Woinarski J.C.Z.,Charles Darwin University |
MacRae I.,Parks Australia |
Flores T.,Parks Australia |
Detto T.,Parks Australia |
And 5 more authors.
Emu | Year: 2016
An endemic subspecies of Buff-banded Rail (Gallirallus philippensis) is restricted to the Cocos (Keeling) Islands, a group of 27 islands, with total area of ∼15km2, in the north-eastern Indian Ocean. Human settlement led to marked environmental degradation of the 26 islands in the southern atoll of the group. The Cocos Buff-banded Rail declined severely, with the last confirmed record from islands in the southern atoll in 1991. The subspecies has persisted, however, with a population of ∼800 individuals, on a single island, Pulu Keeling, 24km north of the southern atoll. A recovery plan for this endangered subspecies recommended reintroduction to a suitable island in the southern atoll. This paper provides a brief overview of the history and status of the subspecies, and describes an April 2013 reintroduction of 39 rails from Pulu Keeling to the 1-km2 Horsburgh Island in the southern atoll. This program has had at least short-term success, with monitoring showing successful recruitment in the reintroduced population, and its increase to ∼54 individuals by October 2014 and ∼121 individuals by June 2015. Much of the world's loss of biodiversity has been from, and continues to occur on, islands: this project demonstrates that well-considered mitigation of threats and translocation programs can provide solutions to this challenge. © BirdLife Australia 2016.
Lindner G.,Parks Australia
Journal of Herpetology | Year: 2013
Populations of Saltwater Crocodiles (Crocodylus porosus) have been monitored in the Northern Territory since the species' protection. This monitoring relies on standardized spotlight surveys in which crocodiles are counted and classified by estimated total length (TL). Although the accurate estimation of TL is important for analyses, often crocodiles are submerged and their TL is estimated from their heads, which may be visible above the water surface. With some variation, it is generally thought that TL of a crocodile is seven times the length of the animal's head. This study examined the ratio of TL to head length (HL) from morphological measurements of 2,755 Saltwater Crocodiles caught in various locations in the Northern Territory. The results showed that the generic ratio for crocodiles ranging from 38 to 503 cm was 7.01. The ratio increased logistically from 6.7 to 7.1 for crocodiles in the 120-420-cm size range in TL in 30-cm intervals. We suggest that TL can be reliably estimated from HL at least for crocodiles in 120-420 cm in the wild, with the use of the generic and size-specific ratios calculated for the various size classes at every 30 cm. The size-specific estimation for animals <120 cm or >420 cm was not possible because of limited sample sizes in these crocodile size ranges, although a few reliable records suggest that a ratio increasingly becomes larger and 1:8 should be used for crocodiles >510 cm in TL. Copyright 2013 Society for the Study of Amphibians and Reptiles.
Fukuda Y.,Environment and the Arts and Sport |
Webb G.,Wildlife Management International Pty. Ltd |
Webb G.,Charles Darwin University |
Manolis C.,Wildlife Management International Pty. Ltd |
And 4 more authors.
Journal of Wildlife Management | Year: 2011
Saltwater crocodiles (Crocodylus porosus) in the Northern Territory of Australia were protected in 1971, after a severe population decline resulting from 26 yr of intense commercial hunting. By that time wild saltwater crocodiles were rarely sighted anywhere and they were commercially extinct in areas where they had once been abundant. Standardized monitoring by spotlight surveys started in 1975 and provided relative density indices over time (1975-2009) as a unique record of the post-protection recovery of a wild crocodilian population. We examined the survey data for populations at 12 major tidal rivers, individually and as a single subpopulation. The pattern of recovery in the subpopulation in both abundance and biomass was approximated by logistic curves, predicting 5.26 non-hatchling crocodiles weighing 387.64 kg sighted per kilometer of river in 2010. We predicted potential carrying capacity as 5.58 non-hatchling crocodiles (5.73% higher than 2010) weighing 519.0 kg (25.31% higher than 2010). Individual rivers showed largely different abundance and biomass among rivers. The statistical model that best described the recovery in individual rivers was not always logistic. However, where it was logistic, expected carrying capacity of different rivers showed considerable variation in abundance and biomass. The variation indicates different habitat quality among the rivers. Recovery occurred despite various consumptive uses, particularly a widespread egg-harvest program, which has been an integral part of the incentive-driven conservation program for saltwater crocodiles in the Northern Territory since 1983. We suggest that the saltwater crocodile population of the Northern Territory is achieving full recovery from uncontrolled hunting in 1945-1971. Although saltwater crocodiles are considered an important natural resource, their increase in number, size, and distribution is posing management issues for public safety. Continuation of human-crocodile conflict management through public education and strategic removal of problem crocodiles will be essential. Copyright © 2011 The Wildlife Society.
