Golden toad  (Bufo periglenes)

The golden toad has not been seen since 1989, and is believed to be extinct (1). This toad displays extreme sexual dimorphism; males are a brilliant orange colour but females are dark and mottled with yellow-edged red blotches. Females also tend to be slightly larger than males. In juveniles, however, the sexes cannot be determined as they are very similar (2).

This species was known from a small area of undisturbed montane cloud forest in northern Costa Rica, Central America. This region has been designated as the Monteverde Cloud Forest Reserve (2).

The golden toad inhabits wet montane forest at 2,000 to 2,100 metres above sea level (2).

Very little is known of the natural history of this species (2). It is active in the day, and breeding is confined to a short space of time between April and June during the rainy season (2). Huge numbers of golden toads once gathered at temporary pools of water, and as the males outnumbered females by 8:1, competition for females was fierce. Once a male forms a bond with a female, the pair are said to be in 'amplexus'; the male clasps the female tightly with his forearms around her back until they mate. During this time the male may face harassment from non-paired males trying to gain access to the female (2). Females produce 200 to 400 eggs, after hatching the larvae remain in the pool for about five weeks before metamorphosis into the terrestrial form occurs. It is thought that this toad feeds on small invertebrates, and may live underground at certain times of the year (2).

The population of golden toads underwent a massive crash in 1987 (2). A few individuals were found up until 1989, but the species has not been seen since then (2). Twenty out of 50 species of frogs and toads (anurans) occurring within a 30 kilometres squared area in Monteverde disappeared after synchronous population crashes in 1987, and have shown no sign of recovery (4). The area is pristine and free of direct human influences (5), a number of reasons have been proposed to explain the decline, including fungal disease, and climatic changes (4) (7).

The probable extinction of the golden toad reflects the current worldwide decline in amphibian populations. The more subtle effects of human activities on the world's ecosystems such as the build-up of pollutants, the decrease in atmospheric ozone, and changing weather patterns are beginning to take their toll. Amphibians may be our first and only early warning that these effects are starting to reach catastrophic levels (6), and may be the first sign of impending ecosystem crashes (7). In 1991, the Species Survival Commission of the IUCN established the Declining Amphibian Populations Task Force (DAPTF), which later merged into the Amphibian Specialist Group, which aims to raise money and promote research into the global amphibian decline (6).

For more information on global amphibian declines see:

• IUCN/SSC Amphibian Specialist Group:
  www.amphibians.org
• Amphibia Web:
  www.amphibiaweb.org//declines

Authenticated (28/07/03) by Andrew Gray, Curator of Herpetology, University of Manchester.