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Why Butterflies, Bees Drink Crocodile Tears

Last December, passengers on a boat trip down Costa Rica‘s Puerto Viejo River were treated to a strange sight: a butterfly and a bee drinking the tears from a crocodile’s eyes.

The encounter between the insects, a Julia butterfly (Dryas iulia) and a bee (Centris sp.), and the spectacled caiman (Caiman crocodilus) lasted more than 15 minutes, as the reptile placidly permitted the insects to sip from its eyes as it basked on a log. (Also see “Crocodiles Really Shed Tears While Eating, Study Says.”)

Photo of a caiman with a bee and a butterfly.
A Julia butterfly and a bee drink the tears of a spectacled caiman in northeastern Costa Rica’s Puerto Viejo River in 2013. Photograph by Carlos de la Rosa, Organization for Tropical Studies

Carlos de la Rosa, an aquatic ecologist and director of the La Selva Biological Station in San Pedro, Costa Rica, led the group and photographed the occurrence. He reported his observations in a peer-reviewed letter in the May edition of Frontiers in Ecology and the Environment.

The chance encounter yielded a remarkable photograph. It also raised questions about “tear-feeding,” a phenomenon otherwise known as lachryphagy, which has been well documented but remains poorly understood.

Why Feed on Tears?

A number of insect species including moths, butterflies, and bees are known to tear-feed, usually on mammals and in some cases even humans.

Tear-feeding on reptiles is less well documented, but in every case the insect seems to be in pursuit of nutrients and minerals—chiefly salt. (See more butterfly pictures.)

“Sodium and some of those other micronutrients are hard to find in nature,” said de la Rosa. “Butterflies and bees consume nectar, and nectar does not have a lot of salt. But they still need salt for egg production and for their metabolism.”


Watch a video of the incident in Costa Rica.

To scavenge the vital mineral, insects look for tears, sweat, feces, urine, and—among hematophagous insects like mosquitos—blood. Those that drink tears are referred to as “lacryphagous,” from lacrima, the Latin word for “tear.” (See “Mouse Tears Are Aphrodisiacs.”)

A similar, and better studied, insect behavior that seems to serve a similar purpose is called “mud-puddling.” Butterflies and other species that employ this strategy will congregate around and drink from puddles containing mineral deposits.

“You see the butterflies down on the [ground], and they drink water, usually to gain salt,” explained Jérôme Casas, an ecology professor at the University of Tours in France. “[The] salt [is] either used for biological purposes or it’s transmitted through the sperm as a gift to the female. So it’s really a valuable item.”

Benefits and Amenities

Whether tear-feeding behavior can be deemed symbiotic depends on your definition. Does symbiosis require mutualism, in which both animals benefit? Or merely a relationship between two organisms in which at least one benefits?

De la Rosa subscribes to the latter definition. While there’s no clear benefit to the animals providing the tears, he says, the behavior doesn’t seem to hurt them either. According to de la Rosa, some species are less bothered by tear-drinkers than others.

“From my few observations, the caimans don’t seem to be bothered at all by all this attention. The river turtles, however, are less tolerant to the bees buzzing close to their eyes. I’ve seen them shaking their heads at the bees and eventually even jumping back in the water.”

Casas speculates that crocodiles and turtles—along with large mammals like cows—are likely targeted by salt-seeking insects due to their placid nature. (See National Geographic’s pictures of alligators and crocodiles.)

“Crocodiles and turtles are very stationary,” he said. “When they sit somewhere, they sit for hours.”

De la Rosa estimates he’s seen the phenomenon at least four or five times in the past two years.

But, he says, it’s hard to quantify how common tear-feeding behavior really is, because it’s so ephemeral. And it would be harder still to reproduce such spontaneous interactions in a lab setting. Yet a wealth of photographic evidence suggests that the phenomenon could be fairly common.

In 2009, Casas and his colleague Olivier Dangles observed a bee drinking the tears of a yellow-spotted river turtle in Yasuní National Park, in the Ecuadorian Amazon. They documented their observations in Frontiers in Ecology and the Environment in 2012.

