Red List Status

Extinctions
Status by Taxonomic Group

A primary goal of the Global Amphibian Assessment is to assess each known amphibian species with respect to the IUCN Red List categories and criteria. These categories provide an explicit framework for determining a species’ conservation status, with an emphasis on identifying those at highest risk of global extinction. In this context, the term “Threatened” refers to those species classified under Red List categories of Vulnerable, Endangered, or Critically Endangered.

Of the 5,918 amphibian species assessed nearly one-third of extant species (32.2%) are globally threatened, representing 1,896 species (Figure 1). This is considerably higher than the comparable figures for birds (12 %) and mammals (23%), the only other animal groups for which comprehensive global assessments have been completed. Thirty-four species are considered to be Extinct (EX), and one Extinct in the Wild (EW). Another 2,604 species are not considered to be threatened at present, being classified in the IUCN Categories of Near Threatened (NT) or Least Concern (LC), while sufficient information was not available to assess the status of an additional 1,383 species.

Figure 1. IUCN Red List Assessment for all 5,918 Known Amphibian Species

Relative to other animal groups, a particularly high proportion of amphibians are in higher threat categories. For example, 7.7% of amphibians are listed as Critically Endangered (456 species) compared with 1.8 % of birds (179 species) and 3.8% of mammals (184 species). Threat levels for amphibians are also undoubtedly an underestimate given that nearly a quarter (23.4%) of species are too poorly known to assess (i.e., Data Deficient), and a significant proportion of these are likely to be globally threatened. Comparable figures for birds and mammals are 0.8 % and 5.3% respectively.

Documenting population trends is a key to assessing species status, and a special effort was made to determine which species are declining, stable, or increasing. The GAA found declines to be widespread among amphibians, with 42.5% of species reported to be in decline. In contrast, 26.6% appear to be stable and just 0.5% are increasing. Because trends information is not available for 30.4% of species, however, the percentage of species in decline may actually be considerably higher.

Extinctions

Extinctions are notoriously difficult to confirm. Using the most conservative approach to documenting extinctions, just 34 amphibians are known to have become extinct since the year 1500. Of greater concern, however, are the many amphibians that are missing and can no longer be found. Until exhaustive surveys probing their disappearance can be carried out, these species cannot be classified in the Red List category of Extinct, but rather are flagged as “possibly extinct” within the Critically Endangered category. The GAA documents 130 such possibly extinct species.

Unfortunately, there is strong evidence that the pace of extinctions is increasing. Of the 34 known extinctions, 9 have occurred since 1980, including such species as the golden toad (Bufo periglenes) of Monteverde, Costa Rica. Among those amphibians regarded as “possibly extinct”, at least 113 have disappeared and not been seen since 1980. Fortunately, a few amphibians that previously were thought to be extinct have been rediscovered. For example, Atelopus cruciger was not seen in its native Venezuela after 1986, until a tiny population was found in 2003.

Status by Taxonomic Group

Amphibians comprise three major groups, or taxonomic orders: Anura (frogs and toads), Caudata (salamanders and newts), and Gymnophiona (caecilians). Significant differences exist among these groups in both species numbers as well as threatened status. For instance, there is an order of magnitude more frogs and toads than salamanders and newts, and even fewer caecilians are known. Frogs and toads, with 5,211 species very much drive the average threat level for amphibians as a whole with 32.1% (1,675 species) either threatened or extinct. Salamanders and newts, however, show significantly higher threat levels, with 46.9% (251 species) of their species threatened or extinct. Caecilians, in contrast, appear to be relatively secure with just 2.9% (5 species) threatened. However, two-thirds (66%) of caecilians are so poorly known that they have been assessed as Data Deficient.

Table 1. Red List Status by Taxonomic Order

Significant difference in threat levels is also exhibited at the level of taxonomic Family, as show in Table 2. Very diverse families of frogs and toads that are more threatened than the global average include the Bufonidae, Leptodactylidae and Rhacophoridae. Sadly both species of the Australian endemic family Rheobatrachidae (the gastric-brooding frogs) are now Extinct. Two other families at severe risk of disappearing altogether are Leiopelmatidae ( New Zealand frogs) and Rhinodermatidae ( Darwin’s frogs in Chile and Argentina). Diverse families that are less threatened than the global average include Ranidae, Microhylidae and Hyperoliidae. Among larger salamander families, Hynobiidae and Plethodontidae exhibit much higher levels of threat than Salamandridae.

Darwin’s frog (Rhinoderma darwini), Chile and Argentina / Photo by Michael and Patricia Fogden	Maud Island frog (Leiopelma pakeka), New Zealand / Photo by Phillip Bishop

Nasikabatrachus sahyadrensis (a frog), India / Photo by S.D. Biju	Seychelles palm frog (Sooglossus pipilodryas), Seychelles / Photo by Justin Gerlach

Southern gastric-brooding frog (Rheobatrachus silus), Australia / Photo by Michael J. Tyler

The number of species in each IUCN Red List category in each of the hundreds of amphibian genera can be accessed here.