Conservation news

Toxic beetles and poisonous plants: Study reveals how southern Africa’s ‘bushmen’ make deadly poison arrows

Southern Africa's San peoples use beetles to increase lethality of their poison arrows. Photos by Caroline Chaboo.

  • A new study sheds light on how Kalahari’s San peoples source and prepare poison for poison arrows.
  • Some communities use toxic beetle larvae, such as those of Diamphidia, as well as plant poisons, such as the juice of Sansevieria aethiopica plants to help reinforce the quality of the poison, researchers have found.
  • Knowledge about the toxic component in the poisonous beetles and plants could potentially have medical applications, researchers add.

In southern Africa, certain hunter-gatherer communities called the San peoples, have traditionally been known to use deadly poison-tipped arrows to hunt big game like gazelles and giraffe.

Now, in a study published in ZooKeys, researchers have documented details about little-known ingredients that makes some of these poison arrows lethal — ground-up beetle larvae paste and some poisonous plants.

“We wanted to find out how and why people used poison,” co-author Robert Hitchcock, an anthropologist at University of New Mexico who has worked extensively with the San peoples, told Mongabay. “It was discussed by travelers who visited the Kalahari and adjacent regions in the 17th, 18th, and 19th centuries, and there was a great fear on the part of people living in southern Africa of those people who used poison. So we wanted to find out more about why poison was used, under what conditions, and whether indeed it was an important part of the cultural traditions of various groups.”

Chaboo interviewing San hunters in Namibia. Photo by H. Vollbrecht.

To answer these questions, beetle expert Caroline Chaboo of the University of Kansas, Hitchcock, and their colleagues, combed through literature — some dating back to the 1700s – and reviewed the various kinds of poison used by the San peoples. These indigenous groups use the so-called “click-languages”, and are also referred to as “bushmen”.

Their literature surveys revealed that many groups of San peoples used plant poisons to increase the lethality of their arrows. They also found that at least eight San groups, and one non-San group, in southern Africa have used — or still use — toxins from colorful leaf beetles to make their arrow poison. These beetles, the researchers found, belong to two main groups: Diamphidia and Polyclada.

To better understand how the hunters collect the beetles and prepare arrow poison, Chaboo interviewed two communities of San peoples living in the Kalahari Desert — Ju|’hoan San in north east Namibia and the Hai||om San at Etosha National Park, Namibia.

Men of the Ju|’hoan community in the Nyae Nyae Conservancy still hunt today, Chaboo said. So in 2007, she spent two weeks in the conservancy, interviewing 12 hunters.

Every day, after an initial interview, Chaboo and her team would head out into the desert with a Ju|’hoan hunter, looking for plants that are hosts to the Bushman arrow-poison beetles (Diamphidia spp). On chancing upon a host plant, the hunter would dig a moat around the plant, sift out the beetle cocoons from the sand using his fingers, and fill an ostrich egg shell with the cocoons, Chaboo said.

Once home, the hunter would break open each cocoon, tap out the beetle larva in it, and smash the larva onto an old giraffe or kudu knuckle bone. Sometimes, a hunter would chew the bark of a plant called Black thorn (Acacia mellifera) and mix his saliva with the larval tissue. The Ju|’hoan hunter would then apply this “beetle paste” to the arrow with a little stick, Chaboo said, using around 10 larvae per arrow.

Diamphidia larvae, mature inside the sand-grain cocoon. Photo by Caroline Chaboo.
San man digging up cocoons (note dark ovals on sand in foreground). Photo by Caroline Chaboo.
The San hunters extract poison from the larvae of the Diamphidia beetles. Photo by Caroline Chaboo.

Unlike the Ju|’hoan San, members of the Hai||om community are not permitted to hunt in Etosha National Park. But Chaboo managed to interview older men in their seventies, who used to hunt when hunting was still legal.

Both communities’ knowledge of the host plants, and the beetles that poison is made from, is extraordinary, Chaboo said.

But the science of how the beetle poison actually works is still murky, the authors write.

Previous studies and observations have shown that the beetle poison kills the target animals slowly. After being hit by a poisoned arrow, the animal continues to run, Chaboo said, but slowly becomes feeble and falls. The hunters then usually hit or club the animals to death, she added.

While the authors’ review of the literature has revealed a number of toxic chemicals in the leaf beetles that could be causing slow paralysis in the animals, the precise mechanism by which the beetle larva poison kills remains unclear, the authors write.

So “modern analyses and comprehensive targeting of the various beetles, along with the host plants, would help greatly in unambiguously answering outstanding questions and doubts about the San arrow poison beetles,” the authors write.

Sometimes, the hunters use plant poisons to boost the lethality of their arrows.

For example, “Ju|’hoan informants at Xai-Xai in Botswana told us that they use the juice of Sansevieria aethiopica plants to help reinforce the quality of the poison,” Hitchcock said.

Arrow-poison beetles of the San people and their host plants (photos: CS Chaboo, or indicated if otherwise). 2 Diamphidia nigroornata Ståhl (=D. simplex Péringuey, =D. locusta Fairmaire), Namibia (Chrysomelidae) 3 Polyclada sp. (Chrysomelidae) 4 Blepharida sp., Kenya (photo: C Smith, USNM) 5 Lebistina sp. (Carabidae) 6 Diamphidia femoralis (above) and its predator-parasitoid enemy, Lebistina (below), on Commiphora plant in South Africa (photo: K Ober) 7 Lebistina sanguinea (Bohe- man) adult beetle on a Commiphora plant in South Africa (photo: E. Grobbelaar, SANC, ARC-PPRI). Image from Chaboo et al, 2016.

Different groups of San communities seem to use different species of beetles, plants, or both, to make arrow poison. But what drives this difference is still unclear, Chaboo said. Moreover, the biological purpose of the toxins in the beetles and the plants themselves is also ambiguous, she said.

“This is the next big glaring question to answer,” Chaboo said in a statement. “We can guess that this protein toxin has some physiological value to the insect, perhaps protecting it from the harsh dry climate above ground or possibly even an anti-predatory defense.”

“I also expect there to be a geographic variation in the poisons,” she told Mongabay. “But overall, I think we’re racing the clock to document these practices.”

This is because very few indigenous groups practice archery today. According to the researchers, the only place in Africa  where indigenous communities can still use bows and arrows, or spears, to hunt is the Nyae Nyae Conservance region. “What this means is that the knowledge of arrow poison could potentially die out in other parts of Africa unless people were purposely teaching the young how to make and use arrow poison,” Hitchcock said.

This loss of indigenous knowledge matters, Chaboo and Hitchcock add, mostly because the natural toxic chemicals could potentially have useful medical applications.

“One of the areas which we would like to explore in more detail is the potential for use of the southern African arrow poison plants and beetles for medical purposes, as can be seen, for example, in South America where curare and other poisons have been found to be useful in anesthesia, surgery and contemporary medical activities,” Hitchcock said.