Determining Microhabitat Use by the Gulf Coast Kangaroo Rat (Dipodomys Compactus) Using Motion Sensitive Cameras and Estimating Population Density at their Northern Distribution Limit
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The Gulf Coast kangaroo rat (Dipodomys compactus) is a rarely studied species endemic to southern Texas. Throughout its range, it is intermittently distributed because of its presumed dependence on deep, sandy soils with sparse vegetation. I conducted my study in Guadalupe County, Texas, the northernmost limit of the species’ distribution. I collected mark-recapture data during April, July, and September 2011 in order to estimate population density. My estimates for these sampling periods were 7.4, 7.3, and 6.8 kangaroo rats per hectare, respectively. I used motion-sensitive cameras to document activity patterns (visitation rates) of individual kangaroo rats at 80 camera stations spaced 4.5 m apart in a 2.5 ha field. The Daubenmire method was used to determine percent cover of five microhabitat variables at each camera station: bare ground, total vegetation, grass, forbs, and dead material. These data were collected during March and April 2012. My goal was to test whether the Gulf Coast kangaroo rat selects to forage on a substrate relatively devoid of dense vegetation as has been found for other Dipodomys species. I found a significant difference in the percent cover of bare ground and total vegetation between visited and non-visited camera stations. On average, visited stations had 45.9% bare ground and 37.8% vegetative cover whereas non-visited stations had 36.9% and 45.5% respectively. Although it inhabits a relatively mesic environment, the Gulf Coast kangaroo rat has similar population densities and selects for a bare foraging substrate, as do most of the arid-adapted Dipodomys species. My study also demonstrates that motion-sensitive cameras can be effectively used to determine microhabitat use of kangaroo rats. Camera surveillance is a valuable tool that could help us better understand this understudied species and other small rodent species.