Primates

“Unsustainable human activities are now the major force driving primate species to extinction.”

(Estrada et al., 2017.)

Primates are our closest biological relatives and some of them, we know quite well: the lemurs of Madagascar, the great apes of Asia and Africa and the diverse monkeys of the tropical world. But there are countless other engaging, peculiar and secretive creatures that most of us have never seen, even on TV: pottos and tarsiers, lorises and galagos, angwantibos and more (IUCN/SSC, 2021).

An angwantibo

Threats to primates:

• 87% of species in Madagascar are threatened
• 73% in Asia
• 37% in mainland Africa
• 36% in the Neotropics

(Estrada et al., 2017)

There are more than 500 known primate species distributed across the Neotropics, mainland Africa, Madagascar and Asia. They are present naturally in 90 countries; however, two-thirds of all species occur in just four countries – Brazil, Madagascar, Indonesia and the Democratic Republic of the Congo. They are an essential component of tropical biodiversity, contributing to forest regeneration and ecosystem health.

Around 60 per cent of the world’s primate species are threatened with extinction because of deforestation, habitat loss and fragmentation, large- and small- scale agriculture, cattle-ranching and over-exploitation. Other drivers of species loss include hunting (bushmeat) and the illegal trade of primates as pets and primate body parts, along with emerging threats such as climate change (Estrada et al., 2017).

The production of commodities such as soya beans, palm oil, natural rubber and beef, scientists say, has direct and indirect impacts on biodiversity and primate populations. A central concern is that global dietary changes, including greater meat consumption because of rising living standards, will encourage many primate-range countries to convert even more forested land into monocultures to meet global demands. To protect primate habitats, it is imperative, they say, to reduce the world’s demand for these agricultural products and the consumption of meat and dairy products (Estrada et al., 2019).

The Primate Specialist Group (PSG) of the IUCN’s Species Survival Commission (SSC), produces a list of the world’s 25 most endangered primates (see below). The Top 25 list has become a biennial review of those species and subspecies in the direst need – some of which now survive only as a few dozen individuals. By highlighting the danger to a selected few, the PSG hopes to draw attention to the need for urgent conservation measures for these species and to the wider issues of primate conservation.

The PSG writes on the critically endangered primates: “These are the names we have nearly lost: these are the primates who just barely survived the 20th century, and who – without our immediate intervention – will never survive the 21st.

“Each of the lineages below is unique, in voice and shape and ancient home; each name speaks to a former multitude, long since broken and scattered to a dwindling few. Each handful of survivors is all that remains of an unknown history, woven through deep ages and written in the substance of themselves – each a vital thread in the weft of our living world.

But all their futures are unravelling now, while we stand in distant witness. These are the primates listed as critically endangered, about whom far too little is known: save that their populations are decimated, their homes are charred and fallen; and without our efforts, they will be lost in a handful of years” (IUCN/SSC, 2021a).

Primates in peril: The world’s 25 most endangered primates 2018-2020.

(Schwitzer et al., 2019.)

Funky gibbons

Described as stunning gymnasts, soulful singers and loving family members, gibbons differ from great apes (chimpanzees, gorillas, orangutans and humans) in being smaller. They can swing from branch to branch (brachiation) for distances of up to 15 metres at speeds up to 35 miles per hour. They’re the only mammal in the world with a ball and socket joint in their wrists (like the ones in our shoulders and hips), making their wrists stronger and more flexible. They can swing skilfully through the trees further and faster than any other ape, making them the quickest and most agile of all tree-dwelling non-flying mammals (IUCN/SSC, 2021b). They can also walk on two feet (bipedally) with their arms raised for balance.

Of the 28 known gibbon species listed by the IUCN, 22 are either endangered or critically endangered and one of these was only recently discovered. In 2017, in the forests of the Gaoligong mountains, which straddle the border between southwest China and northern Myanmar, scientists identified a new species of gibbon distinct from other Chinese gibbons. They named the new gibbon the Skywalker hoolock gibbon (they were Star Wars fans). A full genetic and physical comparison with other gibbons confirmed that they had found a new species that may have diverged from another around half a million years ago.

