Description
The Golden Toad is notable in its genus for being both sexually dichromatic and visually striking (Savage 1966). Male coloration is characteristically bright orange, uniform on the dorsum but sometimes slightly mottled on the venter. Female dorsal pigmentation ranges from greenish-yellow to black and is marked with bright scarlet spots edged in yellow, while the ventral surface is greenish-yellow to flesh colored. Adult female standard length ranges from 47 to 54 mm, while males range from 41 to 48 mm. Other size-based sexually dimorphic traits include a longer, more acute snout in males, and proportionally longer limbs. In both sexes, body surface is relatively smooth with the warts being granular and tipped with small black spines. Supraorbital, postorbital, canthal, and supratympanic external crests are present, which are low and warty. The tympanum is absent, and no vocal sac or slits are present. The iris is black and marked with gold flecks, and set in a horizontally elliptical pupil. Tubercles are not present on the hands and feet, and only the toes are webbed near their base.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Costa Rica

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (21 records).

The Golden Toad is found in a small area (less than 10 square kilometers) contained in the Monteverde Cloud Forest Preserve in the Cordillera de Tilaran, near Monteverde, Provincia de Puntarenas, Costa Rica. The habitat is undisturbed, elfin cloud forest, consisting of an understory of mosses, ferns, and epiphytes, and a canopy including Didymopanex pittieri, Clusia alata, Oreopanax nubigenum, and Zanthoxylum melanostichum (Jacobson and Vandenberg 1991). The area experiences a distinct dry season, dominated by tradewind-based precipitation rising from the Caribbean basin, and a wet season, characterized by convectional storms from the Pacific lowlands (Crump et al. 1992). Mean annual biotemperature ranges from 12 to 18 degrees Celsius, and rainfall annually is over 4000 mm (Savage 1966). The habitat is characterized by Holdridge (1967) as a lower-montane rain-forest lifezone.

Life History, Abundance, Activity, and Special Behaviors
The Golden Toad is a fossorial species, which remains hidden underground throughout the year, emerging only for a short breeding season. During the onset of the wet season (March to June), B. periglenes breeds explosively in shallow pools or depressions (depth up to 0.1 m), particularly those formed by tree roots (Jacobson and Vandenberg 1991). They are gregarious during breeding, and because of a heavily male-biased sex ratio, females become a limiting resource. Intense male agonistic behavior has been observed, both between lone males and against pairs in amplexus (Jacobson and Vandenberg 1991). However, competition seems to manifest mainly as scramble competition for females, as attacking pairs in amplexus seemed to have little effect and no female choice seems to be operating (Jacobson and Vandenberg 1991). Females deposit two to four hundred large eggs at a time, and tadpoles require five weeks to metamorphose (Crump et al. 1992). It has been noted that a prolonged time may be taken for mating, as one pair remained in amplexus 25 hours after their initial marking (Jacobson and Vandenberg 1991).

Jacobson and Vandenberg (1991) describe two call types, one as a release call (usually in combination with body vibrations) and characterized as a low intensity trill, and another which was not linked to any physical interactions (only one male issued the call while in amplexus).

Records and personal observations of B. periglenes document its abundance from 1971 to 1987, after which it abruptly disappeared (with 1,500 individuals recorded in 1987, five individuals found in 1988 and one in 1989; Pounds and Crump 1994), and it has not been seen since (Pounds et al. 1997).

Trends and Threats
The disappearance of the golden toad is perhaps the most striking case of amphibian decline, not only because its habitat and dispersion ability seem to have been unaffected (Pounds et al. 1997), but also because of the abrupt nature of its decline. The documented story is a good one, beginning with Savage's (1966) preliminary description, spanning through the late 1980's when B. periglenes disappeared, and continuing now with extensive causal analysis. The history of abundance begins with Savage's (1966) initial sighting in 1964, when he noted that "within a radius of 5 meters at least 200 toads were visible." In 1977, Jacobson and Vandenberg (1991) counted 988 individuals in a single day, as compared to a greatest daily count of 85 in 1982. The last significant record came from May 1987, when Crump et al. (1992) observed a total of 1500 adult toads over the duration of the breeding season. This count was reduced to a single toad in both 1988 and 1989 (Pounds and Crump 1994), and none have been found thereafter (Pounds et al. 1997). The extremely limited geographic distribution and fragile status of B. periglenes was internationally recognized when the International Union for the Conservation of Nature (IUCN) listed it as Endangered in 1979. In 1996, the status of the Golden Toad was revised to Critically Endangered, and in 2001, the IUCN declared the Golden Toad formally Extinct.

The rapid manner in which this population vanished, from 1500 to none in just a few years, has led to the argument that B. periglenes suffered from a high adult mortality rather than the gradual effects expected from poor juvenile recruitment or unsuccessful breeding (Pounds and Crump 1994). This reasoning, in conjunction with the toad's pristine habitat, have centered causal hypotheses around abiotic factors involving climate change (Pounds et al. 1999).

