Course:ARCL 140 Summer 2020/Term Project Group 22

From UBC Wiki

CHIMPANZEE'S SOCIAL BEHAVIOUR

CONTRIBUTORS & ROLES

Map of Sites

Kiranpreet Boyal: Site 1

Kriveena Chand: Site 2

Danica Torrens: Site 3

Navpreet Boyal: Site 4

All group members worked on the introduction, conclusion, and the map.

MAP

INTRODUCTION

Chimpanzees of Uganda’s Kibale National Park

Social behaviour is crucial to survival in any species, especially in chimpanzees and humans, as it allows a means for cooperation and stability within a group. Chimpanzees have been a very relevant primate in relation to studying social behaviour. They are a widely studied group within fields of archeology and biology, among others. They are the only species, other than humans, to express cultural variations and various behavioural patterns. This shows that they are relevant not only as an independent group but also to human behaviour [1]. They are our closest living relatives, and thus foreshadow what could be human social evolution in the form of behaviour, language and culture [2]. Having these cultural variations, it is interesting to observe them in their lives to find out how similar their actions and reasons are related to us and why they are different.  

It has been noted that variation in chimpanzees has more to do with culture than genetics, showing again their likeness to humans[3]. Many forces influence social behaviour, such as the ecology of primate species. The observation of social behaviour in chimpanzees can allow the human species to understand its origins better.[4] Moreover, by observing their social systems, one can obtain insight as to how chimpanzees operate in groups. They learn by observing one another in groups and through kinship, which is extremely similar to humans.[5] Furthermore, their diets also play a key role in influencing their behavior and the way they interact with each which is through mating and competition [6].

Tanzania, located in East Africa, has been home too many fossil remains of early hominids and has recently become an extremely popular research site for chimpanzee populations in the last 30 years or so. Crucial research has taken place on observing the social behaviour of this primate species, especially in terms of social learning.

The study done from Nimba Mountains showcases how social behaviour is a factor when looking at how chimpanzees choose to nest on the ground rather than the trees. Rather than focusing on the ecological and climatic variations, chimpanzees choose ground nesting based on their own preferences through the knowledge of their region and comfort.

At the Ngel Nyaki Forest Reserve in Nigeria, sex ratio plays an important role in the survival of their kind, the pan troglodytes ellioti, as they are a polygynous society and during maturity, males try to gain social ranking and subsequent reproductive opportunities. They are known to make noise to communicate, similar to humans.

In the Kibale National park which is located in Uganda, ecology plays a crucial role in the social behaviour of a chimpanzee. They live in polygynous communities and their diet influences the way they interact with each other. Female chimpanzees rely on their diets to make them more suitable for male attention as they compete for a mating opportunity, allowing it to be a dominant hierarchy. Moreover, they have much higher feeding times than resting due to the high rates of reproduction. This reproductive behaviour is also similar to humans.

SITE 1: The Mahale Mountains, Tanzania

AUTHOR

Kiranpreet Boyal

LOCATION

The Mahale Mountains are located in Mahale National Park, in western Tanzania, which is in East Africa. (6.2667° S, 29.9333° E)

AGE: 30 000- 20 000 BP

The Isolated Mahale Mountains in Tanzania

Context

The Mahale mountains are located in Tanzania. It is a part of Lake Tanganyika, which is the seventh largest lake in the world, and the second deepest, making it one the most beautiful sights on the planet.[7]  Moreover, it is about 200 km from the highlands of Burundi-Rwanda and approximately 300 km from the highlands of Tanzania, making it extremely remote, thus the chimpanzee population continues to thrive.[8] The mountain is difficult to access because it is unreachable by car. Additionally, the region is home to diverse wildlife, especially a group of chimpanzees, making this a well researched site. Furthermore, the western part of the mountain has seen the growth of unique wildlife that was not present in the past. A large alluvial fan pours out into the lake, creating a rugged terrain.[9] Moreover, Tanzania as a whole, has been home to many different fossil findings of early hominids. Fossils of skulls have been discovered in the Middle Pleistocene age at Lake Eyasi, as well as remains of occipital lobe.[10]

