Nuzzling in the gray short-tailed opossum. II: Familiarity and individual recognition

Nuzzling is a chemosensory exploratory behavior that enables South American gray short-tailed opossums to dissolved dry conspecific odor deposits in naso-oral secretions and incorporate them into their vomeronasal organs. This report documents that male opossums nuzzle novel (unfamiliar conspecific) male odors significantly longer than familiar (own of familiar conspecific) male odors or clean substrates. Such findings suggest that an important ethological function of nuzzling behavior involves individual recognition of conspecifics. The first experiment demonstrates that a very short (3-min) exposure to a conspecific odor is sufficient to establish familiarity. The second experiment reveals that a brief exposure results in prolonged (at least 2 h) odor retention. Both experiments establish that nuzzling by males is normally followed by scent marking; thus, novel male odors also elicit increased scent marking. We have identified four novel forms of scent marking by male Monodelphis domestica (ventral, chin, anal/cloacal, and neck) and our data suggest that marking style may be at least partially dependent on the physical properties of the substrata.