By Dr. Karen Shaw Becker
Nature is full of unlikely partnerships that actually make perfect sense when you delve a bit beneath the surface. Case in point, Rocky mountain elk and birds called black-billed magpies. Some elk tolerate magpies walking on their body and even their face — a risk, since magpies can eat eyeballs, but also a benefit because they eat ticks. Others, however, do not. What factors drive the mutually beneficial relationship between elk and magpies?
Robert Found, Ph.D., a previous doctoral student at the University of Alberta who is now a wildlife biologist for Parks Canada, observed elk for years and presented a novel finding: personality, of both the elk and birds, appears to play an important role. Specifically, shy elk and bold magpies may make a near-perfect match.
Bold Magpies and Shy Elk More Likely to Pair Up
It’s not unusual for large herbivores to be visited by “cleaner birds” who pick the parasites from their skin or hair. The animals benefit from fewer parasites while the birds get an easy meal. Found noticed in his observations, however, that that some elk aggressively rejected magpies when they attempted to land while others were much more tolerable of the behavior.
“I predicted that the personalities of both magpies and elk would influence whether individuals within each species would engage in cleaner–herbivore behavior,” Found wrote in the journal Biology Letters,1 and he created a personality scale to measure elk and magpie tendencies toward boldness or shyness to test out his prediction.
For instance, Found measured how willing elk were to approach unfamiliar objects, how close they let him get, whether they positioned themselves in the interior or exterior of the group, and how often they kept an eye out for predators. Among magpies, Found measured items such as how close he could get before the magpie flew away and their willingness to land on an unfamiliar object (a “bicycle draped with blowing flagging tape and shiny ornaments”).
As suspected, compared to shyer elk, Found noted, bolder elk allowed him to approach more closely before fleeing, spent less time on the lookout for predators, tended to position themselves on the periphery of the group, were more likely to explore novel objects and were more dominant.
Among the magpies, bolder magpies also allowed Found to approach more closely before flying off, were more dominant and were more likely to land on the unfamiliar bicycle. Overall, out of 104 attempted landings by magpies on elk, the adult elk accepted nearly 54 percent of the landings, with shyer elk much more likely to do so than bolder elk. More than 60 percent of the magpies also landed on an artificial elk, and it was the bold magpies who were more likely to do so.
Shy Elk May Gain an Advantage by Allowing More Magpie Landings
Elk do not have the same problem with winter ticks as other species like moose, which don’t engage in the same habitual grooming as elk. So it’s possible that magpie landings on elk are primarily to the bird’s benefit, even making the bird itself a parasite. It’s also unknown whether shy elk are perhaps more likely to be infested with ticks than bolder animals, which would help explain their increased tolerance of magpies.
However, even on elk an infestation of winter ticks can lead to significant amounts of hair loss, hypothermia, inadequate nutrition and lethargy from loss of blood.2 In that way, shy elks may level the playing field to some extent compared to bold elks simply by accepting magpie landings. Found explained:3
“[B]y having greater tolerance for magpies, shy elk may reduce their tick loads compared to bold elk, and this can help them compensate for being out-competed for forage by the more dominant, bold elk. These results may be important for further understanding the impacts of mutualism on biodiversity, and this is a promising avenue for further research.”
Indeed, there’s still much to be learned about animals’ personalities and how that factors into their relationships with each other and other species. The New York Times threw another monkey wrench into the mix, citing Alison Bell, Ph.D., of the University of Illinois, Urbana-Champaign, who studies personalities in fish: “This could be a three-way relationship: What’s the tick’s role? Does tick personality factor in?”4
Also intriguing, personality is already known to play a role in other relationships of mutualism, particularly among fish. One study found that instead of eating parasites off of other fish, cleaner fish with bold personalities would consume their protective mucus, cheating the supposedly mutually beneficial system.5 Even among spiders, personality (or what’s deemed behavioral temperament) such as being aggressive and docile is known to affect relationships.6
Among elk, meanwhile, previous research by Found revealed that shyer individuals are more likely to migrate while bolder elk are more likely to stay put year-round and become habituated to humans.7 He suggests that by identifying behavioral types and personalities in individual animals, it could help “foster greater coexistence of people and wildlife.”
At the very least, it’s interesting to note that while we tend to view wild animals of the same species as largely the same, they are indeed individuals within the group, with each expressing their own unique mix of personality traits.