Lindenmayer D.B.,Australian National University |
Wood J.,Australian National University |
Macgregor C.,Australian National University |
Buckley Y.M.,University of Queensland |
And 7 more authors.
PLoS ONE | Year: 2015
Invasive plant management is often justified in terms of conservation goals, yet progress is rarely assessed against these broader goals, instead focussing on short-term reductions of the invader as a measure of success. Key questions commonly remain unanswered including whether invader removal reverses invader impacts and whether management itself has negative ecosystem impacts. We addressed these knowledge gaps using a seven year experimental investigation of Bitou Bush, Chrysanthemoides monilifera subsp. rotundata. Our case study took advantage of the realities of applied management interventions for Bitou Bush to assess whether it is a driver or passenger of environmental change, and quantified conservation benefits relative to management costs of different treatment regimes. Among treatments examined, spraying with herbicide followed by burning and subsequent respraying (spray-fire-spray) proved the most effective for reducing the number of individuals and cover of Bitou Bush. Other treatment regimes (e.g. fire followed by spraying, or two fires in succession) were less effective or even exacerbated Bitou Bush invasion. The spray-firespray regime did not increase susceptibility of treated areas to re-invasion by Bitou Bush or other exotic species. This regime significantly reduced plant species richness and cover, but these effects were short-lived. The spray-fire-spray regime was the most cost-effective approach to controlling a highly invasive species and facilitating restoration of native plant species richness to levels characteristic of uninvaded sites. We provide a decision tree to guide management, where recommended actions depend on the outcome of posttreatment monitoring and performance against objectives. Critical to success is avoiding partial treatments and treatment sequences that may exacerbate invasive species impacts. We also show the value of taking advantage of unplanned events, such as wildfires, to achieve management objectives at reduced cost. © 2015 Lindenmayer et al.
Gouramanis C.,Nanyang Technological University |
De Deckker P.,Australian National University |
Wilkins D.,Parks Australia |
Dodson J.,Chinese Academy of Sciences
Marine and Freshwater Research | Year: 2016
Numerous saline playa lakes exist across the arid, semiarid and temperate regions of Australia. These playa lakes exhibit a diverse range of hydrological conditions to which the Australian aquatic invertebrate biota have become adapted and which the biota can utilise as refugia in times of hydrological deterioration. Saline playas also yield palaeoenvironmental records that can be used to infer lacustrine and catchment responses to environmental variability. We present a palaeoenvironmental record recovered from Two Mile Lake, a saline playa from southern Western Australia. Dating, based on quartz optical luminescence and 14C accelerator mass spectrometry of biogenic carbonates and organic fibres, suggests that most of the sediment was rapidly deposited at 4.36±0.25 thousand years ago. Ostracods and non-marine foraminifera preserved in the sediment show periods of faunal colonisation of the lake with oscillations between hypersaline and oligosaline conditions. The geochemistry of ostracod valves and foraminifera tests suggests higher-frequency variability within the lake, and palynological changes indicate landscape changes, possibly in response to fire. The Two Mile Lake record highlights the utility of saline playas as archives of environmental change that can be used to guide wetland health management, particularly under the impacts of a changing climate. Journal compilation © CSIRO 2016.
Kool J.,Geoscience Australia |
Appleyard S.,CSIRO |
Bax N.,Institute for Marine and Antarctic Studies |
Ford J.,University of Melbourne |
And 7 more authors.
