3.1. Characteristics of the Gorilla Nesting Environment
Cross River gorillas occupy a habitat that is somewhat intermediate between the high altitude, predominantly folivorous mountain gorillas and the frugivorous western lowland gorillas. Although they are phylogenetically and geographically most closely related to the western lowland gorilla, most Cross River gorilla groups range in ridge forests or at higher elevations (above 500 m a.s.l.) [
31,
35,
41]. The Mone-Oku gorillas were found to nest over an area of 4.5 km
2 south of Nga village, both within the Mone Forest Reserve and just outside of its borders (
n = 30 nest sites; 151 nests) (
Figure 2). At times, nest sites were found within 140 m from the farm–forest boundary and as close as one kilometre to the village. As a result of this proximity, there is a frequent human presence within the gorillas nesting range in the form of forest clearance, collection of nontimber forest products, and hunting. The ER reflects these levels of human activity. Within the gorilla nesting range, the ER of 1.99 signs/km was higher than that recorded across the entire study site (1.70 signs/km).
However, the gorillas appear to be reducing the chance of direct encounters with humans by concealing their night nests within the surrounding environment. An initial multinomial logistic regression of nesting habitat characteristics found vegetation class was not a significant predictor for the location of a gorilla nest site,
Z = 0.638,
p = 0.523, so it was removed, and the analysis was rerun. The second analysis found that elevation and degree of the slope were statistically significant predictors of gorilla nest sites, though canopy cover was not (
Table 4). It is necessary to highlight that the model only accounted for a small amount of the variance (30%), likely a reflection of the small sample size. However, these results suggest the gorillas tend to select nesting locations at lowland elevations (300–450 m a.s.l.) with steep slopes. The Mone-Oku gorillas’ preference to locate nest sites on steep slopes supports the hypothesis that this is a universal behaviour among Cross River gorillas, whereby the relative inaccessibility of the slopes offers the gorillas protection from many human activities, thereby creating safe sleeping sites [
37,
38,
39,
42,
54].
The lowland elevations in the gorillas’ nesting range are largely comprised of old secondary and lowland forest. This area has a rich diversity of tree species dominated by the Leguminosae family (
Figure 3), but a low stand basal area (BA) corresponding to lower levels of canopy cover and an increased density of the forest understory (
Table 5). The understory density was high, but variable, with the most abundant plants being herbs from the Rubiaceae, Marantaceae, and Araceae families. Although the degree of canopy cover was not found to be a significant predictor of nest sites within this sample, the high frequency of nest sites located in areas of very open forest canopy has also been observed in many populations of western gorillas [
42,
59,
69,
70]. Often, these areas of open canopy allow for the growth of preferred gorilla nesting materials [
59,
62,
71]. Significant preferences for some plant species were observed in the construction of both ground (
n = 82) (
Table 6 and
Table 7) and arboreal nests (
n = 58) (
Table 8) by the Mone-Oku gorillas. Structurally, these plants aid in the construction of a comfortable nest such as the densely packed large leaves of the herb
Aframomum spp. or the combination of large leaves and drooping branches in
Pycnanthus angolensis [
5].
The location of nest sites may also be influenced by diet and the potential need to compete successfully with other frugivorous animals. Western lowland gorillas are known to nest close to favoured food sources rather than travel to an ideal nesting site [
56,
59,
71]. In this study, the Mone-Oku gorillas frequently incorporated plants that are known to be a part of their diet into their nests and/or nested in areas that were surrounded by plants known to be consumed (c.f., Mawambi, Cameroon) [
39,
72]. Drawing from an earlier study of the Mone-Oku gorillas’ diet, the gorillas relied heavily on
Palisota spp.,
Aframomum spp., and
Cercestis camerunensis that decrease in abundance as slope and elevation increase, and species within the Marantaceae family were important fall-back foods [
36]. When floristic comparisons were made across the Mone-Oku Forest, the gorilla nesting range has the highest abundance of Marantaceae species, and important food species such as
P. angolensis and
Guarea thompsonii are dominant tree species [
31,
36]. Further, fruiting trees such as
Parkia bicolor are deemed an important food species at other Cross River gorilla sites [
31,
39] and are known to comprise part of the Mone-Oku gorillas’ diet were only recording within the gorilla nesting range. If the Mone-Oku gorillas prefer to nest close to favoured food sources, then the distribution of these plant taxa appear to be influencing the gorillas’ nesting range away from areas of a general conservation focus.