History

The research on Chimpanzees in the Mahale mountains has been ongoing for about fifty years. Mahale officially became a wildlife preserve in 1974. As a result, the forest began to come back to life, and wildlife appeared again. In 1985, the Mahale mountains became a national park after 20 years of research on the chimpanzee population.[11] Moreover, there is a team of Japanese researchers from the University of Tokyo, forming the Mahale Mountains Chimpanzee Research Project (MMCRP). This is only one of the research projects that have been taking place at this site.[12] Additionally, there have also been studies on hunter-gatherer communities and farmers in Tanzania. Furthermore, the Mahale Wildlife Conservation Society, established in 1994, hosts activities that safeguards the wildlife community in Mahale.[13]

Relevance

The Mahale Mountains have become an extremely well known research site due to the chimpanzee population. The research conducted on this site provides insight on their social behaviour. Chimpanzees thrive in groups, as they hunt, feed, and spend most of their lives in groups. Moreover this also allows them to engage in social grooming and social learning.

Chimpanzees in the Mahale Mountains

Social grooming is done in cliques in the larger group, where many chimpanzees have friendships, families, or sexual and political relationships.[14] A type of social grooming that is common is social scratching, however the way it is done varies by geographical location. For instance, the Mahale chimpanzees scratch by bending all of their fingers and stroking the other, whereas the primates in Nogo use a poking motion. Moreover, this also exemplifies social learning, as chimpanzees watch each other and learn the common behaviours of the group.  [15]

Additionally, survival and reproduction rates of chimpanzees also rely heavily on the geographical location. In Mahale, the ratio of males to females has changed from 1:3 to 1:2 in the past 30 years.[16] This is the result of a higher survival rate of females and the unequal migration between males and females of a group, thus there is a higher competition for mates. Furthermore, chimpanzee rearing strategies are similar to those of humans, as their newborns are young and helpless as well, therefore requiring more care. Moreover, maternal figures spend the most time with young chimpanzees, which is extremely similar to humans.

The chimpanzees of the Mahale mountains tell only part of the story of human evolution. The research done at the Mahale Mountains exemplifies the similarities between humans to non-humans.

SITE 2:

AUTHOR: Kriveena Chand

LOCATION: Nimba Mountains near the village of Seringbara in southeastern Guinea, West Africa (7° 37'50.0''N, 8° 27'44.7''W)

AGE: Nimba Mountains in Guinea established in 1944

Context

Shows the upper part above the primary forest

The Nimba Mountains are located on the borders of Guinea, Liberia and Côte d’Ivoire. From information of studies around the region,  the Nimba Mountains show topographical diversity as there are rocky peaks and high altitude meadows [17]. Moreover, the region has deep valleys and rounded hilltops and these hills are covered mostly by the tropical forest dispersed with forested valleys. The climate of the Nimba Mountain ranges of having a rainy season around February and March which stops around November and December [18]. In the forests, there are fruits of the Parinari and this is eaten by the chimpanzees [19]. When looking up in the forests, there are nests made by chimpanzees which are about 10 m above the forest floor [20]. The water in the Nimba Mountains supports the vegetation around at the lower altitudes, however not at the higher ones which makes the trees grow lower. The difference between the past and present of the site has to do with mining activities that are appearing in the area now. There are mining activities in the north western part around the Nimba Massif but the Seringbara side located in Guinea is seen to be steady [21]  The region is threatened with iron mining and this affects the survival of chimpanzees and their connection with the landscape [22]. There is a prevalent shift when it comes to the change in socio cultural shifts which can be drawn from societies changing ideologies of chimpanzees and their life in this region.

History

Maxime Lamotte’s research on the fauna and flora of the Nimba Mountains for two decades and exploration of the wildlife diversity, contributed deeply in the knowledge of the biodiversity and ecosystems that exists in the region [23]. From the acknowledgement of the great biodiversity and ecology, the Nimba Mountains were established as a Nature Reserve in 1943 as the  ‘‘Re´serve Naturelle Inte´grale du Mont Nimba’’ in Côte d’Ivoire [24]. It was established as a Nature Reserve in Guinea in 1944 [25]. Both reserves form a World Heritage Site which was published for Guinea in 1981 and for Côte d’Ivoire  in 1982 [26]. Research dating back to 1976 can be seen by Yukimaru Sugiyama who is an ecologist who interviewed the people at villages of Seringbara , and conducted surveys of the forests surrounding the area to decide if there were an appearance of chimpanzees there [27]. Sugiyama concluded that chimpanzees in the area were only there seasonally [28]. Although, in 1999, there were over 70 nests and feeding leftovers of chimpanzees which were found in the forest behind the village [29]. Moreover, the sounds of chimpanzees were heard in the area. So the research came to conclude that instead of a seasonal group, there was actually a resident group of chimpanzees near the village of Seringbara.

