ORCID Profile
0000-0001-8089-2122
Current Organisation
Northern Territory Government
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Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 10-2003
Publisher: Informa UK Limited
Date: 06-2008
Publisher: Wiley
Date: 02-2002
Publisher: Elsevier BV
Date: 08-2002
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/WR07024
Abstract: Introduced into Australia in 1935, the cane toad (Chaunus [Bufo] marinus) threatens native vertebrate predators. However, there have been few rigorous quantitative studies on species threatened by this toxic invasive species. This study examines the changes in abundance and proportion of sites occupied by Merten’s water monitor (Varanus mertensi) at a site in the Northern Territory following invasion by cane toads. The study was located at Manton Dam Recreation Area, 70 km south of Darwin, and ran for 18 months. Cane toads were first detected at the study site in February 2005, three months after the first survey, and their abundance remained low until February 2006, when an increase was observed. The abundance of V. mertensi declined substantially 8 months after the arrival of cane toads and remained low. The probability of detection of V. mertensi varied considerably within and among surveys, and was higher in the wet season surveys. The proportion of sites occupied by V. mertensi at the start of the study was 0.95 ± 0.03. Site occupancy remained high for 6 months after the arrival of cane toads, but declined gradually to a low of 0.15 ± 0.16 within 12 months. There has been demonstrable change in the abundance and proportion of sites occupied by V. mertensi following the colonisation of cane toads, but the population has been able to persist. Monitoring of populations impacted by cane toads may provide unique opportunities to understand processes underlying local extinction and colonisation of native predators following the impact of invasive species.
Publisher: Frontiers Media SA
Date: 13-04-2017
Publisher: Inter-Research Science Center
Date: 23-02-2017
DOI: 10.3354/ESR00795
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/WR09125
Abstract: Context. Australia has a lamentable history of mammal extinctions. Until recently, the mammal fauna of northern Australia was presumed to have been spared such loss, and to be relatively intact and stable. However, several recent studies have suggested that this mammal fauna may be undergoing some decline, so a targeted monitoring program was established in northern Australia’s largest and best-resourced conservation reserve. Aims. The present study aims to detect change in the native small-mammal fauna of Kakadu National Park, in the monsoonal tropics of northern Australia, over the period of 1996–2009, through an extensive monitoring program, and to consider factors that may have contributed to any observed change. Methods. The small-mammal fauna was s led in a consistent manner across a set of plots established to represent the environmental variation and fire regimes of Kakadu. Fifteen plots were s led three times, 121 plots s led twice and 39 plots once. Res ling was typically at 5-yearly intervals. Analysis used regression (of abundance against date), and Wilcoxon matched-pairs tests to assess change. For res led plots, change in abundance of mammals was related to fire frequency in the between-s ling period. Key results. A total of 25 small mammal species was recorded. Plot-level species richness and total abundance decreased significantly, by 54% and 71%, respectively, over the course of the study. The abundance of 10 species declined significantly, whereas no species increased in abundance significantly. The number of ‘empty’ plots increased from 13% in 1996 to 55% in 2009. For 136 plots s led in 2001–04 and again in 2007–09, species richness declined by 65% and the total number of in iduals declined by 75%. Across plots, the extent of decline increased with increasing frequency of fire. The most marked declines were for northern quoll, Dasyurus hallucatus, fawn antechinus, Antechinus bellus, northern brown bandicoot, Isoodon macrourus, common brushtail possum, Trichosurus vulpecula, and pale field-rat, Rattus tunneyi. Conclusions. The native mammal fauna of Kakadu National Park is in rapid and severe decline. The cause(s) of this decline are not entirely clear, and may vary among species. The most plausible causes are too frequent fire, predation by feral cats and invasion by cane toads (affecting particularly one native mammal species). Implications. The present study has demonstrated a major decline in a key conservation reserve, suggesting that the mammal fauna of northern Australia may now be undergoing a decline comparable to the losses previously occurring elsewhere in Australia. These results suggest that there is a major and urgent conservation imperative to more precisely identify, and more effectively manage, the threats to this mammal fauna.
