Stankowich, T. (2008) Tail-Flicking, Tail-Flagging, and Tail Position in Ungulates with Special Reference to Black-Tailed Deer. Ethology. 114(9): 875-885.

Stankowich (2008) tested the functional significance of assumed anti-predator behaviors in ungulates. The author noted much debate has arisen over the function of many ungulate signals involving their tails and rump-patches due to unclear or overlapping definitions of these signals. Stankowich redefined the behaviors he used in this article to include tail-flicking, tail-flagging, and tail position in distinct categories. The author tested the responses of Colombian black-tailed deer in free-living populations to the approach of humans as potential predators. Stankowich found that the deer were observed tail-flicking and flagging most often in feeding bouts and in alert states, and was more common at the end of alert behavior. Tail-flagging, which is essentially a repeated bout of flicking was interpreted as a signal of increased agitation while flicking alone was most likely linked to movement. This agitation however is not apparently associated with perception of increased danger and thought to not have an anti-predator function. Erect tail position was associated with flight behavior and stotting but the author noted the confounding anti-predator effect of exposing rump patches. He concluded that erect tail position could have anti-predator function but alternative explanations were not ruled out in this study.

This study was surprisingly lacking in evidence for or against function of the investigated signals. The author assumed that free living deer that have had little contact with humans and have not been protected from hunting by humans will perceive and approaching human as a predatory threat. As discussed in class, predator alarm signals can function either to alert members of the social group to the presence of a predator or to act to deter the predator from attacking. In this study, the author did not record the responses of other individuals to changes in tail signals and therefore could not draw conclusions about a conspecific alert function for tail signaling. Also the author did not attempt to show a deterrent function of tail behavior because he gave no evidence that the behaviors in some way would lessen predator success. The author simply provided patterns of occurrence of the behaviors described which does not necessarily elucidate the selective function of the tail signals.