 2016; Pennec et al. 2016)and human-bonobo relationships (Inogwabini et al. 2013;
Narat et al. 2015a) in the Mbali area, and also on conservation (Hickey et al. 2013) and genetics (Kawamoto et al.
2013; Takemoto et al. 2017) in Tshuapa-Lomami-Lualaba(TL2) in the eastern end of bonobo’s range (Figure 1).
However, studies on bonobos’ behavior and society in forest-savanna mosaic environments are extremely limited(but see Druelle et al. 2020; Narat et al. 2015b).

Bonobos are one of humans’ two closest living relatives and display several remarkable similarities to us(Hare & Yamamoto 2015; 2017). To understand humanevolution, it is essential to understand bonobos. However,compared to chimpanzees, research on bonobos is lacking. There are far fewer bonobo research sites, with far
less environmental diversity.
In this article, we introduce our wild bonobo research site located at the southwest end of bonobos’
range in the Forest Concession of Local Communitiesof the Mbali River (hereafter, “Mbali area”, previously
called “Malebo”), in Lac Tumba landscape, Mai-Ndombe
province, Democratic Republic of the Congo (Figure 1).
The site is unique for its forest-savanna mosaic environment, as previous studies on wild bonobos have mainly
been conducted in rich tropical rainforests (Furuichi &Thompson 2010) such as Wamba (Kano 1992), Lomako(Badrian & Malenky 1984) and LuiKotale (Hohmann &Fruth 2003). Inogwabini et al. (2008) recently confirmedthat wild bonobos inhabit a wider range of environments
than previously thought, and since then much attention
has been paid to wild bonobos in forest-savanna mosaic

GENERAL INFORMATION

Mbou-Mon-Tour (MMT), a local NGO for conservation, eco-tourism and community development, started
habituating wild bonobos in the Nkala, Mpelu andManzano sites in 2001. The first two sites have been technically and financially supported by WWF-DRC since2006, and the third site, Manzano, has been supported
by Bonobo-ECO since 2010. MMT has been operating
daily monitoring of bonobos from their morning to nightnests whenever possible. Since 2014, in collaboration with
MMT and WWF-DRC, Kyoto University researchers havestudied the Nkala group (named after the nearest village,2°36'10"S, 16°27'17"E). Thanks to collaborative efforts ofextensive habituation, we have been able to identify all
bonobos in the Nkala group since 2016 and can observe
them from a distance of approximately 10 to 20 m. This
area includes old and young secondary forests, savanna,
crop fields and villages (Figure 2). In the Nkala forest,
we found direct or indirect evidence for 44 species ofmammal including pangolins, civets, duikers, bonobos
and other primates such as Cercopithecus ascanius andFigure 1. Map of bonobo research sites listed in thispaper. The Nkala is one of the field sites in Mbali which islocated in the Lac Tumba landscape.

2Pan Africa News, 27(1): 2–5 (2020)

Figure 2. Aerial photo of Nkala forest taken by a drone. (Phototaken by Ena Onishi)

Figure 3. Marantaceae forest. (Photo taken by EnaOnishi)

Cercopithecus neglectus (Shintaku et al. unpublisheddata). Direct evidence included live observation, hearing
vocalizations and camera trap footage, while indirect evidence included hair, feces, footprints and reports from thelocal people.

forest refers to a forest type where Marantaceae plants
predominate the landscape as shown in Figure 3.
Figure 4 shows monthly habitat use by the Nkala
group. They spent 47.9% of the total time in closed
canopy forest, 50.2% in Marantaceae forest, 1.4% in inundated forest and 0.5% in savanna environments. There
was a significant difference in habitat use between the dryand wet season (dry season: February to March and June
to August; wet season: April to May and September toJanuary (Inogwabini et al. 2008); Fisher’s exact test: pvalue < 0.01). Multiple comparison with Holm correction
revealed that bonobos significantly increased the ratio ofsavanna use in wet season (0.18% in dry season; 0.85% inwet season).
Crossing to a distant forest was the most common useof savanna in our observations (see Video 1 available online at http://mahale.main.jp/PAN/2020/001.html). We observed four
complete savanna crossing events, each spanned less than
10 minutes. We have also observed longer stays (morethan 2 hours) and foraging behavior in the savanna (seeVideo 2 available online at http://mahale.main.jp/PAN/2020/001.html;
we could not identify the food item in the video).

COMPOSITION OF THE BONOBO GROUP

The Nkala group consisted of around 15 individuals
until a drastic population decline in 2018. Table 1 shows
the number of confirmed individuals at the end of eachyear from 2016 to 2019. In 2017, two females disappeared.
An adult female was suspected to have died from naturalcauses and a juvenile female was suspected to have transferred to another group. In 2018, four adult and subadultmales disappeared; one adult male disappeared in lateMarch, two adult males disappeared simultaneously inearly June, and another subadult male disappeared in lateJune. MMT research assistants did not detect any signsof disease or injury in their daily follows, and the infants
survived, suggesting a disease epidemic is unlikely. We
did not find dead bodies of bonobos during the study period. At the end of 2019, the population had only 10 individuals, including 4 juveniles and infants.

