Zoopharmacognosy: Nature's Pharmacy (#743)

From elephants and chimpanzees to macaws and monarch butterflies.

Did animals discover medicine long before humans did?

Imagine an elephant walking through an African forest. She is surrounded by hundreds of species of plants, many of which she could eat. Yet she deliberately selects the leaves of one plant, ignores the others and carries them back to her calf.

Is she simply collecting food? Or does she know something about the medicinal properties of that plant?

Now imagine hundreds of brilliantly colored macaws gathering along a riverbank in the Amazon rainforest. They are not there to drink or search for fruit. They are eating clay.

Or consider a female monarch butterfly selecting a particular species of milkweed on which to lay her eggs, potentially protecting her offspring from parasites.

These apparently unrelated behaviors introduce us to the fascinating world of zoopharmacognosy:

The study of how animals use naturally occurring substances to prevent or treat illness.

The word comes from three Greek roots: zoo, meaning animal; pharmakon, meaning drug or medicine; and gnosis, meaning knowledge.

Literally, it means animals' knowledge of medicine.

But do animals really understand medicine? Or have millions of years of evolution produced behaviors that accomplish much the same thing without conscious understanding?

The distinction is fascinating.

And the more we investigate it, the more we discover that nature's pharmacy has some extraordinary customers.

Elephants: The Forest Pharmacists

A recently reported study of African elephants living around Mount Elgon, on the border between Kenya and Uganda, provides an intriguing example.

Rather than relying exclusively on direct observations of elephants, researchers interviewed local people with extensive experience of the animals and their environment, including wildlife scouts, rangers and community elders.

They documented accounts of elephants consuming nearly 40 different plants and other natural materials that might have medicinal or nutritional properties.

The most intriguing observations concerned elephant mothers.

Local observers reported female elephants mixing plants with their milk before administering the mixture to their calves. They interpreted this behavior as a possible form of immunization.

Other accounts described elephants consuming plants associated with improved digestion, increased appetite or softer stools.

If confirmed, these behaviors would have remarkable implications.

An elephant selecting a plant when she is ill is one thing. An elephant selecting and preparing a medicinal substance for her offspring is quite another.

The latter possibility introduces the concept of allo-medication:

Providing medicinal substances to another individual.

However, an important scientific distinction must be made. The reported observations do not establish that the plants prevent or treat disease, nor do they demonstrate that elephants consciously understand their medicinal properties.

Controlled studies and prolonged behavioral observations would be required to establish those conclusions.

Nevertheless, the findings raise an intriguing question.

Could elephants possess medicinal knowledge that is transmitted between generations?

Elephants have extraordinarily complex social lives. They maintain long-lasting family relationships, demonstrate sophisticated social learning and possess remarkable memories.

Young elephants spend years observing their mothers and other experienced females.

During this prolonged period, they learn where to find food and water, how to navigate their environment and how to respond to danger.

Might they also learn which plants to consume when they are unwell?

If so, the loss of an experienced elephant matriarch might mean more than the disappearance of an important family member.

It could also represent the loss of accumulated ecological knowledge.

Chimpanzees: Medicine Among Our Closest Relatives

Some of the most extensively studied examples of animal self-medication involve chimpanzees.

Researchers have observed chimpanzees swallowing rough, hairy leaves, sometimes without chewing them.

These leaves pass through the digestive tract relatively intact. Their abrasive surfaces appear to help dislodge intestinal parasites, which are subsequently expelled in the feces.

Chimpanzees have also been observed consuming the bitter pith of plants containing biologically active compounds.

What makes these observations especially interesting is that some of these plants are not ordinarily preferred foods.

The animals sometimes consume them infrequently and in unusual ways, particularly when showing signs of illness.

Researchers have also documented chimpanzees applying insects to wounds, although whether the insects possess medicinal properties remains uncertain.

These observations raise an evolutionary question.

Did our ancestors discover medicinal plants independently, or did they inherit certain predispositions toward self-medication from ancestors shared with other primates?