The nesting range of the Mone-Oku gorillas is reflective of their historical widespread distribution in lowland forests [
73]. However, it is unusual compared to what has been observed at other Cross River gorilla sites. Typically, the Cross River gorilla is said to be found in small suboptimal refuge areas, despite the availability of suitable but unoccupied habitat throughout their range [
31,
38,
41,
74]. Alternatively, as Sawyer and Brashares suggest, previous macroscale analyses have failed to incorporate the compromises between resource abundance and potential risks [
43]. The Mone-Oku gorillas appear to be currently benefiting from past anthropogenic habitat alteration that has resulted in large areas of regenerating secondary forest that is also absent of chimpanzee activity. Although the gorillas are wary of humans, the abundance of preferred nesting and food species appears to outweigh the risks posed by higher levels of human activity within their nesting range.
3.2. How Humans Have Contributed to Shaping the Current Gorilla Nesting Range
The forest landscapes we observe today have been shaped by the history of ecological, economic, and political processes [
75,
76,
77,
78]. There is now recognition that most landscapes have been altered by repeated episodes of human activity over multiple millennia and those previous ideals of “pristine” landscapes may have never existed in many instances [
75,
79,
80,
81]. Specific to West African rainforests, Connah acknowledged:
… the conviction remained that much of the rainforest consisted of dense natural vegetation that was unaffected by human settlement and which had few resources to offer. Nothing could be further from the truth and it is now realized that most of the forest has been subject to shifting agricultural exploitation at one time or another, and in some areas many times over [
1] (pp. 112–113).
The archaeological record for the Cross River region is patchy. There is evidence to suggest that modern humans and nonhuman primates have coexisted in the region for at least 40,000 to 50,000 years with hunter-gatherers exploiting the rainforest and its margins around 12,000 years ago [
1]. Remains from Cross River gorillas, Nigeria–Cameroon chimpanzees and drills have been dated to around 5000 BP from the Shum Laka rock shelter near Bamenda [
82]. Here, primates comprised 14% of the total faunal assemblage illustrating that people were hunting in heavily wooded areas through to the late Holocene [
82,
83]. The Western Bantu expansion, believed to have begun with the contraction of the rainforests around the Nigeria–Cameroon borderland, has received more attention across Central Africa [
84,
85]. Coinciding with the expansion is evidence for more sedentary ways of life with slash-and-burn agriculture for the cultivation of yams and oil palms and iron smelting [
1,
84,
85]. However, interpretations of anthropogenic versus ecological dynamics are confounded by the lack of ecological records focusing on the scope and scale of impacts associated with prehistoric agricultural practices [
81].
The oral histories of Nga village did not extend back far enough to provide detail of how people lived in the forest in the distant past. People recount their ancestors living in the forest and moving from place to place during times of warfare, with people coming together to establish the village more recently. Röschenthaler [
86] found that in the precolonial era the Cross River people were highly mobile, moving to new areas due to fighting (including slave-trading), water shortages, depleted soils, or to increase their economic prospects closer to trade routes that were “diffuse and multidirectional” [
87] (p. 64) [
88]. Similar movements involving forest clearance for slash-and-burn agriculture and the subsequent abandonment of farms as people migrate was found to have had a positive influence on forest ecosystems across Central Africa. This is due to the fact that these practices create gaps in the forest canopy suitable for the germination of light-demanding trees such as
Lophira alata (Redwood), which are widely sought after in the current timber industry [
89,
90,
91]. From the 1850s onwards, coinciding with colonial regimes and the widespread forced movement of people out of forests and closer to rivers and roads, there is a noticeable reduction in the regeneration of these tree species believed to be a result of reduced human disturbance in the forest [
89,
90,
91]. These light-demanding timber species were also identified within the Mone-Oku Forest with several species used by the gorillas [
5].
Diospyros spp. (ebony) is perhaps the most significant genera of these trees as it is both a food and nesting source for the gorillas. While
Milicia excelsa (African teak or Iroko) and
Pterocarpus soyauxii (African padauck) offer a wide range of food resources, the Cross River gorilla is known to feed on its fruits, flowers, seeds, leaves, and bark [
31,
36,
39]. These results suggest that a degree of disturbance greater than what occurs naturally is required to maintain certain habitats and tree species within the rainforest. They also demonstrate that a degree of human disturbance within the forest can have positive benefits for the Cross River gorilla, promoting the growth of some tree species used for nesting and feeding.