Relevance

Sleeping on the ground

Nest building is seen as a common activity of the chimpanzees in where they make new nests to sleep in every night and day nests to sleep [30]. In the Nimba Mountains, a study has found that the chimpanzees had no seasonal variation when it came to ground nesting as high speed winds did not influence their choice of where their nests are during the dry season [31]. Moreover, the appearance of ground nests in areas where there is a shortage of steep slopes did not make a difference. However, it can be seen that chimpanzees made a keen choice of making the nests on the ground in areas where there were ample trees available as it is good for their needs in terms of size. This shows how the influence of environmental factors is not a factor for ground nesting which indicates social and cultural factors as a main influence.

Males for example nest on the ground so they can guard a fertile female that is above them in the trees. This shows male chimpanzees' social behaviour behaviour to compete to be at the top of the dominance hierarchy in order to get priority in the access to these females. Having simple day nests are suitable for their day time activities of relaxation, while the night nests might be designed differently for male social strategies[32]. The social behaviour of making ground nests can connect to the lack of predation in their area as well which shows how much knowledge they have in their region. In terms of their evolution, sexual dimorphism is an explanation for why the male's nest on the ground rather than tree nesting.

SITE 3: Ngel Nyaki Forest Reserve, Nigeria

AUTHOR: Danica Eirin Torrens

LOCATION: Ngel Nyaki Forest Reserve in South East Nigeria (7.0876° N, 11.0534° E)

AGE: Established in 1969

Context

The Ngel Nyaki Forest Reserve is located on the Mambilla Plateau, a region in South East Nigeria bordering Cameroon. The altitude there ranges from 1400m up to 1600m and covers 46km2 [33]. Out of that, about 7.5km2 is forested[34]. The rest is made up of scrubland. The climate is distinctly wet from April until late October, there is a dry season with the rainfall averaging 1,800 mm[33]. Importantly, the chimpanzees at that location are almost completely isolated from others[33] so the chances of there being more than community within that forest is unlikely. The specific type of Nigerian-Cameroon chimpanzee which is found here is called a pan troglodytes ellioti[33] (Dutton et. al). In the past 30 years, all predators have become locally extinct leaving humans as the remaining predators to chimpanzees there[35].

History

Not much long-term observational work has been done on the Nigerian-Cameroon chimpanzee until recently. However, an important general trend in chimpanzee behaviour has already been noted to be “cultural rather than genetic”[3].

At Ngel Nyaki, the population of chimpanzees was estimated at only 12.5 - making them very endangered[3]. This is concerning as genetic diversity is the key to evolutionary adaptation and with a small population size, there is the threat of the loss of genetic variation as well as inbreeding rates increasing[3]. Chimpanzees live in co-ed communities, and these range in size[3]. It was found that within pan troglodytes ellioti in Ngel Nyaki, the reproductive system was polygynous[3]. This is a mating system in which one male will mate with multiple females during his lifetime, meanwhile each female mates with only one male[36]  It was found that about 19% of females bred in any particular year and that environment did not change this[3]. It was observed that during maturity, the male chimpanzees would try to gain social ranking and reproductive opportunities, while the females concentrated on their offspring[3].

Sex ratio plays an important role in the survival of chimpanzees in Ngel Nyaki. The sex ratio there was 11:89 (males:females) which aligns with their polygynous society[3]. The ideal number of males is five when the population is 21 or 31 because when the number of males goes above this, it reduces the chances of persistence of the species[3]. This is because of female controlled growth rate. The polygynous mating system allows males to create offspring with more than one female, and the negative effects of having fewer males is outweighed by the overall increase in population growth[3].

An interesting trait known to the Nigeria-Cameroon chimpanzee is their use of noises to communicate. They have been known to use trees to create sounds using their hands and feet, which was believed to serve the purpose of communicating within their community[3]. This shows interconnectedness between the society as they communicate to each other, showing that they rely on one another.

Although a small category of chimpanzees, they seem to be very evolved. In addition to the aforementioned, there is also evidence to suggest that they self-medicate. There were leaves found in feces which were concluded to be attempts at removing parasites through the induction of vomiting[3].

