762 H. Bannister et al.


TABLE 4 The time taken by reintroduced brushtail possums to ac- climatize, based on five measures. Additional data from Bannister et al. (2020) and Moseby et al. (2020).


Acclimatization measure Successfully reproduce


Select safe, suitable shelter sites Establish a stable home range Maintain or gain body mass


Consume a natural, stable diet, relative to availability


FIG. 3 The height distribution of plants grouped by dietary preference (Jacob’s Index values compared to zero, calculated for the year), and the mean per cent of scats containing genera in those size classes. Genera contained in ,5% of both scats and vegetation surveys were omitted, probably reducing the number of non-preferred plants included.


Cruz et al., 2012; Gloury & Handasyde, 2016). This could be a result of the avoidance of predators at ground level, the quality of food in the canopy, or a combination of both. Wefound no significant sex effects in the diet of brushtail


possums. Combined with the presence of pouch young at all times during the study period (Bannister et al., 2020; Moseby et al., 2020), this suggests that lactation demands do not extend to detectable differences in the diet of breed- ing and non-breeding individuals. We suggest post-release diet studies should, at least, span one full breeding season after release, to assess whether food resources are adequate for breeding and the survival of juveniles, and to investigate whether food requirements differ between breeding and non-breeding individuals, or by sex. We were unsuccessful in identifying invertebrate DNA


in brushtail possum scats and therefore do not know the importance of invertebrates in their diet at our study site. Employing a second analysis technique such as microhisto- logical analysis could have benefited our study and facili- tated the identification of invertebrates and other non- plant material in scats. Fungi intake was not measured, but was present in the diet of possums in south-west Australia (How & Hillcox, 2000). The use of two genetic markers, as per Wilkinson et al. (2017), facilitated the detec- tion of a higher number of genera within the diet than the use of one marker alone, but the sensitivity of each marker to genera varied; some genera were only detected by one of the markers. Although DNA sequencing is increasingly being used to study animal diets (e.g. Hibert et al., 2013; Thomas et al., 2014), limitations include not being able to determine which parts of plants are being eaten, an often low resolution of diet content to family or genus, inaccurate proportions of genera within samples, and reliance on a comprehensive and accurate reference library (Hibert et al., 2013; Thomas et al., 2014). Some species identified as hav- ing a high frequency of occurrence in scats using DNA


Time taken 0 days


3 weeks


2–6 weeks 30–60 days .12


months


(e.g. Petalostylis)wereuncommonatour study siteand may in fact be closely related genera. Diet studies of any method are not immune to error and we urge caution in relying sole- ly on DNA studies of diet. Selectivity analyses are subject to the accuracies of the proportions given by the two markers, as well as plant availability data. Finally, with the benefit of hindsight, our study should have extended beyond 12months, given that the possums’ diet had not stabilized within this period.Monitoring the diet over multiple years and compar- ing to the diet of an established, non-reintroduced possum population would also allow seasonal effects to be discerned from effects of post-release acclimatization. The interaction between diet and time since release in


reintroductions has been largely overlooked. Our study demonstrates that a reintroduced population can, over time, decrease its dietary richness and diversity, while in- creasing the consumption of preferred foods. This acclima- tization period is longer than that recorded using move- ment, body condition and reproductive data and suggests a range of indicators should be used to measure acclimatiza- tion at different time scales, to ensure ecological relevance. Although only a small number of genera made up the bulk of each sample, a large number of genera were ingested, sug- gesting some opportunistic feeding and a relatively high consumptive diversity. The availability and consumption of plant species at our site was not a barrier to reintroduction success in the short- or medium-term but drought con- ditions were not experienced and could impact longer-term establishment. We suggest that the acclimatization period should extend past the first drought period for arid zone spe- cies, to ensure that suitable food plants can be sourced under stressful conditions.


Acknowledgements The reintroduction of brushtail possums to the Ikara-Flinders Ranges National Park occurred via a partnership between the South Australian Department for Environment and Water and funding partner the Foundation for Australia’s Most Endangered Species, with the Australian Wildlife Conservancy pro- viding possums for translocation. Additional funding for this research was provided by Holsworth Wildlife Research Endowment, the Field Naturalists Society South Australia, the Linnean Society of New South Wales, and The University of Adelaide. HLB acknowledges the support she received for this research through the provision of an Australian Government Research Training Program Scholarship.


Oryx, 2021, 55(5), 755–764 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319000991


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164