Interspecies competition for limited resources leads to negative impacts on all competing species. Competition may lead to competitive exclusion, but multiple competing species may adapt via niche partitioning. Granivorous desert rodents compete closely for seeds scattered heterogeneously across microhabitats. Microhabitats differ in food quality, availability, and in the protection they provide from predators. Variation in these factors may lead rodents to preferentially select habitat based off of the amount of coverage present, and distance between shrubs and a food source. We examined microhabitat selection of Merriam’s kangaroo rats (Dipodomys merriami), within Gold Butte National Monument in the Mojave Desert. Using mark-recapture methods at 200 traps sites, we examined the correlation between population density, vegetation coverage, and potential refugia, during March 2018. Dominant shrubs in the ecosystem include creosote, burro bush, brittlebush, cheese bush, and Mojave yucca. To test the hypothesis that rodents preferentially select areas with a higher percentage of coverage, we measured total shrub cover within 3 meters of each trap site. To analyze how far from cover rodents are willing to forage, we test a second hypothesis that the distance between a trap and the nearest shrub effect how many rodents will be captured at that site.
Results/Conclusions
An ANOVA test shows a statistically significant correlation (p< 0.05) between average number of captures at a trap, and percentage of coverage within 3 meters of the trap. Rodents showed strong preference for sites with 25-30% coverage, despite only making up 6% of total plots measured. Plots in this range had a capture rate 4.4 times higher than those with 0-5% coverage. We did not find support for the hypothesis that the minimum distance from shrub to trap effects the number of rodents caught at a trap. This suggests that rodents are willing to forage farther away from shrub cover as long as the general percentage of cover in the area is higher. Further research would be needed to analyze why this pattern is shown and isolate out the factors of temperature, seed production, and predation risk. Kangaroo rats are ecosystem engineers, and play an important role in the food chain. Maintaining this higher density of shrubs could be an important factor in protecting desert ecosystems from the effects of increasing global temperatures and invasion of invasive fire prone plant species. Understanding these factors would lend additional understanding the relationship between close competitors in a harsh and changing desert ecosystem.