SPATIAL-DISTRIBUTION OF A POPULATION OF TEXAS HORNED LIZARDS (PHRYNOSOMA-CORNUTUM - PHRYNOSOMATIDAE) RELATIVE TO HABITAT AND PREY

The spatial distribution of a Texas horned lizard population was quant ified with respect to habitat and prey. Horned lizard spatial distribu tion was clustered in three specific areas, whereas ant mounds belongi ng to their primary prey, Pogonomyrmex barbatus, were randomly distrib uted in the study area. An analysis of vegetation cover relative to ho rned lizard spatial distribution suggests that habitat, not prey, gove rned the spatial distribution of this population. In particular, horne d lizards selected disturbed areas where ground cover was less dense. Horned lizards occurred at a density of one lizard/3,636 m2 or nearly three lizards/ha. Pogonomyrmex barbatus mounds occurred at a density o f 15.9 mounds/ha, equivalent to about 196,492 ants/ha. Relative to har vester ants, horned lizards occurred at a ratio of one lizard per six ant mounds or one lizard per 74,148 ants. Compared with a previous stu dy in New Mexico, harvester ant density was considerably greater, howe ver, horned lizard density was less. This may be related to prey avail ability; although ants are less abundant at the New Mexico site, more individuals may be available for consumption due to habitat difference s.