Handstand scent marking: height matters to dwarf mongooses

Abstract

Scent marking is an important means of communication in mammals and many species elevate their scent marks by depositing them on vertical objects. Traditionally, it has been assumed that marks are elevated to increase detectability, but elevated marking may have evolved to convey information about depositor size. Because the height of an elevated mark is typically dictated by the height of the marker, receivers could use the physical location of an elevated scent deposit to indirectly assess the size, and hence the competitive ability, of rivals. Considering that intrasexual competition is one of the primary motivators of mammalian scent marking, and that the ability to assess a rival indirectly would provide very real benefits (eliminating the need for potentially dangerous encounters), it would be surprising if species were not utilizing mark height in this way. Nevertheless, it remains unknown whether any mammal extracts such information from elevated scent marks. I tested whether wild dwarf mongooses, Helogale parvula , discriminate between handstand scent deposits of differing height. Handstand marking is an extreme form of elevated marking, with the marker balancing on its forepaws while flinging its hind legs into the air and smearing anogenital secretions one full body length above the ground. I found that females spent twice as long investigating anal-gland deposits positioned 16 cm above the ground, as compared with those at 10 cm, even though the two were swipes of the same scent deposit and presumably did not differ chemically. A faeces presentation experiment showed that females were more interested in obtaining information about same-sex than opposite-sex conspecifics. I suggest that female dwarf mongooses, which experience extreme intrasexual competition, use the height of handstand scent marks as an indicator of depositor size, allowing them to concentrate their information gathering on same-sex rivals that pose the greatest threat.