A Skywalker hoolock gibbon

The newly discovered Skywalker gibbon is facing an uncertain future and is included on the list of the world’s 25 most endangered primates. Less than 150 individuals are known to exist in China and the population in Myanmar is unknown but likely to be small and highly threatened because of political instability and associated habitat destruction and uncontrolled poaching (Zhang et al., 2020). Agricultural encroachment, commercial logging, habitat fragmentation and isolation, and hunting (for bushmeat and the pet trade) are all major threats for this newly discovered species. Dr Sam Turvey, from the Zoological Society of London, who was part of the team studying the apes, told the BBC: “It’s difficult to get into the reserve. You have to hike up to above 2,500m to find the gibbons. That’s where the good quality forest usually starts – everywhere below there has been logged” (Morelle, 2017).

Mountain gorillas

Gorillas are our second-closest relatives after chimpanzees. We didn’t evolve from them; humans and gorillas took separate evolutionary paths about 10 million years ago, so we share a common ancestor. There are almost eight billion humans on the planet now but there are less than 1,200 mountain gorillas (Gorilla beringei beringei). They are among the most endangered animals on Earth.

Gorillas have inhabited the equatorial regions of Africa for thousands of years but conflict, poaching and agricultural expansion have devastated the population over the last few decades, with numbers in this region falling to as low as 250 individuals in 1981. Conservation efforts have helped restore numbers to around 1,200, with 580 in the Virunga Mountains and a similar number in the Bwindi Impenetrable National Park in Uganda (UNEP, 2021).

Mountain gorillas

In 2018, the IUCN changed the classification of mountain gorillas from Critically Endangered to Endangered. However, progress remains fragile and major threats persist. Legal and illegal human entry into gorilla habitats pose both immediate and long-term risks; human disturbance of the animals, disease, injury and death as non-target species of poaching, purposeful killing, habitat degradation and destruction, and climate change-induced changes of habitat, all jeopardise the persistence of mountain gorillas (IUCN, 2020).

In June 2020, Rafiki, a 25-year-old silverback in the Bwindi Impenetrable National Park was killed by poachers who said they were hunting for bushmeat. Johannes Refisch, a United Nations Environment Programme expert on mountain gorillas and Coordinator of the Great Apes Survival Partnership (GRASP), says: “Gorilla-related tourism, a key source of income for local communities, dried up amid the Covid-19 pandemic. As a result, we have seen an increase in illegal activities, as desperate community members enter the parks in search of wild meat, bamboo, timber and other commodities.”

Poaching presents a serious threat to mountain gorillas. Some are hunted for their meat but snares set for other mammals, particularly forest antelopes, can trap and kill mountain gorillas too. During a population study in the Virungas in 2018, survey teams destroyed over 380 snares but a mountain gorilla was found dead, trapped in one of them (Hickey et al., 2019).

In Uganda, the harvest of wildlife is illegal but bushmeat hunting is commonplace. This has resulted in a covert market with person-to-person exchanges rather than legal open markets. Nearly a third of bushmeat sold in these communities is misrepresented as another species, adding another layer of risk as certain species of wildlife, such as primates and bats, are more often implicated as reservoirs for zoonotic diseases than species like warthog or antelope (Dell et al., 2020).

Hunting, preparing and consuming bushmeat can contribute to the spread of viral diseases such as Ebola or bacterial infections caused by E. coli, Salmonella, Brucella or others. One study, that interviewed 292 women who cook for their households and 180 self-identified hunters from 21 villages bordering Murchison Falls National Park in Uganda, found that almost all respondents were aware of the risk of disease spillover from wildlife to people. However, for the hunters, this awareness did not motivate precautionary measures, financial gain was their primary motivation (Dell et al., 2020).

