Survivorship and reproduction of translocated Tipton kangaroo rats in the San Joaquin Valley, California

摘要

A potential means of mitigating the impact that development has on animals is to move affected individuals to new areas where development will not occur or to release individuals back to a site after activities have ceased. In the case of translocation, the desired outcome is that the majority of the translocated individuals will survive and reproduce in a new, uninhabited and protected site, such that there is no net loss of endangered animals. Because of project displacement, we moved 144 Tipton kangaroo rats Dipodomys nitratoides nitratoides, a state and federally listed endangered species, to a preserve north of Bakersfield, California, USA, in December 2006 that had no Tipton kangaroo rats, but was known habitat. To help determine short-term survivorship, we radio-tracked 22 individuals for 30 d post-release. We placed 14 radio-collared kangaroo rats in cages with artificial burrows (soft release) on site and 8 radio-collared individuals in artificial burrows without cages (hard release). We placed all other kangaroo rats in artificial burrows with (n = 86) or without (n = 36) cages. The percentage survivorship of radio-tagged kangaroo rats that were soft-released (58.3%) was greater than that of radio-tagged animals hard-released (37.5%), but the differences were not significant. Trapping over 3 yr showed a small, but persistent, population of Tipton kangaroo rats. We caught 38 new Tipton kangaroo rats in these 3 yr. Based on an AMOVA of genotypic data from 2 microsatellite loci of Tipton kangaroo rats translocated to the site, unmarked young caught on site are consistent with being offspring of the translocated animals. Future research should address the value of caging kangaroo rats on sites prior to release, the relative merit of short-term removal of competing species, and appropriate habitat management strategies.