Dorsal coloration is mottled light and dark, with ground coloration rangingfrom lime-green to yellow-orange and surface markings in black (from dots touniform coloring). The ventral surface ranges from yellow-green to orange withthe same type of black surface markings. The throat and venter can appear brightscarlet, and the groin can appear blue-green or green. The snout is short,and in profile acute or rounded. The pupil is horizontally elliptical, there is notympanum, and there are no distinct glandular ridges. Paired elongate vocalslits run parallel and lateral to the tongue; males have an internalvocal sac. Males have webbing between the first and second finger, and thefirst finger also bears a nuptial pad. Toes are webbed except for IV, andthere is no tarsal fold (all descriptions from Savage 1972). Snout-ventlength of adult males ranges from 25 to 41 mm, and females are 33 to 60 mm inlength (Savage 1972; Crump 1988). Both bufadienolide andtetrodotoxin skin toxins are present in wild A. varius(Daly et al. 1997).
This once common species was last seen in 1996 (Bolaños pers com) and thought to be extinct. A new population was recently discovered in the Rainmaker project in 2003.
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).
Southern Central America (Costa Rica) south into northwestern South America (Capula, 1989; Staniszewski, 1995).
Biogeographic Regions: neotropical (Native )
Distribution and Habitat
A. varius is found from western Panama to the Canal Zone, throughCentral Talamanca and Chiriqui, and on both the Atlantic and Pacific slopesof the Cordilleras de Tilaran in Costa Rica (Savage 1972). It has beenfound at elevations ranging from 16 to 2000 meters, in life zonesHoldridge (1967) characterizes as Tropical Lowland, Premontane, and LowerMontane. This habitat includes both dry and wet forest following small streamcourses, where the seasonal weather pattern is divided into a wet (late May tomid-November) and dry season (Savage 1972; Crump 1988).
Panama. This species has almost gone extinct in Costa Rica.
Atelopus varius is a small (2.4-- 3.8 cm; 1-- 1.5 in) slim-bodied, pointy-snouted toad of highly variable coloration. Dorsal color is usually black or brown overlaid with a mosaic of spots and streaks that can be almost any combination of orange, red, yellow, blue, or green. Sometimes the lighter colors predominate. The belly is marbled with white, yellow, orange, and/or red. The toes are pointed, without discs (Staniszewski, 1995; Hayes et al., undated).
Other Physical Features: ectothermic ; bilateral symmetry
Species description based on Savage (2002). Medium frog (males 27-39 mm, females 33-48 mm).
Dorsal pattern and coloration extremely variable, but generally consisting of black and one of many colors: bright green, yellow, yellow-orange, or red. Savage (1972) has some excellent photographs showing the range of variation in patterning in this species. The dorsal surface is mostly smooth and lacks any glandular concentrations apparent in some other species of Atelopus.
Iris green. Pupil horizontal.
A.varius inhabits the moist environment of the rainforest floor, from lowlands up to the cloud forests. They often occur in the vicinity of streams, where they breed (Capula, 1989; Hayes et al., no date; Staniszewski, 1995).
Terrestrial Biomes: forest ; rainforest
Habitat and Ecology
Mostly found in premontane and montane forest to 2000 m but also on hills in some lowland sites.
A.varius eats small insects such as flies and gnats (Capula, 1989).
Atelopus varius is an ant specialist, but feeds in small amounts on other arthropods (Toft 1981). They actively search for their prey (Toft 1981).
This species is often encountered on rocks in or along the margins of streams (Crump 1986). At night, they sleep on rocks or vegetation (Crump 1986). Population declines have been documented throughout Costa Rica and parts of Panama (Pounds and Crump 1994). Adult Atelopus varius sometimes become parasitized by flies, which leads to the death of the frog (Crump and Pounds 1985). Frogs are more vulnerable to parasitism during the dry season, when they are forced to aggregate in suitable waterfall spray habitat near streams (Pounds and Crump 1987, Crump and Pounds 1989).
Life History and Behavior
A buzz repeated numerous times (Savage 2002). Atelopus varius also produces chirps that may serve as release calls (Savage 2002). An audiospectrogram of the call can be found in Cocroft et al. (1990).
Behavior and communication
Atelopus varius moves very slowly; presumably the toxins in their skin protect them from potential predators (Crump 1986). During the breeding season, males call to defend territories, but aggressive interactions may escalate to wrestling to establish dominance (Savage 2002). Females are more territorial during the non-breeding season (Savage 2002). This species exhibits homing behavior, returning to the place of capture within a week or less of displacement (Crump 1986).
