A disabled kea parrot is the alpha male of his circus

Main text

h′ = 0.53, p = 0.109). Bruce was clearly dominant, above intermediary males (dominance ranks 2–7) and two distinctly subordinate kea (Taz and Johnny). Among males, dominance rank correlated inversely with faecal glucocorticoid metabolites (fGCM; rho= 0.800, p = 0.010; Figure 1C): the two clear subordinates showed the highest fGCM, while Bruce, at the top, showed the lowest. These data present the first evidence linking dominance to stress physiology in kea, as seen in other taxa, but contrasts with the finding that alpha male status typically elevates stress hormones.

Bruce's status also afforded him preferential access to food across four central feeders. Despite these feeders being deliberately distributed to prevent monopolisation, Bruce was first to arrive on any feeder on 83% of recorded days, was never challenged while feeding, and on 4 days maintained sole access to all four feeders for at least 15 minutes before subordinates visited stations he had vacated. Jousting is a behaviour not observed in other kea, with different motor patterns, that targets a wider range of body parts.

In Japanese macaques (Macaca fuscata), an old male was able to maintain his alpha status as his ability to walk deteriorated through an alliance with the alpha female. Similarly, a chimpanzee (Pan troglodytes schweinfurthii), after losing the use of his arm to polio, attained beta rank by developing novel bipedal charging displays and an alliance with his brother, the new alpha male. Bruce demonstrates that, in captive environments, innovative compensation for impairment is possible outside of primates, and without coalition networks.

Bruce’s innovation demonstrates how these links operate at the individual level in a large-brained parrot species with high behavioural flexibility on traits that have large effects on fitness – namely social dominance. Our results support the emerging view that disability provides a powerful natural lens on behavioural flexibility and resilience in animals and brings into question whether well-intentioned prosthetic assistance for physically impaired animals will always improve positive animal welfare. The bird missing his upper beak has rewritten what disability means for behaviourally complex species.