Scent Marks as Competitive Signals of Mate Quality

Abstract

Much attention has focused on whether particular qualities of an individual's odor are used in mate choice, to maximise offspring fitness. Odors can provide genetic information directly, thus allowing animals to avoid mating with close relatives or with those carrying deleterious alleles. Odor quality can also reflect the physical status of potential mates such as their parasite burdens, social and hormonal status or the quality of their food resources. Under competitive pressure, subordinates may suppress the production of odors attractive to matesif these provoke aggressive competition from dominant animals. In addition to such information inherent in an individual's odor, scent marks deposited in the environment advertise the size and quality of an individual' territory, while counter-marking competitors' marks is an important behavior for advertising social dominance. In this paper we discuss how the pattern of scent marks deposited by competing individuals provides a reliable signal not only of territory ownership or social dominance but also of the current competitive ability of territory owners or animals advertising dominance. Since scent marks remain in the environment, they provide continuous proof of the challenges that have occurred between individuals. We use data from experiments manipulating marks in the territories of male house mice to show how females use this when choosing a mate. Competitive counter-marking appears to be an important signal of a mate's quality which may help to explain the prevalence of counter-marking between neighbours even when they are highly familiar with each other and their respective territory borders.