Amphibian Declines and Climate Disturbance: The Case of the Golden Toad and the Harlequin Frog

Abstract

Al~tract: The endemic go/den toad (Bufo periglenes) was abundant in Costa Rtca's Monteverde Cloud Forest Preserve in April-May 1987 but afterwards disappeare~ along with local populations of the harlequin frog (Atelopus varius). We examine the possible relationship between these sudden declines and unusually warm, dry conditions in 198Z For our analyses of local weather pattern~ we define a 12-month (July-June) amphibian moisture-temperature cycle consisting of four period~. (1) late wet season; (2) transition into dry season; (3) dry season; and (4) post-dry-season (earlywet-season) recovery. The 1986The -1987 cycle was the only one on record (of20 analyzed) with abnormally low rainfall in all four period~ and temperature anomalies in 1987 reached record high~ Flow in local aquifer-fed streams during the dry season and post-dry-season recovery period reached a record low. This climate disturbanc¢ associated with the 1986-1987 El Nifio/Southern Oscillatior¢ was more severe than a similar event associated with the 1982-1983 El Nifi~ though this earlier oscillation was the strongest of the past century. Demographic data for one harlequin fro8 populatiorg gathered during these two climatic event~ support the hypothesis that in 1987, shortly before the population col-lapsea~ the frogs undenaent an unprecedented shift in distri-

Lack of Evidence for the Drought-linked Chytridiomycosis Hypothesis

“…Though 1987 and1988 were the two driest of the 26 yr examined by Lampo et al (2006), these years had the third and fourth highest number of Atelopus collected, a result inconsistent with the hibernaculum hypothesis (it is also worth mentioning that neither chytrid nor population declines were detected in the 1987 dry year). Pounds and Crump (1994) concluded that Atelopus varius actually left their retreat sites en masse during the extreme dry periods of their study.…”

“…One explanation, the climate-linked epidemic hypothesis, has received increased attention in recent years (Pounds and Crump, 1994;Pounds et al, 1999;Kiesecker et al, 2001;Pounds, 2001;Harvell et al, 2002;Ron et al, 2003;Pounds and Puschendorf, 2004;Lampo et al, 2006;Pounds et al, 2006;Santiago-Paredes and La Marca, 2006;Alford et al, 2007;Bosch et al, 2007;Di Rosa et al, 2007;Pounds et al, 2007;Laurance, 2008;Lips et al, 2008). Although it is increasingly clear that various climate anomalies can alter the dynamics of host-pathogen systems (Harvell et al, 2002;Pounds et al, 2007), I suggest caution before accepting the hypothesis that prolonged or intensified dry seasons trigger or exacerbate epidemics of chytridiomycosis, a scenario hypothesized by several authors (Pounds et al, 1999;Ron et al, 2003;Burrowes et al, 2004;Pounds and Puschendorf, 2004;Lampo et al, 2006;Santiago-Paredes and La Marca, 2006), but for which no empirical data exist.…”

“…Interestingly, one of the few reported declines of a terrestrial breeding amphibian community occurred at La Selva, Costa Rica, where a significant increase in rainfall was recorded over the 35-yr study period (Whitfield et al, 2007). One of the few reports of declines in an ephemeral breeder (Bufo periglenes, also in Costa Rica) occurred during an abnormally dry year, yet had ecologic characteristics that the authors (Pounds and Crump, 1994) concluded were inconsistent with those of a decline caused by moisture stress.…”

Epidemic disease decimates amphibian abundance, species diversity, and evolutionary history in the highlands of central Panama

“…In Central America, the decimation of highland amphibian populations was first noted in Monteverde, Costa Rica (35,36), in the late 1980s, and since then the spread of B. dendrobatidis has been moving in an epidemic wave from the northwest toward the southeast through the cordillera of Isthmian Central America (9,(37)(38)(39)(40). Anticipating the arrival of B. dendrobatidis, an intensive field survey and monitoring program was established in 1998 in the G. D. Omar Torrijos H. National Park (latitude 08.667, longitude −080.592) at 800 m elevation, near El Copé, Panama (9).…”

Effect of road traffic on amphibian density

“…Some suggested causes for declines include habitat destruction by deforestation and drainage, introduction of predators and competitors, pollution from pesticides, mining and logging, acid precipitation, increased levels of ultraviolet radiation, consumption by humans, introduction of exotic species, and climate change (Elmberg, 1993;Blaustein et al, 1994;Pounds & Crump, 1994). An additional potential factor is mortality on roads.…”