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Koertner, Gerhard
- PublicationCanine rabies in Australia: Modelling spread through the landscape(Australasian Society for Infectious Diseases, 2014)
;Sparkes, Jessica; ; ; Introduction: Canine rabies, a fatal viral zoonosis, is now less than 300 kilometres from Indonesian archipelago. To respond to this imminent threat, we need to model how rabies will spread through Australian ecosystems, to develop effective rabies management plans. This will improve our chances of minimising reaction times and containing outbreaks. Aims: To quantify contact rates, abundance, population turnover and dog bite frequency, in order to inform models of canine rabies spread. This is essential for identifying critical control points. - PublicationEffects of Sex and Reproductive State on Interactions between Free-Roaming Domestic Dogs(Public Library of Science, 2014)
;Sparkes, Jessica; ; ; Free-roaming dogs ('Canis familiaris') are common worldwide, often maintaining diseases of domestic pets and wildlife. Management of these dogs is difficult and often involves capture, treatment, neutering and release. Information on the effects of sex and reproductive state on intraspecific contacts and disease transmission is currently lacking, but is vital to improving strategic management of their populations. We assessed the effects of sex and reproductive state on short-term activity patterns and contact rates of free-roaming dogs living in an Australian Indigenous community. Population, social group sizes and rates of contact were estimated from structured observations along walked transects. Simultaneously, GPS telemetry collars were used to track dogs' movements and to quantify the frequency of contacts between individual animals. We estimated that the community's dog population was 326±52, with only 9.8±2.5% confined to a house yard. Short-term activity ranges of dogs varied from 9.2 to 133.7 ha, with males ranging over significantly larger areas than females. Contacts between two or more dogs occurred frequently, with entire females and neutered males accumulating significantly more contacts than spayed females or entire males. This indicates that sex and reproductive status are potentially important to epidemiology, but the effect of these differential contact rates on disease transmission requires further investigation. The observed combination of unrestrained dogs and high contact rates suggest that contagious disease would likely spread rapidly through the population. Pro-active management of dog populations and targeted education programs could help reduce the risks associated with disease spread. - PublicationLethal control of eutherian predators via aerial baiting does not negatively affect female spotted-tailed quolls (Dasyurus maculatus maculatus) and their pouch young(CSIRO Publishing, 2021)
;Claridge, Andrew W; ; ; ; Hine, AbbyContext. Outside its breeding season, the marsupial carnivore the spotted-tailed quoll (Dasyurus maculatus) is apparently largely unaffected by aerial baiting for dingoes and other wild dogs (Canis familiaris). However, the potential impact of aerial baiting during spring on female spotted-tailed quolls carrying and weaning young remains unquantified.
Aim. The survivorship of female quolls and their pouch young was investigated after aerial baiting at two sites representing the northern and southern part of their New South Wales range. The null hypothesis was that aerial baiting would not lead to direct mortality of any adult females or higher pouch young mortality over that reported in the published literature under normal conditions.
Methods. In total, nine female quolls with pouch young and eight male quolls were trapped, fitted with GPS/VHF collars containing mortality sensors and released at their point of capture. After trapping ceased, meat baits nominally containing 6 mg of 1080 and 50 mg of the biomarker rhodamine B were deployed by helicopter at both sites at the maximal permissible rate of 40 baits km-1. We monitored collared quolls daily for 4-5 weeks for mortality then retrapped animals and sampled whiskers for evidence of the biomarker. The fate of pouch young was also followed throughout our study by examining pouches of adult females and camera trapping at maternal den sites.
Key Results. No collared quolls died. After the daily monitoring period, 10 quolls, including all six collared female quolls, were trapped at the southern site, and whisker samples taken and assayed for Rhodamine B. Seven (4 females and 3 males) tested positive for rhodamine B, indicating consumption of baits. Separate bands of the biomarker in whisker samples indicated that most animals that tested positive had been exposed to multiple baits. At the northern site, four quolls (including two females and two males) tested positive for rhodamine B from the nine sampled. Post-baiting inspection of pouches of all trapped adult female animals, together with camera trapping at den sites, showed that the development of pouch young was unaffected by the baiting. Camera trapping arrays set across both sites continued to record the animals that were exposed to baits well beyond the baiting events, including evidence of breeding in a subsequent season.
Conclusion. Our aerial baiting programs had no observable impact on the collared female quolls, or their ability to raise and wean young. These findings are consistent with results from all previous field-based experimental studies, which show no population-level impacts of 1080 baits on spotted-tailed quolls.
