GIS-based habitat mapping and population estimation for the Gulf Coast kangaroo rat (Dipodomys compactus) in the Carrizo Sands Region of Texas, USA

Abstract The Gulf Coast kangaroo rat, Dipodomys compactus , is one of five kangaroo rat species occurring in Texas (USA) and probably the least studied. This endemic species has specific habitat requirements, primarily deep loose sand and minimal canopy cover from woody vegetation. On the northern edge of its geographic range, populations of the species are limited to the Carrizo Sands Region and are likely isolated from larger populations farther south. Using a geographic information system (GIS)-based map of suitable habitat coupled with roadside surveys, we determined that habitat of D. compactus is highly fragmented within the Carrizo Sands. Depending on assumed density of individuals we estimated a region-wide population between 50,000 and 240,000 individuals although 50% of this population is expected to be distributed among 11 large (≥ 500 ha) habitat patches. The remainder of the population may be scattered among much smaller habitat patches. In this regard, the overall spatial population structure of D . compactus may be similar to some of the highly endemic Dipodomys species in California (USA). If subpopulations of D . compactus are functionally isolated from one another (due to limited dispersal of individuals) then long-term persistence of the species in the Carrizo Sands region over the next few decades may be in jeopardy. Therefore, distribution and abundance of D. compactus in the Carrizo Sands may need to be routinely monitored particularly if future genetic studies reveal this northernmost population to be genetically unique.