Cameroon’s Cross River region has a colonial history of everchanging boundaries resulting in “developmental” neglect and isolation, which has played an important role in shaping people’s reliance on the Mone-Oku Forest [
5]. It is from this history and the “reopening” of the Akwaya region, both physically and metaphorically, that we see a clear example of the social nature of the forest landscape [
78], and its impact on the nesting range of the Mone-Oku gorillas. Before the 1980s, the people of Nga lived at one site, approximately one kilometre southeast of Nga’s current location. The village is believed to have been established between 100 and 300 years ago but is likely to have emerged as a result of the German administration’s forced amalgamation policies following the 1904 Mpawmanku War [
87]. By 1924, British ethnographic surveys reveal Nga as a small village (ca. 77 adults and children) involved in farming and collecting oil palm kernels (
Elaeis guineensis) to supply the African and Eastern Trade Corporation based in Mamfe [
92]. Sharwood-Smith and Cantle reported on farming within the region:
As everywhere the bulk of agricultural work is done by the women. The men clear new bush and set their Plantains after which they do little else. The area is cultivated by one woman, including her husband’s plantain patch, is approximately one acre, of which two fifths is plantains, two fifths is cocoyams, and one fifth luxury crops (corn, beans, pepper, groundnuts, pumpkins and gourds or tobacco) [
92] (p. 40).
The elder men of Nga support these views of past farming practices. They said the first farms were small, no larger than one hectare, and close to the village. This was due to the fact that people were only planting what they needed for food and a small income, such as plantains, cocoyams, kola nuts, and oil palm, which self-germinated.
Although mostly described as farmers, the Nga people also hunted for subsistence throughout the Mone-Oku Forest, using a combination of trapping pits, snares, and den guns where available. Information about the historical hunting of the gorillas mostly came from the elder men within Nga. They explained that in the past, people did not fear the repercussions of hunting the apes, but this was also tempered by the role gorillas played as totems within their traditional practices [
5]. Hunters killed the gorillas to feed their families, for medicine, and to gain prestige. One elder animatedly said he was a great hunter in his time, but hunting was mostly for food as there was no market to sell the meat. He recalled:
Ku [gorilla] sleep for ground, broken sticks put them for ground. As you get close, they call and you stay quiet. I kill gorilla when eating chop [food], then carried them to use for country juju [medicine]. When die, put Ku for seat and tie up place where shot … After tied to chair, carry Ku to that back place where women would dance and dance before butchering.
The celebrations that occurred after the death of a gorilla were due to the gorillas’ designation as “village beef”; therefore, they are for all to share and could not be sold even if a market were available. Accounts indicate that before the 1920s hunting of the gorillas at Nga was limited with one killed approximately every four to five years [
5].
As Nga’s population grew (est. 321 people in 1967) [
93], it became increasingly difficult to locate suitable sites to construct new homes as the old village site was stony. Ojong Solomon remembered, “… The stones were plenty and some people died falling from the stones, so they decided to move further down to Tito”. The site of Tito appealed for several reasons; the first was that it allowed people to be closer to the proposed road and thereby closer to “development”. One Mammi from Nga recalls they moved “because they were too far in the bush, wanted to move closer to the road. I decided to stay as I have all bush, all things for here”. The second reason for the move was political, to ensure the people of neighbouring villages, Akwa and Bantaco, would no longer encroach on their forest to hunt or clear farmland. Establishing the Tito site appeared fraught with difficulty as one elder described:
… we came to here to clear black bush [primary forest], burn all the bush. For night elephant comes for church house, tigers [leopards] came, carry goats to bush, I was the greatest hunter, I go shoot dem tigers through the door with dem powder guns. Corn was fine for here, as was mushroom from trees that had been felled. That time no palm, so we went bush to cut those tall ones, aye, we suffered those times… Some go back, as said the Tito place is bad. People shooting others with guns, me shot here [ribs] sutee!! After death where one shot, they scattered. Some decided for here and some for up.
While buffalos, elephants, and chimpanzees were remembered as causing a lot of damage as Tito was established, but they are no longer seen to be an issue. One farmer said that he “sees with the opening of farms, animals are going further into the bush. Animals reduced a bit due to the increase of population and hunters—elephants, buffalo, water beef [chevrotain], sleeping deer [Bay duiker], giant pangolin”. The impact the move and resulting forest clearance around the Tito site had on the gorillas remained curiously absent from our discussions. AW’s roles as a researcher, a “white man”, “Wildlife”, a New Zealander, a woman, and her interests in the welfare of both the human participants and the apes influenced participants’ perceptions and the information they choose to provide. In the village, AW was of unusual standing and did not fit into the typical preconceived categories of village life. She was unable to disassociate herself from being perceived as “Wildlife” and part of this perception was likely to have arisen from the collaboration with, and introduction, from the WCS. These perceptions are likely to have prevented discussion around topics such as bushmeat hunting with some participants. As AW gained rapport with several key informants, she was able to have discussions about any bushmeat they had collected and what they had seen in the forest throughout their travels. Official reports state the last Mone-Oku gorilla hunted was in 1996, an approximately 20-year reprieve at the time of the research [
94]. Tito has since become a well-established site for the majority of the Nga people. Farms are now mature and contain valued nontimber forest products (e.g., njansan, bush mango) that were transplanted to reduce the need to travel into the forest. Although, large tracks of lowland forest immediately surrounding Tito are also being cleared as people seek to capitalise on the cacao trade (see below).
