National Geographic
Menu

Animal Pharm: What Can We Learn From Nature’s Self-Medicators?

Birds do it. Bees do it. Butterflies and chimpanzees do it. 

These animals and many others self-medicate, using plants and other surprising materials to improve not only their own health but also the health of their offspring.

Monarch butterflies picture

Monarch butterflies swarm a tree in Sierra Chincua, Mexico. Photograph by Joel Sartore, National Geographic

video of capuchin monkeys at the Edinburgh Zoo shows them rubbing onions and limes on their skin and into their fur as an antiseptic and insect repellent. Biologists have noticed that parasite-infected female monarch butterflies are more likely to lay their eggs on anti-parasitic milkweed, giving their offspring instant medication, while uninfected females show no preference. And urban birds who incorporate cigarette butts into their nests may be doing so because chemical properties in the smoked cigarettes may repel parasites, according to a 2012 study.

While cigarette-butt wallpaper may not appeal to most of us, other ways that animals self-medicate might be worth watching. Mark Hunter, a University of Michigan ecologist who was involved in the monarch research, says there is plenty to be learned from observing the way animals use the entire outdoors like one big drugstore. It’s something our own species probably once did—and might do well to revisit with modern pharmaceutical engineering and computer modeling techniques.

“It’s not the only way, but it seems to me that a sensible way [to aid in human drug development] would be to watch what animals do in nature to see how they exploit the natural products, the pharmaceuticals that are available to them in the environment, and try to learn from them,” he says.

Earlier this year, Hunter spent time with people of the Shangaan tribe in South Africa.

“If you go for a walk with somebody, every plant you pass has a cultural or medicinal significance, and many of those have been learned from watching animals,” Hunter says. The bark of the black monkey thorn tree, for example, is used as a stomach medication, a choice based on watching how elephants behave.

Diverse “Doctors”

Not long ago primates were thought to be the only animals smart enough to self-medicate. Mark Bowler, the San Diego Zoo Global Institute for Conservation Research postdoctoral fellow who made the capuchin video, says that chimpanzees use a range of medicinal plants, “including some that have a physical, not chemical action: They swallow wads of hairy leaves whole, and the leaf hairs appear to physically ‘brush’ certain parasites out of the gut. I tested some of this with Edinburgh Zoo’s chimps, and they seem to do it spontaneously—no learning process involved.”

The capuchins’ behavior in the video—rubbing the body with a particular chemical or scent—is called “anointing,” and other animals do it, too. Bowler is currently studying whether anointing behavior in some other primates is scent-marking or something else, but says that at least in capuchins, the purpose appears to be self-medication. Anointing can also be a form of self-defense: Ground squirrels chew rattlesnake skins and then lick their fur, a trick likely to deter that particular predator.

Insects have been found to be prolific self-medicators, too. Take the arresting case of the fruit fly Drosophilia melanogaster, which uses alcohol to protect itself against parasitic wasps. The wasps lay their eggs in the fruit fly larvae; the developing wasp grubs will eventually eat the flies from the inside out and burst forth from their dead bodies.

Larvae that consume high doses of alcohol from fermented fruits, however, are less likely to be infected—and if they are, the invading wasp grubs die quite nastily with their internal organs being ejected out of their anus. Moreover, fruit fly mothers who see female parasite wasps nearby will give their young instant protection by laying their eggs in alcohol-soaked environments—which means they see and remember their nemesis. (Related: “Flies Use Alcohol to Protect Their Young From Body Snatchers.”)

“Not a bad defense,” says Hunter, adding that this demonstrates the idea that “the cost we’re willing to pay for a medicine depends on the consequences of not using it.” While the alcohol isn’t necessarily good for the flies (though some species of Drosophilia melanogaster show a resistance to its ill effects), the flies will die if parasitized.

“The alcohol has worse effects on the parasites than it does on them. So it’s worth laying your eggs in a high-alcohol environment if it will save your offspring,” he says.

Bee Benefits

Honey bees self-medicate by protecting their home. The bees traditionally “line their nests with resins that they collect from plants, and those resins contain a wide variety of antimicrobial compounds,” Hunter says. The resulting mix of resins and beeswax is called propolis, and it’s been used as a traditional medication for centuries.

But because beekeepers didn’t want to deal with those sticky resins every time they opened a hive, Hunter says this resin deposition may have been selected out of most commercial bee populations over the years. After the bee genome was sequenced, scientists realized that bees have different immune systems than other insects—“probably because they’ve been relying on this resin,” says Hunter. Disease is one of the many suspected causes of bee die-offs, along with decreased plant diversity (and thus fewer places to get resins from) and pesticides, so encouraging propolis collection is probably a good idea.

Do animals learn to self-medicate, or is it pure instinct? Well, plenty of intelligent animals self-medicate, so it’s not always clear. But in the case of the monarch, Hunter points out, the mothers don’t hang around to see what happens to their babies, so there’s no learning involved. In this case, “the only possibility is that it’s a genetically determined behavior. It’s instinct.”

So the next time you’re on your way to the drugstore and pass a monarch hovering around a milkweed, or a bird who seems to have taken up a smoking habit, consider that they might actually be running an errand, just like you.

Follow Liz Langley on Facebook and Twitter.

Comments

  1. melissa Larson
    United States
    March 31, 7:39 pm

    Hello there Liz, great article! Im actually in a University class right now called Disease and Behavior, and I am very interested in writing my final paper on animal self-medicating practices. I was wondering if you had additional sources from this article that would be helpful in my research.
    Thankyou!

  2. Liz Langley
    October 22, 2013, 3:42 pm

    Very glad so many people connected with this piece – I learned a lot from it and think it’s going to make me take animal activity less for granted, to wonder if there’s more motive behind certain behaviors than I’d have previously thought.

