Keystone species have large impacts on community and ecosystem properties, and create important ecological interactions with other species. Prairie dogs (Cynomys spp.) and banner-tailed kangaroo rats (Dipodomys spectabilis) are considered keystone species of grassland ecosystems, and create a mosaic of unique habitats on the landscape. These habitats are known to attract a number of animal species, but little is known about how they affect lizard communities. Our research evaluated the keystone roles of prairie dogs and kangaroo rats on lizards at the Sevilleta National Wildlife Refuge in central New Mexico, USA. We evaluated the impacts of these rodents on lizard communities in areas where prairie dogs and kangaroo rats co-occurred compared to areas where each rodent species occurred alone. Our results demonstrate that prairie dogs and kangaroo rats have keystone-level impacts on these lizard communities. Their burrow systems provided important habitats for multiple lizard species, especially the lesser earless lizard (Holbrookia maculata). At the landscape-scale, the total number of lizards was two-times greater on the where both prairie dogs and banner-tailed kangaroo rats co-occurred than where only kangaroo rats occurred.
Mound-scale plots: To evaluate lizards associated with mound disturbance patches and rodent burrow systems, we established replicate mound-scale plots with paired "non-mound" control plots. The mound and non-mound plots were spatially intermixed within each landscape-scale plot. Lizards were sampled around 10 kangaroo rat mounds on the Krat plot, 10 prairie dog and 10 kangaroo rat mounds on the Pdog+Krat plot, and on paired non-mounds located 10 m away from sample mounds, in areas with minimal rodent disturbance.
Lizards were visually sampled along strip transect lines established through each mound-scale plot. Strip transects on the mound-scale plots measured 1 m x 5 m.
Lizards were sampled by walking slowly along each transect. Individuals were counted and identified to species. Lizards were sampled thoughout the spring and summer from spring 2000 through spring 2002.
Additional Information on the personnel associated with the Data Collection / Data Processing
Field Crew Member: Julie McIntyre
Additional Study Area Information
Study Area Name: Pino Gate
Study Area Location: The study site was located near the base of the Los Pinos mountains and directly adjacent to the nothern fencline of the SNWR at Pino Gate
Elevation: 1600 m
Vegetation: Burrograss (Scleropogon brevifolius), sand dropseed (Sporobolus ryptandrus), and black grama (Bouteloua eriopoda) were the dominant vegetation.
Soils: Deep clayey loam soils
Geology: On an upper bajada slope, in a broad swale
Climate: Long-term mean annual precipitation is 243 mm, about 60% of which occurs during the summer. Long-term mean monthly temperatures for January and July are 1.5°C and 25.1°C, respectively.
Site history: Historically, prairie dogs were common throughout the area, but were exterminated by the early 1970’s (John Ford, United States Department of Agriculture Wildlife Services, personal communication). Gunnison’s prairie dogs began to re-colonize the study site from adjacent private land in 1998. During our study, the colony occurred within a 5 ha area, near the base of the Los Piños Mountains in an area with deep clayey loam soils. The site has been long inhabited by kangaroo rats, and represents typical northern Chihuahuan Desert grassland.
North Coordinate:34.406954South Coordinate:34.406954East Coordinate:106.606269West Coordinate:106.606269