The majority of the original Nga farms are now regenerating secondary forest that are favoured nesting and feeding environments for Mone-Oku gorillas. Although this human habitat alteration is unlikely to result in a long-term abundance of herbaceous vegetation [
95], it will increase the germination frequency of light-demanding tree species, including those preferred by the gorillas [
89,
90,
91]. Similarly, shifting settlement systems in Mali have been demonstrated to modify habitats in such a way that they are both attractive and available to chimpanzees, supplementing natural habitats both spatially and temporally [
76]. People’s recollections about the move from old Nga to Tito also highlights our lack of understanding about community ecology in the region. For example, how do gorillas interact with other mammals and what are the effects of feeding competition on their ranging behaviour? The Mone-Oku gorillas and chimpanzees have distinct nesting ranges and appear to occupy different habitats as a likely response to feeding competition [
5]. However, has the decrease in forest buffalo and elephants in the Mone-Oku Forest due to human hunting reduced feeding competition, further allowing the gorillas to occupy open areas with greater herb and fruit availability? Limited studies on forest buffalo suggest there is dietary overlap in both staple and fallback herb species that may affect the ranging behaviour of both taxa, especially in times of low fruit availability [
31,
36,
96,
97]. In Gabon, elephants were found to competitively exclude western lowland gorillas in times of low herb availability, irrespective of fruit abundance, where both taxa were competing for fruit [
98]. The large areas of “unoccupied” but suitable Cross River gorilla habitats may be a result of competitive exclusion in areas of sympatry and remain in need of further investigation.
Human land-use patterns and hunting pressures have played a significant role in shaping the wider Cross River landscape. Still, there has been a bias towards focusing on negative anthropogenic interactions (e.g., hunting and habitat loss) without consideration given to how anthropogenic habitat alteration has shaped the forest over time with the potential to create favourable new microhabitats even if they are temporary. The focus on the anthropogenic in Cross River gorilla conservation means that interspecies interactions and the effects of competition on the gorillas’ ranging and feeding behaviours have been neglected.
3.3. Cacao and Wider Connections
The villages around the Mone Forest Reserve, including Nga, have been labelled as threats to the conservation of the Cross River gorillas due to the recent rapid expansion of their cacao farms [
30]. However, the situation is complex. Through the reconfirmed presence of the Cross River gorilla during the early 1990s, Akwaya Subdivision became repopulated in the eyes of the international scientific community [
35,
54,
99,
100,
101,
102]. At the same time, Akwaya was also establishing a network of connections to the remainder of Cameroon through roading projects and economic developments. This has resulted in a landscape where local practices have been shaped by external forces but only the local outcomes are realised as key threats to the conservation of the Cross River gorilla.
The lack of access to Akwaya Subdivision became highlighted in the 1960s when the Southern Cameroons voted to be reunited with the Republic of Cameroon. Upon independence, Mamfe (approx. 48 km from Nga) became the main commercial and administrative town for the region, yet the subdivision could only be reached via foot (approximately 2–3 days walk) within Cameroon. Early attempts to construct a road were made by the Western Cameroonian Ministry in the late 1960s, but the project was abandoned when the then Federal Government refused to contribute funds [
101]. It was the belief that this road was going to be constructed that played an instrumental role in the people of Nga’s decision to relocate to the Tito site. It was not until 1991 that the first motorable bridge was constructed across the Cross River by a Lebanese timber company which received a logging concession in the region [
102]. This bridge and the seasonal earth road that slowly followed began to fully connect the subdivision to Mamfe and Cameroon. As the road was established many sought to take advantage of the benefits that arose from increased market access with increases in hunting, harvesting of nontimber forest products, and forest conversion to farmland recorded [
101]. Contributing to the forest clearance was a series of political and economic changes that turned cacao into a profitable cash crop.
