HAGERTY, B.E.; SANDMEIER, F.; TRACY, C.R.; University of Nevada, Reno; University of Nevada, Reno; University of Nevada, Reno: Quantitative review of the adequacy of knowledge of different age stages of the desert tortoise, Gopherus agassizii

Implementation of effective management strategies to recover the federally-listed Mojave population of Gopherus agassizii requires accurate characterization of population structure, species biology, habitat requirements, and threats to population persistence. Desert tortoises are long-lived organisms, with a life history strategy characterized by low juvenile survival rates, delayed sexual maturity, and high adult survival rates. Determining life history traits, such as age-specific survivorship, is critical and requires large sample sizes and long study periods. Typically, this type of information is difficult to determine in wild populations, particularly for early life stages. Few studies have been conducted on survivorship, recruitment rates, and mortality in young Gopherus tortoises as juveniles are notoriously difficult to find due to their cryptic morphology and behavior. As a result, they are underrepresented in censuses, and are rarely studied. Recently there have been many studies on juvenile and hatchling biology and ecology. However, most have been performed in semi-natural, but predator-free enclosures and/or laboratories. The biology of juvenile tortoises has been demonstrated to be different from adults, resulting in behavioral differentiation and different ecological requirements. We have quantified differences in the knowledge base for different age classes of G. agassizii and we show serious gaps in knowledge of the biology of adolescent tortoises where new data are strongly needed to fill the information gaps important to our general knowledge of the biology of desert tortoises and to the management of tortoise populations.