As gorilla habitats become increasingly encroached upon, the likelihood of conflict, over resources such as food and water that humans perceive to be theirs, increases (Hockings and Humle 2009). Conflicts arise from gorillas crop-raiding agricultural fields adjacent to parks, smallholder cattle encroaching into protected areas and incidents of direct killing of mountain gorillas by farmers living adjacent to parks. Bwindi gorillas have been known to crop-raid because of the availability of palatable foods (eg bananas, eucalyptus and sweet potatoes) close to the park (Seiler and Robbins 2016). Grazing livestock that encroach into parks may interact with gorillas, negatively impacting them through displacement or disease transmission. As human populations grow and make deeper incursions into the natural habitat of great apes, such conflicts will become more prevalent (Hockings and Humle 2009).

As their habitat is encroached upon, mountain gorillas are now increasingly threatened by the risk of disease transmission from both humans and livestock. One study found that gorilla populations whose habitats overlapped with people and livestock harboured E. coli that were genetically similar to human and livestock bacteria, whereas E. coli from gorillas whose habitat did not overlap were more distantly related. Alarmingly, 17 per cent of E. coli samples from gorillas living alongside people and livestock were resistant to at least one antibiotic used by local people (Rwego et al., 2008).

Gorillas are naturally afraid of humans, but through repeated contact, they have become habituated (Robbins et al., 2011). Research shows how this increases their vulnerability. One study found that between 1967 and 2008, 26 habituated Virunga mountain gorillas were killed by humans. Three poaching deaths resulted from gorillas being caught in snares set for other animals, 15 were shot by militia groups and eight were killed by villagers or poachers for other reasons – including for bushmeat, to stop crop-raiding and capturing their young for the pet trade. A further 16 died from respiratory diseases, but it is unknown whether these were transmitted from humans.

Great apes are susceptible to human pathogens because of their genetic relatedness to us. In other words, if a viral or bacterial infection affects us, it will likely affect them too. In January 2021, several captive gorillas at a San Diego zoo in the US tested positive for Covid-19, with some experiencing symptoms. In September of the same year, more than a dozen gorillas tested positive for Covid-19 at another US zoo, this time in Atlanta, Georgia. Officials said they believed a member of their animal care team, who was asymptomatic when she came to work, probably transmitted the virus.

The IUCN estimates that 264 to 880 people come into close proximity with mountain gorillas every day (IUCN, 2020). Such tourism can help support the conservation of great apes and their habitats but should only be developed if the benefits outweigh the risks. The IUCN have published guidelines for best practice in great ape tourism; recommending, for example, that tourists do not go any closer than seven metres to habituated apes if wearing an N95 surgical respirator facemask, or 10 metres if not wearing one (Macfie and Williamson, 2010).

Scientists warn that climate change is also likely to affect mountain gorillas with increased temperatures and disrupted rainfall patterns (Thorne et al., 2013). These conditions will likely cause changes in habitat quality and the availability of foods such as bamboo, which is dependent on seasonal rainfall (McGahey et al., 2013). This demonstrates another link between animal agriculture and the loss of wildlife as a fifth of all anthropogenic greenhouse gases, driving the climate crisis, come from livestock production.

There is some good news, however, despite ongoing civil conflict, illegal poaching and encroaching human populations and agriculture, both populations of mountain gorillas (in the Virunga Mountains and the Bwindi Impenetrable National Park in Uganda) have increased in numbers. However, we can’t afford to be complacent; even land within protected areas is not safe from clearing. In 2004, for example, illegal settlers cleared 3,700 acres of gorilla forest in Virunga National Park. With the vast majority of unprotected forests being opened up to selective logging and habitat loss and degradation, it is vital that we step up our efforts to conserve the great apes (Strindberg et al., 2018).

Chimpanzees

Chimpanzees (Pan troglodytes) are a species of great ape native to the forest and savannah of tropical Africa. They have four subspecies: Western chimpanzee, Central chimpanzee, Eastern chimpanzee and Nigeria-Cameroon chimpanzee. The last three are listed by the IUCN as Endangered but the Western chimpanzee is listed as Critically Endangered.

