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We investigated the vocalizations produced by adult pine voles during various social interactions by presenting an experimental animal with either an anesthetized or awake (unanesthetized) conspecific. Ultrasonic vocalizations (USVs) occurred frequently during tests in which an awake male was present, but were rarely detected in tests involving only awake females, or when a female was presented with an anesthetized conspecific. Higher rates of USVs were produced when males were tested with a familiar female than when tested with an unfamiliar male or female. Equivalent rates were produced when males were presented with either anesthetized or awake animals, but female-soiled bedding failed to elicit USVs from males. Sonic vocalizations (SVs) were produced by both sexes and were associated with aggressive behavior, but occurred only in tests between awake, unfamiliar animals. Castration greatly reduced and testosterone therapy restored USVs emitted by males in response to anesthetized conspecifics. Our results suggest that (i) USVs are emitted predominantly by males; (ii) familiarity enhances USV response; (iii) SVs are produced during aggressive interactions; and (iv) androgens regulate the production of USVs by males. Possible roles for pine vole vocalizations are discussed.

Detection of reproductive status from chemical signals at sandbathing loci was examined in Merriam's kangaroo rat. Castrated and intact males were attracted similarly to the sandbathing loci of four classes of scent donors: intact males, castrated males, estrous females, and nonestrous females. This suggested that reproductive status was not communicated to males at sandbathing loci. In a control test, castrated males were attracted to disturbed sand that contained no olfactory cues whereas intact males were not. Castration caused a significant decrease in the size of a specialized sebaceous gland on the dorsum. Castration did not affect total pelage lipids, however, indicating that lipid-producing cells have a baseline level of secretion that is necessary for pelage maintenance.