The historic range of A. varius stretched from the Pacific and Atlantic slopes of the Cordilleras de Tilaranmountain 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 .
Habitat and ecology
A. varius is a diurnal frog often found on rocks or in crevices along streams in humid lowland and montane forests. It is primarily a terrestrial species, only entering the water during breeding season, relying on spray from streams for moisture. 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. Its main food source is small arthropods that are most abundant during the dry season. The only known predator of A. varius is a parasitic sarcophagid fly 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.
Conservation status
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. 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. In Panama, mass mortality has drastically reduced populations of A. varius in recent years and it is now believed to be locally extinct. 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.. More recently, an observed global decline in amphibian species richness has been linked to an outbreak of the pathogenic chytrid fungus Batrachochytrium dendrobatidis. 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. Current attempts to preserve A. varius include a recently initiated captive breeding program as well as continued efforts to protect vital forest habitat.