Relevance

As noted in a report done by USAID, “primates such as gorillas and chimpanzees are close relatives to humans, and we can learn much about ourselves through study of those few gorillas and chimpanzees that remain”[37]. Studying the primate social behaviour of primates in various locations, we can not only understand them but better understand humans too. Things like the communication methods used by chimpanzees here lead us to better understand how humans communicate now.

SITE 4: The Kibale National Park

AUTHOR: Navpreet Boyal

LOCATION: Kibale National Park is located in western Uganda.( 0.4862° N, 30.3897° E).

AGE: The park was discovered in 1932[38]

Context

Kibale national Park is located in western Uganda. This evergreen rainforest is nested at 1100- 1600 meters in elevation and is home to 13 primate species, including chimpanzees.  Kibale national park covers approximately 774sq km of area and is dominated by semi-deciduous tree species and harbours four communities of chimpanzees [39] . Furthermore, this national park is significant in the tourism industry due to its chimpanzee populations. The Kanyawara community hold about sixty chimpanzees, Ngongo with 200 chimpanzees in the central part of the park, Kanyachu which is found in the southern side and Sebitole which is the northern side of the park [40]. Moreover, Kibale is one of the last remaining lowland and montane forests left in Africa, which is home to a range of wildlife species. The evergreen enriched terrain creates a suitable environment for species such as chimpanzees and other primates to thrive on a folivorous diet. Additionally, there are many activities for tourists to enjoy such as hiking and nature walks such as chimpanzee trekking, which allows people to have an up close experience with the primate.

History

Kibale national park was established in 1932 however, it was gazetted as a logged forest area by the British [41]. The purpose of this forest was to provide companies with hardwood and exploit its rich evergreen terrain. Furthermore, the British planted the forest with exotic trees, replacing the ones they cleared for hardwood. By the 1950’s hardwood timber demand hiked due to the opening of the Kilembe copper mines so the forest was clearing up rapidly [42]. Moreover, in 1993, the Kibale forest was established as a forest reserve and Uganda took control of the conservation of this forest and banned the deforestation for timber[43]. In 1996, the government merged several national parks across the country into the Uganda WildLife authority, who are now working to restore the forest.

Relevance

The Kibale national park has been an ongoing research and conservation site for chimpanzee communities for almost 30 years. Recent studies have explored their social behaviour through their dietary restrictions, feeding, and reproductive behaviour as well as analyzing their ability for social learning.

    These studies show that chimpanzees in the Kibale national park tend to be more folivorous and frugivores. due to vegetation availability. Furthermore, the female chimpanzees suffer from more sexual swelling in this national park due to their diet since they also consume drupe fruits [44]. This ecological factor has influenced the reproductive rates within chimpanzees in Uganda, since their energy concentrations are also impacted [45]. Moreover, the availability of fruit is a key variable in limiting reproductive performance in chimpanzees. Moreover, this also impacts the male chimpanzee population since not many females would be ready to mate due to the lack of fruit.

    The Kibale chimpanzees display a social behaviour that is controlled by their diets. Female chimpanzees in the Kibale national park can only attract a potential mate if they promote swelling creating male competition[46]. In addition, these chimpanzees live in polygynous communities, therefore, they travel in groups for food for their offspring. Similarly, female chimpanzees have a lower resting time since they must travel to find the specific fruits in order to mate. Moreover, an ecological factor plays a crucial role in the social behaviour of these chimpanzees and are similar to a humans reproductive system since they both need proximate levels of energy.

CONCLUSION

Chimpanzee social behaviours are extremely significant in learning human evolutionary processes, as the species is our only closest living relative. Drawing back to the reproductive and social strategies observed in the sites of the Mahale Mountains and Ngel Nyaki Forest Reserve, chimpanzees rely on complex social systems in their daily lives. The ongoing research being conducted at both these sites exemplifies the importance of social learning. Social grooming is an ideal example of cultural habits, as young chimps observe adults, especially maternal figures, in their groups and tend to emulate those behaviours, one of which is social scratching. Similarly, in the Kibale national park, diet plays a crucial role in reproduction strategies as well as male competition. This type of behaviour is influenced by ecological availability and can also be an ideal example of social learning. Furthermore, competition of mates is one aspect that is common all throughout these sites.There are fewer males than females in chimpanzee groups, thus increasing the competition between male chimpanzees,

The study of the human evolutionary process heavily relies on the observation of the chimpanzee primate species. They are the only other species that expresses cultural behaviours and patterns. Many human practices, such as child rearing and sexual strategies are similar to chimpanzees. In terms of factors influencing nesting, there is a greater value on social factors than seasonal variations when it comes to ground nesting in the Nimba Mountains. The social behaviour in choosing comfort and having this knowledge of no dangerous predators influences the choice of ground nesting and gives males chimpanzees an opportunity to reach the top of the dominance hierarchy.

