Range-restricted endemics under-represented in ex-situ conservation breeding programmes

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Species endemic to tropical montane and tropical island ecosystems, such as the Sulawesi Bear Cuscus are less likely to have an ex-situ captive breeding programme than their more generalist close relatives

Conservation organisations rightly focus on habitat protection and in-situ management. However, ex-situ breeding programmes can provide a critical stop-gap for many species on the brink of extinction in the wild. But new research has demonstrated that many species groups representing the highest extinction risk are actually underrepresented in zoo breeding programmes. In particular, mammal and bird species restricted to ecosystems considered to be at very high short-term risk from habitat destruction and climate change, including tropical montane forests and tropical islands, are less likely to have an ex-situ conservation ‘safety net’ than their non-endemic close relatives.

The study, recently published in ‘Animal Conservation’, first collated a list of all mammal and bird species currently being bred in high-quality zoos and other ex-situ breeding organisations worldwide – a total of 647 mammal and 1,183 bird species. To control for as many extraneous variables as possible, each species was then paired with its closest evolutionary relative not currently held in any zoos. It was possible to identify single-species matched pairs for a total of 165 mammal and 228 bird species. Members of these ‘in-zoos’ vs ‘not-in-zoos’ species pairs were then scored for a range of ecological and biogeographical variables, including IUCN threat score, spatial range, and several measures of endemism. Differences between pairs were then analysed using a range of univariate and multivariate statistics.

Island and montane ecosystems

Results demonstrated, perhaps surprisingly, that species held in zoos were at once significantly less endangered than their close relatives not held in zoos, had significantly larger spatial ranges, and were significantly less likely to be endemic to tropical island or montane ecosystems.

Under-representation of island and montane endemics in ex-situ conservation projects appears to occur in absolute terms as well as in these relative comparisons with close relatives. For example, of the 262 endemic bird species occurring on the island ecosystems of the Wallacea biodiversity hotspot (including those found in Operation Wallacea’s Buton forest research site), just 14 (5.3%) are the subject of a captive breeding programme. Even more notably, of the 70 species of bird which breed exclusively in forest ecosystems at >1000m altitude in the Mesoamerican biodiversity hotspot (including the highland endemics found in Operation Wallacea’s Cusuco National Park research site), just one (1.4%) is currently the subject of an ex-situ breeding programme.

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Green-throated Mountain Gem

The reason for this may be due to the isolation and associated ecological specialisation of these range-restricted endemics. Small islands and tropical montane forests are both relatively inaccessible to collectors (and were especially so in the colonial period when many captive breeding programmes were first established) and also support a large proportion of endemic species specialised to very narrow ecological niches which may prove hard to recreate in captivity. It could therefore be that if ex-situ conservation planners have the choice of selecting either a lowland or continental species with simple requirements for a breeding programme, or a closely related, aesthetically similar specialised endemic that may be hard to obtain, difficult to keep, and with an unknown record of breeding success, it is more rational to choose the former.

Elevated risk of extinction

Regardless of the reasons, the finding that tropical montane and island endemic mammals and birds are currently heavily under-represented in ex-situ breeding programmes is a cause for concern. The small, fragmented spatial ranges and narrow ecological specialisation inherent in many species endemic to these habitats facilitate an elevated risk of extinction from habitat destruction, climate change, and introduced predators.

A simple gauge of this vulnerability is the example that more than 85% of the birds which have become extinct since 1600 AD have been island endemics (even though island endemics make up <10% of all bird species). Recent models predict that these ecosystem types could face among the highest extinction rates of all habitat types in the short and medium-term future. Therefore, as most of these species currently exist only in their natural habitat, once they are extirpated from their relatively small natural ranges they will cease to exist anywhere on Earth.

In-situ conservation work is all the more urgent for the future survival of  these specialised endemic species

There are numerous examples of how ex-situ conservation programmes can allow for the survival (and later aid in the recovery) of species extinct or on the brink of extinction in the wild, especially in the case of island endemic birds (well-known examples include the Mauritius Kestrel, the Hawaiian Crow, and Socorro Dove). However, as it stands only a tiny percentage of island endemics have this ex-situ conservation safety net. Creating further ex-situ breeding programmes for other island and tropical montane endemics could provide extra security for these species.

However, doing so may not always be practical due to the issues of isolation and specialisation discussed, and because progressively stricter barriers now exist for establishing new captive breeding programmes for tropical species in more economically developed (non-tropical) countries, where most high-quality ex-situ institutions are based.

One solution may be to transfer greater responsibility for ex-situ conservation to high quality projects within countries where these endemics are native, as has recently been done with other taxa. That said, it remains unlikely that captive breeding programmes for a large proportion of the world’s island and montane endemics can be established in the short to medium term future. Given what we know about the pressures on these endemics in the short to medium term, this makes in-situ conservation work, such as that being conducted by Operation Wallacea scientists, all the more urgent for the future survival of  these specialised endemic species.

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