Development - Life Cycle: metamorphosis
In Monteverde, Costa Rica, oviposition takes place during October-December (Savage 2002). In Sante Fe, Panama, an amplectant pair was found in June, but only non-calling males were observed in July (CoCroft et al 1990).
Eggs are laid in two strings and are white (Starret 1967). Eggs are probably affixed to rocks to prevent them from flowing downstream (Starrett 1967). Eggs hatch 6 days after oviposition (Starrett 1967).
The dark brown body is very small, rather flat and looks square from above (Savage 2002). The mouth is very large (Savage 2002). The ventral surface has a large disk that likely serves as a sucker to help tadpoles adhere to rocks in fast-moving water (Savage 2002, Duellman and Lynch 1969). An excellent illustration of the tadpole can be found in Starrett (1967). Tooth rows are 2/3 (Starrett 1967).
Status: captivity: 10 years.
Lifespan, longevity, and ageing
A.varius reproduces mostly along streams and other sources of moving water. During amplexus, the female deposit 30-- 75 eggs in long strings in shallow water, as the male fertilizes them. The eggs hatch in about 36 hours. Tadpoles have a flattened body and an abdominal sucker which keeps them from being swept away in the current (Capula, 1989; Staniszewski, 1995).
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)
Physiology and Cell Biology
The skin of Atelopus varius contains tetrodotoxin (Kim et al. 1975).
2N = 22 (Duellman 1967, Schmid 1980)
A.varius has begun to disappear from places in Costa Rica where it was common only a few years ago, and is considered an endangered species. Its main habitat is rainforest and these forests are being destroyed at an alarming rate; in addition, these little toads may be vulnerable to mysterious fungal infections which seem to be affecting frogs in many parts of the world (Capula, 1989; Staniszewsli, 1995; USGS, 1999). One subspecies, A. v. zeteki, is listed on Appendix I of the CITES Treaty, and is considered endangered by the U.S. Fish and Wildlife Service (Levell, 1997).
US Federal List: endangered
CITES: appendix i
IUCN Red List of Threatened Species: critically endangered
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2004Critically Endangered
Life History, Abundance, Activity, and Special Behaviors
The Harlequin Frog is diurnal. It is usually found sitting on rocks and logs near a stream or in rock crevices during the day, and within crevices orlow vegetation at night (Crump and Pounds 1985). It is a poor swimmerthat rarely enters streams, and appears to depend on wetsurfaces in the splash zone for moisture (Pounds and Crump 1994). It feeds on smallarthropods (generally no larger than 7 mm in size) which are more abundantduring the dry season (Crump 1988). It is slow-moving, sedentary, andless wary than other local frogs; these characteristics appear to be adaptivebehaviors related to aposematism (Crump and Pounds 1985). Someindividuals are long-lived and have been recaptured over 3 consecutive years(Crump and Pounds 1985). Over the year, Harlequin Frogs tend to aggregate in waterfall splash zones with the progression of the dry season (Pounds and Crump 1987; Crump and Pounds 1989). The only knownpredator or parasite is the sarcophagid fly, Notochaeta bufonivora, (Crump and Pounds 1985). The fly larviposits on the posterior surface of the frog's thigh,and the larvae subsequently burrow and feed within it, killing the frogwithin a matter of days (Pounds and Crump 1987).
Males begincalling and defending territories at the onset of the wet season, and pairingbegins 2 to 5 months later, from mid-August through early December(Pounds and Crump 1987; Crump 1988). The sex ratio is male-biased, and males often enter into amplexus early and remain with thefemale for as long as 32 days (Crump 1988). Females deposit eggs in thewater from the end of the wet season to the early dryseason, October to December (Pounds and Crump 1987).
Crump (1988) has documented the aggressive behavior of A. varius, which occurs within and between the sexes and is characterizedby forelimb and foot wagging, chasing, pouncing, and squashing. Male-male antagonism isgenerally longer than female-female aggression and involves chirp-likeadvertisement calls and wrestling behavior. Male aggression isheightened both during the breeding season and in high density situations(Crump 1988). Female-female aggression lacks wrestling and calling,is generally less intense and less frequent, and seems to be related to thedefense of foraging and/or shelter sites (Crump 1988). Intersexualaggression is almost always female to male; females will chase, pounce on, and squash males who have invaded their territory, and they willattack males whom they have dislodged from amplexus. The only hostilebehavior of males towards females is holding the amplectant position despite afemale's efforts to disengage. In a series of invasionexperiments, Crump (1988) demonstrated that territorial residents havethe advantage in combat and higher success despite size differences.
