Mutualistic birds roost in the armpits and bellies of giraffes

This is a short but sweet report on a new 3-page paper documenting the nocturnal activities of the yellow-billed oxpecker (Buphagus africana). It shows that, at night, these birds actually roost on the bodies of large mammals in Africa.

There are actually two species of oxpecker in Africa: the yellow-billed and the red-billed (Buphagus erythrorhynus). Their niches are somewhat different, with the red-billed found on 15 host species ranging in size from impala to elephants, and the yellow-billed specializing in larger animals that have big surface areas, like buffalo, eland, rhinos, and giraffes.

Both are presumably mutualists, for they land on the mammalian hosts and consume arthropods like ticks, and the mammal benefits by getting cleaned (they therefore tolerate the birds). A single yellow-bill, for instance, can eat 100 engorged ticks per day or 13,000 tick larvae. They also will take some of the mammals’ blood, sipping at the wounds. But on the whole this looks as if both animals benefit from the association, so it’s probably a mutualism.

Here’s a yellow-billed oxpecker cleaning a mammal (species unknown). They scissor their bills through the fur, picking up parasites:

And some red-billed oxpeckers cleaning an impala:

A new article in the African Journal of Ecology by Meredith Palmer and Craig Packer (reference below, free access, pdf here) used a combination of camera traps and citizen science volunteers (who identified the birds) to reveal that the oxpeckers don’t all go back to the trees at night, but some actually spend the night roosting on the mammals. Studies at Serengeti National Park in Tanzania revealed 25 instances of yellow-billed oxpeckers resting on mammals. Most were on giraffes (20), but some were on eland and buffalo. The birds tend to roost in the “armpits” and bellies of the animals (see photos below), with about 3.3 birds roosting on each giraffe examined and 1.6 on eland and buffalo.

(From paper): F IGURE 1 Camera trap images depicting the nocturnal roosting habits of yellow-billed oxpeckers on (a) giraffe, (b) eland and (c) buffalo. Yellow-billed oxpeckers can be identified by their distinctive coloured bills. [Colour figure can be viewed at]

The birds also changed where they hang out from day to night. During the day, yellow-bills hang out on buffalo (seven times more frequently than on giraffe or eland), while at night they roost on giraffes far more often (7 times more often on giraffe than on other species). Despite the much greater abundance of buffalo than giraffe in the Serengeti, the birds clearly like to spend the night clinging to a giraffe.

Why is that? Look at the pictures. The authors suggest (just a hypothesis, of course), that “the tall stature and long legs of giraffe may present warmer, safer nooks in which to spend the night, supported by our observations of oxpeckers congregating on to the undersides, rather than the more exposed flanks).

Red-billed oxpeckers didn’t seem to roost on any species at night, though they forage on giraffe and buffalo during the day. The authors further speculate that since the red-billed oxpeckers can exploit a wider range of hosts, they don’t need to stay with a single host at night.

That’s the story; as I said, short and sweet, but nice. I’m not sure if this is the first report of a bird roosting regularly on a large mammal; readers can enlighten us here. And it must be a restless night hanging on to the armpits of a giraffe. The birds in Figure 1a look like their perch is a bit precarious!

Oh, and congrats to the volunteer citizen-scientists who pored through the photos identifying birds (their IDs were checked, of course). If you get an opportunity to participate in a project like this, try it—it’s fun!

UPDATE: Reader John called my attention to a 2000 paper suggesting that the oxpeckers aren’t mutualists but perhaps VAMPIRES! Here’s the abstract (pdf here). The claim that the tick load doesn’t go up when oxpeckers are excluded does suggest that maybe they’re in it for the blood (that is, they’re parasites), and the mammals get no benefit. But this article uses cattle, not wild mammals, and I don’t know where scientific opinion stands these days.

h/t: Tom


Packer, C. and M. S. Palmer. 2018.  Giraffe bed and breakfast: Camera traps reveal Tanzanian yellow-billed oxpeckers roosting on their large mammalian hosts. African J. Ecology, early view, doi 10.1111/aje.12505


  1. mikeyc
    Posted February 28, 2018 at 1:10 pm | Permalink

    Birds who roost like in photo 1a better hope their host isn’t an old male with an enlarged prostate. A precarious and damp roost.

