| Edwards Air Force Base initiated an Agassiz's desert tortoise (Gopherus agassizii) head start program in 2002. Head-start pens were installed and adult females from surrounding areas were used to deposit eggs from 2003 through 2010. A staggered release of 119 juveniles commenced in 2013, occurred in three seasonal groups and at two release locations: (1) fall 2013 - 35 juveniles released at Leuhman Ridge; (2) spring 2014 - 36 juveniles released at Baker-Nunn; and (3) fall 2014 - 48 additional juveniles released at Leuhman Ridge. As of October 2015, 63 (53%) are known to be alive, 17 (14%) are dead and 39 (33%) are missing. Survival has varied among release groups. The majority of dead animals appear to have been killed by small mammals, with a novel observation of a predation attempt by a glossy snake (Arizona elegans). Since release, we observed seasonal shifts in condition indices, with median values approaching a prime index value (0.64) in spring and falling below a level expected for dehydrated tortoises (0.45) in fall. Growth in midline carapace length has been minimal, a possible consequence of recent drought and/or stunting as a result of high densities in the head-start pens. |