Feasibility, repeatability, and regional differences in thermal threshold and cold thermal latency testing in bearded dragons (Pogona vitticeps)

Abstract

Ventral thermal burns are frequent in bearded dragons (Pogona vitticeps), raising questions about reptile thermal nociception. This randomized, Latin-square experimental study compared thermal threshold (TT) and cold thermal latency (CTL) in six healthy, adult bearded dragons at three anatomical sites (inner thigh, dorsum, and ventrum). A 0.5 °C/s thermal ramp was applied to each anatomical location in triplicate, until a response (kicking/jumping, turning) was observed. Similarly, CTL was evaluated using a 0 °C probe applied at the same locations. Safety cut-offs of 55 °C for TT and 60 s for CTL were applied. The experiment was repeated four weeks later for test-retest reliability. Thermal threshold and CTL were compared among sites using extended Mantel-Haenszel statistics. Repeatability and test-retest reliability were assessed by coefficient of variation and Spearman's correlation coefficient. Median [interquartile range (Q1, Q3)] TT recorded 47.55 °C (40.33, 51.63 °C) at the inner thigh, 52.68 °C (49.57, 55 °C) at the ventrum, and 51.82 °C (51.03, 54.33 °C) at the dorsum. Thermal threshold was significantly higher at the ventrum than the thigh (P = 0.02). Median (Q1, Q3) CTL were 38.83 s (34.33, 41.67 s) at the inner thigh, 55.33 s (41.00, 60.00 s) at the ventrum, and 49.00 s (35.67, 51.00 s) at the dorsum, with significantly longer CTL at the ventrum (P < 0.01) and dorsum (P = 0.03) than the thigh. Thermal threshold demonstrated excellent repeatability but poor test-retest reliability, whereas CTL had low-to-moderate repeatability and good test-retest reliability.

Keywords: Bearded dragon; Cold perception; Nociception; Pain assessment; Quantitative sensory testing; Reptile.