To examine problem solving in turkey vultures (Cathartes aura), six captive vultures were presented with a string-pulling task, which involved drawing a string up to access food. This test has been used to assess cognition in many bird species. A small piece of meat suspended by a string was attached to a perch. Two birds solved the problem without apparent trial-and-error learning; a third bird solved the problem after observing a successful bird, suggesting that this individual learned from the other vulture. The remaining birds failed to complete the task. The successful birds significantly reduced the time needed to solve the task from early trials compared to late trials, suggesting that they had learned to solve the problem and improved their technique. The successful vultures solved the problem in a novel way: they pulled the string through their beak with their tongue, and may have gathered the string in their crop until the food was in reach. In contrast, ravens, parrots and finches use a stepwise process; they pull the string up, tuck it under foot, and reach down to pull up another length. As scavengers, turkey vultures use their beak for tearing and ripping at carcasses, but possess large, flat, webbed feet that are ill-suited to pulling or grasping. The ability to solve this problem and the novel approach used by the turkey vultures in this study may be a result of the unique evolutionary pressures imposed on this scavenging species.
This is a preview of subscription content, log in to check access.
We would like to thank Dr. Elliott Marchant for acting as a consultant during this project. We would also like to thank Gill and Robyn Radcliffe of Pacific Northwest Raptors, Julie Mackey of the North Island Wildlife Rescue and Devin Manky of the Grouse Mountain Wildlife Refuge for allowing us to work with their vultures, and for their continued support and enthusiasm. We would also like to thank Ron Ydenberg for funding the research at Grouse Mountain for his helpful insights and discussion. This study was funded by the Biology Department at Vancouver Island University.
Online Resource 1 A turkey vulture (Judge Dredd) using a novel approach to solve the string-pulling problem (MPG 8494 kb)
Clayton NS, Dickinson A (1999) Scrub Jays (Aphelocoma coerulescens) remember the relative time of caching as well as the location and content of their caches. J Comp Psychol 113:403–416PubMedCrossRefGoogle Scholar
Colbert-White EN, Monteen E, Sharpe DI (2013) String-pulling behaviour in a Harris’s Hawk Parabuteo unicinctus. Ibis 155:611–615CrossRefGoogle Scholar
Devault TL, Rhodes OE, Shivik JA (2003) Scavenging by vertebrates: behavioral, ecological, and evolutionary perspectives on an important energy transfer pathway in terrestrial ecosystems. Oikos 2:225–234CrossRefGoogle Scholar