ADJUSTMENT OF BASKING POSTURES IN THE HIGH-ALTITUDE IBERIAN ROCK LIZARD (LACERTA-MONTICOLA)

We studied the relationships between thermoregulatory basking pastures and heating rates in the Iberian rock lizard (Lacerta monticola). Hea ting rates were high when body size was small, the substrate temperatu re was high, and the angle of incidence of the sun's rays was high (i. e., the rays were perpendicular to the lizard's body). However, heatin g rates were not related to the compass orientation of lizard's body a xis to the sun (perpendicular versus in line with the sun). In the fie ld, the slopes of the body axis of basking individuals were higher dur ing the early morning. However, neither the cardinal orientation of a lizard's body axis to the sun nor the frequency of flattening varied d uring the morning. Postural adjustments to select an adequate angle of incidence of the sun's rays on the dorsal part of the body suggest th at this behaviour might enhance absorption of solar radiation.