What chimpanzees know about drug delivery

This article was originally published on The conversation and has been republished under Creative Commons.

Jhe chimpanzees of the Rekambo community in Gabon, West Africa, never fail to surprise. For starters, they are known to kill and eat turtles, which sets them apart from any other chimpanzee community. Now they have been seen displaying another unique behavior, behavior that has never been seen before despite many years of painstaking research.

Ina new study published in the journal Current biologythe researchers described how they saw chimpanzees in Rekambo apply insects to their own open wounds and, even more surprisingly, to the wounds of other members of the community.

EEven in itself, treating wounds with insects is a groundbreaking observation – but so far no other animal, apart from humans, has been seen treating the wounds of others.

HHumans have used local remedies (such as roots, leaves, bark, and other animals) as medicine for at least 5,000 years, a practice that has been passed down from generation to generation in societies around the world.

JHere is also a use of invertebrates in traditional human medicine. For example, leeches were used to clean wounds, slugs and snails to treat inflammation, cobwebs to bandage wounds, and termite tongs to inject medicine under the skin.

IIs it possible, perhaps, that such a cultural use of plants and animals to treat injuries and illnesses was inherited from a common ape-like ancestor millions of years ago?

SELF-MEDICATION IN ANIMALS

AAs in humans, self-medication in wild animals is not uncommon – for example, individuals of a wide range of species, including chimpanzees, select particular plant foods that contain chemicals known to treat infection with parasites.

NOTNotably, caterpillars ingest plant toxins when infected with parasitic flies, and gorillas consume a wide variety of plants that contain compounds known to be important in traditional human medicines.

SSome species, such as wood ants, even anticipate infection by adding antimicrobial resin from nearby trees to their nests, which reduces the colony’s exposure to microbes.

JTo date, however, this widespread behavior is almost always centered around self-medicating with plant material. Never before has the use of insects on wounds been observed.

INNOVATIVE CHIMPANZEES

OOver a 15-month period, starting in November 2019, the team observed 76 open wounds on 22 different chimpanzees. There were 22 insect application events by 10 different chimpanzees. On 19 occasions, various individuals were seen applying an insect to one of their own wounds.

A female chimpanzee applies an insect to a wound on the face of a male chimpanzee. Tobias Deschner/Ozouga Chimpanzee Project

Jhe chimpanzees caught an insect in the air, which they immobilized by squeezing it between their lips. Then they placed it on an exposed surface of the wound and moved it around with their fingertips or lips. Finally, they extracted the insect from the wound.

BBut the use of insects did not stop there. In a remarkable act of ‘allocare’ (caring for another individual), a mother was seen applying insects to the wound of her offspring, and two other adult chimpanzees tended the wounds of a another member of the community.

WHY IT’S IMPORTANT

Jesearchers do not yet know which insects were used, whether they have any associated chemical properties or, most importantly, whether their application to wounds has any health benefits. But what they do know is that chimpanzee behavior is extraordinary for a variety of reasons.

FFirst of all, this is probably an example of allo-medicating (healing others) behavior in monkeys, which has never been seen before.

JThe authors believe this is possible prosocial behavior, defined as behavior that benefits another individual. Humans are characterized by our propensity to volunteer, share and cooperate with each other, but it is unknown if other species, especially our closely related cousins, also exhibit this type of behavior.

JHere is evidence of prosociality in captive bonobos (our other closest living relative), where they were seen helping an unknown, non-group member obtain food during an experimental task.

Bbut so far, its presence in chimpanzees is controversial. The current study undoubtedly pushes the needle towards their sharing of certain prosocial tendencies with humans.

SSecond, self-medication has long been associated with the ingestion of plants with specific medicinal properties. In a recent study, orangutans were shown to mix saliva with plant leaves containing anti-inflammatory properties and apply it to various parts of their bodies – the first recorded case of topical self-medication in animals.

BBut never before have scientists observed chimpanzees (or any other animal) essentially “treating” a wound or applying a different animal species to a wound.

IIn this sense, the observations are distinguished by what these chimpanzees do and how. What is commonly called “ointment”, the rubbing of a material, object or substance on a body surface, has been observed in many species.

Mmammals are particularly known to rub against trees and rocks or fruit and arthropods to pick up a particular scent, and birds have been seen to capture and rub centipedes on their plumage, likely to deter ticks.

IIn primates, the anointing behavior is also very common. It is not yet clear whether the chimpanzees in Rekambo actually rub insects. But since they only target open wounds, that suggests it could well be a medical procedure.

AND AFTER?

IIdentification and analysis of the insect species used by Rekambo chimpanzees will be key to revealing the purpose and effectiveness of this recently reported drug behavior. Perhaps the insects of Gabon will prove to have healing or anti-inflammatory properties, much like the plants used by orangutans.

FFinally, although the cultural diversity of chimpanzees is little disputed, the chimpanzees of Rekambo continue to stand out for their uniqueness. This begs the question, what else do these chimpanzees have in store for us?