Publisher: Cambridge University Press (CUP)
Date: 12-05-2016
DOI: 10.1017/S0007114516001690
Abstract: The aims of the present study were to provide nationally representative data on fruit and vegetable consumption in Vietnam, and to assess the accuracy of the reported numbers of ‘standard servings’ consumed. Data analysed were from a multi-stage stratified cluster survey of 14 706 participants (46·5 % males, response proportion 64·1 %) aged 25−64 years in Vietnam. Measurements were made in accordance with the WHO STEPwise approach to surveillance of non-communicable diseases (STEPS) protocols. Approximately 80 % of Vietnamese people reported having less than five servings of fruit and vegetables daily in a typical week. Fruit and vegetable intake reported in ‘standard serving’ sizes was positively correlated with levels of education completed and household income ( P ·001 for trend). The correlations between summary values for each province reflect some known demographic, geographical and climatic characteristics of the country. For ex le, provinces at higher latitude had higher mean servings of vegetables ( r 0·90), and provinces with higher proportions of urban population had higher mean servings of fruit ( r 0·40). In conclusion, about eight in ten Vietnamese people aged 25–64 years did not meet WHO recommendations for daily consumption of at least five servings of fruit and vegetables. On the basis of the consistency of the data collected with other estimates and with physical and demographic characteristics of the country, the WHO STEPS instrument has construct validity for measuring fruit and vegetable intake, but with two issues identified. The issues were seasonal variation in reporting and a limitation on the usefulness of the information for associative analyses.
Publisher: Society for the Study of Amphibians and Reptiles
Date: 03-2007
Publisher: Elsevier BV
Date: 06-2015
Publisher: Wiley
Date: 10-2005
Publisher: Wiley
Date: 14-07-2010
Publisher: Elsevier BV
Date: 11-2015
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/ZO05074
Abstract: The rock-dwelling macropod species of the tropics of the Northern Territory, Australia, are behaviourally elusive and difficult to observe in their rugged habitats. Hence, little is understood about their ecology. We evaluated the potential of using scats (faecal pellets) as a survey tool for this faunal assemblage by: (1) developing a key to the scats of the species (2) examining the rates of loss and decomposition of short-eared rock-wallaby (Petrogale brachyotis) scats in these tropical environments and (3) comparing the distribution of scats of P. brachyotis with the species’ use of space and habitats as determined with radio-telemetry. Classification tree modelling discriminated the scats of the seven macropod species, primarily on the basis of width. The reliability of identification was greatly improved with larger s le sizes and inclusion of a habitat parameter. Rates of scat loss and decay were variable and the greatest losses occurred in the wet season, particularly on sandy soils. Scat censuses underestimated the total area used by P. brachyotis but the distribution of scats showed the same broad pattern of habitat use found by radio-telemetry. We conclude that scats can accurately indicate the presence and habitat preferences of rock-dwelling macropod species.
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/BT04123
Abstract: An experimental wild harvest of Cycas arnhemica K.D. Hill, an understorey plant in tropical eucalypt savannas, was conducted in central Arnhem Land, Australia. Replicated harvest treatments were monitored over 2 years with tagged in iduals. A range of a priori candidate statistical models were compared to determine the effect of wild harvest and environmental factors such as fire frequency and disturbance from feral animals on survival, recruitment and stem growth. The mean density of C. arnhemica was 1630 ha–1 and ranged from 550 to 2250 ha–1. Harvesting intensity in the 0.04-ha quadrats varied between 10 and 32% of all cycad stems (excluding seedlings). There was no clear effect of harvest treatment on stem survival, seedling abundance and stem growth on the remaining C. arnhemica 2 years after the harvest treatments were applied. Survival of woody stems was higher than that of seedlings but there was considerable overlap among the larger size classes. Seedling abundance was generally low and variable across the three sites, and seedlings were entirely absent from quadrats burnt twice during the study period. Stem growth varied considerably across the three sites and was similar between small and large stems. We suggest that the wild harvest of this abundant Cycas species in a remote region of northern Australia will have minimal impact on wild populations if focused on juvenile stems and return time is extended to 15–40 years at harvested locations. Future harvest management of this and other Cycas species in northern Australia will benefit from further research on stochastic population models to determine the most suitable harvest strategies, particularly for smaller Cycas populations.
