The endangered Stephens’ kangaroo rat

One of the studies that I have been lucky enough to participate in at the San Diego Zoo Institute for Conservation Research is the Stephens’ kangaroo rat project. The Stephens’ kangaroo rat (SKR) is one of 19 species of kangaroo rat in the genus Dipodomys in the family Heteromyidae. It as listed as endangered by both the federal and state governments. The main threat to the species is loss of habitat due to urban development in its native range. Of the available habitat that remains to the SKR, much of it is unsuitable due to invasive grass species. These exotic grasses form a thick mat on the ground that restricts the movement of the nocturnal rodent and doesn’t allow them to sand-bathe, which is a behavior they need for healthy pelts and social interaction. This project was the first to establish a viable population of SKR via trans location.
Six circular experimental plots were set up on the Southwestern Riverside County Multi-Species Reserve. Each plot was divided into six slices, two slices per treatment. Two slices from each plot were mowed, grazed by sheep, and burned to see which treatment was most effective in removing the thick layer of exotic grasses. Of the two slices per treatment, one was left as an control and the other was planted with native bunch grasses to see which method prevented the establishment of the exotic grasses best. The arrangement of the different treatment slices within each circular plots were randomly chosen. Ten thousand grasses were planted in 2011, and again in 2012 for a total of 20,000 grass seedlings. Each seedling was planted in a shallow basin to maximize the benefits of rainfall and supplemental watering. For the first year that the seedlings were planted they were protected by a blue plastic tube that minimized the effects of detrimental weather and offered extra protection. The seedlings were also given extra water once a month during the dry parts of the year.
On the animal side of the project, 200 SKR were caught and trans-located to the experimental plots. They were divided into four groups, with 50 individuals per treatment (mowed, burned, grazed and control). Trans-locations are fairly complicated, they tend to be more successful when there are social bonds between the individuals that are moved, and there must already be artificial burrows in place before they are released.
I had never participated in a restoration project prior to this internship and I had no idea how much time and energy would be required. It took us almost three full weeks to plant all of the seedlings, and that was with volunteers and the extra help of prison work crews. Because we were in the second year of the project we were able to see how successful the first year had been, and it was really encouraging! The plots where the native grasses had been planted were much more open, with hardly any invasive species present. Many of the slices were also dotted with SKR burrows and there were patches of cleared soil where sand-bathing could occur. Next month I will be going out with a team from the Applied Animal Ecology Department to trap the SKRs. I’ll get to see them up close! Its really interesting to connect the science behind both the plant and animal sides of big studies like the SKR project, and I feel very lucky to have had this unique experience.


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