912 S. P. Mahood et al.


et al., 2018). These changes lead to lower mortality in captiv- ity but cause higher mortality among released captive-bred individuals compared to wild birds, as is also the case with captive-reared great bustards (Burnside et al., 2012;Dolman et al., 2018). Perhaps unsurprisingly, like most reintro- duction attempts (Fischer & Lindenmayer, 2000; Bowkett, 2009), no reintroduction of bustards has been completely successful (Dolman et al., 2015; Ashbrook et al., 2016). There is a significant chance that any reintroduction of the Bengal florican will also fail to establish a self-sustaining wild population, even if the species persists in captivity. A major impediment may be lack of habitat. If the wild popu- lation is extirpated, protection of the remaining fragments of grassland on the Tonle Sap floodplain may become hard- er, so habitat of the kind that is currently associated with the species may not be available for reintroduction. Although this situation is relatively common for amphibians and reptiles, which are frequently maintained in captivity until suitable conditions exist in the wild for their release (Turtle Conservation Fund, 2002; Krajick, 2006; Zippel et al., 2011), it is relatively rare in birds (BirdLife International, 2018a). In general, birds are harder to maintain in captivity than herptiles, but easier than mammals. The Guam king- fisher Todiramphus cinnamominus is so far the only bird species Extinct in the Wild never likely to be returned to its native range, because the snakes that drove it extinct can- not be eradicated, although it may be introduced to a nearby island (Laws & Kesler, 2012). The little spotted kiwi Apteryx owenii has recently been reintroduced to predator-free sanctuaries on the New Zealand mainland; prior to this it persisted for decades only in captivity and on tiny offshore islands where it had never occurred naturally (Holzapfel et al., 2008). For these reasons, and because ex situ management is


costly and risky, it can only be justified if less intrusive al- ternatives are unlikely to secure species persistence (Snyder et al., 1996). By using the IUCN guidelines to assess the po- tential role of ex situ conservation in preventing the extinc- tion of the Bengal florican, we were able to make a decision that comprehensively considered all of the risks, and we concluded that ex situ conservation should be attempted immediately. A similar process was used to evaluate the po- tential role of ex situ conservation for the South Australian subspecies of glossy black-cockatoo Calyptorhynchus latha- mi halmaturinus, which concluded that although techni- cally feasible, captive management would be costly and the population would probably recover without it (Crowley et al., 1999). This proved correct: the population recovered from 195 individuals in 1995 to c. 356 individuals in 2014 without captive management (Morgan et al., 2015). In con- trast, based on information available to us at the time, we concluded that we should proceed with captivemanagement of the Bengal florican and begin egg harvest in 2019 because the wild population is likely to decline at an accelerated rate


owing to new threats that are affecting the only stable pop- ulation, and because the chance of establishing a captive population is relatively high if we draw on global bustard husbandry expertise to minimize adult mortality in captiv- ity. We did not consider how best to manage the captive population to maximize genetic variation; this could have been integrated into the assessment process, but instead the breeding programme will be planned using molecular data obtained from any chicks that hatch from harvested eggs (Hogg et al., 2018). At the time of writing we received additional information


on breeding parameters of captive little bustards fromCentro de Cría de Aves Esteparias. Using these data we repeated the population modelling to inform our ex situ conservation programme. Demographic modelling indicated that the chance of persistence of a captive population was better than we had predicted at the time of the workshop under all scenarios except below-average. Our estimate of prob- ability of persistence of a captive population for 50 years under an above-average scenario increased from 60 to 79% at egg harvest rates of five per year for 5 years, and from 83 to 97%if harvest rates are 10 per year. The probabil- ity of producing sufficient individuals for release was.75% for above-average and best possible scenarios under egg har- vest rates of at least five per year for 5 years, indicating that there was a much greater chance of releasing captive-bred Bengal floricans within 50 years than we had anticipated, but failure is still possible. Although we used the same demographic model as


Dolman et al. (2015), and our model outputs are unsurpris- ingly similar, the conclusions that we reached are different. There are three reasons for this: (1) differences in data used to parameterize the model, (2) differences in characteristics of the counterfactual no ex situ scenario, and (3) local stake- holders led the assessment process. To parametrize the model we used data from the Bengal florican and little bus- tard, where it was available, in addition to the data from larger bustard species used by Dolman et al. (2015). How- ever, this had relatively little impact on model outputs; for instance, with egg harvest rates of five per year for 5 years, Dolman et al. (2015) report probability of extinction over 50 years for the great Indian bustard under a best possible scenario of 17%, compared with 11% for Bengal florican (al- though we report this as an 89% probability of persistence); we interpret this as an indication that if ex situ manage- ment is done well it is likely to prevent the extinction of the species. These results are compared with a counterfactual scenario for the wild population in which no egg harvest takes place.Webelieve that we formulated a plausible future scenario for the wild population of the Bengal florican, given trends, threats and resources available for additional in situ conservation (Mahood et al., 2019). For instance, although we believe that we know how to manage areas under rice cultivation (such as Sankor) for the Bengal florican, we do


Oryx, 2021, 55(6), 903–915 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319001510


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