Ex situ conservation of the Bengal florican 905
2013b; Mahood et al., 2019) as a result of habitat loss, agri- cultural intensification, hunting, and predation by free- ranging domestic dogs (Packman et al., 2013a; Ibbett et al., 2019). In 2018 the population was estimated to be 138 (95% CI 119–156) birds at four sites where display activity still oc- curred, and one site (Koup Preah Buong Trea) where a few additional birds remain (Mahood et al., 2019). Intensive in situ conservation efforts stabilized population trends at one site, Stoung-Chikreang Bengal Florican Conservation Area (Mahood et al., 2019), but that population is now threatened by a newly-constructed power line that could lead to local extinction (Mahood et al., 2016).Given the dire situation fa- cing the species there have been calls from within Cambodia to consider captive management to prevent its global extinc- tion (
M.Meyerhoff, pers. comm., 2018). Mindful of the need to make a timely decision on whether to proceed with captive management, but aware of the potential risks of making the wrong decision, we use the IUCN Guidelines to make a decision about ex situ conservation of the Bengal florican. Instructions for using the guidelines are available (McGowan et al., 2017), but not tools for each step or a worked example. We developed simple tables to evaluate the issues for consideration under Steps 3 and 4, and a deci- sion tree for Steps 2 and 5.We use a demographicmodel de- veloped byDolman et al. (2015)to informStep 3 and explore the probability of success of ex situ conservation (Addison et al., 2013). We show how these tools enabled us to make a decision about ex situ conservation of the Bengal florican and hope that the decision tree will assist other conservation managers facing similar predicaments.
Methods
Development of tools We first conducted a review of the status of the Bengal flori- can (Mahood et al., 2019), following Step 1 of the guidelines (IUCN/SSC, 2014). We created a decision tree that com- bined Step 2 (identification of the potential role of ex situ conservation in the conservation of the species) with the part of Step 4 that evaluates risk to the wild population from ex situ conservation (Fig. 1). We created a table to evaluate the practical considerations associated with ex situ conservation of the species (Table 1: Step 3), and a similar table to evaluate practical risks (Table 2:Step 4). The prac- tical risks were separated from risks to the wild population because they can be mitigated, unlike biological risks for which mitigation is often difficult or impossible.
Demographic modelling
To inform our evaluation of practical and biological risks to the wild and captive populations (Step 3), and evaluate
whether ex situ management would increase the probability of persistence, we used a publicly available demographic model developed for evaluating the efficacy of captive breeding for the great Indian bustard Ardeotis nigriceps (Dolman et al., 2015). We retained the same parameters as Dolman et al. (2015), who used data from a range of medium and large-sized bustard species, except where data existed for Bengal florican or the more similarly-sized little bustard Tetrax tetrax, or where variation was expected based on the smaller body size of the Bengal florican (Supplementary Tables 1 & 2). As these parameters include data from a number of bustard species that are larger and possibly slower to mature than the Bengal florican, they are likely to yield a conservative estimate of the chance of persistence (see Dolman et al., 2015, for detailed methodology; only key points are summarized here). Where we differ most from Dolman et al. (2015) is in the nature of the situation with which we compare captive breeding. They compared the ef- fect on the wild population of either pursuing a programme of captive breeding and subsequent release, or improving the efficacy of in situ conservation in the absence of captive breeding. In our case, with or without ex situ conservation the wild population continues to decline at an accelerated rate, even though since 2005 everything possible (within the constraints of relevant socio-economic and political factors) has been attempted to maintain it. The model allowed us to evaluate the chance of persis-
tence of a captive population under various strategies for collecting eggs from the wild, and the probability that individuals could be released within 50 years. We did not consider capture of adults from the wild because captive fa- cilities that breed bustards advised against
it.Wedid not use our model to evaluate the probability of persistence of the wild population because we had insufficient data to para- meterize the model, but the current trajectory, based on data from 12 years of population monitoring, suggests that the Bengal florican will be functionally extinct by 2023 (Mahood et al., 2019). The captive breeding model assumes that we can collect amaximum of five or 10 eggs in the first year (the mean number of eggs found annually during 2014– 2018 is 7.4;Wildlife Conservation Society, unpubl. data), but that this will decline by two eggs per year for 5 years as the wild population declines. The release model assumes that all released birds are ,1 year of age, to minimize behavioural adaptation to captivity (Inchausti & Bretagnolle, 2005). Following Dolman et al. (2015), releases do not occur until the captive population has reached 20 mature females so as not to jeopardize the persistence of the captive population (IUCN/SSC, 2013); we set the minimum group size of re- leased birds to five because a minimum of four males plus one female is required for a Bengal florican exploded lek to function (Gray et al., 2009). For captive management mod- els, we considered four scenarios of performance quality to account for variation in demographic performance of
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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