Life History, Abundance, Activity, and Special Behaviors
Declines of A. variushave been documented in the Cordillera de Tilaran,near Monteverde, Costa Rica. Census studies conductedbetween 1982 and 1983 reported an average of 751 adults along a 200 m transect(Crump and Pounds 1985), a number which appeared stable up to the late1980's. Surveys conducted between 1990 and 1992, however,did not detect a single frog (Pounds and Crump 1994). It remains absentfrom the Monteverde area.
Several causal explanations for this disappearance have beenproposed, most involving climatic factors in a direct or synergistic manner.Pounds and Crump (1994) examined weather data and noted the correlationbetween the adults' disappearance and the 1982-1983 and the 1986-1987El Niño/Southern Oscillation events. This led them to hypothesize severalclimate-based causes of the decline: moisture stress, temperature stress,a climate-linked epidemic, and a climate-linked contaminant pulse.Recent studies have linked this and other declines to more subtle but cumulativeweather changes caused by global warming. Pounds et al. (1999) conducteda careful analysis of precipitation, air temperature, sea surface temperature,and stream flow patterns as they related to tropical anuran, avian, and anolinelizard communities. They concluded that declines like that of the Harlequin Frog were not simply aneffect of the El Niño/Southern Oscillation, but rather of a long-term warming trendwhich crossed a threshold in late 1980's and precipitated a broad tropical anurandecline. This decline was accompanied by a decline in anoline lizard communities and significant restructuring of tropical avian communities.
Of theproposed causes, the climate-linked epidemic hypothesis(Pounds and Crump 1994) appears particularly important in the decline ofA. varius in light of the discovery of the parasitic fly N. bufonivora in 1982 (Crump and Pounds 1985; Pounds and Crump 1987). The fly seems to cause density-dependent mortality(Crump and Pounds 1985), as clumping of frogs during the dry season of1982 (an El Niño year) was correlated with increased fly parasitism. Parasitism is particularly intense near waterfall spray zones,where Harlequin Frogs aggregate when extreme dry conditions threaten their waterbalance (Pounds and Crump 1987).
An additional epidemic anddensity-dependent threat to A. varius has appeared in the form of anovel pathogen. In 1997, Berger et al (1998) documented three deceasedA. varius specimens from Fortuna, Panama which had been killed by achytridiomycete fungus. This fungal pathogen invades keratinized body surfaces and kills postmetamorphic anuranswithin several weeks. Tests show that the chytrid fungus can be spread by skin scrapings fromother individuals, and may impair cutaneous respiration and osmoregulation whenit attacks the hypervascularized pelvic patch (Berger et al 1998). It hasbeen documented as fatal in adults from 18 other species, both in South Americaand Australia, and has been implicated as a widespread cause of anuran decline(Berger et al 1998).
Relevance to Humans and Ecosystems
Harlequin toads are popular in the commercial pet trade, despite being very difficult to maintain successfully (Staniszewski, 1995).
They are undoubtedly important insect predators of the forest floor.
The Costa Rican Variable Harlequin Toad (Atelopus varius), also known as the clown frog, is a neo-tropical true toad from the family Bufonidae (Crump 1986). Once ranging from Costa Rica to Panama, A. varius is now listed as critically endangered and has been reduced to a single remnant population near Quepos, Costa Rica (rediscovered in 2003) and is presumed to be extinct in Panama (IUCN). Recent variation in air temperature, precipitation, stream flow patterns, and the subsequent spread of a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) linked to global climate change have been the leading cause of decline for A. varius (Lips et al. 2003 and Pounds et al. 2006). A. zeteki has been considered a subspecies of A. varius, but is now generally considered a separate species (Savage, 2002).
The historic range of A. varius stretched from the Pacific and Atlantic slopes of the Cordilleras de Tilaran mountain range in Costa Rica into western Panama. Suitable habitat includes both pre-montane and lower-montane zones as well as some lowland sites along rocky streams in hilly areas (ranging from 6 to 2000m in elevation) (Savage 1972). At present, A. varius is restricted to a single lowland site along a stream and small tributary on the Pacific coastal range near Quepos, Costa Rica (personal correspondence 2007).
Habitat and ecology
A. varius is a diurnal frog often found on rocks or in crevices along streams in humid lowland and montane forests (Crump and Pounds 1985). It is primarily a terrestrial species, only entering the water during breeding season, relying on spray from streams for moisture (Pounds and Crump 1994).
The Costa Rican variable harlequin frog is slow moving and often remains in the same area for long periods of time. The conspicuous or aposematic coloration of A. varius likely serves as a warning to potential predators of the toxicity of the frog's integument which contains tetrodotoxin, a potent neurotoxin (Crump and Pounds 1985). Its main food source is small arthropods that are most abundant during the dry season (Crump 1988). The only known predator of A. varius is a parasitic sarcophagid fly (Notochaeta bufonivora) which deposits its larvae on the surface of the frog's thigh. The larvae then proceed to burrow inside the frog and eat it from within (Pounds and Crump 1987). In addition, large land crabs have recently been observed attempting to prey on A. varius but it is unclear what, if any, effect this has on the population (personal correspondence 2007).