Drawing on all this information, it can be concluded that chimpanzees are unique compared to other mammals and primates as they have complex social behaviours as seen through nesting, grooming, dietary restrictions and reproduction strategies. There are commonalities and differences between chimpanzees in different locations or sites, showing their diversity. Chimpanzees and humans are both a complex species, and show many similarities, thus making this primate species a widely researched arena.

REFERENCES

  1. ↑ Jaffe, Karin Enstam. “Primate Ecology and Behavior.” EXPLORATIONS: AN OPEN INVITATION TO BIOLOGICAL ANTHROPOLOGY, American Anthropological Association, Arlington, VA, 2019, pp. 31–32.
  2. ↑ Jaffe, Karin Enstam. “Primate Ecology and Behavior.” EXPLORATIONS: AN OPEN INVITATION TO BIOLOGICAL ANTHROPOLOGY, American Anthropological Association, Arlington, VA, 2019, pp. 31–32.
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 Knight, Alexander. “The Genetic Structure and Dispersal Patterns of the Nigeria-Cameroon Chimpanzee (Pan Troglodytes Ellioti).” University of Canterbury , University of Canterbury Biological Sciences , 2013.
  4. ↑ Stier, Karen. “Primate Social Behaviour.” American Journal of Physical Anthropology 165, no. 4 (March 25, 2018). https://doi.org/https://doi-org.ezproxy.library.ubc.ca/10.1002/ajpa.23369.
  5. ↑ Fiore, Anthony Di. “Molecular Genetic Approaches to the Study of Primate Behavior, Social Organization, and Reproduction.” American Journal of Physical Anthropology 122, no. S37 (2003): 62–99. https://doi.org/10.1002/ajpa.10382.
  6. ↑ Kevin B. Potts, David P. Watts, and Richard W. Wrangham, “Comparative Feeding Ecology of Two Communities of Chimpanzees (Pan Troglodytes) in Kibale National Park, Uganda,” International Journal of Primatology 32, no. 3 (February 2011): pp. 669-690, https://doi.org/10.1007/s10764-011-9494-y.
  7. ↑ Nakamura, Michio et al. (arg.). 2015. Mahale Chimpanzees: 50 Years of Research. Cambridge: Cambridge University Press. doi:10.1017/CBO9781107280533.
  8. ↑ Nakamura, Michio et al. (arg.). 2015. Mahale Chimpanzees: 50 Years of Research. Cambridge: Cambridge University Press. doi:10.1017/CBO9781107280533.
  9. ↑ Nakamura, Michio et al. (arg.). 2015. Mahale Chimpanzees: 50 Years of Research. Cambridge: Cambridge University Press. doi:10.1017/CBO9781107280533.
  10. ↑ Domínguez-Rodrigo, M., A. Mabulla, L. Luque, J.w. Thompson, J. Rink, P. Bushozi, F. Díez-Martin, and L. Alcala. “A New Archaic Homo Sapiens Fossil from Lake Eyasi, Tanzania.” Journal of Human Evolution 54, no. 6 (2008): 899–903. https://doi.org/10.1016/j.jhevol.2008.02.002.
  11. ↑ Nakamura, Michio et al. (arg.). 2015. Mahale Chimpanzees: 50 Years of Research. Cambridge: Cambridge University Press. doi:10.1017/CBO9781107280533.
  12. ↑ Nakamura, Michio et al. (arg.). 2015. Mahale Chimpanzees: 50 Years of Research. Cambridge: Cambridge University Press. doi:10.1017/CBO9781107280533.
  13. ↑ Nakamura, Michio et al. (arg.). 2015. Mahale Chimpanzees: 50 Years of Research. Cambridge: Cambridge University Press. doi:10.1017/CBO9781107280533.
  14. ↑ Nishida, Toshisada. 2011. Chimpanzees of the Lakeshore: Natural History and Culture at Mahale. Cambridge: Cambridge University Press. doi:10.1017/CBO9781139059497.