Cacao has a long history within Cameroon. The German Administration introduced it to the Southwest in 1886 and rapidly established plantations that resulted in cacao becoming the main agricultural export by 1913 [
103,
104], but cacao only became an important cash crop within Nga village and the wider subdivision in the 1990s. There appear to be two key reasons for the shift to farming cacao. The first relates to the dangerous nature of harvesting oil palm kernels, the main cash crop prior to this period. As one elder from Nga commented, “it was dangerous to go up the trees to find money. However, now cocoa is a new thing and it is safer because it is on the ground”. The second reason given behind the shift to cacao was the increase in the purchase price that arose from the severe economic crisis Cameroon suffered in the early 1990s. This crisis was partly a result of the falling prices of raw materials on the international market that saw Cameroon reform local markets following the implementation of structural adjustment loans from the World Bank [
105]. While international cacao prices gradually increased across the 1990s, Cameroon’s economic reforms removed the fixed purchase price, opening the competitive world markets to Cameroonian farmers [
103,
106].
Cacao has since become an integral crop to the people of Nga and it is quickly becoming interwoven into the fabric of society. The size of a man’s cacao farm appears to dictate his standing among his peers, with those who dedicate their time and energy into their farm accumulating great wealth and power within the community. In contrast, there was a stigma attached to the few men who did not have a cacao farm and often struggled to provide for their family and perhaps, more importantly, their children’s education. Most men within the village have cleared forest specifically for cacao farms, with many expressing a desire to increase their farmland. As Tuku wished: “If I was feeling strong, I would clear as I go and never look back”. Despite these desires, the village has certain rules surrounding forest clearance that practically limits the size of most farms to two or three hectares as a farmer must be able to maintain the land that is cleared.
However, the desires to increase cacao production are not only local. In 2009, President Bia announced his intention to transform Cameroon from a developing to an emerging nation by 2035. As part of the 2035 emergence drive, the Cameroon Government sought to capitalize on the expected increase in demand for cacao and triple its cacao production by 2020 (an increase of 600,000 tonnes per year), to become one of the world’s top three producers [
107]. To facilitate these goals, President Bia announced at Mamfe in 2015 that the Akwaya Road would be tarred, finally fully connecting Akwaya to the rest of Cameroon, although the project has not commenced in 2021 [
108].
The combination of local, political, and international economic processes favouring cacao farming within Akwaya certainly has the potential to cause widespread deforestation. With limited access to education on or support for farming cacao, the general practice within Akwaya is to clear the nonuseful trees within a farms’ boundaries, as this allows more sunlight and greater harvests. Nutrient absorbing food crops (e.g., cassava and cocoyams) are also grown with cacao increasing the potential for soil depletion and barren land [
109]. However, it is not necessary to grow cacao this way. Across Africa and Brazil are long-established complex agroforests where cacao is cultivated with a mixture of fruit and forest tree species [
110,
111,
112,
113,
114]. These agroforests have demonstrated greater long-term viability of cacao farms while retaining the soil nutrients, allowing for the potential regeneration of the forest should the farms be abandoned for social or economic reasons.
The rapid forest clearance in Indonesia for oil palm plantations and the precarious plight of orangutans demonstrates how powerful world market forces can be in small locales [
115]. With cacao production playing a large role in Nga, initiatives seeking to conserve the Cross River gorilla are likely to gain greater community support if they can find mutually beneficial ways to support cacao farming. Positive relationships and guidance on making cacao farms more productive and long-lasting has the potential to preserve negotiated forest corridors throughout the gorillas’ range. Ultimately, how far cacao farms expand throughout the Mone-Oku Forest and the wider region depends as much on the development of local infrastructure and global markets as it does on the local farmers.
It is also necessary to remember that the situation is not static. Since the completion of this fieldwork in 2015, Cameroon has experienced internal hostilities between the Anglophone regions and the largely Francophone Government that appear to be once again reshaping people’s relationships with the forest and the animals within. Since 2016, it is estimated that over 2000 people have died and over half a million people are displaced, with both the Cameroon Government and separatist forces committing serious abuses against the civilian population [
116]. Large numbers of people are taking refuge in the forests along the Nigeria–Cameroon border as villages are set alight, with many reporting to be living off what they can hunt and gather in the forest [
117]. In January 2021, there remains little intervention from the international community or negotiation between the Anglophone and Francophone factions. The situation may be further compounded as Cameroon experiences its second wave of the COVID-19 virus, with humanitarian organisations struggling to gain access to the area to provide healthcare and education [
118]. The fate of the people, wildlife, and forests across Southwest Cameroon remains unknown; however, lessons are available from regions that have experienced previous armed conflicts. Where wildlife populations have declined during a period of armed conflict, population recovery has been possible when food insecurity and supply chains are addressed at local levels and support is provided to local and governmental institutions that manage conservation-related activities [
119,
120,
121].