An Activity Study of a Radioisotope-Tagged Lizard, Sceloporus Undulatus Hyacinthinus (Sauria: Iguanidae)

A northern fence lizard was tagged externally with gold-198 and released on a restricted area at Texas A&M University. Hourly observations of the lizard's position and activity were made for 3 days in October, 1964, and sporadic observations were made for an additional 2 weeks. A Geiger-Muller survey meter was used to detect the position of the lizard. Activity of the lizard was restricted to the daylight hours, and initiation and cessation of this activity was correlated with temperature and sunlight. During the period of intensive observation, the lizard spent 61% of its time in one large tree and 39% within a radius of 20 feet of this tree. Vertical movement varied between ground level and 20 feet, with 50% of the time being spent above 5 feet. Selection of a resting position for the night was correlated with both temperature and wind velocity.