ISSN 1026-0269 FROGLOG Newsletter of the IUCN/SSC Declining Amphibian Populations Task Force August 1997, Number 23. In light of the resultant probability account for most precipitation during Golden Toads, distributions, the declines at the dry season. As moisture-laden Null Models, Monteverde appear to go well beyond trade winds meet the windward and Climate natural fluctuations. Even when we (Caribbean) slope of the cordillera and Change doubled our initial probability estimate, flow upward, they cool adiabatically, our conclusions were the same. We producing a large orographic cloud believe that the results confirm the bank. I hypothesize that atmospheric By J. Alan Pounds naturalist's intuition; it is indeed warming has raised the mean height A decade after the 1987 population extraordinary that so many at which condensation begins and collapse that led to the disappearance populations would crash and thereby has increased the average of the endemic golden toad (Bufo disappear. altitude at the base of this cloud bank. periglenes), amphibians in the A comparison with breeding birds Because higher clouds may pass over Monteverde region of Costa Rica's in the same area puts the loss of the cordillera with reduced turbulence Cordillera de Tilarán show little sign of anuran diversity in perspective and drag, they may be less likely to recovery. Twenty species of frogs and (Pounds et al., in press). The relative produce low-intensity precipitation toads (40% of the anuran fauna) have frequency of absences for frogs and (mist) before dissipating on the been missing from a 30 km2 study toads was much greater than that for leeward (Pacific) side. Local area throughout the 1990s (Pounds et breeding birds in general. It was temperature trends, viewed in relation al., in press). similar to that for invasive open- to the modulating effects of clouds, In the debate over the country birds whose habitats had are consistent with global warming significance of amphibian declines in largely reverted from farmland to and this condensation-height model. undisturbed highland areas, forest after being annexed to the Biological patterns also follow the arguments have hinged on standards Monteverde Cloud Forest Preserve. model's predictions. Many of scientific proof and the absence of Amphibian habitats, however, seemed premontane breeding bird species long-term demographic data for most unchanged. have invaded lower-montane habitats, species. Long-term data are essential Climate may have been a key whereas some lower-montane species to judge whether a particular factor in the declines (Pounds, in have retreated up the mountain population is in decline. Diverse press). Although there is growing slopes. In multiple regression tropical faunas, however, afford an evidence that epidemic disease has analyses, patterns of daily approach that does not rely on these been an important proximate cause of precipitation during the dry season data. mortality, different pathogens have account for most of the year-to-year My co-workers and I asked been implicated in declines on variation in the rate of invasion by whether the observed number of different continents. The patterns premontane bird species. The same disappearances exceeds that suggest the existence of a common patterns are strongly correlated with expected for naturally fluctuating denominator, and global warming abundance in highland populations of populations (Pounds et al., in press). could fill this role through various anoline lizards that have declined and To formulate null models that estimate mechanisms. disappeared. For both climate and the expected number of At Monteverde, there is a strong biological responses, fluctuations in disappearances, we examined long- 24-year trend toward more severe dry sea-surface temperature (i.e. the term studies of other amphibian seasons. Previous analyses signal of El Niño) account for much of assemblages. We chose studies that suggested that climate had played a the variation superimposed on the were conducted on spatial scales role in the 1987 crash (Pounds and long-term trends. The most extreme appropriate for comparison with Crump 1994). They did not reveal patterns of daily precipitation were Monteverde and that illustrated how major trends, however, because they associated with the 1986-87 warm unstable populations can be. From focused on monthly and annual data episode, which immediately preceded these studies, we estimated the rather than day-to-day patterns. the collapse of amphibian populations. probability that a single species would Variability of daily precipitation has The condensation-height model disappear in response to a natural increased, leading to drier extremes, and evidence for it are summarized in disturbance such as a drought. without affecting monthly or yearly an overview of the biology of Substituting this value in a binomial averages. Days with no measurable Monteverde's amphibians and reptiles distribution, we calculated the precipitation have become more in relation to the declines (Pounds, in likelihood that