Preliminary observations of the behavior of male, flat-tailed horned lizards before and after an off-highway vehicle race in California

Animal movements are influenced by many factors, including he need for food and other resources necessary for survival; searching for mates or nest and brood sites; and response to stress, including escape from predators and environmental extremes. Although it is often difficult to determine the exact cause for particular movements by animals, movement, nonetheless, reflects an organism's response to its immediate and changing environment.

The flat-tailed horned lizard, Phrynosoma mcallii, is found in extreme southern California, southwestern Arizona, and northwestern Mexico. It was proposed for listing as a threatened species under the federal Endangered Species Act, but the proposal was withdrawn (USFWS³ 1997). A variety of threats were identified in the listing proposal, including habitat destruction and direct mortality due to off-highway vehicle (OHV) activity. Large areas of habitat occupied by flat-tailed horned lizards are negatively impacted by OHV activity (Lovich and Bainbridge 1999). In addition to direct impacts, OHV activity may modify the behavior and possibly, habitat use of this species (Wone and Beauchamp 1995, Beauchamp et al. 1998). In the paper we compare the rates of movement, activity areas, and mean vectors of movement of 3 radio-tagged, male, flat-tailed horned lizards before and after an OHV race.