The Ant, the Shaman and the Scientist

When he pointed to the tree trunk and said the scars were from fires set by invisible forest spirits, I had no idea this supernatural observation would lead to a new discovery for tropical ecology. Mariano, the eldest shaman of the Matsigenka village of Yomybato in Manu National Park, Peru, had first showed me the curious clearings in the forest that form around clumps of Cordia nodosa, a bristly tropical shrub related to borage (Borago officinalis). Both the Matsigenka people and tropical ecologists recognize the special relationship that exists between Cordia and ants of the genus Myrmelachista: the Matsigenka word for the plant is matiagiroki, which means “ant shrub.”

For scientists, the clearings in the forest understory around patches of Cordia are caused by a mutualistic relationship with the ants. Cordia plants provide the ant colony with hollow branch nodes for nesting and bristly corridors along twigs and leaves for protection, while the ants use their strong mandibles and acidic secretions to clear away and poison competing vegetation. Local Quechua-speaking colonists refer to the clearings as “Devil’s gardens” (supay chacra).

For the Matsigenka, these clearings are the work of spirits known as Sangariite, which means ‘Pure’ or ‘Invisible Ones’. Matsigenka shamans like Mariano come to these spirit clearings and consume powerful narcotics and hallucinogens such as tobacco paste, ayahuasca (Banisteriopsis), or the Datura-like toé (Brugmansia). With the aid of these visionary plants, the shaman perceives the true nature of these mundane forest clearings: they are the villages of Sangariite spirits, which are unimaginably distant and inaccessible under ordinary states of consciousness. While in trance, the shaman enters the village and develops an ongoing relationship with a spirit twin or ally among the Sangariite, who can provide him or her with esoteric knowledge, news from distant places, healing power, artistic inspiration, auspicious hunting and even novel varieties of food crops or medicinal plants.

As proof of the existence of these invisible villages, Mariano pointed out to me the scars on adjacent tree trunks all around large, dense Cordia patches: “The scars are caused by fires the Sangariite set to clear their gardens every summer,” he explained.

Douglas Yu, an expert on ant-plant interactions, was researching Cordia populations in the forests around Yomybato. I told him about the Matsigenka’s shamanic practices involving Sangariite villages, and pointed out the scars on the adjacent trees. In his years of research, Yu had never noticed the trunk scars. Intrigued, he cut into the scars and found nests teeming with Myrmelachista ants that appeared to be galling the trunks to create additional housing. As detailed in a 2009 publication in American Naturalist this is the first recorded example of ants galling plants, though other kinds of insects are known to do so.

My ongoing collaborations as an ethnobotanist with Yu and other tropical biologists in indigenous communities have highlighted how important it is to pay attention to local people’s rich and often underappreciated knowledge about forest ecosystems: sometimes even those elements of folklore that appear quaint or “unscientific” contain astute insights about natural processes.