Dynamics and predicted distribution of an irrupting ‘sleeper’ population: fallow deer in Tasmania

Cunningham, Calum X.; Perry, George L.; Forsyth, David M.; Driessen, Michael M.; Appleby, Matt; Brook, Barry W.; Hocking, Greg; Buettel, Jessie C.; French, Ben J.; Hamer, Rowena; Bryant, Sally; Taylor, Matt D.; Gardiner, Riana; Proft, Kirstin; Scoleri, Vincent P.; Chiu-Werner, Antje; Travers, Toby; Thompson, Liam; Guy, Tom; Johnson, Christopher N.

doi:10.1007/s10530-021-02703-4

Cited by 18 publications

(61 citation statements)

References 62 publications

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“…Fallow deer and chital deer have large and expanding distributions in Australia (Moriarty 2004;Crittle and Millynn 2020;Cunningham et al 2022), and helicopterbased shooting is increasingly being used to control some populations. Our study, which is the first to quantify the effectiveness and costs of helicopter-based shooting for deer in Australia, demonstrated that this method can quickly reduce the densities of these two species over large areas.…”

Section: Discussionmentioning

confidence: 99%

“…Fallow deer have been subject to control for many decades in New Zealand (Nugent and Asher 2021) and are increasing in geographic range and abundance in the eastern Australian states (Moriarty 2004;Crittle and Millynn 2020;Cunningham et al 2022). Chital deer are increasing in range and abundance in Qld and NSW (Moriarty 2004;Crittle and Millynn 2020).…”

Section: Discussionmentioning

confidence: 99%

“…Fallow deer and chital deer have large and expanding distributions in Australia (Moriarty 2004; Crittle and Millynn 2020; Cunningham et al . 2022), and helicopter-based shooting is increasingly being used to control some populations.…”

Section: Discussionmentioning

confidence: 99%

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Effectiveness and costs of helicopter-based shooting of deer

Bengsen,

Forsyth,

Pople

et al. 2022

Wildlife Res.

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Context. Helicopter-based shooting has been widely used to harvest deer or control overabundant populations in Australasia, but the effectiveness and cost of this method as a deer control tool has seldom been evaluated. Aims. We evaluated the effectiveness and costs of helicopter-based shooting of fallow deer (Dama dama) and chital deer (Axis axis) in eastern Australia by quantifying (1) reductions in density, (2) the relationship between numbers killed per hour and deer density (i.e. the functional response), (3) the costs of control and (4) the effort-outcome and cost-outcome relationships. Methods. We evaluated the costs and effectiveness of 12 aerial shooting operations aiming to reduce fallow deer (n = 8) or chital deer (n = 4) population densities at nine sites in eastern Australia. Sites were characterised by fragmented woodland, and all but one operation aimed to reduce grazing competition with livestock. We used precontrol population density estimates and operational monitoring data to estimate the costs and outcomes of each operation. We combined data from all operations to estimate the relationship between shooting effort and population reduction, as well as costs associated with different levels of effort. Key results. Population reductions for operations ranged from 5% to 75% for fallow deer, and from 48% to 88% for chital deer. The greatest population reductions occurred when effort per unit area was greatest, and the largest reductions in deer density occurred when shooting was conducted in consecutive years. The functional response of hourly kills to deer density was best described by a modified Ivlev model, with the asymptotic kill rate estimated to be 50 deer per hour. There was no support for the existence of a prey refuge, that is, a threshold population density below which no deer could be shot. Helicopter charter was the primary cost of helicopter-based shooting programs, followed by labour; firearm and ammunition costs were relatively minor. Conclusions. Helicopter-based shooting can rapidly reduce deer populations over large geographic areas, but the magnitude of the reduction depends on the effort (hours of shooting) per deer per km 2 . Implications. Aerial shooting operations should include a pre-control population survey so that (1) measurable objectives can be established, (2) the likely level of effort and cost required for objectives to be met can be estimated and planned for, and (3) the realised population reduction can be estimated.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Effectiveness and costs of helicopter-based shooting of deer

Bengsen,

Forsyth,

Pople

et al. 2022

Wildlife Res.

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“…The fallow deer (Dama dama; adult females 38 kg, adult males 59 kg; Bentley 1995) is the most numerous and most widely distributed non-native deer species in the world (Chapman and Chapman 1997;Long 2003;Nugent et al in press). The species occupies a wide range of biomes and climates, but prefers pasture and cropping areas interspersed with scrub, forest or woodland; hence, the distribution of fallow deer almost entirely coincides with vegetation modified by humans or domesticated livestock where mosaics of grassland and woodland meet their requirements for both forage and cover (Chapman and Chapman 1997;Cunningham et al 2022).…”

Section: Introductionmentioning

confidence: 99%

“…Globally, non-native species from a wide range of taxonomic groups have become established in agricultural areas, where they can have undesirable impacts (Pyšek and Richardson 2010). In Australasia, non-native deer are colonising agricultural areas through natural dispersal, farm escapes and human-assisted liberations (Moriarty 2004; Nugent and Asher 2021; Nugent and Forsyth 2021; Cunningham et al . 2022).…”

