last update July 7, 2000
Overall, the total number of species found and the total number of reptiles sighted at each of the eight sites was low. Barrel Springs, Commune and Palo Verde Wash had the highest density and diversity. This is probably due to the unique habitat within these sites. The mesquite dune system of Barrel Springs and the creosote scrub of Commune seem to be the most productive of all the sites. The vegetation at these sites appeared to be fairly dense and is probably sufficient in providing food and shelter for herbivorous reptiles. In addition, the vegetation is probably successful in attracting insects and small rodents which serve as food for insectivorous and carnivorous reptiles. If this is an accurate trend regarding these habitat types, then it would be expected that similar habitats found throughout Ocotillo Wells SVRA would exhibit similar densities and diversities. Further sampling at the sights with similar habitat types might yield data in support of this hypothesis.
The sites with the lowest density and diversity were Shell Reef, SanFelipe Wash, andCove (experimental). As noted earlier, the reptile population at ShellReef is in poorcondition and can be attributed to the sparse vegetation cover as a resultof a two yeardrought in this area. Two possible reasons that reptiles were not observedat Cove(experimental) include high OHV use and the presence of high winds duringthe sampleperiod. Due to time constraints, it was not possible to resample thissite.
RECOMMENDATIONS
If one of the goals of this monitoring program is to determine the effects of OHV activity on reptile populations, then it is advantageous to use a mark and recapture method. This involves capture, mark and release, and subsequent recapture or resighting of a specimen. By using this method, one can estimate a population size, demographic parameters (survival rates), space use patterns (home range size and utilization), and individual growth rate.
It is recommended that sampling be performed under favorable conditions. Time of day is an important factor since there are both diumal and nocturnal species of reptiles found in the same habitat. Thus care must be taken to sample for both diurnal and nocturnal reptiles in order to obtain an accurate measure of diversity and density. In addition, sampling should be carried out more than once each year. It is suggested that sampling be performed at least once in late spring and early summer (May through July).
The mesquite dune system which occurs at Barrel Springs is the most productive of the different habitats surveyed. It is recommended that this site should be further protected by fencing off the entire area. Also, the other mesquite dune systems within the park should be surveyed and protected from OHV use in order to preserve this unique habitat.