Casas says the phenomenon could help shed light on “the surprising world of insect-vertebrate interactions. We always think about mosquitos biting us, but there is way more than [that].”

A Closer Look

How important is such behavior to a given ecosystem?

“That’s one of the bigger questions,” said de la Rosa. “We don’t know how essential these relationships are to the survival of those species. It could be that it’s just an occasional, fortuitous, or opportunistic source of salt. Or it could be absolutely essential.”

To find the answer, de la Rosa and Casas both stressed the importance of  traditional field research—without which such serendipitous observations wouldn’t be possible—in a world of increasingly computerized research methods.

“The scientific community has drifted very strongly toward high-tech types of studies [like] genomics,” said de la Rosa.

“And natural history itself, which is simple observations of events and phenomena in nature, has [been on the decline]. I’m all for technology, but it doesn’t replace the observations of phenomena in the field.”

Follow Stefan Sirucek on Twitter.

Comments

  1. Nat Turner
    May 17, 4:43 am

    This is an interesting article and concept,
    in my mind it should be linked to another recent piece I’ve just read.
    Aside from the crocodile being a source for tear feeders, noted is also turtles, mammals including cows and even humans
    One must also consider the benefits for the drinkers as alluded to in terms of, yes, the salts, but also other nutrients and minerals, and what these may be used for in a metabolic sense and the “really … valuable item” in egg production .
    it cannot be for all the eggs as the volume would be too great and involve much more tear feeding than is assumed to take place, is it for a particular class of egg / offspring ?
    How many millions of years has this been going on would be interesting to note.
    What I have found lately in a study about the tears of humans is that according to the emotion we are experiencing at the time, so is our tear composed vis. it’s composition of varying nutrients etc “All tears contain organic substances including oils, antibodies, and enzymes and are suspended in salt water. Different types of tears have distinct molecules. Emotional tears have protein-based hormones including the neurotransmitter leucine enkephalin, which is a natural painkiller that is released when we are stressed.” The article goes on to make further interesting findings known.
    So I beg the question is the crocodile, turtle, cow etc tears also changed according to it’s current emotion ?
    Should one wish to deny them emotions because they are animals, then think in terms of rest mode, pain, fear etc.

    Article
    http://www.the-open-mind.com/looking-at-tears-under-a-microscope-reveals-an-amazing-fact/

  2. Bill Grenoble
    Accokeek Maryland
    May 15, 4:07 pm

    There was a lot of loose talk about crocodile tears, but the ugly reptile is a Caiman, not a crocodile. The Caiman belongs in the alligator family and never the croc’s relatives.
    Someone commented that the butterfly is really a humming bird. Does National Geographic have any expert on that?

  3. wayne roberts
    toronto canada
    May 15, 10:54 am

    This provides almost a spiritual sense of how symbiosis works in nature. Makes me wonder if we should place a little salt in our garden plants designed to host butterflies.
    It is tragic that scientists working on pesticides aren’t required to study the science of ecology and learn about how symbiosis works.
    One of the tragedies of cheap food, which I outline in The No-Nonsense Guide to World Food, is that we dirty the nest we eat in; our pesticides kill pollinating insects (the good insects,so-called), which are no longer available to perform a critical function in nature and the seeding bed of agriculture.
    Thanks for this lovely story.

  4. Kamel
    Abu Dhabi
    May 15, 3:17 am

    Nice article Stefan. Three short comments: 1- No matter how small or big, all the creatures have a positive role to play in this world. 2- There are lot of lessons to learn and mimic from observing the behaviour of any creature. 3- More importantly is to be thankful to the great creator who provided us with the observations and analysis skills.

  5. janey kelf
    Sydney Australia
    May 15, 1:37 am

    Amazing closest I have seen to this is bees drunk on nectar
    colapsing in a stupor

  6. krishna
    India
    May 14, 11:36 pm

    First of all Great Pics!!! The natures rules and the way things are placed is just amazing. Butterflies and Bees finding salt in the tears of a croc??? Keep up this good job stefan.. more stories of such sorts are of great interest..