    • Simon Hayward
      Posted February 28, 2018 at 1:50 pm | Permalink

      Wow, you just sent me down a rabbit hole. Or perhaps up a giraffe urethra, to see what is known about their prostate. I’ve seen papers on bovine, cervine and camelid prostates but never saw anything on the giraffe. Turns out there is an 1838 paper by Richard Owen: “Notes on the anatomy of the nubian giraffe” in Transactions of the Zoological Society of London, that briefly covers prostate structure in these animals. Not too useful in predicting BPH symptoms though 🙂

      Owen considered the giraffe to be “a modified deer” which is not too far from the modern taxonomy. Google books is an amazing resource.

  2. Posted February 28, 2018 at 1:15 pm | Permalink

    “Oxpecker” is such a lovely name. It reminds me of a kind of juvenile, but funny, variety of humor involving made-up common names for animals. For example, the aggressive guard donkeys mentioned in a recent WEIT post are obviously American canine kickers. For extra credit and yucks, you can also try for its fake Latin name.

  3. BobTerrace
    Posted February 28, 2018 at 1:17 pm | Permalink

    Do oxpeckers peck upon ox? I assume so, since castrated buffalo are oxen. But why aren’t oxpeckers called bovinepeckers? But then there are giraffe, etc.

    • mikeyc
      Posted February 28, 2018 at 1:28 pm | Permalink

      How many oxes could an oxpecker peck if an oxpecker picked a peck of oxes?

      • BobTerrace
        Posted February 28, 2018 at 1:35 pm | Permalink

        Oxen, not oxes. That is for foxes.

        • mikeyc
          Posted February 28, 2018 at 1:39 pm | Permalink

          Yeah I know but I liked how oxes sounds. They’d have to be tiny oxes to fit in a peck too.

          • Posted March 1, 2018 at 11:22 am | Permalink

            After all, the plural of “axe” is “axes”, not “axen”.

            • ThyroidPlanet
              Posted March 1, 2018 at 11:41 am | Permalink

              And axis!

      • Brad
        Posted February 28, 2018 at 6:29 pm | Permalink

        Cute & Clever! Great science, great story!

  4. Michael Fisher
    Posted February 28, 2018 at 1:32 pm | Permalink

    I have my own personal pecker – I’ve never noticed it take flight though

    • BobTerrace
      Posted February 28, 2018 at 1:37 pm | Permalink

      Not even a flight of fancy? Also known as a pipe dream.

  5. Michael Fisher
    Posted February 28, 2018 at 1:39 pm | Permalink

    Roosting behaviour and host selection of oxpeckers (Aves: Buphaginae) in Moremi Wildlife Reserve, Botswana, and eastern Caprivi, South West Africa

    Irene M. Stutterh & K. Panagis



    Roosting behaviour and host preferences of oxpeckers were investigated In Moremi and eastern Caprivi. Redbilled oxpeckers were found on six mammal species in Moremi and two in Caprivi. Yellowbilled oxpeckers were found on two host species in Moremi and one in Caprivi. Redbilled oxpecker roosts were located in palm trees in Moremi, while yellowbilled oxpeckers roosted on their host species. Roosting by yellowbilled oxpeckers on their hosts is thought to be the result of their more limited choice of host species.

  6. Posted February 28, 2018 at 1:45 pm | Permalink

    Interesting that there is not, as far as I know, any North American bird that really specializes in that niche. Am I wrong? Does anyone out there know of any non-African examples?

    • Stephen Barnard
      Posted February 28, 2018 at 2:42 pm | Permalink

      I’ve seen black-billed magpies perched on moose, apparently in a similar mutual relationship. It’s not common, though, and I wouldn’t call it a magpie specialization. (They’re famously opportunistic birds.)

