Survival of Translocated Heermann’s Kangaroo Rats (Dipodomys heermanni) in the San Joaquin Desert of California Using Hard and Soft Release Methods

—Translocation of endangered kangaroo rats in the San Joaquin Desert, California, has often been proposed as a mitigation strategy for populations impacted by land development activities, but has largely been unsuccessful. In a 2006 translocation experiment, soft-released Tipton kangaroo rats (Dipodomys nitratoides nitratoides), an endangered species, had higher 30-d survival rates than hard-released individuals, although differences were not significant. In this experiment, we completed a translocation of D. heermanni, a non-protected species. To determine survivorship of D. heermanni, we placed radio-transmitters on 10 hard-released and 11 soft-released individuals. We predicted that our study would support softrelease as an effective way to improve survivorship. However, we found that hard-released individuals had the highest rate of survivorship to 30 d (60%), while survival was lowest for soft and semi soft-released individuals (27%). One factor that may have contributed to the success of hard-released individuals in our study was the unusually high number of available burrows of Botta’s Pocket Gophers (Thomomys bottae) on the translocation site, which provided immediate refugia. We conclude that soft-release may not be necessary if translocation sites have both high quality habitat and ample refugia, but recommend more research on soft-release methods.