Time to adjust: changes in the diet of a reintroduced marsupial after release
HANNAH B AN NI ST ER,ADAM CRO X F O R D,ROB E R T BRANDLE DAV I D C. PAT O N and KAT H E R I N E MOS E B Y
Abstract An important component of reintroduction is acclimatization to the release site. Movement parameters and breeding are common metrics used to infer the end of the acclimatization period, but the time taken to locate pre- ferred food items is another important measure.Westudied the diet of a reintroduced population of brushtail possums Trichosurus vulpecula in semi-arid South Australia over a 12 month period, investigating changes over time as well as the general diet. We used next-generation DNA sequencing to determine the contents of 253 scat samples, after creating a local plant reference library. Vegetation surveys were con- ducted monthly to account for availability. Dietary diversity and richness decreased significantly with time since release after availability was accounted for. We used Jacob’s Index to assess selectivity; just 13.4% of available plant genera were significantly preferred overall, relative to availability. The mean proportion of preferred plant genera contained within individual samples increased significantly with time since release, but the frequency of occurrence of pre- ferred plants did not. Five genera (Eucalyptus, Petalostylis, Maireana, Zygophyllum and Callitris) were present in more than half of samples. There was no difference in diet- ary preferences between sexes (Pianka overlap = 0.73). Our results suggest that acclimatization periods may be longer than those estimated via reproduction, changes in mass and movement parameters, but that under suitable condi- tions a changeable diet should not negatively affect reintro- duction outcomes. Reintroduction projects should aim to extend post-release monitoring beyond the dietary acclima- tization period and, for dry climates, diet should be moni- tored through a drought period.
Keywords Acclimatization, Australia, brushtail possum, diet, marsupial, reintroduction, translocation, Trichosurus vulpecula
HANNAHBANNISTER (Corresponding author,
orcid.org/0000-0002-1784-5216), DAVID C. PATON and KATHERINE MOSEBY*(
orcid.org/0000-0003-0691-1625) School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia. E-mail
hannah_bannister@outlook.com
ADAM CROXFORD Plant Research Centre, The University of Adelaide, Adelaide, Australia
ROBERT BRANDLE Department for Environment and Water, Port Augusta, Australia
*Also at: Ecological Horizons Pty Ltd, Kimba, Australia
Received 21 January 2019. Revision requested 11 April 2019. Accepted 16 August 2019. First published online 2 June 2020.
Supplementary material for this article is available at
doi.org/10.1017/S0030605319000991
Introduction
factors or conditions. In a reintroduction context, acclima- tization can be defined as the period of time that released animals take to exhibit normal physiological processes or condition and normal behaviour, and may include producing young, maintaining or increasing body mass, establishing normal activity and movement patterns (often a stable home range), sheltering in suitable locations, locat- ing conspecifics and consuming a typical diet (Armstrong et al., 2017; Stadtmann & Seddon, 2018). If many individuals fail to do so, the reintroduction will not succeed. Typically, the acclimatization of released animals is measured by monitoring changes in body mass, post-release movement, reproductive status and the cause of death for released ani- mals that have died (Hardman & Moro, 2006; Hamilton et al., 2010; Short & Hide, 2015). Starvation or malnutrition can occur when released animals fail to locate food resources soon after release (Islam et al., 2008; Jule et al., 2008); thus, post-release diet is an important, yet often overlooked, component of reintroduction biology. In addition to short- term survival, the availability of stable or seasonally-reliable food resources is critical for reproduction and long-term persistence (Nolet et al., 2005; Moorhouse et al., 2009; Carlson et al., 2014). The post-release acclimatization period depends on a
A
species’ dietary breadth and movement patterns, and could take days, weeks or months. For example, European mink took c. 1 month after release to shift from an atypical to a typical diet (Põdra et al., 2013), and Gilbert’s potoroos Potorous gilbertii increased the number of truffles in their diet with time since release, presumably as they were able to locate new food sources (Bougher & Friend, 2009). The acclimatization period is often unknown a priori and some- times assigned arbitrarily as a fixed period (Armstrong et al., 2017). If post-release effects are not accounted for, the per- ceived likelihood of reintroduction failure may be much higher (Panfylova et al., 2016). Some post-release diet stud- ies have assessed diet at various time points after release, rather than monitoring changes over time. For example, 15
This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike licence (
http://creativecommons.org/licenses/by-nc-sa/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the same Creative Commons licence is included and the original work is properly cited. The written permission of Cambridge University Press must be obtained for commercial re-use. 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
cclimatization is defined as both physical and behavioural responses to changes in environmental
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