Field studies reported complete egg desiccation in both 1982 (Jacobson and Vandenberg 1991) and in 1987 (Crump et al. 1992). This seems readily explainable by the warming of the pools and the low level of precipitation, which produced drier conditions overall (Pounds and Crump 1994). However, a causal explanation for the disappearance of the adult toads is not as forthright. Certain factors have been ruled out, such as the detrimental effects of Ultraviolet (UV) exposure and pH contamination. Crump et al. (1992) argue that the Golden Toad's fossorial lifestyle and the heavy cloud cover of the montane environment should prevent damaging UV radiation, while their tests of pH change in cloud water, convective and advective precipitation turned up negative. Examining weather data, Pounds and Crump (1994) noted the correlation between the desiccation events and the adult disappearance, and the 1982-1983 and the 1986-1987 El Niño/Southern Oscillation. This led them to propose several climate-based hypotheses: moisture stress, temperature stress, climate-linked epidemic hypothesis (see Pounds et al. 2006), and the climate-linked contaminant pulse hypothesis. Pounds et al. (1999) added support to the climate-induced decline in their careful analysis of precipitation, air temperature, sea surface temperature, and stream flow patterns in relation to tropical anuran, avian, and anoline lizard communities. They concluded, as did Pounds et al. (2006) that it was not simply the effect of the El Niño/Southern Oscillation, but rather a global warming trend in general (this trend remained significant with the El Niño fluctuations included) which crossed a threshold in late 1980's and precipitated a broad tropical anuran decline. This was matched by a decline in anoline lizards, and resulted in significant restructuring of tropical avian communities. However, Lips et al. (2008) reanalyzed the data of Pounds et al. (2006), and argued that the climate-linked epidemic hypothesis was not supported, as did Rohr et al. (2008). Anchukaitis and Evans (2010) reconstructed a century of climatic data for Monteverde, Costa Rica, and suggested that cloud forest ecology changes have been driven by natural variability in the local climate (in particular, extreme dry periods associated with El Niño weather patterns) rather than by anthropogenic climate forcing.

Possible reasons for amphibian decline

Prolonged drought
Long-distance pesticides, toxins, and pollutants
Weakened immune capacity
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
See photos and film clip of Bufo periglenes at the ARKive site: http://www.arkive.org.uk/species/display.asp?id=17

A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).

References

Anchukaitis, K. J., and Evans, M. N. (2010). ''Tropical cloud forest climate variability and the demise of the Monteverde golden toad .'' Proceedings of the National Academy of Sciences, online before print, http://www.pnas.org/content/early/2010/02/25/0908572107.abstract. .

Crump, M. L., Hensley, F. R., and Clark, K. L. (1992). ''Apparent decline of the Golden Toad: Underground or extinct?'' Copeia, 1992(2), 413-420.

Holdridge, L. R. (1967). Life Zone Ecology. Tropical Science Center, San Jose, Costa Rica.

Jacobson, S. K. and Vandenberg, J. J. (1991). ''Reproductive ecology of the endangered Golden Toad (Bufo periglenes).'' Journal of Herpetology, 25(3), 321-327.

Lips, K. L., Diffendorfer, J., Mendelson, J. R., III, and Sears, M. W. (2008). ''Riding the wave: Reconciling the roles of disease and climate change in amphibian declines.'' PLoS Biology, 6, e72.

Pounds, J. A., Fogden, M. P. L., Savage, J. M., and Gorman, G. C. (1997). "Tests of null models for amphibian declines on a tropical mountain." Conservation Biology, 11(6), 1307-1322.

Pounds, J. A., Fogden, M. P. L., and Campbell, J. H. (1999). ''Biological response to climate change on a tropical mountain.'' Nature, 398(6728), 611-615.

Pounds, J. A., and Crump, M. L. (1994). ''Amphibian declines and climate disturbance: The case of the Golden Toad and the Harlequin Frog.'' Conservation Biology, 8(1), 72-85.

Rohr, J. R., Raffel, T. R., Romansic, J. M., McCallum, H., Hudson, P. J. (2008). ''Evaluating the links between climate, disease spread, and amphibian declines.'' Proceedings of the National Academy of Sciences, 105, 17436–17441.

Savage, J. M. (1966). ''An extraordinary new toad (Bufo) from Costa Rica.'' Revista de Biologica Tropical, 14(2), 153-167.

Species Account Citation: AmphibiaWeb 2010 Incilius periglenes: Sapo Dorado <https://amphibiaweb.org/species/253> University of California, Berkeley, CA, USA. Accessed Nov 25, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 25 Nov 2024.

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