Multiyear Home-Range Ecology of Common Side-blotched Lizards in Eastern Oregon with Additional Analysis of Geographic Variation in Home-range Size

Abstract

We studied the spatial ecology of Common Side-blotched Lizards (Uta stansburiana) in the northern Great Basin desert of eastern Oregon. Over 3 yr (2007–2009) we collected 3675 coordinates from 51 males and 60 females during the breeding season (mid-May to early July). We found significant variation among years and between the sexes in home-range size, but contrasting evidence for a relationship between body size and home-range size. Lizard home ranges overlapped those of other lizards extensively and the number of overlapping home ranges within and between the sexes as well as the percentage of unique home range varied among study years. However, we found no evidence that lizards are minimizing their overlaps with the same sex and maximizing their overlaps with the opposite sex. By studying home ranges over multiple years we found that lizards exhibit strong year-to-year fidelity in home-range location, which may be a consequence of relatively high interannual survival. We also present long-term data on the home ranges of Common Side-blotched Lizards from a population in central California that were studied for 8 (females) or 10 (males) consecutive yr as well as new analyses of Tinkle's (1967a,b) 6-yr dataset from west Texas. We found that winter rainfall, population density, and lizard sex were significant predictors of home-range size across years within both sites, though the effects of density and sex appear to be more robust than rainfall. By combining data on home-range ecology from nine study populations of Uta stansburiana, we tested for the effects of latitude of origin, rainfall, population density, and lizard sex on home-range size across the geographic distribution of this species. Similar to our results within sites, rainfall, density, and sex have significant effects on home-range size when comparing sites, but again the effects of density and sex appear to be more robust than rainfall. Latitude of origin also appears to explain variation in home-range size independent of ecosystem productivity (i.e., rainfall, density). Thus, we conclude that ecosystem productivity is an important determinant of density and spatial ecology of lizard populations and that even modest fluctuations in productivity may influence population density and home-range ecology, but that latitude of origin remains important independent of these factors.