Chimpanzees are at risk of being eaten into extinction
Chimps are killed by hunters for food almost everywhere they live, despite being critically endangered. It's devastating their populations - and it's also threatening our own health.
What is bushmeat?
Across the markets, towns and cities of Africa hundreds of different species of animal are regularly sold as bushmeat, defined as any wild animal killed for food.
Animals including bats, porcupines, buffalo, crocodiles, antelope, lizards, monkeys and snails are all hunted for their meat.
Much of this trade is legal and bushmeat is an important source of protein. But as hunters unselectively target any wild animal in the forest they also end up killing chimps, gorillas and bonobos. Today the threat faced from being eaten by humans is endangering the very survival of these primates.
No different to how deer and pheasant are hunted in the UK, people have been consuming bushmeat in central and western Africa for tens of thousands of years.
As populations in urban centres of Africa have been increasing the demand has risen accordingly. This has been exasperated by a huge expansion of logging and mining in the region.
Marcus says, 'You now have urban centres that are well connected to the surrounding rural areas where the bushmeat is sourced. As those transport links get better then it is easier to move that bushmeat into the markets.'
It is now thought that up to five million tonnes of bushmeat are traded each year across the Congo basin.
'In urban centres bushmeat is increasingly becoming a luxury, because the amount that can be produced is not sufficient to satisfy those very large populations,' says Marcus.
'This means prices are going up, and it is increasingly becoming a status symbol.'
Why are chimpanzees endangered?
While chimpanzees, gorillas and bonobos might not form a large part of the trade, their biology and ecology mean that they are disproportionately affected by the threat of hunting.
Apes are long-lived and have a slow life history. Chimpanzees can live up to 35 years in the wild, but females may only give birth once every five years. This means that even low levels of hunting can decimate entire groups.
When this is combined with other impacts such as deforestation and climate change, the result is devastating for their populations.
At the turn of the twentieth century, it is thought that there were as many as a million chimpanzees roaming the vast forests of central Africa. Today there are as few as 172,000. Current estimates suggest that within three decades chimpanzees could be extinct in the wild.
Scratching the surface
The scale of chimpanzee hunting for bushmeat is difficult to quantify. Hunting tends to occur in remote rainforests across central Africa, yet the meat is only occasionally found for sale in markets.
By using the number of orphaned chimps that are taken in by sanctuaries - often the result of the bushmeat trade as they are simply too small to be worth killing - researchers can start to build a picture of the extent of the impact.
It is estimated that for every chimpanzee in a sanctuary between four and nine adults were probably killed. Even then, this is not the whole picture.
Not all infants taken from the wild will make it to a sanctuary. With the vast majority of orphans dying from wounds or in transport, or ending up as pets, it has been suggested that only one in five will make it to orphanages.
This means that each orphan could represent 25 adult chimpanzees taken from the wild - and yet this is still most likely an underestimate.
With up to 1,000 apes being housed in sanctuaries, thousands more will have been killed. As it takes up to 15 years to replace an adult breeding chimp in the wild, the result is devastating.
The emptying of forests is not the only issue when it comes to bushmeat, particularly when this involves eating primates.
Marcus says, 'Eating bushmeat has the potential to create huge disease risks.
'It's pretty well evidenced now that HIV, for example, had origins in ape populations and probably crossed the species boundary through hunting.'
Researchers have traced the crossover of the virus from chimpanzees to humans to the 1920s in Kinshasa, Democratic Republic of Congo, likely after someone came into contact with contaminated blood as an infected chimp was butchered. Six decades later, the virus would become a pandemic of worldwide proportions.
These leaps from apes to humans - and vice versa - are not confined to the past.
The Ebola virus can infect humans, chimpanzees and gorillas indiscriminately. It is initially thought to have emerged in the 1970s through eating infected bats, but has quickly spread throughout central and west Africa, significantly affecting both humans and apes.
'There are potentially many other viruses that could come from bushmeat,' explains Marcus. 'It's hard to put your finger on what those might be, but we do know that there is a low risk of very serious pathogens emerging.'
The bushmeat crisis in Africa is a complex problem, and many organisations are working to provide long-term food security to populations that are most in need.
The current demand for bushmeat seems to show no sign of slowing, but there are hints that a generational shift might be appearing, particularly among the growing young urban population.
'The one slight glimmer of hope is that in urban centres we find that younger people are perhaps not showing quite such a strong attachment to bushmeat as their older peers,' says Marcus.
'It might be too early to say that that is a genuine trend yet, but there are definitely some indications.'