  15. ↑ Nishida, Toshisada. 2011. Chimpanzees of the Lakeshore: Natural History and Culture at Mahale. Cambridge: Cambridge University Press. doi:10.1017/CBO9781139059497.
  16. ↑ Nakamura, Michio et al. (arg.). 2015. Mahale Chimpanzees: 50 Years of Research. Cambridge: Cambridge University Press. doi:10.1017/CBO9781107280533.
  17. ↑ Koops, Kathelijne, Richard W. Wrangham, Neil Cumberlidge, Maegan A. Fitzgerald, Kelly L. van Leeuwen, Jessica M. Rothman, and Tetsuro Matsuzawa. 2019. "Crab-Fishing by Chimpanzees in the Nimba Mountains, Guinea." Journal of Human Evolution 133: 230-241.
  18. ↑ Koops, Kathelijne, Richard W. Wrangham, Neil Cumberlidge, Maegan A. Fitzgerald, Kelly L. van Leeuwen, Jessica M. Rothman, and Tetsuro Matsuzawa. 2019. "Crab-Fishing by Chimpanzees in the Nimba Mountains, Guinea." Journal of Human Evolution 133: 230-241.
  19. ↑ Matsuzawa, Tetsuro and Tetsuro Matsuzawa. 2017. "The Nimba Mountains in Guinea." Primates 58 (1): 1-3
  20. ↑ Matsuzawa, Tetsuro and Tetsuro Matsuzawa. 2017. "The Nimba Mountains in Guinea." Primates 58 (1): 1-3
  21. ↑ Matsuzawa, Tetsuro and Tetsuro Matsuzawa. 2017. "The Nimba Mountains in Guinea." Primates 58 (1): 1-3
  22. ↑ Humle, Tatyana. 2016. "Franco-Japanese and Other Collaborative Contributions to Understanding Chimpanzee Culture at Bossou and the Nimba Mountains." Primates 57 (3): 339-348.
  23. ↑ Humle, Tatyana. 2016. "Franco-Japanese and Other Collaborative Contributions to Understanding Chimpanzee Culture at Bossou and the Nimba Mountains." Primates 57 (3): 339-348.
  24. ↑ Humle, Tatyana. 2016. "Franco-Japanese and Other Collaborative Contributions to Understanding Chimpanzee Culture at Bossou and the Nimba Mountains." Primates 57 (3): 339-348.
  25. ↑ Humle, Tatyana. 2016. "Franco-Japanese and Other Collaborative Contributions to Understanding Chimpanzee Culture at Bossou and the Nimba Mountains." Primates 57 (3): 339-348.
  26. ↑ Humle, Tatyana. 2016. "Franco-Japanese and Other Collaborative Contributions to Understanding Chimpanzee Culture at Bossou and the Nimba Mountains." Primates 57 (3): 339-348.
  27. ↑ Humle, Tatyana. 2016. "Franco-Japanese and Other Collaborative Contributions to Understanding Chimpanzee Culture at Bossou and the Nimba Mountains." Primates 57 (3): 339-348.
  28. ↑ Humle, Tatyana. 2016. "Franco-Japanese and Other Collaborative Contributions to Understanding Chimpanzee Culture at Bossou and the Nimba Mountains." Primates 57 (3): 339-348.
  29. ↑ Humle, Tatyana. 2016. "Franco-Japanese and Other Collaborative Contributions to Understanding Chimpanzee Culture at Bossou and the Nimba Mountains." Primates 57 (3): 339-348.
  30. ↑ Koops, Kathelijne, Tatyana Humle, Elisabeth H. M. Sterck, and Tetsuro Matsuzawa. 2007. "Ground‐nesting by the Chimpanzees of the Nimba Mountains, Guinea: Environmentally Or Socially Determined?" American Journal of Primatology 69 (4): 407-419.
  31. ↑ Koops, Kathelijne, Tatyana Humle, Elisabeth H. M. Sterck, and Tetsuro Matsuzawa. 2007. "Ground‐nesting by the Chimpanzees of the Nimba Mountains, Guinea: Environmentally Or Socially Determined?" American Journal of Primatology 69 (4): 407-419.
  32. ↑ Koops, Kathelijne, Tatyana Humle, Elisabeth H. M. Sterck, and Tetsuro Matsuzawa. 2007. "Ground‐nesting by the Chimpanzees of the Nimba Mountains, Guinea: Environmentally Or Socially Determined?" American Journal of Primatology 69 (4): 407-419.