CONSERVATIONHABITAT USE

Nkala villagers (Bateke people) have a strong traditional taboo against eating bonobos (Inogwabini et al.
2013). Due to the MMT’s long-term efforts in the Mbaliarea (e.g. Narat et al. 2015b), the Nkala forest is protectedby the community. Hunting of bonobos is strictly prohibited, though hunting of small animals with traditional
methods is permitted. Unfortunately, during their regularpatrolling of the forest twice a month, MMT forest rangers have found numerous banned metal-wire traps andcartridges. They found 38 traps and 57 cartridges between

Since 2016, in collaboration with MMT local assistants, we have recorded bonobos’ activity and habitat use
every 30 minutes on full day follows whenever possible.
We analyzed their habitat use throughout 2018; 280 daysof data were collected (23.3±5.0 days in a month on average) including 6997 data points. During observation,
research assistants recorded bonobos’ location with four
categories: closed canopy forest, Marantaceae forest, inundated forest and savanna (Tutin et al. 1994). Marantaceae

Table 1. Group composition of Nkala group from 2016 to 2019adult/subadult adult/subadult juvenile
male
femalemalejuvenile
femaleinfantTOTAL

2016

54212142017

53202122018

3300392019

33022103

Pan Africa News, 27(1): 2–5 (2020)

Figure 4. Habitat use by the Nkala bonobos in 2018. The black line along thex-axis represents dry season and the dotted line represents wet season.

ries. This perspective is supported by the differential timespent in the savanna between dry and wet seasons, though
this should be investigated further. Future research, especially cross-site comparisons, can help reveal their adaptation to forest-savanna mosaic environments, which may
prove insightful for understanding human evolution insimilar environments.
Despite the evident scientific value of this field site,
the Nkala group is at a critical risk of extinction. The
traps and cartridges found in the forest indicate it is possible that the decline in group size was due to illegal
poaching, though there is no direct evidence of bonobo
hunting. Poaching for the commercial bushmeat trade isone of bonobos’ main threats (IUCN & ICCN 2012), andthe situation in Nkala may be especially critical because
the forest is directly beside a village. Thus, community
development is key for conservation, and establishment ofa sustainable economic alternatives to hunting activities
is essential. Eco-tourism may be one of the most effective
and sustainable strategies, thanks in part to the site’s close
proximity to the country’s capital, Kinshasa (1-hour flightor 1-day boat trip). For this purpose, an international presence at this site must be established to attract tourists.
MMT has detected several other bonobo groups
around the Nkala forest besides the Manzano and Mpelu
groups, but intergroup relationships and migration patterns are not yet known. Green-corridor planting projects
like those at Bossou-Nimba, Guinea (Matsuzawa et al.
2011) might help ensure connectivity and migration between forest fragments despite savanna, crop and grazingfields, and roads separating them. As scientific researchers, we would like to continue our efforts to study the wildbonobos in this area, promote their scientific importance,and acknowledge and support the local community thathas made tremendous efforts to conserve the forest andthe bonobos. We hope this report can help raise awarenessof the conservation issues and the research possibilities inJuly 2018 and May 2019 (Table 2). Suspected poacherswith guns were also recorded by our camera traps.

DISCUSSION

Our preliminary survey and analyses on the Nkala
bonobos’ habitat use shows constant and strong preference for forest and Marantaceae forest over inundated
forest or savanna. Bonobos spent just 0–2.1% of time insavanna, despite the fact that 40% of their habitat by area
is savanna (Inogwabini et al. 2008), suggesting that bonobos constantly and strongly avoid use of savanna. This isunsurprising considering the savanna has greater visibility, lower food availability and increased human activity.
However, based on our observations, we can also predictthat bonobos forage for plants or insects in the savanna
which are not available or rare in the other habitat categoTable 2. Number of traps and cartridges foundin Nkala forest between July 2018 to May 2019year

month

trap

cartridge

2018

July

18August

67

September

37October

36

November

1

4

December

2

4

January0

7

February

33

March

24April

15

3May

2420194

Pan Africa News, 27(1): 2–5 (2020)
Nkala.

Democratic Republic of the Congo. Ecohealth 12: 621–633.
https://doi.org/10.1007/s10393-015-1058-8

Narat V, Pennec F, Bisson, LL et al. 2015b. Bonobo conservation as a means for local development: An innovative local
initiative of community-based conservation in Democratic
Republic of Congo. J Primatol 4: 100127.
Narat V, Pennec F, Simmen B et al. 2015c. Bonobo habituation in a forest–savanna mosaic habitat: Influence of apespecies, habitat type, and sociocultural context. Primates
56: 339–349.

ACKNOWLEDGMENTS

We thank Mbou-Mon-Tour for their support and permission to conduct our research at the field site. We also thank Prof.
Raymond Lumbuenamo of World Bank, ERAIFT and WWFDRC for their continuous collaboration in this project. Support
from the local community at Nkala is also greatly appreciated.
We are also grateful to Dr. Victor Narat for his valuable comments on our earlier version of this manuscript. This research
was financially supported by the Leading Graduate Programin Primatology and Wildlife Science of Kyoto University andJSPS grant-in-aid for scientific research (KAKENHI 15H05309
and 19H00629 to Shinya Yamamoto).

https://doi.org/10.1007/s10329-015-0476-0

Pennec F, Krief S, Hladik A et al. 2016. Floristic and structural vegetation typology of bonobo habitats in a forestsavanna mosaic (Bolobo territory, D.R.Congo). Plant Ecol
Evol 149: 199–215.
https://doi.org/10.5091/plecevo.2016.1157

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