a particular number of frequent and have increasingly press). Supporting data and analyses species would disappear coalesced into dry periods. are in a forthcoming paper (A. simultaneously. The patterns suggest a change Pounds, M. Fogden, and J. Campbell, in the advective processes that unpubl.), which will be presented in the BirdLife International/WWF Conversion to organic tea The leaf litter quadrats effectively workshop "Impacts of Climate Change production in this region has sample the fossorial and terrestrial on Flora and Fauna" in September at contributed greatly to the re- frogs and the nocturnal transects the National Center for Atmospheric establishment of populations of local sample virtually all the visible frogs. Research (NCAR) in Boulder, frogs. While tremendous gains have The TLOs typically have education Colorado. been made among local amphibian levels equivalent only to US grades 1 Global warming is an important populations by this conversion, and or 2. However, because the methods threat to highland biological the cessation of biocide spraying, the require only basic literacy and communities. The Monteverde Cloud question of an agricultural landscape numeracy skills, utilizing TLOs has Forest Preserve announces the with an efficient, lined drainage proven to be useful, effective, and formation of the Monteverde Climate system still remains. feasible for long-term monitoring of Panel, an interdisciplinary group that The microhabitat potential of the frog populations in Papua New will focus on this problem. We also natural landscape has been lost in the Guinea. announce completion of the Golden design of the modern tea garden. To Leaf litter sampling is conducted Toad Laboratory for Conservation address this feature, a Sri Lankan at randomly selected locations (GTLC), devoted to research, applied company, Lanka Organics Ltd., plans determined using a random number conservation, and education. Details to begin work with a local NGO, the table. Each quadrat is a 5 x 5 meter will be given in a future issue of NeoSynthesis Research Centre, to square and is worked by a team of Froglog. build up amphibian microhabitats in four TLOs, one for each side of the Work on amphibian declines has their organic tea garden. The tea thus plot. After the limits of the plot have been supported by the Tropical produced will be certified as benefiting been determined, the beginning Science Center, Stanford University's local biodiversity (in the first instance, sampling time is recorded, and each Center for Conservation Biology, the amphibians) as well as being TLO searches slowly through the leaf MacArthur Foundation, Chicago's produced organically. litter and ground detritus to locate Brookfield Zoo, and the U.S. National For more information contact: frogs. A general sweep is conducted Science Foundation. Ranil Senanayake, Earthkind, Sri by each TLO on each side so that Pounds, J.A. (in press) Amphibians Lanka. respective layers of leaf litter are and Reptiles. In: The ecology and 100232.3435@compuserve. brushed from inside the plot to the natural history of Monteverde, Costa com outside, from in front of the worker, to behind him. In this way, no animals Rica: A background for conservation. Kamal Melvani, Neosynthesis N.M. Nadkarni & N.T. Wheelwright can escape without at least being Research Center, Sri Lanka. seen. When frogs are located, they (Eds.), Oxford University Press, [email protected] Oxford, UK. are captured and immediately T.J.Raj, Lanka Organics, Sri Lanka. transferred to a plastic bag. After each Pounds, J.A., and Crump, M.L. (1994) [email protected] TLO has met in the center of the plot, Amphibian declines and climate the ending time is recorded, along with disturbance: the case of the golden Using Local People data on the species, sex, SVL, toad and the harlequin frog. to Monitor Frog location, and mass of each frog. Each Conservation Biology 72-85. 8: Populations in frog is then released and habitat Pounds, J.A., Fogden, M.P.L., Papua New Guinea variables are recorded. This is an Savage, J.M. and Gorman, G.C. (in especially powerful technique when press) Tests of null models for In an effort to begin long-term properly deployed as it can be used to amphibian declines on a tropical monitoring of the virtually unknown inventory fossorial and terrestrial mountain. Conservation Biology. frog populations of Papua New species present at a site, as well as to Contact: J. Alan Pounds, Golden Toad Guinea, David Bickford of the determine species densities and Laboratory for Conservation, University of Miami has developed a relative abundances. Moreover, since Monteverde Cloud Forest Preserve training program based on a series of each quadrat is randomly chosen and and Tropical Science Center, Santa standard methods to be utilized by independent, changes in species Elena, Puntarenas 5655, Box 73, local people on a long-term basis. By assemblages over time can be COSTA RICA. utilizing trained local observers detected, an important goal of [email protected] (TLO's) in long-term monitoring, two monitoring.