Publisher: Wiley
Date: 30-10-2008
Publisher: Wiley
Date: 27-11-2009
Publisher: Wiley
Date: 2003
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/WR08128
Abstract: Context. World-wide, primary forest is in decline. This places increasing importance on understanding the use by bio ersity of regrowth (secondary) forest, and on the management of such regrowth. Aims. This study aimed to compare the terrestrial vertebrate assemblages in tropical eucalypt forests, regrowth in these forests (following clearing for pastoral intensification) and cleared land without regrowth, to provide evidence for developing management guidelines for regrowth vegetation in a region (the Daly catchment of the Northern Territory) subject to increasing demands for land-use intensification. Methods. The terrestrial vertebrate fauna was surveyed consistently at 43 quadrats s ling forest, 38 s ling regrowth and 19 s ling cleared land (formerly forest), and the faunal composition was compared with ordination and analysis of variance. Further analysis used generalised linear modelling to include consideration of the relative importance of disturbance (condition) of quadrats. Key results. Faunal assemblages in regrowth vegetation were found to be intermediate between cleared land and intact forest, and converged towards the faunal assemblage typical of intact forest with increase in the canopy height of the regrowth. However, even the tallest regrowth quadrats that were s led supported relatively few hollow-associated species. The management of fire, weeds and grazing pressure substantially affected the faunal assemblages of the set of regrowth and intact forest quadrats, in many cases being a more important determinant of faunal attributes than was whether or not the quadrat had been cleared. Conclusions. In this region, regrowth vegetation has value as habitat for fauna, with this value increasing as the regrowth structure increases. The convergence of the faunal composition of regrowth vegetation to that of intact forest may be substantially affected by post-clearing management factors (including fire regime and level of grazing pressure and weed infestation). Implications. Regrowth vegetation should be afforded appropriate regulatory protection, with the level of protection increasing as the regrowth increases in stature.
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/WR03077
Abstract: Forty-seven 50 m × 50 m quadrats were s led systematically for vertebrates at Litchfield National Park, northern Australia, in both 1995–96 and 2001–02. A total of 184 vertebrate species was recorded from this s ling, of which 92 species were recorded from five or more quadrats. There was substantial change in the reported species composition of these quadrats between these two periods: the mean Bray–Curtis index for similarity in species composition from the baseline to subsequent s ling of a quadrat was only 22.1 (for an index that varies from 0 for complete turnover in species to 100 for unchanged composition). For in idual species, correlations across quadrats in the abundance scores from baseline to res ling varied from –0.12 to 0.85. Matched-pairs testing showed that there was significant change in abundance for 18 species from the baseline to repeat s ling, and significant increase in total bird species richness and total native mammal abundance, but significant decrease in reptile species richness. Fire history was recorded biannually for 40 of the 47 quadrats. Fire was very frequent, with quadrats being burnt in an average of 3.65 years of the six years between fauna s les. Three aspects of this fire history (total number of years of fires, number of fires in the late dry season, and interval from the last fire to the date of res ling) were related to change in the fauna composition of quadrats. Neither the similarity in species composition, nor change in richness or total abundance of all vertebrates or of the four taxonomic classes considered (frogs, reptiles, birds and mammals) were significantly correlated with these components of the fire history of s led quadrats. This lack of association was possibly because the monitoring period was too short to show pronounced directional change, because the system was responding to many factors other than fire, because the variations in abundance were too large and the number of s les too small to detect true associations, or because fire histories preceding baseline s ling were not considered. The apparent instability of fauna species and communities in this system provides a considerable challenge for broad-brush (that is, vertebrate community–wide) monitoring. Power analysis demonstrated that, for most species, more than 1000 s le sites are needed to be 90% certain of detecting a 20% change in abundance, and with a 10% chance of accepting a Type I error. This level of s ling effort is commensurate with the current level of vertebrate s ling in this region. Broad-brush monitoring approaches such as described here are valuable, but need also to be complemented by more targetted monitoring for in idual threatened species or species of particular management interest.