      • glen1davidson
        Posted February 28, 2018 at 2:54 pm | Permalink

        Magpies really are on the parasitic side, happy to peck away at wounds on animals. At least that’s what the farmers say. Farmers hate magpies. Magpies might eat the occasional tick, I don’t know, but appear to be the opposite of mutualists with the ungulates.

        Cowbirds are known for riding cattle, and buffalo (bison) in the Americas. This seems to be a commensal relation, as they’re out to eat the insects that the animals stir up.

        Glen Davidson

  7. glen1davidson
    Posted February 28, 2018 at 2:13 pm | Permalink

    I’d guess that giraffes likely move about less than buffalo, and probably more smoothly as well.

    Less chance of being lurched awake.

    Glen Davidson

    • Michael Fisher
      Posted February 28, 2018 at 2:18 pm | Permalink

      buffalo lie down for a kip

    • Diane G.
      Posted March 1, 2018 at 8:12 pm | Permalink

      W/o even clicking on the link, I just read on Google that “[t]he adult giraffe’s legs are taller than the average human…”. If you’ve got a giraffe, who needs a tree?

  8. rom
    Posted February 28, 2018 at 2:14 pm | Permalink

    Just curious
    At high school commensalism was described as what mutualism is today.

    Has the meaning changed or is my memory faulty … I am talking some 48 years ago now.

    There first science post of the year 🙂

    • Michael Fisher
      Posted February 28, 2018 at 2:23 pm | Permalink

      Mutualism: Both organisms benefit.
      Commensalism: One organism benefits while the other organism is not harmed.
      Communism: Organisms cheat – honesty is disadvantagous

      • nicky
        Posted February 28, 2018 at 2:28 pm | Permalink

        You beat me to it… 🙂

      • rom
        Posted February 28, 2018 at 7:22 pm | Permalink

        So has the meaning changed or is my memory fallible in this case, assuming the teacher taught correctly?


        • Michael Fisher
          Posted February 28, 2018 at 7:40 pm | Permalink

          Bedbugs appeared in the house of the secretary of the regional Communist Party Committee. The Party boss summoned an expert & asked him how to get rid of bedbugs. The expert said, “The best way is to organize them into a collective farm, half of them will flee & the rest will starve to death”

          • rom
            Posted February 28, 2018 at 7:45 pm | Permalink

            Thank you Commissar Fisher.

          • rickflick
            Posted February 28, 2018 at 8:05 pm | Permalink


        • Diane G.
          Posted March 1, 2018 at 8:32 pm | Permalink

          To answer your question, yes definitions of these relationships have changed over time.

          When I was in college, symbiosis was defined as what is now called mutualism…I do like today’s defs better, but the first time I was called out and then insisted I was right…well, you know how that goes!

    • nicky
      Posted February 28, 2018 at 2:24 pm | Permalink

      IIRC commensalism is sharing the same place, while mutualism is if both parties are gaining some advantage from that.

  9. ThyroidPlanet
    Posted February 28, 2018 at 2:14 pm | Permalink


  10. nicky
    Posted February 28, 2018 at 2:26 pm | Permalink

    As a bird, I could think of worse and unsafer places to spend the night than a giraffe’s groin. 🙂

    • Diane G.
      Posted March 1, 2018 at 8:34 pm | Permalink

      Plus, you get some body heat! (Maybe not all that necessary in SA?)

  11. David Coxill
    Posted February 28, 2018 at 2:27 pm | Permalink

    I read somewhere that Oxpecker’s make small wounds on the beastie’s back to attract insects .

  12. mirandaga
    Posted February 28, 2018 at 2:38 pm | Permalink

    This isn’t an example of mutualists but it’s a phenomenon I’ve noticed in my backyard bird feeder—namely, that I often seen chickadees there without nuthatches present but never nuthatches without chickadees. A friend of mine tells me that this is because chickadees have a warning call but nuthatches don’t, so the latter depend on the former to alert them to predators. I like the theory but have never found it confirmed anywhere. Can anyone tell me if my friend is right?