  3. Liz Langley
    October 22, 2013, 3:06 pm

    @ragini thanks for sharing with your class, I hope your students enjoyed it!

  4. Dinesh Patel
    Canada
    October 16, 2013, 8:22 am

    Necessity is mother of invention is proved here.

  5. Ankita Roy
    India
    October 16, 2013, 6:12 am

    Nice! very interesting

  6. Mitch Ward
    October 16, 2013, 4:19 am

    Fantastic if we could just stop and observe nature we could all as humans really learn.

  7. ragini
    Guragon,India
    October 16, 2013, 3:09 am

    Truly enjoyed … being a science teacher m looking forward to share it wid my kids tomorrow
    thanks

  8. Leenoh
    October 16, 2013, 2:44 am

    We could learn something not selfish from any nature things. It is so gentle and nice~^^

  9. enkidu
    US
    October 15, 2013, 8:35 pm

    http://www.firstpeople.us/FP-Html-Legends/Origin-Of-Disease-And-Medicine-Cherokee.html

    “When the plants, who were friendly to Man, heard what had been done by the animals, they determined to defeat the latter’s evil designs. Each Tree, Shrub and Herb, down to even the Grasses and Mosses, agreed to furnish a cure for each one of the diseases named, and each said: “I shall appear to help Man when he calls upon me in his need.” Thus came medicine; and the plants, every one of which has its use if we only knew it, furnish the remedy to counteract the evil wrought by the revengeful animals. Even weeds were made for some good purpose, which we must find out for ourselves. When the doctor does not know what medicine to use for a sick man the spirit of the plant tells him”

  10. Ghazaleh
    Minneapolis, USA
    October 15, 2013, 4:43 pm

    Animal instincts are behaviors that have been naturally included with the animal since its’ birth. Often times these instincts are used for survival. Amazing.

  11. KEITH LITTLE
    Westerville, ohio
    October 15, 2013, 1:15 pm

    I would like to add that the scientific community needs to get out of the academic rut of “door number one “instinct or “door number two “learned behavior.” There has to be another cause or many causes unknown to us that make these fellow Earth inhabitants behave they way they do. I’ve seen spider’s build webs near lights to catch the bugs that are its prey. Since the artificial light was developed by mankind this could not be anything less than reasoning by the spider and had to take place after 1879 when the incandescent light began to become wide spread. So I say to the scientific world to please think out of the deep pit that you’ve dug yourselves in and look for another answer or answers to this magnificent world’s creatures behaviors.

  12. KEITH LITTLE
    Westerville, ohio
    October 15, 2013, 1:13 pm

    I would like to add that the scientific community needs to get out of the intellectual rut of “door number one “instinct or “door number two “learned behavior.” There has to be another cause or many causes unknown to us that make these fellow Earth inhabitants behave they way they do. I’ve seen spider’s build webs near lights to catch the bugs that are its prey. Since the artificial light was developed by mankind this could not be anything less than reasoning by the spider and had to take place after 1879 when the incandescent light began to become wide spread. So I say to the scientific world to please think out of the deep pit that you’ve dug yourselves in and look for another answer or answers to this magnificent world’s creatures behaviors.

  13. Susan Welsh
    California
    October 15, 2013, 11:44 am

    Mother nature is the most incredible and smartest thing I know and I will follow her anywhere and everywhere. Great article. I love it.

  14. jacinta cabrera
    venezuela
    October 15, 2013, 7:35 am

    cut super bella esta foto

  15. Bipul Saha
    Kolkata. India
    October 15, 2013, 1:13 am

    Very interesting topics, not heard about it earlier. Thanks for the post. Would further follow.

  16. OHTSUKA Tadashi
    Japan
    October 15, 2013, 1:02 am

    How smart these animals are!

  17. Jackie
    United States
    October 15, 2013, 12:42 am

    Since animals are unable to shop in pharmacies for their medicinal needs, they are the ultimate consumers of natural medicines.

  18. Bells
    Australia
    October 14, 2013, 7:29 pm

    I enjoyed this write up. Very interesting.

  19. El Gabilon
    October 8, 2013, 7:22 pm

    Whoever or whatever set this universe in motion is one smart entity. Whether or not the medicinal use of plants etc. by animals other than our own species is genetic or learned it is an indication that IT expected illness to be a problem and provided for it. Is “pot” “grass” “maryjane” a medication provided for medicinal use by humans? Which poses another question…are drugs derived from plants more effective than drugs developed from man made compounds that do not involve natural ingredients?
    In the scientific world there is much to learn, we only hope that what we need to learn comes before we destroy ourselves. Some readers of our comments may think we are anti-science which is not the case. Rather, we believe that science must be controlled to prevent mishaps, some scientists should lose their inflated egos, and ideological beliefs not be allowed to interfere with human progress. The clock is ticking and time waits for nothing.

  20. doudou
    mauritania
    October 8, 2013, 5:10 am

    Realy we human being we are nothing and we have to learn from all animals.Look at this bird who knows about nicotine and other propeties of cigarettes.Thank you mister Hunter and N G

  21. Ima Ryma
    October 8, 2013, 2:52 am

    The honey bees are in decline,
    The reasons varied probably.
    It’s now known that honeybees line
    Nests with resins protectively.
    Antimicrobial compounds
    Collected from all kinds of plants.
    Beekeepers, in making hive rounds,
    Deemed resins sticky disenchants,
    And so found ways and means to rid
    The hives of resins that well could
    Be why honey bees did in did.
    Let the resins be for bee good.

    Beekeepers, leave bee resins, please,
    For more daughters and sons of bees.