Behavioural responses to scent marks of increasing age in Klipspringer Oreotragus oreotragus

Klipspringers Oreotragus oreotragus are small antelopes which use scent marks to demarcate and defend their territory. The strength of behavioural response to the introduction of unfamiliar scent was measured in order to estimate the effective lifespan of scent secretion. The total number of scent marks deposited during the experiment was higher than control levels when fresh scent was introduced, but not when older scent was introduced. However, the proportion of marks deposited on introduced twigs remained higher than control levels until scent was aged at least 7d. The probability of licking twigs immediately before scent-marking was much higher than control levels when scent aged up to 3d was introduced, but not when scent was aged 7d or more. These results indicate that preorbital gland scent retains at least some degree of efficacy for up to 7d. The decreasing level of response to scent aged 0-7d is most likely to be due to decay of the scent signal. However, in contrast to the total number of marks deposited and the probability of licking before scent-marking, which both consistently decreased in response to older scent, the proportion of marks deposited on scent aged 3d was higher than over fresh scent. It is suggested that, in view of the role that scent-marking plays in territory defence, this difference in the timing of peak response between the three variables may represent an adaptive response to the perceived threat of encounter with an adversary, which is mediated by the age of the scent marks