IS THE COACHELLA VALLEY FRINGE-TOED LIZARD (UMA INORNATA) ON THE EDGE OF EXTINCTION AT THOUSAND PALMS PRESERVE IN CALIFORNIA?

A BSTRACT Reliable estimates of extinction time for small populations of threatened and endangered species based on long-term field surveys provide crucial information for species conservation. We estimated population parameters and extinction times for Coachella Valley fringe-toed lizard (Uma inornata), which is listed as a federally threatened species and a California state endangered species. We used field survey data from 2 transects (TPP1 and TPP2) at Thousand Palms Preserve, California, from 1986 to 2003. We also used data from another subpopulation (TPP3) of this species 6 km from TPP1 and TPP2, where this species became extinct in 2001, to estimate uncertainty of extinction time. Our results indicated that the difference between modeled extinction time and the real extinction time of the subpopulation on TPP3 was about 2 y. The extinction times for U. inornata at TPP1 and TPP2 would be about 23 to 50 y. The extinction time estimate has good relationship with the habitat area; thus, in larger effective habitat area, there will be an increase in the estimated time to extinction. Assuming all available habitats have population connectivity, the estimated extinction time would be about 78 y. There was a trend toward a decrease in the mean reproductive productivity of the lizard during the study. Although there were cycles in population dynamics, the population density trajectories on phase diagram became close to 0. For fragmented sand-dune habitats ,100 to 200 ha, the persistence of subpopulations of U. inornata is doubtful. The main cause for the decrease of this subpopulation might be the shortage of food resources during the frequent, severe droughts.