Implications. Land managers should not be concerned about impacts of aerial baiting for wild dogs on spotted-tailed quolls, either in autumn or in spring during the breeding season. - PublicationRabies disease dynamics in naȉve dog populations in Australia(Elsevier BV, 2016)
;Sparkes, Jessica ;McLeod, Steven; ; ; Currently, Australia is free from terrestrial rabies but an incursion from nearby Indonesia, where the virus is endemic, is a feasible threat. Here, we aimed to determine whether the response to a simulated rabies incursion would vary between three extant Australian dog populations; free-roaming domestic dogs from a remote indigenous community in northern Australia, and free-roaming domestic and wild dogs in peri-urban areas of north-east New South Wales. We further sought to predict how different management strategies impacted disease dynamics in these populations. We used simple stochastic state-transition models and dog demographic and contact rate data from the three dog populations to simulate rabies spread, and used global and local sensitivity analyses to determine effects of model parameters. To identify the most effective control options, dog removal andvaccination strategies were also simulated. Responses to simulated rabies incursions varied between the dog populations. Free-roaming domestic dogs from north-east New South Wales exhibited the lowest risk for rabies maintenance and spread. Due to low containment and high contact rates, rabies progressed rapidly through free-roaming dogs from the remote indigenous community in northern Australia. In contrast, rabies remained at relatively low levels within the north-east New South Wales wild dog population for over a year prior to an epidemic. Across all scenarios, sensitivity analyses revealed that contact rates and the probability of transmission were the most important drivers of the number of infectious individuals within a population. The number of infectious individuals was less sensitive to birth and death rates. Removal of dogs as a control strategy was not effective for any population modelled, while vaccination rates in excess of 70% of the population resulted in significant reductions in disease progression. The variability in response between these distinct dog groups to a rabies incursion, suggests that a blanket approach to management would not be effective or feasible to control rabies in Australia. Control strategies that take into account the different population and behavioural characteristics of these doggroups will maximise the likelihood of effective and efficient rabies control in Australia. - PublicationDenning behaviour of female spotted-tailed quolls during the breeding seasonWe monitored some aspects of maternal care in Australia's second largest extant marsupial predator, the spotted-tailed quoll. We radio-collared six females carrying young at an early pouch stage in the Byadbo Wilderness in southern New South Wales in August-September 2016. When these young were deposited at a maternity den at a still altricial state we monitored den activity of the female and her young with motion-triggered camera traps. Lactating females remained in the same den for up to 39 days before moving to a new den, usually only a few hundred metres away. Females furnished dens with nesting material, but were never observed to carry prey nor were the young seen consuming solid food. They were also surprisingly tolerant towards visits and den use by wombats, rabbits, possums and male quolls. Females showed predominantly nocturnal activity, but usually returned at least once per night. Short daytime activity was also common. In contrast, juveniles were initially exclusively diurnal, probably to facilitate behavioural thermoregulation, and only later extended their playing and exploring towards dawn and dusk. Hence interactions between mother and young were rarely observed. Apparently, the young received little training from their mother and simply ventured further and for longer periods away from the den until independence.
- PublicationContact rates of wild-living and domestic dog populations in Australia: a new approach(Springer, 2016-12)
;Sparkes, Jessica; ; ;van de Ven, RemyDogs (Canis familiaris) can transmit pathogens to other domestic animals, humans and wildlife. Both domestic and wild-living dogs are ubiquitous within mainland Australian landscapes, but their interactions are mostly unquantified. Consequently, the probability of pathogen transfer among wild-living and domestic dogs is unknown. To address this knowledge deficit, we established 65 camera trap stations, deployed for 26,151 camera trap nights, to quantify domestic and wild-living dog activity during 2 years across eight sites in north-east New South Wales, Australia. Wild-living dogs were detected on camera traps at all sites, and domestic dogs recorded at all but one. No contacts between domestic and wild-living dogs were recorded, and limited temporal overlap in activity was observed (32 %); domestic dogs were predominantly active during the day and wild-living dogs mainly during the night. Contact rates between wild-living and between domestic dogs, respectively, varied between sites and over time (range 0.003-0.56 contacts per camera trap night). Contact among wild-living dogs occurred mainly within social groupings, and peaked when young were present. However, pup emergence occurred throughout the year within and between sites and consequently, no overall annual cycle in contact rates could be established. Due to infrequent interactions between domestic and wild-living dogs, there are likely limited opportunities for pathogen transmission that require direct contact. In contrast, extensive spatial overlap of wild and domestic dogs could facilitate the spread of pathogens that do not require direct contact, some of which may be important zoonoses.