Section: Introductionmentioning

confidence: 99%

Diet and impacts of non-native fallow deer (Dama dama) on pastoral properties during severe drought

2023

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Context There is concern about potential competition between non-native fallow deer (Dama dama) and livestock for food, particularly during times of low rainfall when pasture is scarce.Aim We aimed to estimate the extent to which a high-density fallow deer population (~37 deer per km2) competed with livestock for food during a severe drought on pastoral properties on the Liverpool Plains, New South Wales, Australia.Methods We collected rumen contents from 125 fallow deer shot from helicopters during control operations in June and August 2018, and used microhistology to quantify their diets. We then used the diet data to adjust published estimates of stock unit equivalence from farmed fallow deer. Fallow deer sex and age class abundances and stock unit equivalences were multiplied to estimate the grazing pressure of the fallow deer population pre- and post-control relative to recommended sheep and cattle stocking rates. Finally, we estimated density–impact relationships for fallow deer.Key results Fallow deer diet was dominated by monocots (primarily grasses), but some individuals consumed large amounts of dicots (commonly Eucalyptus). Fallow deer were grazers to intermediate mixed feeders. Fallow deer dry-sheep equivalents (DSEs, based on a 50-kg merino wether) varied from 1.01 (juveniles) to 1.85 (adult females and adult males). Assuming complete diet overlap, the pre-control fallow deer population was equivalent to approximately 60.3 DSEs per km2 and reduced the potential stocking rate of domestic livestock by 50.2%. Discounting the fallow deer DSEs by the amount of browse in the diet resulted in a pre-control population of 45.7 DSEs per km2. The helicopter-based shooting reduced the fallow deer population by 26%, increasing the stocking rate in natural pasture by 22.0% (complete overlap) or 13.8% (discounting for browse).Conclusions When food is limiting, fallow deer at high density can exert strong competitive pressure on livestock, reducing carrying capacity. Browsing, including on Eucalyptus, likely helped fallow deer to persist at high densities during the severe drought of 2018, when properties had destocked.Implications Helicopter-based shooting reduced the competitive effects of fallow deer on livestock in our study area to only a small extent, but more intensive shooting would have led to a greater reduction. The helicopter-based shooting of deer was received positively by landholders at a time of severe stress, suggesting that deer control in agricultural areas can have other important benefits.

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Restoring landscape burning is compatible with conservation and livestock production in a southeast Australian grassland fragment

French,

Prior,

Johnson

et al. 2024

Ecol Sol and Evidence

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Lowland grassland fragments in southeast Australia are valued for both sheep grazing and conservation. Many fragments are now rarely burnt, despite being shaped by millennia of Aboriginal fire‐use. Restoring fire could potentially reduce fuels, control exotic plant species, promote native species and renew Aboriginal cultural burning. However, this requires understanding of how fire and large herbivores, both native and exotic, are coupled and influence vegetation. We implemented a single round of low‐intensity experimental burns in an area of remnant grassland and patchy eucalypt woodlands in Tasmania that is managed for conservation, albeit intermittently grazed by sheep, as well as by native and exotic wild herbivores. We compared herbivore activity between burnt and unburnt areas over 2 years using cameras and scat transects, and assessed how fire and herbivory influenced herbaceous biomass and the cover of broad vegetation classes with and without herbivore exclusion. Contrary to expectations, burnt areas did not disproportionately attract the main herbivores: domestic sheep, introduced deer and native wallabies. In the predominant grassy sward, grazing and fire both reduced herbaceous biomass but we found no support for our hypothesis that grazing reduces biomass more strongly after burning. This contrasts with isolated patches of Poa tussock grassland, where fire reduced biomass much more strongly than grazing, and grazing effects on biomass were more pronounced following burning. The cover of broad vegetation classes was little affected by burning, but excluding herbivores increased exotic grass cover in both burnt and unburnt plots. Practical implication. In degraded fragments of lowland native grassland, burning and grazing do not necessarily act as strongly synergistic disturbances. Grazing by sheep and wild herbivores can help to control exotic grasses and reduce herbaceous biomass, although burning is much more effective than grazing for reducing biomass of unpalatable Poa tussock grassland. Our results suggest that returning occasional low‐intensity fires to our study system, and other degraded grassland‐woodland fragments, can be compatible with livestock production and conservation goals, but this requires caution and adaptive management.

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Dynamics and predicted distribution of an irrupting ‘sleeper’ population: fallow deer in Tasmania

Cited by 18 publications

References 62 publications

Effectiveness and costs of helicopter-based shooting of deer

Effectiveness and costs of helicopter-based shooting of deer

Diet and impacts of non-native fallow deer (Dama dama) on pastoral properties during severe drought

Restoring landscape burning is compatible with conservation and livestock production in a southeast Australian grassland fragment

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