No Evidence for Across-Population Scent Discrimination of Cloacal Gland Secretions in Tuatara (Sphenodon punctatus)
Chemically mediated interactions are an important component of reptile life. Tuatara (Sphenodon punctatus) have been documented to locate prey by olfaction, and the recent discovery of a cloacal gland secretion (tuataric acid) suggests chemicals may be used as social signals. Social discrimination of recognized Tuatara populations (i.e., Cook Strait and northern versus Brothers) via chemosensory means has yet to be determined. To explore whether Tuatara react to cloacal gland odors or respond differently to the odor of a different population, three response variables were measured within 60 cm and 30 cm of a scent source within a captive colony: 1) time of first approach; 2) total number of approaches; and 3) total time. Ten male Cook Strait Tuatara were sequentially presented with three treatments: control (distilled water); male North Brother odor; and male Cook Strait odor. Although no significant differences in response were detected across odors and the control, on average, cloacal gland secretions were investigated faster, more often, and for longer than the water control. Further, four of the 10 test subjects made physical contact with the treatment containers when they contained cloacal gland secretions—this never occurred under control conditions. Although preliminary, our study provides insight into the potential role of chemical signals in Tuatara.Abstract

Medial view of the lateral wall of the nasal cavity of Sphenodon punctatus showing the location of the vomeronasal organ within the internal nares. Arrows denote direction of chemosensory odorants into the olfactory organ and vomeronasal organ. Diagram modified from Hoppe (1934). Anterior concha (AC), choanal fold (CF), choanal tube (CT), dorsal pocket of the choanal tube (DPC), external nares (EN), nasal cavity (NC), ventral conchal space (VCS), vomeronasal organ (VNO).

(A) Bird's-eye view of relative locations of all 12 Tuatara burrows and an expanded view of the test arena for each burrow. (B) Detail of mesh cage staked to the ground with odor sample in a sterile petri dish.

Probability that the tested Tuatara that had yet to approach the (A) 60-cm circle and (B) 30-cm circle across time. Probability of 1 denotes no Tuatara entered the circles, and probability of 0 denotes all experimental Tuatara have entered the circles. 1,400 min was appended to the end of experimental trial.