BBC Science Focus - 03.2020

Q&A

DO ANIMALS USE MEDICINE?

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CROWDSCIENCE

There’s growing evidence that animals are

able to ‘self-medicate’ using a variety of

plants and insects. Chimpanzees, for

example, have been observed swallowing

whole the rough leaves fromAspiliaplants.

These leaves are believed to brush

parasitic worms from their gut wall, so that

they can poo the worms out of their body.

Meanwhile, more than 200 species of bird

have been observed ‘anting’, where the

birds rub ants along their feathers, or roll in

ant nests. This could be another form of

parasite control – the birds mostly use ant

species that spray toxic formic acid. There’s

even evidence that African elephants

self-medicate, eating a plant from

the borage family in order to help

induce labour.

WHAT KINDS OF MEDICINE DO ANIMALS USE?

As with every evolved trait, it’s down to
natural selection. An animal that comes
across a new behaviour that’s beneficial in
some way is more likely to survive and pass
that behaviour on to its offspring. A nice
example of this comes from monarch
butterflies, the caterpillars of which only feed
on milkweed plants. Monarch butterflies are
often infected with deadly parasites, and
infected female monarchs tend to lay eggs
on milkweed species that have higher
concentrations of parasite-killing chemicals
called ‘cardenolides’. Prof Jaap de Roode of
Emory University in Atlanta, US, has shown
that this can reduce levels of infection in the
butterflies’ caterpillars, and that uninfected
monarch butterflies don’t show the same
milkweed preference.

HOW DOES MEDICINE

USE E VOLV E?

Myths and folklore often cite animals as the

source of medical knowledge, and today’s

pharmacologists are increasingly looking to

self-medicating animals for inspiration. The

Aspiliaplants used by chimps to flush out

parasites have also been found to have

antibacterial properties, so compounds

extracted from these plants could help to

treat infected wounds. Orangutans in

Indonesia have been observed rubbing a

foamy mixture of saliva and leaves from

another plant,Dracaena cantleyi, on their

body, and local indigenous people use this

plant in a similar way to relieve joint and

muscle pain. Scientific analysis of this plant

has since shown that it does indeed have

anti-inflammatory properties. The natural

world, it seems, is full of healing

compounds, and animals can help to point

us in the right direction.

WHAT CAN ANIMALS TEACH US ABOUT MEDICINE?

Rory Gallowayis the producer ofHow did humans discover medicine?

• an episode ofCrowdSciencethat can be streamed at:
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