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The inadequate global zoo response to the amphibian extinction crisis

  • Amphibians have experienced massive declines worldwide.
  • The 6.2% of globally threatened amphibians held by zoos compares poorly with global totals for birds (15.9%), mammals (23%), and reptiles (38%).
  • There is a feeling of disappointment in the conservation community regarding the response of zoos to the amphibian crisis.

Amphibians have experienced massive declines worldwide, and scientists estimate that as many as 200 frog species have been lost in just the last two decades. A recent study, published in the journal Conservation Biology, analyzes how captive amphibian collections, held by a global network of zoos, have changed over the past 20 years in response to declines in the wild. With only 6.2% of globally threatened amphibians currently represented in worldwide collections, researchers are calling on zoos to step up conservation efforts to stem the tide of amphibian extinctions.

The 6.2% of globally threatened amphibians held by zoos compares poorly with global totals for birds (15.9%), mammals (23%), and reptiles (38%). The global total for amphibians is much lower, despite them being the most threatened group.

“Amphibians are in crisis and have been for a long time. They’re at the vanguard of what is now being called the sixth mass extinction. Despite this they still receive much less attention from the conservation community than other groups,” explained Jeff Dawson, lead author of the study and Amphibian Program Manager at the Durrell Wildlife Conservation Trust.

The authors of the new study examined twenty years of records from zoo institutions registered in the International Species Information System (ISIS) between1994 and 2014. Those dates encompass the 10 years before and 10 years after the Global Amphibian Assessment (GAA) of 2004 which first revealed that almost one third of the known 5,743 amphibian species were threatened with extinction. The researchers analyzed changes in zoo amphibian collections before and after the GAA to determine any increase in the proportion of globally threatened species held, how amphibian holdings varied by zoo region, and the conserved species’ region of origin.

The information on global amphibian holdings used in ISIS was taken from a network of more than 800 zoological institutions registered with the World Association of Zoos and Aquariums (WAZA) from across 84 countries.

Frog headstarting pod at the Durrell Wildlife Park. Note tadpoles in the top right tank. Photo by Matt Goetz.

Amphibian conservation efforts disappointing

There is a feeling of disappointment in the conservation community regarding the response of zoos to the amphibian crisis, note the authors, who state that “most conservation organizations still have not addressed the crisis, as amphibians are significantly underrepresented in the number of in situ [natural habitat] projects, often spearheaded and funded in major part by zoos, indicating their slow response.” Amphibian collections also “fall considerably short of the number of species for which ex situ [captive] management may be desirable,” say the researchers.

The study speculates that threatened amphibians may be the victims of ‘collection bias.’ The authors go further in explaining that “Zoos have to balance the needs of providing a visitor experience and dedicating resources to biodiversity conservation. While many amphibians make attractive displays, many threatened species are small, cryptic, and dully colored. This makes them less popular exhibits.”

“GTS [globally threatened species] are also more expensive than non-GTS to keep, and the geographic and ecological factors that increase extinction risk may also act as barriers to their representation in zoos. Zoos with limited expertise in amphibian husbandry will likely stick with easier, better established species,” the authors explain.

To increase the number of GTS in zoos therefore requires increased expertise.

The Dendrobatid breeding room at the Durrell Wildlife Park on Jersey Island (UK). Photo by Matt Goetz.

Increases in amphibian conservation after 2004

The study analyzed data for each species to determine the total number of zoos and total number of individuals held every year from 1994 to 2014. Amphibian species were categorized into two groups based on their current IUCN Red List status: GTS included all species listed by the IUCN Red List as Extinct in the Wild, Critically Endangered, Endangered, and Vulnerable; all other categories were grouped as non-GTS. Species were also categorized by region of origin.

The study found that between 1994 and 2014 the number of species held globally increased from 256 to 506 and the number of GTS increased from 44 to 121.

In respect to species’ region of origin, North American species comprised the largest proportion of all species (22.6%) and all GTS (20.3%) held from 1994 to 2014. European species were also well represented. For all the known GTS species, North America and Oceania were best represented with South America and Asia being the most poorly represented with only 2.5% and 3.1% of all GTS species held, respectively.

Zoos in all three ISIS regions — North America, Europe, and the rest of the world (ROW) —saw an increase in the total numbers of species held from 1994 to 2014. However, the rate of increase was greater after 2004 in Europe and ROW, while there was no rate change for North America.

The critically endangered giant ditch frog (Leptodactylus fallax), is the focus of Durrell’s flagship amphibian conservation project. Known locally as the mountain chicken, it is native to the Caribbean islands of Dominica and Montserrat. This is a male mountain chicken calling on a rock. Photo by S.L. Adams.

The number of GTS held, and the proportion of regional holdings that were GTS, increased significantly in all three regions from 1994 to 2014. This increase was greater after 2004 than before in North America and ROW, but in Europe there was no difference in the rate before or after 2004.

“Although overall numbers and proportions of GTS increased over the last 20 years,” researchers conclude, “amphibians are still very poorly represented within zoos in most regions and globally.”

The mountain chicken breeding facility at Durrell Wildlife Park. Photo by Matt Goetz.

Moving forward with amphibian conservation

It’s unclear whether the increase in number and proportion of GTS held in international zoos since 2004 is a direct response to the global amphibian crisis or a reflection of change in general global zoo policy. While the trends may be positive, the absolute numbers of GTS, particularly Critically Endangered and Endangered species, are still very low. In 2014 there were 121 GTS in ISIS zoos (23.9% of all amphibian species, and just 6.2% of globally threatened amphibians).

The study authors particularly emphasize the need to maintain the genetic diversity of all captive amphibian species. Large captive populations help achieve genetic sustainability, and “given their captive requirements it may well be easier to maintain genetically viable populations of amphibians than for larger mammals and birds,” Dawson pointed out.

Based on results showing that globally threatened amphibians are poorly represented in ISIS zoos, the study proposes that more capacity within existing collections should be given to GTS.

Understanding the barriers to increasing numbers of globally threatened amphibians in zoos is crucial. With this knowledge, measures can be undertaken to increase the numbers and proportions of globally threatened amphibians in conservation programs. Full knowledge of all global amphibian conservation efforts, both in the field and in zoos, and including all institutions, is essential to creating effective programming for preventing further amphibian extinctions.



Dawson, J., Patel, F., Griffiths, R. A. and Young, R. P. (2015) Assessing the global zoo response to the amphibian crisis through 20-year trends in captive collections.Conservation Biology.