Desert horned lizard (Phrynosoma platyrhinos) locomotor performance: The influence of cheatgrass (Bromus tectorum)

摘要

Vegetation plays a critical role in lizard activities such as thermoregulation. Less understood is the influence of vegetation Structure Oil lizard mobility. This study examined the influence of cheatgrass (Bromus tectorum) patches on: 1) distribution patterns of the desert horned lizard (Phrynosoma platyrhinos) using transect Surveys along an elevational gradient, and 2) sprint performance of adult and juvenile P platyrhinos using raceways established tinder field conditions. There was a significant negative association between cheatgrass cover and lizard scat abundance across the study gradient, suggesting horned lizards might avoid areas with higher cheatgrass cover. Adult and juvenile sprint performance were reduced on grass raceways by 50 to 70% of their bare-substrate speeds; adult speeds decreased from 0.93 m/s on bare substrate to 0.26 m/s on grass, and juvenile speeds decreased from 0.41 to 0.11 m/s. The findings were consistent based on 2 independent measures of velocity (burst and sustained). These results demonstrate the negative effect of cheatgrass on horned lizard mobility and highlight the potential consequences of cheatgrass invasion on patterns of local Phrynosama distribution in western North America.