Flehmen is a behavioral pattern that has been observed in almost all species of ungulates and in some felids. An individual flehmens when it detects an interesting smell -- urine, faeces, a female's vulva or even a chemical substance such as ether or valerian (Schneider, 1930). McHugh (1958) for example reports that wild female bison, Bison bison, have flehmened while nosing a rotten skeleton, human urine, a newborn calf and the torn scrotum of a bull.
Usually flehmen occurs in an ungulate after it has collected urine in its mouth. The animal then holds its head forward and parallel with or above the level of its extended neck. It remains motionless for up to two minutes or more with its upper lip curled up and everted.
In an effort to understand flehmen we first observed its use within a single species over an extended period of time. Next we studied the muscles that produced the upper lip eversion and finally using the information thus gathered, we tried to explain the nature of flehmen.
To find under what conditions flehmen occurred in an ungulate species, a herd of 18 giraffe at the Taronga Zoo in Sydney was observed over an eight month period by Dagg. These observations are noted in Part I.
It was not possible to dissect the heads of giraffe. However, since goats were available, their upper lip structure was analyzed instead. The rostral musculature was studied electrophysiologically initially, and then anatomically, principally by Taub. Dissections were also carried out on other species to verify the observations on goats. This work is detailed in Part II.
The only recent extensive work on the function of flehmen is that of Knappe (1964), who believed that the Jacobson's organ is closely associated with it. In the course of our dissections we studied this organ and concluded that Knappe's theory was no correct. In Part III we also postulate an alternative function of flehmen and suggest possible extentions related to similar behavior.