Humans have a long history of spotting superior abilities in other animals, and then training those animals to use those abilities to advance our own interests. Everyone’s familiar with how we’ve trained pigs to sniff out truffles for us with their sensitive snouts and how we’ve domesticated dogs to herd our livestock, alert us to intruders, guide us when our vision fails, and perform other services. Similar but less well-known examples include our training bees to detect the odor of explosives, cormorants to catch fish for us, and llamas to guard our sheep from coyotes and other predators.
It’s far less common, though, to find relationships where non-humans participate on a more equal footing, where they appear to train us at least as much as we train them. (People who are owned by cats should feel free to rebut this statement in the comment section below.)
Today’s post features one such relationship, the partnership between humans and the greater honeyguide (Indicator indicator), a bird that lives in the trees of sub-Saharan Africa.
Honeyguides and humans have very complementary appetites. Honeyguides get most of their food from beehives, feasting on larvae and wax that they extract from honeycombs (yes, they actually eat and can digest the wax!). Of course humans, too, seek out beehives, although our interest lies more in the bees’ sweet honey, and we’re generally more than happy to leave the wax and grubs for others to enjoy.
The bee-related skills of humans and honeyguides are relatively complementary as well. Honeyguides can fly swiftly across large areas and are expert at locating bee colonies, but have difficulty in extricating the combs on their own. Humans move more slowly along the ground and aren’t so adept at finding colonies, but once we have one in our sights, we’re able to overcome bee defenses and dig the combs out, even when the bees have nested deep within rock crevices and other hard-to-reach locations.
Out of this opportunity for mutualistic benefit, honeyguides and humans have worked out an elaborate interspecies communication system that allows them to work in tandem with certain signals understood by both parties. This partnership has been formally documented in a three year field study conducted in the dry bush country of northern Kenya, focusing on the interactions between honeyguides and the nomadic Boran people who populate the area.
I’m the *real* Greater Honeyguide – don’t let imposters lead you astray! Visit me at http://safari-ecology.blogspot.com/ and see first comment below.
Each partner knows how to get the other’s attention. To attract the birds, the Borans call them with a penetrating whistle (known in the Boran language as Fuulido) that can be heard over a distances of greater than a kilometer and that is made by blowing air into clasped fists, modified snail shells, or hollowed-out palm nuts. Comparably, hungry honeyguides flag down humans by flying up close, moving restlessly from perch to perch, and emitting a double-noted, persistent “tirr-tirr-tirr-tirr” call. (Side note: I’ve been practicing this at home, and it doesn’t seem to attract much other than odd stares and raised eyebrows.)
The joint food expedition commences when the honeyguide flies briefly out of sight and then returns to a nearby, conspicuously visible perch. When the human companion approaches this perch, the honeyguide takes off, displaying its white outer tail feathers, and flies to a new resting place a short distance away, calling loudly when it lands. The Boran partner then approaches the new perch and the bird flies off again, repeating the pattern. As the Borans work with the bird, they whistle and shout to keep the bird interested in guiding. (Again, this doesn’t seem to work too well at home.)
The researchers found that the honeyguides signal the path and distance to the bee colony in a variety of ways. First, they indicate the correct direction through their flight paths, traveling consistently in the direction of the nest and increasing their precision as they near the target. It appears that the know in advance where the nests are located, as the researchers observed the honeyguides briefly visiting nests before dawn, peering into the entrances while it was still dark and the bees were docile.
Also, the honeyguides vary their behavior depending on distance to the hive. For example, when the hive is relatively distant, the birds begin the process with a relatively long disappearance during their first flight; conversely, their first disappearance is briefer when the hive is relatively nearby. Further, the honeyguides stop more frequently and the legs between perches become shorter as they and their human followers approach the nest, especially during the last 200 meters. Finally, the honeyguides select increasingly lower perches as they close in on the colony.
Upon arrival at the destination, the honeyguides perch close to the nest and emits an “indication call.” The researchers describe the scene as follows:
This call differs from the previous guiding call in that it has a softer tone, with longer intervals between successive notes. There is also a diminished response, if any at all, to whistling and shouting by humans. After a few indication calls, the bird remains silent. When approached by the searching gatherer, it flies to another perch close by, sometimes after circling around the nest. The resulting flight path finally reveals the location of the colony to the gatherer. If the honey collector does not (or pretends not to) detect the nest, the bird gives up after a while. It may then leave the area either silently or start a guiding session to another colony. In the latter case, it switches from the indication call to the guiding call and resumes a fairly direct flight pattern. Once the human team members find the nest, it becomes their turn to go to work and hold up their part of the bargain. After using smoky fires to reduce the bees’ aggression, the Boran honey gatherers use tools or their hands to remove the honey comb, and then break off pieces to be shared with their honeyguide partners.
To sum things up, here’s a great BBC video (featuring David Attenborough!) that describes the bird-human partnership and shows the honeyguides in action:
Isack, H., & Reyer, H. (1989). Honeyguides and Honey Gatherers: Interspecific Communication in a Symbiotic Relationship Science, 243 (4896), 1343-1346 DOI: 10.1126/science.243.4896.1343.