  7. NatGeo4Life
    May 14, 9:57 pm

    this a bit off topic but…I once saved a bees life twice in 30 minutes. it first landed on my kitchen table dragging it’s little body until it completely stopped and laid on it’s side. I thought it was dead, then I touched it with a straw and nothing. after a minute I touched it again and it moved. with the straw I put a drop of water next to the bee and I watched it move towards it. sure enough it began drinking. several minutes passed and the bee still seemed out of it. then I gave it a drop of fruit juice and it began drinking it very quickly. after several minutes it completely revived and began buzzing and flying around my kitchen looking for an exit. it ended up getting caught in a cob wed. then I said, “oh bee, why you do this to me?” somehow I managed to untangle it from that thick, old cobweb and it flew out the window. I still think about that bee and wonder if it lived a full life.

  8. Jared Kelley
    May 14, 12:43 pm

    That is very clearly a hummingbird (Trochilidae) , not a bee. HAHA. What a joke NG.

  9. Adedotun Ajibade
    Nigeria
    May 12, 7:22 pm

    An educative article! I look forward to observing something like this. For now, it’s only the mud- and fruit-puddling butterflies of which I have had the privilege to make photographic collection.
    Here a few of my shots >>
    http://yourshot.nationalgeographic.com/photos/3603875/
    http://yourshot.nationalgeographic.com/photos/3126539/
    http://yourshot.nationalgeographic.com/photos/3126194/

  10. Dipanjan Mitra
    India
    May 10, 8:42 am

    The biggest mistake of human civilization has been to try and understand NATURE !! Nature is way too intense for man to fathom.

  11. kaa s gyoh
    nigeria
    May 10, 3:56 am

    Helo people.rewarding photo.I’ve often observed some insects especially flies apparently consuming in some way discharge from the eyes of a number of animals like crocs horses and particularly dogs and cattle. k9s sometimes discharge a fluid that soon becomes snot like and tho he’s less tolerant than the bovine,the flies r relentless.it makes sense that they’re after minerals tho I doubt they r concious of that fact,but my impression is that they also benefit since the discharge could impair optimum vision plus its sticky and may sometimes be irritating and itchy as is evident from the relief and gratitude dogs and cattle exhibit when one gentle cleans and scraches their eyes with a finger

  12. Jong
    Philippines
    May 9, 7:19 pm

    Few days ago I just woke up in the morning and had a sty on my right eye. I knew instantly that some insect bit me in the eye and I am asking myself why my eye when my arms and legs are more exposed to them. And then I saw this article…

  13. Lari Issakainen
    Finland
    May 9, 6:27 pm

    I used to had banana fly problem in my home and i noticed when i was sweating and dirty they keep coming to walk in my skin.It was annoying so i take shower and after that they did not wanted me at all.Now i know why thanks! :) All They wanted was nutritious dirty sweat!

  14. Paul Wilkinson
    United Kingdom
    May 9, 4:36 pm

    I got a similar photo a few years ago but butterflies on both eyes… http://yourshot.nationalgeographic.com/photos/230566/

    • Stefan Sirucek
      May 9, 5:16 pm

      That photo is fantastic! The upturned eyes, the smile on its face…and the butterflies almost look like a bow. Hope you got some recognition for this. Thanks Paul!

  15. Ricky Dewet
    South Africa _ Gauteng
    May 9, 1:45 pm

    This is abosolutely the fine Balance of ou Creator! Makes me love HiM SOooo much! Thankyou for excellent info! Beautiful!

  16. Sohail Khan
    srinagar Kashmir India
    May 9, 1:07 pm

    Its the flawless mechanism of God Almighty. HE shows us signs through these beautiful connections, But most of us not understand. Analysing the photo I have come to this conclusion, that tears have toxics and harmful nutrients which might be disastrous for Crocodile’s vision but beneficial for flying insects (bees and butterflies) in order to balance their existence in nature.

