Experimental removal reveals only weak interspecific competition between two coexisting lizards

Competition for resources is an important mechanism that shapes ecological communities. Interspecific competition can affect habitat selection, fitness, and abundance in animals. We used a removal experiment and mark-recapture to test the hypothesis that competition with the larger and more abundant Striped Plateau Lizard (Sceloporus virgatus H.M. Smith, 1938) limits habitat selection, fitness, and abundance in Ornate Tree Lizards (Urosaurus ornatus (Baird in Baird and Girard, 1852)). Ornate Tree Lizards in the plots where Striped Plateau Lizards were removed switched between habitat types more frequently and moved farther than Ornate Tree Lizards in control plots. However, there were no significant changes in the relative densities of Ornate Tree Lizards in each habitat type or in microhabitat use. We also found no changes in growth rates, survival, or abundance of Ornate Tree Lizards in response to the removal of Striped Plateau Lizards. Our results suggest that interspecific competition was not strong enough to limit habitat use or abundance of Ornate Tree Lizards. Perhaps interspecific competition is weak between coexisting species when resource levels are not severely depleted. Therefore, it is important to consider environmental conditions when assessing the importance of interspecific competition.