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).

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).

Southern Central America (Costa Rica) south into northwestern South America (Capula, 1989; Staniszewski, 1995).

Biogeographic Regions: neotropical (Native )

Countries

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).

Adult

Species description based on Savage (2002).  Medium frog (males 27-39 mm, females 33-48 mm).

Dorsal

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.

Eye

Iris green. Pupil horizontal.

• Terrestrial
• Freshwater

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

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).

Diet

Atelopus varius is an ant specialist, but feeds in small amounts on other arthropods (Toft 1981). They actively search for their prey (Toft 1981).

Ecology

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).

Call

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).

Breeding season

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).

Egg

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).

Tadpole

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).

Average lifespan

Status: captivity: 10 years.

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).

Physiology

The skin of Atelopus varius contains tetrodotoxin (Kim et al. 1975).

Karyotype

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

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.

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).

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.