An ever-increasing body of literature has been published in the last two decades about the global amphibian crisis and the rapid rate of amphibian species extinction in the face of threats such as habitat loss and degradation as well as disease, especially chytridiomycosis. This recent extinction crises, believed to have been responsible for the loss of at least 200 amphibian species, was first documented in the Global Amphibian Assessment in 2004, revealing the scale of the phenomenon and estimating that around 30% of all amphibian species were threatened with extinction, compared to 12% of birds and 23% of mammals. Current figures are even more worrying, putting the threatened species category at over 40%, thus making amphibians the most threatened group of species and clearly indicating the huge scale of resources, funding and efforts urgently needed in order to prevent further declines and extinctions in several hundred or even thousands of amphibian species worldwide. Part of the solutions requires both salvaging species currently critically endangered in the wild and encouraging captive breeding in order to be able hopefully to reintroduce them back into the wild to either augment an existing population or to replace a lost one.
Captive breeding, mainly by zoos, has often been praised for directly reversing otherwise imminent extinctions in threatened species, including some already extinct in the wild, such as the European bison (Bison bonasus) and Californian condors (Gymnogyps californianus) and arguably, no other group is greater need of such measures than amphibians given their overall status. Equally, given the catastrophic declines in amphibian species affected by the chytrid fungus and the lack of a tested solution for dealing with the infection in the wild other than the recent example in Mallorca (Bosch et al. 2015), for many amphibians the creation of a safety population in captivity might be crucial for their immediate survival.
However, a recent publication (Dawson et al. 2015) reveals that following an investigation of records from ISIS’s Zoological Information Management System, representing over 800 zoological institutions dealing with captive breeding animal facilities in 84 countries the numbers and percentages of threatened amphibians in such programmes have remained very low despite some gains compared to 10 years ago. Splitting the species into two categories based on their IUCN status, between 1994 and 2014 the number of species held globally increased from 256 to 506 and the number of globally threatened amphibian species increased from 44 to 121. Of these, North American species comprised the largest proportion of all species while South America and Asia were the poorest represented, despite both being extremely diverse and rich in rare, declining and endemic amphibian species.
The numbers of the threatened amphibian species, particularly in the Critically Endangered and Endangered categories, remained overall very low at 121 species representing just 6.2% of globally threatened amphibians. Interestingly, this category of species, while potentially the one in the most urgent need, represented only 24% of the total number of amphibian species in zoos and other captive breeding facilities. These figures are worse than for other groups such as birds and mammals and a worrying sign of the very slow pace of action in relation to the catastrophic amphibian declines worldwide. The reasons for this might involve the fact that some amphibian species do not make good zoo attractions being cryptic and small but also the fact that many globally threatened species face geographical and expertise barriers to implementations of captive population programmes.
This study forms a very important step in better understating the current situation in relation to captive breeding of threatened amphibian species as well as the urgency is improving and radically changing the number and proportion of amphibian species kept in these centres, especially from the most endangered categories.
Jaime Bosch, Eva Sanchez-Tomé, Andrés Fernández-Loras, Joan A. Oliver, Matthew C. Fisher, Trenton W. J. Garner (2015) Successful elimination of a lethal wildlife infectious disease in nature; Biology Letters. DOI: 10.1098/rsbl.2015.0874
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