Ex situ conservation planning is more complicated than prioritizing the keeping of threatened species in zoos

The role of zoos and similar organizations in conservation has long been controversial. Zoos can be seen as preadapted for the intensive management of threatened species (Conway, 1995), can provide a huge global audience for conservation advocacy (Gusset & Dick, 2011) and can collectively provide a significant proportion of global funding to in situ conservation (Gusset & Dick, 2010). On the other hand, the value of ex situ conservation has been questioned (Rahbek, 1993), the advocacy and educational impacts of zoos are difficult to measure (Marino et al., 2010) and critics accuse zoos of misleading the public as to their commitment to conservation (Born Free Foundation, 2007). Martin et al. (2014) use a novel comparison of paired species to show that species held in zoos are on average less threatened according to International Union for Conservation of Nature (IUCN) Red List criteria than closely related species not held in zoos. Furthermore, zoo species are less likely to meet several other criteria that might be associated with high conservation priority, such as having small spatial ranges or being found in high-risk ecosystems. This valuable analysis adds to a body of evidence showing that the majority of species in zoos are not globally threatened with extinction (Conde et al., 2011, 2013). Rather than critique Martin et al.’s careful study, I focus here on the assumption that the proportion of threatened species held reflects the conservation impact of zoos, discuss some of the factors that might explain the observed pattern and suggest some areas for future research. It may seem obvious that if the majority of species held in zoos are not threatened then zoos are failing to direct their ‘ex situ resources’ where they are most needed. However, there are several reasons why this may not be the case. Firstly, it may not be a good indicator of investment compared with more direct measures such as the financial cost of maintaining captive populations. It is plausible that non-threatened species are inexpensive to maintain while the majority of funds are spent on threatened species. After all, many of the charismatic species most often associated with zoos, such as elephants and rhinoceros, are both highly threatened and expensive to keep in captivity (Balmford, Leader-Williams & Green, 1996). Secondly, zoos may have recognized that captive breeding programmes outside of a species’ native range are rarely the most appropriate conservation strategy for recovery (Snyder et al., 1996) and instead selected larger and more attractive species to attract visitors (e.g. Frynta et al., 2013) and thereby financially support conservation in the wild. Collectively, World Association of Zoos and Aquariums members are the third largest financial supporter of in situ species conservation (Gusset & Dick, 2010). Thirdly, zoos may have decided not to discriminate between species on the basis of threat given the potential for non-threatened species to become highly threatened in the future. Examples of species commonly held in zoos whose Red List status has changed rapidly to a more highly threatened category include the hippopotamus Hippopotamus amphibious and lar gibbon Hylobates lar. Finally, zoos may hold large numbers of non-threatened species selected for their indirect conservation value. Potentially, this could include broader roles in environmental education or representing threatened ecosystems. Perhaps more tangibly, zoos might hold species that are locally or regionally threatened but globally assessed as Least Concern, such as European wild cats Felis silvestris in the United Kingdom, or are being held as model species to develop recovery methods for closely related threatened species in the wild. All the above reasons have likely influenced decisions concerning the inclusion of particular species in institutional or regional collection plans. However, if these factors were sufficient to explain the results of recent studies (Conde et al., 2013; Martin et al., 2014), they would be reflected in ex situ conservation policy documents. In reality, the history of ex situ conservation planning consists largely of compiling aspirational lists of candidate species (Bowkett, 2009) and then collectively failing to establish viable captive populations for the majority of those suggested. Examples include the Global bs_bs_banner