Bulletin of Marine Science | Year: 2015
Marine scientists and environmental managers engaged in a roundtable discussion at the Australian Marine Sciences Association conference in July 2014 to identify areas where linkages could be improved between the two groups. Here, we summarize the key themes and outcomes from the discussion, including the need to clearly define management objectives, to identify the scale of the issue, to conduct effective science communication, to address uncertainty, and to perform iterative engagement. We also discuss some of the challenges inherent in establishing new linkages, and provide a set of examples where effective collaborations have been achieved between marine ecologists and environmental managers working in Australia. © 2015 Rosenstiel School of Marine & Atmospheric Science of the University of Miami.
PubMed | Australian National University, University of Minnesota, University of Western Australia, Parks Australia and Trinity College Dublin
Type: Journal Article | Journal: PloS one | Year: 2015
Invasive plant management is often justified in terms of conservation goals, yet progress is rarely assessed against these broader goals, instead focussing on short-term reductions of the invader as a measure of success. Key questions commonly remain unanswered including whether invader removal reverses invader impacts and whether management itself has negative ecosystem impacts. We addressed these knowledge gaps using a seven year experimental investigation of Bitou Bush, Chrysanthemoides monilifera subsp. rotundata. Our case study took advantage of the realities of applied management interventions for Bitou Bush to assess whether it is a driver or passenger of environmental change, and quantified conservation benefits relative to management costs of different treatment regimes. Among treatments examined, spraying with herbicide followed by burning and subsequent re-spraying (spray-fire-spray) proved the most effective for reducing the number of individuals and cover of Bitou Bush. Other treatment regimes (e.g. fire followed by spraying, or two fires in succession) were less effective or even exacerbated Bitou Bush invasion. The spray-fire-spray regime did not increase susceptibility of treated areas to re-invasion by Bitou Bush or other exotic species. This regime significantly reduced plant species richness and cover, but these effects were short-lived. The spray-fire-spray regime was the most cost-effective approach to controlling a highly invasive species and facilitating restoration of native plant species richness to levels characteristic of uninvaded sites. We provide a decision tree to guide management, where recommended actions depend on the outcome of post-treatment monitoring and performance against objectives. Critical to success is avoiding partial treatments and treatment sequences that may exacerbate invasive species impacts. We also show the value of taking advantage of unplanned events, such as wildfires, to achieve management objectives at reduced cost.
Lindenmayer D.B.,Australian National University |
Macgregor C.,Australian National University |
Dexter N.,Parks Australia |
Fortescue M.,Parks Australia
Ecological Management and Restoration | Year: 2013
A 10-year science-management partnership has focussed on three key issues within Booderee National Park in eastern Australia: the impacts of fire on native biota, the response of vertebrates to feral animal control and the control of Bitou Bush. What has been achieved to date and what are the partnership's key ingredients? © 2013 Ecological Society of Australia.
