DONKEYS are the backbone of many farming villages in developing countries. But if current trends continue, the world’s rural poor may soon need to find a new beast of burden. The animals’ ranks have thinned dramatically in many African countries: Kenya’s donkey population, for example, has fallen by half since 2009, to 900,000. The primary cause is neither disease nor declining demand for live donkeys, but instead a burgeoning market for their pelts.

Since ancient times the Chinese have consumed ejiao, a gelatine made by boiling and refining donkey skin to produce a tonic taken as an elixir. As the country grew richer in the 1990s and 2000s, demand for the product grew and fewer donkeys were needed for agriculture and transport. As a result, there were only 5m donkeys in China in 2016, down from 11m in 1990. Because donkeys are relatively poor breeders, China no longer has enough of them to satisfy its thirst for ejiao. One solution is to fake the product using the skin of other animals, such as pigs. But some manufacturers have now instituted DNA testing to ensure their ejiao is genuine. The other option is to import from abroad.

China’s biggest sources are African. In Kenya, the price of a donkey soared by 325% during a six-month period last year. From 2011 to 2016, the number of donkeys fell by 60% in Botswana and a fifth in Lesotho. But countries all over the world are getting in on the act. In Kyrgyzstan, which borders China, and in India, the populations fell by a fifth during 2015 and 2016 alone. Farther afield, Colombia lost almost a tenth of its donkeys and Brazil around 5% over the same period. Some South American donkeys are transported more than 1,000km for slaughter, demonstrating the reach of the Chinese demand.

Poor farmers can hardly be blamed for selling their donkeys for sums that dwarf their value as draft animals. But in many cases, the vendors are not the actual owners. Instead, thieves have begun stealing donkeys in order to take advantage of the surging prices, leaving farmers without their most prized labourers. In response, around 15 countries have taken measures to curb the donkey trade, such as refusing permits for exports. In 2015 Pakistan became the first country to ban the export of donkey hides. Several African countries, including Botswana, now prohibit exports to China. The Donkey Sanctuary, a charity, wants an immediate halt to the trade. But with ejiao popular among China’s middle classes, its government isn’t listening. In January it boosted the industry by reducing the tariff on imports of donkey skins from 5% to 2%.

Correction (April 3rd, 2018): An earlier version of the map had Kenya mislabelled. This has been corrected.