Bruce surprised researchers by turning his disability into such a successful advantage, both behaviourally and physiologically.

Bruce the Kea on a rock checking the photographer out. Despite lacking his entire upper mandible, this parrot is a formidable rival and alpha male in his small group. (Credit: Alex Grabham)

Alex Grabham

recently published study reports on a parrot that’s missing his entire upper beak who developed a behavioral innovation that allowed him to reach the top of his circus. (A “circus” is the collective noun for a group of Kea.) This parrot is an endangered Kea, Nestor notabilis, known as Bruce (or Kati). He resides in captivity at the Willowbank Wildlife Reserve in Christchurch, New Zealand.

“Bruce is the alpha male of his group,” the study’s lead author, behavioral ecologist Alexander Grabham, a Post-Doctoral Fellow at Te Whare Wānanga o Waitaha (the University of Canterbury).

“He achieved this status by himself with the aid of a completely novel fighting technique — a jousting thrust with his exposed lower beak — that beak-intact kea cannot replicate,” Dr Grabham explained.

During jousts, Bruce targets the head, wings, beak and legs of his opponents in close contact without making physical contact with them. When his opponents are farther away, Bruce will run and jump and kick at them as he jousts. These competitive jousts have effectively intimidated his rivals leaving his social dominance unrivalled.

Keas are well-known for their intelligence, curiosity and behavioral flexibility but this is the first time that any animal with a physical disability has managed to compensate for their disability and achieve alpha male social status.

“Bruce shows us that behavioral innovation can help bypass physical disability, at least in species with the cognitive flexibility to develop new solutions,” Dr Grabham elaborated in email.

“Previous research has shown links between large brains, behavioral flexibility, and survival at the species level. Bruce demonstrates how those links play out in a single individual, on traits that matter day-to-day, like social dominance.”

How did Bruce lose his upper mandible?

“We don’t know how he lost his upper beak, but we suspect he attempting to access food in a rat trap,” Dr Grabham told me in email. “He was approximately two years old when he was found with his upper beak missing.”

Bruce was found in 2013 by bird expert Raoul Schwing in the mountainous Arthur’s Pass where many Keas live, with his upper beak already missing. He was brought into captivity at Willowbank Wildlife Reserve in Christchurch because it was believed he would have a better chance of survival. Initially, because he was so small, Bruce was mistaken for a female and named Kati before genetic testing revealed he was a male.

To map out these captive Keas’ social interactions and to assign dominance ranks to each of them, Dr Grabham and collaborators recorded 227 agonistic interactions over 4 weeks amongst the 12 captive Willowbank Kea (Figure 1A & B). This group includes nine males and three females. Out of 162 interactions between males, Bruce won all 36 interactions that he was part of.

“We watched agonistic encounters (so not just physical fights), and we determined who left first as the loser,” Dr Grabham explained in email.

The findings confirmed Bruce as the clear winner and dominant alpha male of the group.

Dr Grabham and collaborators wanted to know if these social interactions were stressful, so they collected feces from all Keas to measure their stress hormones (corticosterone). They found that Bruce, contrary to their predictions, had the lowest level of corticosterone in the group (Figure 1C).

Their observations reveal that Bruce dominates not only in agonistic interactions but also socially during feeding.

“He completely dominates the feeding platform. There are four central feeding trays in the aviary at Willowbank, and the other birds just totally let him go to each feeding tray and he picks his own favourite foods without any interruption from the other birds.”

“The other birds just watch from the side, and once he’s done with the four trays, then the other birds come along.”

But how does Bruce eat?

“Bruce usually pushes his food against something solid, such as a rock or piece of wood, to help him eat,” Dr Grabham replied in email. “He also uses his tongue to help hold and move food.”

Bruce is especially clever, even for a Kea. A few years ago, Dr Grabham and collaborators published a paper describing Bruce’s innovative method of self-care tool use (ref) to preen his feathers. In addition to using stones to preen his feathers, Bruce also enjoys non-mate allopreening — as well as removing left-over food from his lower beak — by other members of the group, including males.

“The bird missing his upper beak has rewritten what disability means for behaviorally complex species,” the study authors write (ref).

Although Keas aren’t known to use tools in nature, they have a well-deserved reputation for being clever pranksters, possibly because they must rely on their ability to locate and dig up tubers or grubs. This may cause us to wonder if the ability to innovate behaviors is restricted to animals, like Kea, with complex cognition? Perhaps not. Take, for example, Veronika, the pet cow, who spontaneously began using a deck brush to scratch herself (ref) or, even more remarkably, bumblebees learning to perform a task by observing trained demonstrator bees to open two-stage puzzle boxes to obtain a food reward (ref). Neither species is perceived to be particularly clever (but perhaps we should rethink this idea?).

Why hasn’t Bruce been fitted with a prosthetic beak (as was done for this bird)?

“Well-intentioned prosthetic intervention may actually reduce the quality of Bruce’s life, and so care should be taken when considering such action for other animals.”

Clearly, we have much to learn about animal minds by observing the animals around us. What does Bruce’s disability, and his successful efforts to overcome it, teach us?

“Bruce has innovated to overcome challenges associated with his disability. It is important to know that Bruce is thriving in this captive setting, not just surviving,” Dr Grabham summarized in email. “It is hard to know if his dominance would translate to conditions in the wild, but our research highlights the capacity for animals to overcome disability by using their impairments to their advantage.”