ASPECTS OF OLFACTORY COMMUNICATION IN THE DWARF HAMSTER (PHODOPUS SUNGORUS) AND THE NAKED MOLE-RAT (HETEROCEPHALUS GLABER)

Abstract

Olfactory communication is an understudied phenomenon, likely due to human bias against this modality of communication. I expanded our knowledge of olfactory communication by testing the following hypotheses: self-grooming is a form of olfactory communication in the dwarf hamster Phodopus sungorus; naked mole-rats (Heterocephalus glaber) are capable of social-dominance-based discrimination of odor; and rolling behaviors of naked mole-rats function as a form of scent-marking. Self-grooming is ubiquitous among mammals, yet our knowledge of the functions of this behavior beyond cleaning the body surface is limited. Dwarf hamsters were exposed to cotton nesting material scented by same-sex and opposite-sex conspecifics, as well as an unscented control. As predicted, subjects self-groomed more in response to conspecific odor than unscented controls, an important first step in demonstrating communication. Furthermore, self-grooming in response to opposite-sex odor was higher than same-sex odor and unscented controls, which did not differ from each other, suggesting that its communicative function is to attract a mate. Naked mole-rats live in underground eusocial colonies in which social dominance plays important roles in their reproductive division of labor, cooperation, mate choice, and access to food. Three colonies were tested using a T-choice apparatus in which each stimulus arm contained the whole-body odor of one of two fellow colony members that differed in dominance rank. Subjects were tested with several pairs of stimulus odor donors that varied in dominance status, sex, breeding status, and body weight, and subjects were analyzed separately according to sex, breeding status, absolute dominance rank, and relative dominance rank. The overall results were consistent: naked mole-rats mostly preferred to enter the arm containing dominant odor. Naked mole-rats perform rolling behaviors in which an individual’s dorsum contacts the floor, and these behaviors may function in scent-marking. A plastic tube in each of three test colony tunnel systems was replaced on alternating days with a clean tube, to stimulate scent-marking, or a “dirty” tube that had been part of the colony tunnel system for 24 h prior. For both sexes, rolling behaviors were more frequent in the clean than the dirty stimulus tube condition within 2.75 h of tube replacement.