  33. ↑ 33.0 33.1 33.2 33.3 Dutton, Paul, Paul Dutton, Hazel Chapman, and Hazel Chapman. 2015. "New Tools Suggest Local Variation in Tool use by a Montane Community of the Rare Nigeria–Cameroon Chimpanzee, Pan Troglodytes Ellioti, in Nigeria." Primates 56 (1): 89-100.
  34. ↑ Dutton, Paul and Hazel Chapman. 2015. "Dietary Preferences of a Submontane Population of the Rare Nigerian‐Cameroon Chimpanzee (Pan Troglodytes Ellioti) in Ngel Nyaki Forest Reserve, Nigeria." American Journal of Primatology 77 (1): 86-97.
  35. ↑ Dutton, Paul, Elena Moltchanova, and Hazel Chapman. 2016. "Nesting Ecology of a Small Montane Population of the Nigerian/Cameroon Chimpanzee (Pan Troglodytes Ellioti) in Nigeria." Folia Primatologica; International Journal of Primatology 87 (6): 361.
  36. ↑ Polygyny, 1988, web.stanford.edu/group/stanfordbirds/text/essays/Polygyny.html.
  37. ↑ Chemonics International Inc. USAID, 2008, NIGERIO BIODIVERSITY AND TROPICAL FORESTRY ASSESSMENT , pdf.usaid.gov/pdf_docs/PNADN536.pdf.
  38. ↑ Catrina A. Mackenzie, “Changing Perceptions of Protected Area Benefits and Problems around Kibale National Park, Uganda,” Journal of Environmental Management 200 (2017): pp. 217-228, https://doi.org/10.1016/j.jenvman.2017.05.078.
  39. ↑ Catrina A. Mackenzie, “Changing Perceptions of Protected Area Benefits and Problems around Kibale National Park, Uganda,” Journal of Environmental Management 200 (2017): pp. 217-228, https://doi.org/10.1016/j.jenvman.2017.05.078.
  40. ↑ Catrina A. Mackenzie, “Changing Perceptions of Protected Area Benefits and Problems around Kibale National Park, Uganda,” Journal of Environmental Management 200 (2017): pp. 217-228, https://doi.org/10.1016/j.jenvman.2017.05.078.
  41. ↑ Catrina A. Mackenzie, “Changing Perceptions of Protected Area Benefits and Problems around Kibale National Park, Uganda,” Journal of Environmental Management 200 (2017): pp. 217-228, https://doi.org/10.1016/j.jenvman.2017.05.078.
  42. ↑ Catrina A. Mackenzie, “Changing Perceptions of Protected Area Benefits and Problems around Kibale National Park, Uganda,” Journal of Environmental Management 200 (2017): pp. 217-228, https://doi.org/10.1016/j.jenvman.2017.05.078.
  43. ↑ Catrina A. Mackenzie, “Changing Perceptions of Protected Area Benefits and Problems around Kibale National Park, Uganda,” Journal of Environmental Management 200 (2017): pp. 217-228, https://doi.org/10.1016/j.jenvman.2017.05.078.
  44. ↑ Richard W. Wrangham, “Diet and Reproductive Function in Wild Female Chimpanzees (Pan Troglodytes Schweinfurthii) at Kibale National Park, Uganda,” American Journal of Physical Anthropology 135, no. 2 (2008): pp. 171-181, https://doi.org/10.1002/ajpa.20718.
  45. ↑ Richard W. Wrangham, “Diet and Reproductive Function in Wild Female Chimpanzees (Pan Troglodytes Schweinfurthii) at Kibale National Park, Uganda,” American Journal of Physical Anthropology 135, no. 2 (2008): pp. 171-181, https://doi.org/10.1002/ajpa.20718.
  46. ↑ Hogan M. Sherrow, “Adolescent Male Chimpanzees at Ngogo, Kibale National Park, Uganda, Have Decided Dominance Relationships,” Folia Primatologica 83, no. 2 (2012): pp. 67-75, https://doi.org/10.1159/000341168.
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