Publisher: Springer Science and Business Media LLC
Date: 10-06-2011
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/WR05032
Abstract: It is widely recognised that the use of fixed diurnal shelters by rock-wallabies greatly affects their ecology. However, the details of how shelters and surrounding habitats are used, and how similar these characteristics are across rock-wallaby species, remain scarcely understood. The dry season home range, and use of habitats and den sites, of the short-eared rock wallaby (Petrogale brachyotis) were examined at Litchfield National Park, Northern Territory, Australia. We radio-tracked 10 in iduals on foot to locate diurnal shelters, and with fixed towers to determine their nocturnal positions. P. brachyotis used a range of rock piles and outcrops for dens, and showed a strong preference for rocky habitats and adjacent woodland. On average, animals used four dens within outcrops, as well as more exposed resting sites. In idual rock-wallabies sometimes shared dens, but there appeared to be male–male intolerance of simultaneous use of dens. Mean home range in the dry season was 18.3 ha, and there was no significant difference in home-range area between sexes. Use of space by P. brachyotis was very similar to that reported for another tropical rock-wallaby species, P. assimilis, and many behavioural traits were also similar to those found in other species of Petrogale.
Publisher: Wiley
Date: 19-04-2002
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/WF14026
Abstract: Fire is a natural disturbance that exerts an important influence on global ecosystems, affecting vegetation distribution and structure, the carbon cycle and climate. However, human-induced changes to fire regimes may affect at-risk species groups such as small mammals. We examine the effect of fire on small mammals and evaluate the relative sensitivity to fire among different groups using a systematic review methodology that included critiquing the literature with respect to survey design and statistical analysis. Overall, small mammal abundance is slightly higher, and demographic parameters more favourable, in unburnt sites compared to burnt sites. This was more pronounced in species with body size range of 101–1000g and with habitat requirements that are sensitive to fire (e.g. dense ground cover): in 66.6 and 69.7% of pairwise comparisons, abundance or a demographic parameter were higher in unburnt than burnt sites. This systematic review demonstrates that there remains a continued focus on simple shifts in abundance with regards to effect of fire and small mammals, which limits understanding of mechanisms responsible for change. Body size and habitat preference were most important in explaining variation in small mammal species’ responses to fire.
Publisher: CSIRO Publishing
Date: 1994
DOI: 10.1071/WR9940203
Abstract: Mark-recapture studies of northern quoll (Dasyurus hallucatus) were conducted in lowland savanna in Kakadu National Park during two periods: in 1985-87 when total mammal abundance was high, and in 1989-91 when total mammal abundance was low. Population characteristics from these studies are compared with results from a 1977-79 study in sandstone escarpment country 40 km to the south-east and from studies in a range of habitats on the Mitchell Plateau in the Kimberley. Populations in rocky country are most dense with animals often surviving two or three years. In contrast, populations in savanna are more sparse, with males and females rarely surviving beyond one mating season. While all populations seem to undergo an annual period of stress, it is the savanna populations that seem most vulnerable. An analysis of the distribution of northern quolls shows a 75% recent range reduction, from being widespread over much of northern Australia to six smaller rocky regions. Possible causes of the decline include cattle, cane toads and exotic disease.
Publisher: Informa UK Limited
Date: 12-2011
Publisher: Elsevier BV
Date: 03-2013
Publisher: Springer Science and Business Media LLC
Date: 25-07-2012
DOI: 10.1007/S00267-012-9911-9
Abstract: We describe the population ecology of two tropical deciduous trees, Bombax ceiba leiocarpum A. Robyns and Brachychiton ersifolius R. Br., which are in high demand for Indigenous sculpture production in Arnhem Land, Australia. We monitored tagged populations of both species at two locations for 2 years to examine their reproduction, growth, and survival rates and their response to harvest. Both species have similar life histories: they reproduce during the dry season (June-November) producing a high seed load, seed predation was high, seeds did not survive in the soil past the following wet season to form a seed bank, and germination rates were low and variable for both species. Average annual circumference growth rates were 1.07 cm year(-1) for B. ceiba and 0.98 cm year(-1) for B. ersifolius, with most of the growth occurring during the early wet season. Most (65-88 %) of the harvested B. ceiba and B. ersifolius stems coppiced. Coppice and stem size class were the main factors influencing tree growth rates with coppice stems growing up to six times faster than similar sized non-coppice stems. The survival of B. ceiba and B. ersifolius stems was size class dependent and affected by local site factors (e.g. fire and other disturbances) so that the smaller size classes had a low probability of survival. Given the resprouting potential of both species, their wild harvest is likely to have only minimal local impact on wild populations. However, further population modelling is required to determine whether the small and disjunct B. ceiba populations can sustain harvesting at current levels.
