Indication of the Sense of Smell in the Turkey Vulture, Cathartes aura (Linnaeus), from Feeding Tests

Abstract

Two turkey vultures, Cathartes aura (Linnaeus), were employed in a series of feeding trials. Birds were presented individually with leaf-filled pans in one of which meat was concealed from view. Pans were presented in the open, concealed from direct view behind screens, or concealed in boxes with single openings. In each type of feeding trial pans with food were selected first a significant number of times. Evidence of a sense of smell is believed afforded. Inter- pretations of results suggest that smell may be of a degree of im- portance varying with the situation confronting the bird. Preference for freshly-killed chicks over other types of fresh and decaying meat was shown. Various observations of the behavior of the captive birds are included. Importance of the olfactory sense in the orientation of feeding activities of birds is poorly understood. Relative importance of the exteroceptors functional in food-finding by carrion-eating birds has long been of particular question. There seems to be little, if any, conclusive evidence that a sense of smell even exists in such species. The purpose of this investigation was to determine by means of feeding experiments whether a sense of smell could be demonstrated to exist in the Turkey Vulture, Cathartes aura (Linnaeus). Literature pertaining to the possibility of olfaction in the Turkey Vulture or other species of the family Cathartidae is considerable. Many of the references are confusing or of questionable scientific value. Audubon (1859: 15), Darwin (1860: 175-176), and others presented negative evidence or rejected the possibility altogether. Beebe (1909: 467) gave conflicting evidence. Indications of a sense of smell have been given by Rhoades (1883), Gurney (1922: 241), and Howell (1932: 162). Strong (1911) indicated an intact well- developed olfactory nervous system in the Turkey Vulture. North- ington (1936), however, has pointed out that the functional capacity of a sensory nerve may not be proportional to the size of the associated structure. Two Turkey Vultures, sex undetermined, were trapped alive in Dade County, Florida, during the fall of 1953. They were housed in individual compartments consisting of an outer portion measuring 5' x 5' x 8' in height, screened to the outside and provided with two perches each approximately six feet long, and a continuous inner por- tion of solid walls and ceiling, with dimensions of 9' x 8' x 8'. A door provided with one-way vision mirror-glass was situated in the far wall of each inner compartment. After a period of eight weeks conditioning to confinement, con- trolled feeding was initiated. Canned dog food (largely horse meat), 200