News Article | December 3, 2016
Have you heard the one about the wasp that kills the bug that feeds the ants that kill the crabs that keep the forests healthy on Christmas Island? If not, that’s because it hasn’t happened yet, but it is a tale worth telling. In the coming weeks, Parks Australia will release a 2mm wasp on Christmas Island to control the island’s yellow crazy ant infestation. Crazy ants are a big threat to the island’s wildlife, including its famous red crabs. Biological control – when we use one species to control another – is infamous for giving Australia its cane toad invasion. So, how do we know this one will work? Christmas Island is a unique natural habitat with many endemic species. The national park covers two-thirds of the island, which has been referred to as the Galapagos of the Indian Ocean. Many people are aware of the red crabs whose mass migration to the sea has been described as one of the wonders of the natural world. Christmas Island has many other species of crabs, including the impressive robber crabs. These may be the largest land-dwelling arthropod (the group that insects and crustaceans belong to) on earth. Together these abundant land crabs clear the forests of leaf litter and maintain burrows that prevent soil becoming compacted, creating an open and diverse forest. But this thriving natural system was disrupted when an invasive ant species became abundant on the island. In the early 20th century, yellow crazy ants (Anoplolepis gracilipes) found their way to Christmas Island. These ants now form super-colonies, with billions of individuals across hundreds of hectares. The crazy ants spray formic acid in the eyes and leg joints of the crabs, which immobilises them. The crabs soon die and become food for the ants. In some cases, crabs that live in areas free of crazy ants are killed during their annual migration and so never return to their original forest. This creates crab-free zones even where the ants do not live. With fewer crabs, the forest has become less diverse, with a dense understory and compacted soils due to the collapse of crab burrows. Other invasive species such as the giant African land snail have become common where crabs declined. Parks Australia has been trying lots of different methods from aerial to hand-baiting to reverse the impact of yellow crazy ants on red crabs. The impact was so severe that a chemical control program targeting the super-colonies began in 2001. This program has slowed the decline of crab populations but is expensive and time-consuming, so researchers began to look into other options, including using other species. Super-colonies of yellow crazy ants require a reliable food source and this is provided by yet another invasive species: the yellow lac scale insect (Tachardina aurantiaca). Scale insects (a type of true bug) suck the sap of trees and produce a sweet secretion from their anal pore called honeydew, which ants then harvest. It seems that the super-colonies of these crazy ants could not survive without the carbohydrate-rich honeydew provided by abundant scale insects in a patch of forest. There is evidence that the scale insects increase ant reproduction and make them more likely to attack other species. One large field experiment demonstrated that if we stopped the ants getting access to the scale insects, ant activity on the ground fell by 95% in just four weeks. The scale insects may need the ants as much as the ants need the scale insects. Some ants protect the scale insects in the same way that humans protect their livestock, by chasing away other predators. The interaction between these two invasive species has allowed them to build their populations to extremely high densities, something known as invasional meltdown. The good news is that scale insects, unlike ants, are amenable to biological control. For instance, Australian lady bugs were spectacularly successful in controlling the cottony cushion scale in North America. The search began to find a species that could control the scale insect on Christmas Island. And we found it: a tiny wasp known as Tachardiaephagus somervillei, which attacks the yellow lac scale insect in its native Southeast Asia. This wasp lays its eggs in mature female scale insects and kills them from the inside, producing more wasps that then lay eggs in more females. This wasp (and other predators) are so effective that the yellow lac scale insect is rare in its native habitat. Obviously, we had to test that the wasp wouldn’t attack other species. Researchers did this in the field in Malaysia, an unusual approach that yielded excellent results. The scientists exposed eight closely related scale insects to the wasp, and none were harmed. This proves that no other scale insect population on Christmas Island is at risk if the wasp is introduced, with the possible exception of another introduced scale insect that is a pest in its own right. Researchers also checked that the wasps would still work when the scale insects are being tended by yellow crazy ants – and they still attacked. After years of research it is exciting to be on the verge of releasing this wasp on Christmas Island. We all know the biological control stories that went wrong. The introduction of cane toads to control cane beetles in Australia backfired spectacularly. In Hawaii, the introduction of mongooses to control rats failed because mongooses are active during the day and the rats were active at night. In both those cases, those species were introduced without sufficient research. But these examples changed the rules and laws around introducing species. Today governments are much more aware of the risks of invasive species. Rigorous experiments and risk assessments are required before any introduction can occur. In this case, researchers from La Trobe University have worked closely with Parks Australia and the Forest Research Institute of Malaysia to collect enough data to satisfy the Australian government. We believe that this is the most closely scrutinised biological control project in Australia. When the wasps arrive on Christmas Island in a few weeks, we are confident that this will set an example for best-practice conservation. Fewer ants means more crabs, healthier trees, fewer African snails and better soil. And it will save money being spent on expensive conservation efforts for years to come. • Parks Australia has produced a special animation on the program – http://www.parksaustralia.gov.au/christmas/news/biocontrol.html. • Susan Lawler is senior lecturer, department of ecology, environment and evolution, La Trobe University • Peter Green is head of the department, college of science, health and engineering, school of life sciences, La Trobe University