    • Michael Fisher
      Posted February 28, 2018 at 2:44 pm | Permalink

      “Nuthatches can tell if a raptor poses a high or low danger from the chickadee’s alarm call […] Templeton showed that the chickadees’ familiar chick-a-dee-dee-dee alarm calls contained a surprising amount of information, including a complex alarm system that contains details if the size and risk of potential predators. Nearby chickadees respond to the alarm and mob the predator to drive it away.

      The Telegraph, 2007 has more detail

      • mirandaga
        Posted February 28, 2018 at 3:08 pm | Permalink

        Thanks so much for this info and the link. I’ll pass it on to my friend.

  13. Posted February 28, 2018 at 2:54 pm | Permalink

    Reblogged this on The Logical Place.

  14. Mark R.
    Posted February 28, 2018 at 4:44 pm | Permalink

    Very interesting.

    Perhaps giraffes act like moving trees to the birds; these oxpeckers feel safer on a tall giraffe, and I imagine their location is also warmer under there.

    • Diane G.
      Posted March 1, 2018 at 8:36 pm | Permalink

      Would’ve saved me a couple of posts above had I only read your comment first. Credit where credit is due. 🙂

  15. BJ
    Posted February 28, 2018 at 5:10 pm | Permalink

    Do the words mutualism and symbiosis mean different things, or are they exact synonyms?

    • Michael Fisher
      Posted February 28, 2018 at 5:18 pm | Permalink

      Symbiotic association is the umbrella term – it divides into three categories:

      Commensalism or

  16. rickflick
    Posted February 28, 2018 at 5:40 pm | Permalink

    If the oxpecker were doing serious harm you’d think they would be shooed away by the big beasts. It’s at least Commensalism.

  17. Posted February 28, 2018 at 6:27 pm | Permalink

    Support for science post!

  18. cyan
    Posted February 28, 2018 at 7:05 pm | Permalink

    ” .. oxpeckers spent more time wound-feeding when a less-preferred tick type was available and when tick abundance was low compared to when a preferred tick type was available and when tick abundance was high. However, oxpeckers still wound-fed even when offered a large number of the ticks they prefer.”

    I couldn’t find on google scholar if all individuals in each species of oxpeckers have red on their beaks. All photos on google images are of those with red on the beaks (the whole beak in the case of red-beaked oxpeckers and the tip of the beak of yellow-beaked oxpeckers.)

    If all do have red on the beaks (and not just a certain percentage), it seems that the redness must have some survival advantage. I wonder what it might be?

    Do other birds who might be potential feeding rivals instinctively process the red as blood, signifying sharp beaks that might attack and wound them, and so stay away, leaving the oxpeckers to feed unbothered?

    • Diane G.
      Posted March 1, 2018 at 8:56 pm | Permalink

      “All photos on google images are of those with red on the beaks (the whole beak in the case of red-beaked oxpeckers and the tip of the beak of yellow-beaked oxpeckers.)”

      As far as I know (& my African field guides support this), both species always have red on their bills but only the Yellow-billed also have yellow.

      (The Red-billed, however, does have a yellow eye-ring, which the Yellow-billed does not. Juvenile bills of both spp are black.)

      Red is not that unusual in African bird bills–it’s seen on some spp of kingfishers, weavers, helmetshrikes, waxbills, and more…Though in some of those it occurs only on adult males, so there’s probably some sexual selection involved there.

  19. Posted March 1, 2018 at 11:27 am | Permalink

    Couldn’t there be some individuals (or behaviours) which are parasitic and some which are mutualistic?

  20. Charles Sawicki
    Posted March 1, 2018 at 1:03 pm | Permalink

    Possibly armpits are a good place to roost at night to avoid predators like owls and long giraffe legs keep you farther from the predatory snakes?

  21. Posted March 4, 2018 at 5:02 pm | Permalink

    That’s really cool!

  22. Posted March 10, 2018 at 2:53 pm | Permalink

    I think that the oxpecker study was long overdue, and other similar studies are needed.

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