Perhaps the origins of medicine are considerably older than humanity itself.

Orangutans: A Botanical Wound Dressing

In 2024, researchers studying wild Sumatran orangutans in Indonesia reported an extraordinary observation.

An adult male orangutan named Rakus sustained a facial injury, apparently during a fight with another male.

Three days later, researchers observed him selectively collecting leaves from a climbing plant known locally as Akar Kuning (Fibraurea tinctoria).

He chewed the leaves and repeatedly applied the resulting juice directly to his wound.

He then covered the injury with the chewed plant material.

The plant contains compounds with documented biological activities, including antibacterial and anti-inflammatory effects.

His wound subsequently healed.

The observation was particularly significant because Rakus appeared to select the plant, prepare it and apply it directly to the affected area.

The researchers described it as the first systematically documented example of a wild animal actively treating a wound with a plant known to contain biologically active substances.

One observation cannot establish that the plant caused the wound to heal. Nor can it demonstrate whether Rakus understood its medicinal properties.

Nevertheless, it provides a remarkable example of behavior consistent with deliberate self-medication.

It is difficult not to be impressed by an orangutan apparently preparing his own botanical wound dressing.

Macaws: The Amazon's Clay Pharmacies

Deep in the Amazon rainforest, hundreds of brilliantly colored macaws gather along exposed riverbanks.

Their destination is neither a fruiting tree nor a source of drinking water.

It is a wall of clay.

These gathering places, known as clay licks, are among the most spectacular wildlife sights in South America.

But why would birds deliberately eat soil?

For many years, scientists proposed that clay acts as a natural detoxifying agent.

Macaws consume seeds and other plant materials containing potentially harmful chemical compounds. Certain clays can bind some of these substances, potentially reducing their absorption during digestion.

Subsequent research revealed another important explanation.

Some Amazonian clay deposits contain relatively high concentrations of sodium, an essential mineral that can be scarce in the birds' predominantly plant-based diets.

Today, mineral supplementation is considered an important explanation for clay consumption, although detoxification may also contribute under certain circumstances.

This behavior, known as geophagy, introduces an important distinction.

Not every behavior that improves an animal's health necessarily qualifies as self-medication.

Macaws may be visiting nature's pharmacy, but they may also be visiting its mineral supplement department!

Interestingly, elephants also consume soils and clays.

These similarities illustrate how unrelated species may develop comparable strategies for obtaining essential substances from their environments.

Monarch Butterflies: Medicine for the Next Generation

Monarch butterflies provide one of the most fascinating examples of possible preventive medicine.

Their caterpillars feed on milkweed plants containing compounds called cardenolides.

These compounds can protect caterpillars against certain predators, but they may also influence infections caused by protozoan parasites.

Researchers have demonstrated that female monarch butterflies infected with parasites preferentially lay their eggs on milkweed species that can reduce parasite development in their offspring.

The remarkable feature is that the mother does not necessarily benefit directly from this behavior.

Instead, she selects a plant that may improve the health of her developing young.

Scientists describe this phenomenon as transgenerational medication.

Unlike an elephant mother potentially teaching her calf about medicinal plants, the monarch's behavior may be largely inherited rather than learned.

Two very different evolutionary pathways may therefore produce behaviors with remarkably similar consequences.

One may involve sophisticated social learning.

The other may be an instinctive response shaped by natural selection.

Both can potentially improve the health of the next generation.

European Starlings: A Medicinal Nursery?

Some birds incorporate fresh aromatic vegetation into their nests.

European starlings, for example, collect green plants during the breeding season and place them among their nesting materials.

Why?

One hypothesis is that these plants release volatile compounds that repel parasites or inhibit microbial growth.

Experimental studies have produced mixed results, although some have demonstrated benefits for nestling development or health.

The behavior raises questions like those surrounding monarch butterflies.

Could an animal provide health benefits to its offspring without possessing any conscious understanding of medicine?