A young chimpanzee

Along with the bonobo (Pan paniscus), the chimpanzee is the closest relative to humans and like us, they are complex, social, intelligent, curious and capable of brutality and kindness. They live in groups of up to 150 individuals, make and use tools, hunt in groups and share food. They separate into smaller groups when foraging during the day but come back together to sleep at night. It’s been suggested that chimpanzees provide a window into the lives of our common ancestors: male-dominated, warlike, monkey hunters. However, others have challenged this view, pointing out the characteristics of our other closest living relatives, bonobos; female-dominated pacifists that substitute sex for aggression (Wilson, 2021).

Chimpanzees have by far the widest geographic distribution of any great ape, with a range of over 2.6 million square kilometres (IUCN, 2016). They can be found from southern Senegal across the forested belt north of the Congo River to western Tanzania and western Uganda. They are now extinct in four of their 25 range countries; Gambia, Burkina Faso, Togo and Benin. Where they numbered perhaps one million at the turn of the 20th century, today it’s estimated there are 172,000 to 300,000 chimpanzees remaining (IUCN, 2016).

Although there are more chimpanzees than many other endangered primates, their numbers in the wild are rapidly declining. This is largely because, even though they are listed as Endangered or Critically Endangered, chimpanzees are still hunted for their meat. All killing, capture or consumption of great apes is illegal, however, the IUCN says that poaching remains the greatest threat to most chimpanzees (IUCN, 2016).

While bushmeat was a popular source of protein for local communities in the past, the scale of hunting has increased dramatically and has become heavily commercialised with much more of the meat now going to urban residents. Growing human populations and the increasing urban demand has led to the emergence of a booming bushmeat trade with unprecedented harvest (kill) rates and the consequent decline of numerous wildlife populations (Cawthorn and Hoffman, 2015). The Jane Goodall Institute say: “The commercial bushmeat and illegal exotic pet trades give poachers incentives to kill even nursing mothers.”

Large-scale biodiversity loss is now globally recognised as an ecological disaster with substantive evidence revealing many places where once vibrant wildlife populations have been hunted to extinction. The ‘bushmeat crisis’, a term coined to describe the overharvesting of wildlife for food, is now seen as the greatest threat to biodiversity in some regions. Most large mammal species in Kilum Ijim in Cameroon, for example, have become locally extinct due to hunting over the last 50 to 60 years, including elephants, buffalo, bushbuck, lions, leopards and chimpanzees (Cawthorn and Hoffman 2015).

Another main threat to chimpanzees is the conversion of forest to farmland across Africa. Expanding agriculture, livestock farming, urbanisation and felling of trees for timber, firewood and charcoal burning, and widespread fires are all contributors to forest losses. Subsistence, or slash-and-burn agriculture, has severely reduced the availability of chimpanzee habitat (IUCN, 2016). Such habitat loss is especially acute in West Africa, where it is estimated that more than 80 per cent of the region’s forest cover had been lost by the early 2000s (Kormos et al., 2003).

The so-called ‘cattle corridor’ of Uganda stretches from the northeast (eg Kotido District), through central (eg Nakasongola District) to southwest Uganda (eg Rakai and Ntungamo Districts). The constant grazing of large herds of livestock during the dry season in the central forest reserves in this region causes damage to young trees through compaction of soils, rendering them prone to erosion and nutrient loss (Kagolo, 2010). In the past, communal land ownership and limited cultivation enabled farmers to move livestock more easily, which reduced the pressure on the land. Changes in land ownership and land use have reduced mobility as a coping strategy to drought, thus contributing to the degradation of rangelands (Byenkya et al., 2014).