  17. Ima Ryma
    May 9, 12:56 pm

    I am just sitting on a log.
    A butterfly and a bee land.
    Beneath each of my eyes they clog
    A little space – I understand.
    Some humans come by in a boat,
    And watch the three of us a while.
    The bugs do drink, the humans note,
    From the eyes of this crocodile.
    The humans are without a clue,
    That for their eggs bugs do need salt.
    The nectar from flowers won’t do,
    So bugs come to me by default.

    It’s not as strange as it appears,
    Some bugs drinking crocodile tears.

    • Stefan Sirucek
      May 9, 1:54 pm

      A very nice poem :)

  18. Ejaz
    pakistan
    May 9, 3:00 am

    I’ve noticed ants drinking water from dishwasher spills in my kitchen. May be they don’t know that water doesn’t have minerals for them.

    • Stefan Sirucek
      May 9, 1:54 pm

      Water is important no matter what!

  19. Doggale Augustino
    Juba, south sudan
    May 9, 2:59 am

    i been seen butterflies nave been attracted to flowers and other rotting things because of sugar and alcohol

  20. Jacob Pilich
    Canada
    May 9, 1:40 am

    This is a similar behaviour to ants and aphids. The aphids provide the ants with sugar, so they defend and use the aphids. The crocodile uses the insects to clear out its retinal fluids… thus making it flush out more hence helping it clean out its mucus glands. makes sense to me.

    Have you had your eyes tear up when something gets in them?

  21. Heather
    May 9, 12:01 am

    I’m curious to know what type of bee that is because it is HUGE!!

    • Stefan Sirucek
      May 9, 1:58 pm

      Hi heather, yeah the bee is called Centris sp. and is quite big! The second scientist I interviewed observed the same species of beer drinking tears from a river turtle and estimated that the bee was several inches long.

  22. Tanmoy Das
    Vadodara, gujarat, india.
    May 8, 11:28 pm

    Wonderful article. Very informative. Thanks Stefan for such a lovely write. Keep illuminating us. God bless.

  23. KURT ROZE LIRIANO
    united states
    May 8, 10:16 pm

    There is an ancient mayan legend that speaks of four crocodiles that mysteriously came into existence to support the entire earth. They were able to keep it’s delicate balance in-tact by using the strength of their backs and the power of their determination. There may not be much information into why exactly this happens, or of which animal may benefit, but I believe it is a beautiful. Thanks for sharing.

    • Stefan Sirucek
      May 9, 1:59 pm

      Very interesting…These crocs and caimains certainly seem to be helping out the local insects. Thanks Kurt!

  24. Crystal
    Chouteau, OK
    May 8, 9:26 pm

    Hi Robert, My understanding for why butterflies eat rotting fruit is to obtain the carbs that are released. Such as those in old bananas

  25. Stefan Sirucek
    May 8, 1:42 pm

    Hi Robert. I think it’s more likely that butterflies flocking towards old fruit are looking for sugar. There’s been some evidence that the alcohol in fermenting fruit can cause fruit flies to get drunk so perhaps the butterflies are looking for a buzz!

  26. Kelly Clark
    May 8, 9:27 am

    Actually any long-relationship between two organisms is a form of symbiosis. In this case, since only the butterflies or bees are benefiting and are likely doing no harm to the caiman, this would be a form of commensalism, not mutualism.

    • Stefan Sirucek
      May 8, 2:04 pm

      Thanks Kelly. My understanding is that there’s some debate in the scientific community regarding the exact definition of symbiosis and whether it extends past mutualisms to commensalistic relationship like you mention. The biologist who took the photo certainly agrees with that definition and if you’re a science professional I’d be curious to hear whether this is now the generally accepted view. Thanks again!

  27. Robert C Brooke
    May 7, 5:40 pm

    I’ve seen butterflies attracted to rotting fruit. Would this be in search of minerals? has anyone else reported seeing butterflies feeding on fruit?