Atelopus varius

Costa Rican Variable Harlequin Toad
Conservation status
Critically Endangered  (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Amphibia
Order:	Anura
Family:	Bufonidae
Genus:	Atelopus
Species:	A. varius
Binomial name
Atelopus varius (Linnaeus, 1771)

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 a few declining populations in Panama (last recorded in 2002) (IUCN). It is believed that 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).

The dorsal coloration of A. varius is characterized by light and dark patches, with ground coloration ranging from lime-green to yellow-orange and surface markings of black. The ventral surface ranges from yellow-green to orange with the same type of black surface markings. The throat and venter can appear bright scarlet, and the groin can appear blue-green or green. The snout is short, and appears rounded in profile. The pupil is horizontally elliptical, there is no tympanum, and there are no distinct glandular ridges. Paired elongate vocal slits run parallel and lateral to the tongue; males have an internal vocal sac. Males have webbing between the first and second finger, and the first finger also bears a nuptial pad. Toes are webbed except for IV, and there is no tarsal fold. Snout-vent length of adult males ranges from 25 to 41 mm. Females are 33 to 60 mm in length (Savage 1972, Crump 1988).

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 location on the Pacific coastal range near Quepos, Costa Rica as well as a few protected areas in Panama (IUCN).

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 entugement 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 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 eliminated some populations while others have managed to persist (Lips 1999). The last recorded sighting of A. varius in Panama occurred in 2002 (IUCN).

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 80’s and early 90’s 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 achytridiomycete 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).

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.

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 (London), 398(6728), 611-615.

Savage, J.M. 1972. The harlequin frogs, genus Atelopus, of Costa Rica, and western Panama. Herpetologica 28: 77-94.

http://www.iucnredlist.org/search/details.php/54560/all

http://www.iucnredlist.org/- IUCN Red List of Endangered Species

http://www.rainmakercostarica.com/- The Rainmaker Project