- PublicationBrushtail possum terrestrial activity patterns are driven by climatic conditions, breeding and moonlight intensity(Springer, 2023)
; ; ; ; ; Ecological studies of common brushtail possums (Trichosurus vulpecula) in their extant range have been limited by technology and the species' nocturnal habit. However, camera traps now allow the investigation of possum ethology without observer interference. Here, we analysed terrestrial possum activity patterns using a large dataset collected over 3 years from 133 camera traps in mesic eucalypt woodland and open forest in three national parks on the New England Tablelands, New South Wales, Australia. We investigated how weather and moonlight intensity infuenced possum activity patterns throughout the night, and across seasons and years, by using the timestamps assigned to each detection by the camera trap. Terrestrial possum activity increased as ambient temperatures decreased in autumn and peaked in winter when females were rearing ofspring. Nightly possum detections decreased signifcantly with rain and increasing mean temperature. Possums were almost exclusively nocturnal, with most terrestrial activity earlier in the evening in winter and later at night in summer. During longer nights, higher temperatures also delayed activity. While nightly detection rates were not afected by lunar phase, possums preferred parts of the night with the highest moonlight intensity, and this efect was stronger on brighter nights. Overall, brushtail possums were most active on the ground when temperatures were mild and moonlight bright, presumably assisting foraging and predator avoidance, and during the breeding season" they avoided rain. These patterns suggest that reproduction, thermoregulation and risk of predation strongly shape the nocturnal activity cycle. Furthermore, our research adds to the evidence that camera traps can help greatly expand our knowledge of the ecology and behaviour of nocturnal mammals.
- PublicationQuantifying effects of wild dogs, domestic dogs and humans on the spread of rabies in Australia(2016-10-22)
;Sparkes, Jessica Louise; ; ; Rabies is a preventable viral zoonosis that causes inflammation of the brain, and eventually death, in infected mammals. With few exceptions, including Australia, terrestrial rabies can be found worldwide. More than 55,000 deaths from rabies infection are reported annually; these are mainly in Asia and Africa where the primary reservoir is the domestic dog.
Despite ongoing control efforts in Indonesia, canine rabies remains a disease of critical concern there. Although rabies is not endemic in Australia, at less than 300km away in Indonesia, a rabies incursion is a likely and imminent threat.
To improve preparedness for a canine rabies outbreak in Australia, I collected data on a number of extant dog populations in northern and eastern Australia. I used a range of methods including self-administered questionnaires, GPS telemetry collars, camera trapping and mark-recapture studies. Using my own data and parameters collected from the wider literature, I developed state-transition models to determine how rabies could spread through these dog populations. Finally, I used these same models to evaluate a range of control strategies, including dog removal and vaccination, to identify the most effective options for reducing impacts in Australian communities following a rabies incursion.
Model outputs suggested that rabies will progress differently within functionally different dog populations present within Australia. Restrained domestic dogs posed limited risk for rabies transmission, because interactions with other dogs were limited and generally supervised by owners. Free-roaming domestic and hunting dogs will likely play an important role in rabies transmission in some situations only, primarily based on their ability to roam, access to other free-roaming dogs and their interactions within and between dog groups. Wild dogs (including dingoes) proved the most critical type of dog for rabies spread and maintenance in Australia, because they are widely distributed, often in high abundance, roam over large distances and frequently interact.
I found that time to detection for rabies in wild dogs will likely be lengthy, probably due to low infection rates prior to an epidemic and limited contact with humans, relative to the other categories of dog that I studied. Further, the capacity of authorities to implement effective control strategies for wild dogs will likely be restricted because of limited access to individual animals. The economic costs of controlling a rabies outbreak involving wild dogs will be substantial and likely equivalent to the costs for extensive aerially-based wild dog control that are currently used in some areas of Australia (~Aus$34 km-2).
Australia’s current plans to address rabies incursions, which were developed in the 1990s are clearly outdated. My findings reveal that revision of these plans, taking specific account of relevant differences between restrained domestic dogs, free-roaming domestic dogs and extensive wild dog populations is necessary to ensure that Australia is adequately prepared for the arrival of canine rabies.
- PublicationHome range and activity patterns measured with GPS collars in spotted-tailed quolls
The spotted-tailed quoll (Dasyurus maculatus) is the largest marsupial carnivore on mainland Australia. It usually occurs at relatively low population densities and its cryptic nature makes it exceedingly difficult to observe in its natural habitat. On the mainland the species is also listed as nationally endangered and more information is needed to direct any meaningful conservation effort. In this study we aimed to elucidate quolls’ spatial requirements and activity patterns using GPS collars on 10 males and 4 females. Quolls were predominantly nocturnal but some individuals showed pronounced daytime activity. There was no apparent seasonal shiftin thetiming of activity. The movement of quolls appeared to be confined to home rangesthat were relatively large for predators of their size. Furthermore, males used home ranges about three times as large as that of the smaller females. There appeared to be some spatial segregation between not only females, which have been considered territorial, but also males. Overall, it is likely that the larger areas used by males is partly caused by the sexual dimorphism in body mass that entails differences in prey requirements and spectrum, but probably is also a function of a promiscuous mating system. All of these could explain the observed more unidirectional movement and larger distances travelled per day by males.