The answer may lie in natural selection.

Over thousands of generations, individuals that incorporated beneficial plants into their nests may have produced healthier offspring.

Consequently, the behavior could become established without requiring the birds to understand the plants' pharmacological properties.

In this case, the pharmacy is incorporated directly into the nursery.

Dolphins: An Underwater Pharmacy

Even marine mammals exhibit behaviors that suggest possible self-medication.

Researchers studying Indo-Pacific bottlenose dolphins in the Red Sea observed them deliberately rubbing their bodies against corals and marine sponges.

The dolphins appeared selective, repeatedly visiting certain species rather than rubbing indiscriminately against available surfaces.

Some of these marine organisms contain biologically active compounds, including substances with antimicrobial properties.

Researchers have proposed that rubbing against them may help dolphins maintain healthy skin or treat skin infections.

However, the medicinal benefits have not been experimentally established.

The behavior nevertheless provides a fascinating example of animals potentially obtaining useful chemical substances from organisms in their environment.

Nature's pharmacy, it seems, has an underwater department.

Bears: Scratching an Itch or Treating Parasites?

Bears frequently rub against trees, sometimes returning repeatedly to locations.

The behavior is primarily associated with scent marking and communication.

However, rubbing may also help remove external parasites or provide relief from irritating insects.

There is insufficient evidence to classify ordinary tree rubbing as deliberate medicinal behavior.

Nevertheless, it illustrates the difficulty scientists face when investigating zoopharmacognosy.

An animal may engage in a behavior for several reasons simultaneously.

A bear rubbing against a tree may be communicating with other bears, removing irritating insects or simply enjoying a good scratch.

Determining whether a behavior is genuinely medicinal requires evidence that it produces a health benefit and is associated with preventing or treating a particular condition.

Insects: Medicine Without a Medical Degree

Perhaps the most surprising examples of zoopharmacognosy come from insects.

Certain species alter their feeding or reproductive behavior when infected with parasites.

Some caterpillars increase their consumption of plant compounds when parasitized.

Other insects preferentially select substances that reduce parasite development or improve the survival of their offspring.

Social insects provide additional examples.

Honeybees collect plant resins and incorporate them into their hives as propolis.

Propolis possesses antimicrobial properties and contributes to the colony's defence against certain pathogens.

Unlike an individual chimpanzee selecting a medicinal plant, honeybees demonstrate a form of collective disease defence.

The colony benefits from the behavior of individual workers.

This raises an intriguing question.

Does medicine require intelligence?

Apparently not.

Natural selection can favor behaviors that improve survival and reproduction without requiring animals to understand the mechanisms involved.

A honeybee does not need to understand microbiology to benefit from antimicrobial plant resins.

Indigenous Knowledge: Learning From Those Who Observe

There is another important dimension to the Kenyan elephant research.

The scientists did not identify these possible medicinal behaviors simply by following elephants through the forest.

They learned about them by listening to people who had been observing elephants for decades.

Local communities possess extensive knowledge of their environments, including the traditional medicinal uses of plants.

The researchers discovered considerable overlap between plants considered medicinal by local people and plants reportedly selected by elephants.

Some observers also described how people had learned about potentially useful plants by watching elephants.

This introduces an intriguing possibility.

Humans may have acquired some botanical knowledge by observing other animals.

However, plants beneficial to elephants are not necessarily safe for humans. Differences in physiology, metabolism and dosage make such assumptions potentially dangerous.

The broader lesson is that Indigenous ecological knowledge and modern scientific investigation can complement one another.

Traditional observations can identify biological relationships that researchers might otherwise overlook.

Scientific investigation can then test those observations and explore their underlying mechanisms.

Both forms of knowledge have important contributions to make.

From Forest Pharmacy to Modern Pharmacology

Modern medicine already owes an enormous debt to the natural world.

Aspirin originated from investigations of compounds associated with willow and other plants.