Extensive land conversion in eastern Democratic Republic of Congo, western Rwanda and western Uganda has destroyed much of the forest used by chimpanzees in the foothills and lower slopes of mountain ranges there. Rising human populations are expected to lead to further widespread conversion of forest to agricultural land. Along the northern border of the forest-savannah boundary, forests are also being lost to fires and grazing of livestock (IUCN, 2016). Uganda’s natural forests are being lost and degraded at one of the highest rates in the world through encroachment, deforestation and degradation as forest land is converted for farming and other land uses. Chimpanzees are also sometimes killed intentionally – even poisoned – by farmers protecting their crops or as retribution for crop-raiding (Brncic et al., 2010).

In Sierra Leone, for example, agriculture is primarily small-scale subsistence farming that relies on the practice of slash-and-burn. As the population increases, demand for land grows, farms are pushed into steeper slopes and more difficult terrain and require ever more forest clearance and shorter periods of fallow. All of these have serious consequences for chimpanzees who lose habitat and are more likely to raid crops from the encroaching farms. Such trends are likely to increase as more natural habitat is converted for agriculture (IUCN, 2016).

Farmers burn land to clear areas for planting, while herders burn to increase grazing for cattle and
hunters burn to be able to spot their prey more easily. A report from the Ugandan Ministry of Water and Environment says that many fires are intentionally set by herders at the onset of the dry season to encourage re-growth of new grass for livestock during the rainy season. Some of the fires are set by hostile communities neighbouring forest plantations in retaliation to the planters’ refusal to allow them to use parts of the licensed areas to grow crops (Ministry of Water and Environment, 2016).

The effects of climate change are also being felt as uncommonly long dry seasons lead to the accumulation of dry matter in and outside forests, leading to ideal conditions for the rapid spread of fires. When fires are not controlled, vegetation and wildlife can be unnecessarily destroyed. One village in south-eastern Koinadugu District in Sierra Leone reported a large group of chimpanzees that were trapped and killed by an out-of-control bush fire (Brncic et al., 2010).

Zoonoses and disease outbreaks are a significant threat to chimpanzees; Ebola, for example, is a major driver of decline in central chimpanzee populations (IUCN, 2016). Viruses that are relatively benign in humans can also be lethal in ape populations. Respiratory viruses of human origin, for example, have caused disease in wild apes across Sub-Saharan Africa and pose a significant and growing threat to chimpanzees.

Respiratory diseases, thought to be transmitted from people, are the leading cause of illness and death among chimpanzees in Gombe Stream National Park in Tanzania and Kibale National Park in Uganda. Other respiratory viruses that can jump from humans to chimpanzees have been found in Cote d’Ivoire and Tanzania. Rhinovirus C has caused chimpanzee deaths in Uganda and coronavirus OC43 of human origin has caused mild respiratory disease in Cote d’Ivoire (Negrey et al., 2019). Common human coronaviruses, including types OC43, 229E, NL63 and HKU1 usually cause mild to moderate upper-respiratory tract illnesses in people, like the common cold (CDC, 2020). Of course, this raises concerns about Covid-19 being transmitted from humans as it too is caused by a coronavirus.

As well as the IUCN guidelines previously mentioned – minimum observation distances and facemasks – other measures have been taken. At Gombe National Park in Tanzania, giving chimpanzees bananas has been discontinued as, along with season, it was seen to be the strongest predictor of chimpanzee respiratory illness.

Chimpanzee

Due to high levels of poaching, loss of habitat caused by expanding agriculture and other human activities and infectious diseases, chimpanzees have experienced huge declines over the last three decades or so and it is feared that this will continue (IUCN, 2016). Although conservation efforts have increased significantly, the IUCN say that populations may continue to suffer losses based on the rapid growth of human populations in sub-Saharan Africa, continuing poaching for bushmeat, the commercial bushmeat trade, the arrival of industrial agriculture (which requires clear-cutting of forest), corruption and lack of law enforcement, lack of capacity and resources and political instability in some areas (IUCN, 2016).

