Evidence of chemical communication in the spiny rat Trinomys yonenagae (Echimyidae): anal scent gland and social interactions

Behavioral and histological data reveal that Trinomys yonenagae, a colonial and fossorial caviomorph rodent, emits direct chemical signals through a single, highly developed, eversible anal sebaceous gland. Connective tissue covers the secretory portion of the gland, dividing it into smaller incomplete lobules. Well-defined layers of striated muscle fibers, which are organized in a crisscrossed manner, surround the external surface of the gland. These features indicate active secretion, and may be important for gland eversion. The frequency of gland eversion was zero when either males or females explored a new territory singly. However, when two unacquainted adults were paired independently of the sex, the anal gland was everted without scent being applied to the substrate or conspecifics. The chemical signaling was concomitant with the occurrence of investigative behaviors such as nose–nose, nose–rump, and nose–anus contact. Anal-gland protrusion did not evoke avoidance responses and agonistic behaviors were never observed. The data do not support the function of the short-lived signal as either a sex attractant or a scent mark. The potential importance of chemical signaling in T. yonenagae by means of an eversible gland may lie in recognizing individuals or classes of individuals, minimizing aggression, and increasing social cohesion, all of which are important to colonial animals.