Forrestfield, Australia
Forrestfield, Australia

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Spencer P.B.S.,Murdoch University | Hampton J.O.,Ecotone Wildlife Veterinary Services | Pacioni C.,Murdoch University | Kennedy M.S.,Invasive Species Science | And 4 more authors.
Journal of Wildlife Management | Year: 2015

The Judas animal control technique relies on the social nature of some invasive species to betray the location of their companions. It is an effective method of enhancing shooting programs in highly gregarious mammal species. We used social genetic data to examine the utility of the Judas technique in a novel species: wild dromedary camels (Camelus dromedarius). Firstly, we used molecular data (13 microsatellite markers from 1,050 camels) to characterize genetic diversity and relatedness within and between observed social groups. Genetic estimates of relatedness between pairs within a group (r = -0.058) were not different from a comparison between any 2 randomly selected individuals. We did not find relatedness within and between social groups to be significantly different for 78% of social groups, suggesting a fission-fusion social structure conducive to applying the Judas technique. Secondly, we performed an operational trial of the Judas technique to assess the predictions of the genetic data. We tracked 10 collared Judas camels using a combination of satellite- and radio-telemetry for 9.0 ± 5.0 (mean ± SD) months between 2008 and 2010. We found Judas animals with a cohort of animals on 96% of occasions. Cohorts displayed no significant size difference prior to shooting (9.3 ± 9.9 animals), and after shooting (9.2 ± 7.5 animals). Genetic and operational data indicate that the Judas technique may be of utility in controlling camels at low population densities. This study also suggests that social genetic data can be used to assess applicability of the Judas technique for novel species. © 2014 The Wildlife Society.

Campbell S.,Invasive Species Science | Roberts E.J.,AEC Group Pty Ltd. | Roberts E.J.,Edith Cowan University | Craemer R.,Econtext | And 5 more authors.
Australasian Journal of Environmental Management | Year: 2015

The common starling (Sturnus vulgaris) has a proven invasion history in many countries, and at a continental scale in North America and Australasia. In Australia, starlings are firmly established throughout the eastern states and Tasmania. Incursions of starlings into Western Australia (WA) represent a significant threat to this State’s agricultural, public amenity and biodiversity assets. We present models of starling population dynamics that incorporate environmental and control effort variability. We incorporate knowledge of starling ecology with economic data to assess the potential economic cost of starlings establishing in WA, evaluating the cost–benefits for each management scenario. We calculated starling population size will approach carrying capacity in WA within as little as 30 years if left unchecked. A population of this size could cost the WA economy up to $43.7 million annually in 2011/2012 dollars. Over a 50 year horizon, the conservative benefit–cost ratio for ongoing detection and control at the current level of expenditure is 6.03:1. However, even under current levels of control, starling numbers are projected to increase to almost 11 million by 2061. Further improvements in the efficiency of starling detection and control and/or an increased level of expenditure on detection and control are required. © 2015 Environment Institute of Australia and New Zealand Inc.

Gallagher R.V.,Macquarie University | Randall R.P.,Invasive Species Science | Leishman M.R.,Macquarie University
Conservation Biology | Year: 2015

The ability to predict which alien plants will transition from naturalized to invasive prior to their introduction to novel regions is a key goal for conservation and has the potential to increase the efficacy of weed risk assessment (WRA). However, multiple factors contribute to plant invasion success (e.g., functional traits, range characteristics, residence time, phylogeny), and they all must be taken into account simultaneously in order to identify meaningful correlates of invasion success. We compiled 146 pairs of phylogenetically paired (congeneric) naturalized and invasive plant species in Australia with similar minimum residence times (i.e., time since introduction in years). These pairs were used to test for differences in 5 functional traits (flowering duration, leaf size, maximum height, specific leaf area [SLA], seed mass) and 3 characteristics of species' native ranges (biome occupancy, mean annual temperature, and rainfall breadth) between naturalized and invasive species. Invasive species, on average, had larger SLA, longer flowering periods, and were taller than their congeneric naturalized relatives. Invaders also exhibited greater tolerance for different environmental conditions in the native range, where they occupied more biomes and a wider breadth of rainfall and temperature conditions than naturalized congeners. However, neither seed mass nor leaf size differed between pairs of naturalized and invasive species. A key finding was the role of SLA in distinguishing between naturalized and invasive pairs. Species with high SLA values were typically associated with faster growth rates, more rapid turnover of leaf material, and shorter lifespans than those species with low SLA. This suite of characteristics may contribute to the ability of a species to transition from naturalized to invasive across a wide range of environmental contexts and disturbance regimes. Our findings will help in the refinement of WRA protocols, and we advocate the inclusion of quantitative traits, in particular SLA, into the WRA schemes. © 2014 The Authors. Conservation Biology published by Wiley Periodicals, Inc. on behalf of Society for Conservation Biology.

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