In recent decades, A. varius has become increasingly rare throughout its geographic range. The first incidence of its disappearance was recorded after a census conducted between 1990 and 1992 near Monteverde, Costa Rica revealed zero individuals where its population had previously peaked at 751 adults (Crump and Pounds 1985 and Pounds and Crump 1994). By 1996, A. varius was believed to be extinct throughout Costa Rica. However, subsequent surveys carried out by the rainmaker project in 2003 and 2005 rediscovered a population of the endangered frog on the Pacific coastal range near Quepos (IUCN). In Panama, mass mortality has drastically reduced populations of A. varius in recent years and it is now believed to be locally extinct (Lips 1999, personal correspondence 2007). At present only a single population of an estimated 60-95 individuals remains in an isolated location in Costa Rica (personal correspondence 2007).
Several theories related to changes in climatic patterns have been put forth to account for the rapid decline of A. varius. A trend toward rising temperatures across the tropics in the late 1980s and early 1990s has been implicated in the declines of multiple lizard and amphibian species including several Atelopus spp. (Pounds et al. 1999). More recently, an observed global decline in amphibian species richness has been linked to an outbreak of the pathogenic chytrid fungus Batrachochytrium dendrobatidis (Pounds et al. 2006). This pathogen can be transmitted between individuals through shed skin cells and is known to infect keratinized body surfaces where it can impair cutaneous respiration and osmoregulation thus resulting in mortality (Pounds et al. 2006). Current attempts to preserve A. varius include a recently initiated captive breeding program as well as continued efforts to protect vital forest habitat (IUCN).
Recent testing indicates that the remaining population of A. varius is presently free of chytrid infection. In order to avoid future transmission, monitoring is carried out twice annually by a small group of researchers following strict decontamination protocols. Additionally, the persistence of A. varius is threatened by predation, habitat alteration, and the potentially detrimental effects of inbreeding. Current conservation efforts consist of population and microclimate monitoring, genetic studies, and habitat protection. Although evidence suggests that the current population is reproductively active and relatively stable, the long-term prognosis for A. varius is uncertain (personal correspondence 2007).
- Crump, M.L. 1986. Homing and site fidelity in a Neotropical frog, Atelopus varius (Bufonidae). Copeia 1986(4): 1007-1009.
- Crump, M.L. 1988. "Aggression in harlequin frogs: male-male competition and a possible conflict of interest between the sexes." Animal Behaviour 36(4): 1064-1077.
- Crump, M.L., and J.A. Pounds 1985. "Lethal Parasitism of an Aposematic Anuran (Atelopus varius) by Notochaeta bufonivora (Diptera: Sarcophagidae)." Journal of Parasitology 71(5), 588-591.
- Lips, K.R. 1999. Mass mortality and population declines of anurans at an upland site in western Panama. Conservation Biology 13: 117-125.
- Lips, K.R., Green, D.E. and Papendick, R. 2003. Chytridiomycosis in wild frogs from southern Costa Rica. Journal of Herpetology 37: 215-218.
- Personal correspondence with Twan Leenders of the Rainmaker Project. May 24, 2007.
- Pounds, J.A., Bustamante, M.R., Coloma, L.A., Consuegra, J.A., Fogden, M.P.L., Foster, P.N., La Marca, E., Masters, K.L., Merino-Viteri, A., Puschendorf, R., Ron, S.R., Sánchez-Azofeifa, G.A., Still, C.J. and Young, B.E. 2006. Widespread amphibian extinctions from epidemic disease driven by global warming. Nature 439: 161-167.
- Pounds, J.A., and Crump, M.L. 1987. "Harlequin Frogs Along a Tropical Montane Stream: Aggregation and the Risk of Predation by Frog-Eating Flies." Biotropica 19(4): 306-309.
- 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: 72-85.
- Pounds, J.A., Fogden, M.P.L., and J.H. Campbell 1999. "Biological response to climate change on a tropical mountain." Nature 398(6728): 611-615.
- Savage, J.M. 1972. The harlequin frogs, genus Atelopus, of Costa Rica, and western Panama. Herpetologica 28: 77-94.
- Savage, J.M. 2002. The Amphibians and Reptiles of Costa Rica. University of Chicago Press, Chicago. ISBN 0-226-73537-0
- IUCN 2006. 2004 IUCN Red List of Threatened Species.<http://www.iucnredlist.org/>. Downloaded on 6 May 2007.
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