Publisher: Wiley
Date: 06-2015
DOI: 10.1890/ES14-00519.1
Publisher: Copernicus GmbH
Date: 28-04-2016
Abstract: Abstract. The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is 2000 mm yr−1 (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall 2000 mm yr−1.
Publisher: Wiley
Date: 02-03-2011
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/WR11213
Abstract: Context A previous study reported major declines for native mammal species from Kakadu National Park, over the period 2001–09. The extent to which this result may be symptomatic of more pervasive bio ersity decline was unknown. Aims Our primary aim was to describe trends in the abundance of birds in Kakadu over the period 2001–09. We assessed whether any change in bird abundance was related to the arrival of invading cane toads (Rhinella marina), and to fire regimes. Methods Birds were monitored at 136 1-ha plots in Kakadu, during the period 2001–04 and again in 2007–09. This program complemented s ling of the same plots over the same period for native mammals. Key results In contrast to the decline reported for native mammals, the richness and total abundance of birds increased over this period, and far more in idual bird species increased than decreased. Fire history in the between-s ling period had little influence on trends for in idual species. Interpretation of the overall positive trends for bird species in Kakadu over this period should be tempered by recognition that most of the threatened bird species present in Kakadu were unrecorded in this monitoring program, and the two threatened species for which there were sufficient records to assess trends – partridge pigeon (Geophaps smithii) and white-throated grass-wren (Amytornis woodwardi) – both declined significantly. Conclusions The current decline of the mammal fauna in this region is not reflected in trends for the region’s bird fauna. Some of the observed changes (mostly increases) in the abundance of bird species may be due to the arrival of cane toads, and some may be due to local or regional-scale climatic variation or variation in the amount of flowering. The present study provides no assurance about threatened bird species, given that most were inadequately recorded in the study (perhaps because their decline pre-dated the present study). Implications These contrasting trends between mammals and birds demonstrate the need for bio ersity monitoring programs to be broadly based. The declines of two threatened bird species over this period indicate the need for more management focus for these species.
Publisher: Springer Science and Business Media LLC
Date: 12-2006
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/WR13057
Abstract: Context Failure to acknowledge potential bias from imperfect detection of cryptic organisms such as frogs may compromise survey and monitoring programmes targeting these species. Aims The aims of the present study were to identify proximate factors influencing detection probabilities of a range of frog species in monsoonal northern Australia, and to estimate the number of repeat censuses required at a site to have confidence that non-detected species are absent. Methods Data on detection or non-detection of frog species based on calling in iduals were recorded during 10 wet-season censuses of 29 survey sites in the Darwin region. Factors influencing detection probabilities were identified using occupancy models model selection was based on the Akaike information criterion. S ling effort for in idual species was calculated using model predictions at different stages of the wet season. Key results The covariate water temperature featured in the best-supported models for 7 of the 14 frog species. Six of these species were more likely to be detected when water temperatures were below 30°C. Detection probabilities were also correlated with the number of days since the commencement of the wet season, time since last significant rainfall, air temperature and time after sunset. Required s ling effort for in idual species varied throughout the wet season. For ex le, a minimum of two repeat censuses was required for detection of Litoria caerulea in the early wet season, but this number increased to 13 in the middle stage of the wet season. Conclusions Variability in environmental conditions throughout the wet season leads to variability in detection probabilities of frog species in northern Australia. Lower water temperatures, mediated by rainfall immediately before or during surveys, enhances detectability of a range of species. For most species, three repeat surveys under conditions resulting in a high detection probability are sufficient to determine presence at a site. Implications Survey and monitoring programmes for frogs in tropical northern Australia will benefit from the results of the present study by allowing targeting of conditions of high detection probability for in idual species, and by incorporating sufficient repeat censuses to provide accurate assessment of the status of in idual species at a site.
No related grants have been discovered for Tony Griffiths.