Population dynamics and growth patterns of reintroduced Gunnison’s prairie dog colonies at the Sevilleta National Wildlife Refuge, and their impact on the preexisting vegetative community

Background/Question/Methods

A keystone species, Gunnison’s prairie dogs were reintroduced to the Sevilleta National Wildlife Refuge, New Mexico, in 2005. Initially, 355 individuals were placed in artificial burrows on three replicate 100m² plots. The objective of this study was to examine the dynamics and growth patterns of the colony, over time, in addition to its impact on the preexisting vegetative community. GPS data for active burrow locations were collected in 2005-2008 and again in 2010, by Sevilleta LTER personnel and then convert to GIS raster data for spatial analysis. The population was analyzed at three spatial scales, the colony (100m² plots), the colony plus inter-colony spaces (300m² plots), and the total site area (900m x 1100m). Through these analyzes I examined burrow percent coverage, patch/matrix relationship, burrow patch connectivity, and colony growth patterns. Vegetation data were also recorded over thirty six .25m² subplots, which were arranged in a 6x6 grid pattern over the three colony plots, in addition to three unoccupied control plots of equal size. Taxonomy, species richness, and percent coverage were recorded in each vegetation subplot.

Results/Conclusions

Spatial analysis results indicate population density decreased at the local scale, while increasing over the total site area. Burrow percent coverage stabilized at the local scale, while increasing at larger scales. Average number of burrow patches initially increased and then stabilized. Burrow connectivity remained constant at the local level, but decreased at a larger scale, representing outward growth. Inter-patch distance remained at a consistent 25.1 meters over all levels, meaning the population maintains a consistent pattern of growth. There was no significant variation in inter-patch distance (p=3.01x10^-29), showing that burrow spacing was non-random. These results show that the population has grown outward, away from the original artificial burrow sites while maintaining consistent burrow patch spacing. Vegetative analysis results indicated species richness initially decreased, but has increased over the past two years. Invasive species were eradicated in the first year. Vegetation percent coverage decreased. Vegetation percent coverage at treatment sites had a positive correlation with burrow connectivity (p=3.35x10^-3), and negative correlation with average number of burrow patches (p=0.0258). This show the vegetative community benefits most from the presence of Gunnison’s prairie dogs when burrow patches are fewer and more concentrated; this can be seen at both local and larger scales.