Digitalis, used in treating certain cardiac conditions, was developed from compounds found in foxgloves.

Many antibiotics and other important medicines originated from naturally occurring substances.

Could observing animals identify additional pharmacologically active plants?

Quite possibly.

But there is an important difference between identifying a plant that an animal consumes and establishing that it contains a useful medicine.

Scientists must determine whether the plant has genuine therapeutic activity, identify its active compounds, establish appropriate dosages and investigate possible toxicity.

Animal behavior can provide clues, but it cannot replace pharmacological research.

There is also an ethical consideration.

The discovery of potentially valuable medicinal plants must not become another justification for exploiting vulnerable wildlife populations or appropriating Indigenous knowledge without recognition and appropriate benefit-sharing.

The animals and communities contributing to these discoveries deserve protection and respect.

Biodiversity: Protecting Nature's Pharmacy

Perhaps the most important implication of zoopharmacognosy concerns biodiversity conservation.

We generally think about habitat destruction in terms of lost food, shelter and breeding opportunities.

But what if destroying a forest also destroys an animal's pharmacy?

An elephant might survive the disappearance of one food plant by consuming another.

It might not be so easy to replace a plant possessing particular medicinal properties.

Similarly, the disappearance of milkweed species could influence the relationship between monarch butterflies and their parasites.

The destruction of coral reefs might eliminate organisms that dolphins potentially use for maintaining healthy skin.

Furthermore, if medicinal knowledge is socially transmitted, the consequences of losing experienced individuals could extend beyond the loss of reproductive capacity or social stability.

Their deaths might also mean the disappearance of accumulated ecological knowledge.

These possibilities offer another reason to protect complete ecosystems rather than concentrating exclusively on charismatic animal species.

Protecting elephants means protecting the plants, soils, minerals and ecological relationships upon which their lives may depend.

Protecting macaws means conserving the mineral-rich riverbanks and surrounding forests that sustain them.

Protecting monarch butterflies means preserving the diversity of milkweed species and the ecological relationships associated with them.

Conservation is not simply about protecting individual species.

It is about preserving the complex biological relationships that make life possible.

Who Discovered Medicine?

The ancient Roman author Claudius Aelianus wrote about an elephant that reportedly recovered from wounds inflicted by spears and arrows after consuming olive flowers and oil.

His account, written approximately eighteen centuries ago, is not scientific evidence.

But it demonstrates that humans have long wondered whether animals possess medicinal knowledge.

Modern zoopharmacognosy is beginning to transform that ancient curiosity into a serious scientific discipline.

The challenge is to distinguish genuine therapeutic behavior from coincidence, ordinary feeding and instinctive responses that happen to provide health benefits.

It is equally important to resist the temptation to attribute human reasoning to animals without sufficient evidence.

Yet we should not underestimate them either.

Consider the remarkable diversity of behaviors we have examined.

An elephant mother reportedly prepares plants for her calf.

A chimpanzee ingests rough leaves that may help expel intestinal parasites.

An orangutan prepares and applies a botanical dressing to a facial wound.

A macaw consumes mineral-rich clay.

A monarch butterfly selects milkweed that may protect her offspring from parasites.

A starling incorporates aromatic vegetation into its nest.

A dolphin rubs against selected corals.

And a honeybee collects antimicrobial plant resins to protect its colony.

These animals differ enormously in their anatomy, physiology, intelligence and evolutionary histories.

Yet each demonstrates a relationship with its environment that may contribute to maintaining health.

Some behaviors may be inherited. Others may be learned. Some may involve sophisticated decision-making, while others may be simple physiological responses shaped by natural selection.

What unites them is the possibility that the natural world provides far more than food and shelter.

It may also provide the means to prevent and treat disease.

Perhaps the most interesting question is not whether animals practise medicine exactly as humans do.

It is whether humans have been too quick to assume that medicine is exclusively our invention.

The forest was a pharmacy long before anyone built a hospital.

We are only beginning to understand who its customers might be.

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