Future challenges

All great apes are protected by national laws and international conventions; it is illegal to kill, capture or trade live individuals or their body parts, wherever they occur. Despite this protection, the combination of widespread illegal poaching, agricultural expansion and Ebola has been catastrophic for gorillas and chimpanzees.

Another emerging threat is industrial-scale forest conversion for agriculture. For example, as tropical Asia nears capacity for oil palm plantations, producers are now heading to African countries with appropriate rainfall and suitable soil and temperature conditions (Rival and Lavang 2014). Unfortunately, these areas also tend to be ideal great ape habitats and it is predicted that expansion is likely to hit chimpanzee populations hard in coming years (IUCN, 2016). While subsistence agriculture has slowly encroached on great ape habitats across Africa, global agribusiness could rapidly destroy large swathes of quality habitat. Even worse than selected logging, large plantations require clear-cutting and would increase forest loss with catastrophic consequences for great apes and other wildlife (Strindberg et al., 2018).

Around 90 per cent of oil palms grow in areas that were once tropical forests in Malaysia and Indonesia – islands containing some of the greatest biodiversity on Earth. Smaller areas are planted in Africa and Latin America. Slash-and-burn deforestation has been used to clear the way for plantations in Southeast Asia which have come at the expense of species-rich and carbon-rich tropical forests (Vijay et al., 2016). This has led to a huge loss of wildlife there, with substantial numbers of elephants, rhinos, tigers and orangutans losing their homes and lives. There is an urgent need to develop guidelines in Africa to minimise the impact of the expansion of oil palm on primates and other wildlife there (Wich et al., 2014).

Oil palm is native to West Africa and is found at relatively high densities in areas where people use it to produce palm oil for domestic and commercial use (Humle and Matsuzawa, 2004). Western chimpanzees in Bossou in West Africa rely heavily on oil palms for feeding and nesting. Recent evidence suggests that oil palms are also an important food and nesting resource for other chimpanzee communities in human‐impacted areas across West Africa (Bryson-Morrison et al. 2020).

Despite the widespread awareness about its detrimental effects on tropical biodiversity, land conversion to oil palm continues and future expansion seems likely in Africa. A study assessing how this could affect African primates found a high overlap between areas deemed suitable for oil palms and areas of high conservation priority for primates (Strona et al., 2018). If plantations are adjacent to chimpanzee habitats, they will likely raid the plantations for easy and nutritious food, increasing the risk of conflict.

Palm oil is used in close to half of all the packaged products we find in supermarkets – it’s also used in animal feed. In 2011, a study for the UK Government revealed that more than a tenth of all the world’s palm kernel meal – a lucrative by-product of the production of palm oil – is fed to British animals in livestock and pet food, none of which was from certified sources (DEFRA, 2011). The animal feed sector is not subject to the same level of scrutiny, market interest or pressure for sustainability.

Reconciling a large-scale development of oil palm in Africa with primate conservation will be a great challenge – which is no surprise given the dramatic detrimental effects of oil palm cultivation on biodiversity in Southeast Asia (Strona et al., 2018). The IUCN says effective policies are needed to stop the clearing of tropical forests for new oil palm plantations. You can also help by choosing products that use sustainable palm oil, cutting down on the amount of palm oil you buy and of course, by going vegan.

If primate habitats continue to be destroyed by human activities such as poaching, encroachment, deforestation, agricultural expansion and so on, it seems likely that more species will face extinction – the long-term consequences of which remain unclear. Great apes, for example, play key ecological roles in forest ecosystems; without these large-bodied seed dispersers, forests will fail to regenerate (Strindberg et al., 2018). A significant increase in regional, national and global awareness is needed along with a change in political will with financial commitments to endangered species conservation.

The problems facing primate conservation have deep roots, according to the Jane Goodall Institute, including human population growth, the staggering scale of poverty and disease, lack of economic opportunity, political indifference and corruption, conflict and a lack of community involvement in managing natural resources. They say: “To begin to make a difference in the face of such fundamental challenges requires a holistic, multi-pronged response” (Jane Goodall Institute, 2022).

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