High Turnover Rates in Remnant Populations of the Harlequin Frog Atelopus cruciger (Bufonidae): Low Risk of Extinction? Margarita Lampo 1,3 , Sen ˜ aris J. Celsa 2,4 , Argelia Rodrı ´guez-Contreras 1,2 , Fernando Rojas-Runjaic 2 , and Carmen Z. Garcı ´a 1 1 Centro de Ecologı ´a, Instituto Venezolano de Investigaciones Cientı ´ficas, Apartado 21827, Caracas, 1020-A, Venezuela 2 Museo de Historia Natural La Salle, Fundacio ´ n La Salle de Ciencias Naturales, Apartado 1930, Caracas, 1010-A, Venezuela ABSTRACT Atelopus is among the most threatened of all amphibian genera. Most species of harlequin frogs disappeared more than two decades ago and only a few still exist. From ten critically endangered Atelopus species endemic to Venezuela, Atelopus cruciger is the only one that can be located at present. To assess the status of remnant populations of A. cruciger and to provide the demographic data for designing in situ management programs, we estimated: (1) the population size; (2) the apparent survival; and (3) the recruitment rates of one remnant population using mark-recapture data. The adult population size varied (69–117), and this variation was not related to that of abundance indices based on visual counts at the river margins. Thus, caution is recommended when using visual counts as an index of abundance in Atelopus, because capture rates differ significantly among months and between seasons. Despite the observed variations, this popula- tion appears to be stable. Previous reports suggest that species of Atelopus are long-lived. For populations of long-lived species to remain approximately constant, recruitment must be low. Our mark-recapture study, however, showed that adults tend to remain in the popula- tion for approximately 15 mo, but an average of 165 new frogs are recruited every year. Although immigration and emigration are pos- sibilities, the site fidelity and the absence of nearby streams suggests that movement in and out of the study area is less important than births and deaths. Under the proposed hypothesis of a short life expectancy/high recruitment, the risk of extinction must be lower than previously thought. Abstract in Spanish is available in the online version of this article. Key words : abundance; Atelopus; chytridiomycosis; density; disease prevalence; mark-recapture; recruitment; survival; Venezuela. AMPHIBIAN POPULATIONS ARE DECLINING ACROSS THE GLOBE AT AN ALARMING RATE, with one-third of all extant species threatened with extinction (IUCN [Conservation International, NatureServe] 2008). The Neotropical harlequin frogs (Atelopus genus) are among the most endangered amphibians. Of the 92 described Atelopus species, 3 have been classified as Extinct, 70 Critically Endangered (4 Possibly Extinct), 6 Endangered, 5 Vulnerable, 4 Data Deficient, and 3 have not been evaluated yet (IUCN 2008, Coloma et al. 2010b). Most of these species were moved to higher threat categories during the last 20 yrs (Lötters 2007). In addition, many species have uncertain conservation status because they are, as yet, undescribed (Coloma et al. 2010b), or require further systematic revision in light of recent phylogenetic analyses (Lötters et al. 2011). Although the causes of population declines are still a matter of debate, an emerging disease caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd) (Berger et al. 1998, Bonaccorso et al. 2003, Lips et al. 2006), climate change (Ron et al. 2003, Pounds & Crump 1994, Pounds et al. 2006) and, in few cases, habitat loss (Stuart et al. 2008) have been asso- ciated with population crashes of harlequin frogs. In 2005, the Amphibian Conservation Action Plan convened four kinds of interventions to revert the ongoing global amphib- ian loss (Gascon et al. 2007). One of these, emergency responses to immediate crises, propose the implementation of rapid response teams and captive survival assurance programs to react to disease outbreaks (see Appendix I, Gascon et al. 2007). According to IUCN, most critically endangered Atelopus species have suffered reductions in their population sizes of 80 percent or more during the last ten years or three generations. Moreover, most of them are known to be from very restricted distribu- tions (Rueda-Almonacid et al. 2005, Stuart et al. 2008). Although captive programs are now developing in Colombia, Costa Rica, Ecuador, Panama, U.S.A., and Canada to assure the ex situ sur- vival of some of these harlequin frogs, a captive population with sufficient founder individuals has been maintained only for Atelopus zeteki (Poole 2008, Coloma et al. 2010b). The demo- graphic data required for designing reintroduction strategies from captive population—selection of adequate life stages, minimum viable population, and time frames over which ‘success’ can be realistically assessed—are also lacking for all species. The recent discovery of a few Atelopus species in different regions (e.g., Carv- ajalino-Fernández et al. 2008, Rodríguez-Contreras et al. 2008) suggests that some populations have not been affected by disease or climate, or may be recovering. Their ability to stand epidemic outbreaks, climate changes or any other disturbance, however, will ultimately depend on a balance between survival and recruit- ment rates. Thus, there is an urgent need for estimating demo- graphic parameters in remnant populations of harlequin frogs. Received 11 April 2011; revision accepted 05 August 2011. 3 Corresponding author; e-mail: mlampo@ivic.gob.ve 4 Corresponding author; e-mail: josefa.senaris@fundacionlasalle.org.ve 420 ª 2011 The Author(s) Journal compilation ª 2011 by The Association for Tropical Biology and Conservation BIOTROPICA 44(3): 420–426 2012 10.1111/j.1744-7429.2011.00830.x