Christopher Dickman - Profile on Academia.edu (original) (raw)
Papers by Christopher Dickman
Research Square (Research Square), Dec 15, 2021
An important but understudied modality for eavesdropping between predators and prey is olfaction,... more An important but understudied modality for eavesdropping between predators and prey is olfaction, especially between non-mammalian vertebrate predators and their prey. Here we test three olfactory eavesdropping predictions involving an apex reptilian predator, the sand goanna Varanus gouldii, and several species of its small mammalian prey in arid central Australia: 1) small mammals will recognise and avoid the odour of V. gouldii; 2) V. gouldii will be attracted to the odour of small mammals, especially of species that maximise its energetic returns; and 3) small mammals will be less mobile and will show higher burrow delity where V. gouldii is absent compared with where it is present. As expected, we found that small mammals recognised and avoided faecal odour of this goanna, feeding less intensively at food patches where the odour of V. gouldii was present than at patches with no odour or a pungency control odour. Varanus gouldii also was attracted to the odour of small mammals in arti cial burrows, and dug more frequently at burrows containing the odour of species that were energetically pro table than at those of species likely to yield diminished returns. Our third prediction received mixed support. Rates of movement of three species of small mammals were no different where V. gouldii was present or absent, but burrow delity in two of these species increased as expected where V. gouldii had been removed. We conclude that olfaction plays a key role in the dynamic interaction between V. gouldii and its mammalian prey, with the interactants using olfaction to balance their respective costs of foraging and reducing predation risk. We speculate that the risk of predation from this apex reptilian predator drives the highly unusual burrow-shifting behaviour that characterises many of Australia's small desert mammals.
Animal mortality during fire
Global Change Biology, Jan 6, 2022
Earth's rapidly warming climate is propelling us towards an increasingly fire‐prone future. C... more Earth's rapidly warming climate is propelling us towards an increasingly fire‐prone future. Currently, knowledge of the extent and characteristics of animal mortality rates during fire remains rudimentary, hindering our ability to predict how animal populations may be impacted in the future. To address this knowledge gap, we conducted a global systematic review of the direct effects of fire on animal mortality rates, based on studies that unequivocally determined the fate of animals during fire. From 31 studies spanning 1984–2020, we extracted data on the direct impacts of fire on the mortality of 31 species from 23 families. From these studies, there were 43 instances where direct effects were measured by reporting animal survival from pre‐ to post‐fire. Most studies were conducted in North America (52%) and Oceania (42%), focused largely on mammals (53%) and reptiles (30%), and reported mostly on animal survival in planned (82%) and/or low severity (70%) fires. We found no studies from Asia, Europe or South America. Although there were insufficient data to conduct a formal meta‐analysis, we tested the effect of fire type, fire severity, fire regime, animal body mass, ecological attributes and class on survival. Only fire severity affected animal mortality, with a higher proportion of animals being killed by high than low severity fires. Recent catastrophic fires across the globe have drawn attention to the plight of animals exposed to wildfire. Yet, our systematic review suggests that a relatively low proportion of animals (mean predicted mortality [95% CI] = 3% [1%–9%]) are killed during fire. However, our review also underscores how little we currently know about the direct effects of fire on animal mortality, and highlights the critical need to understand the effects of high severity fire on animal populations.
The evolution and classification of marsupials
Cambridge University Press eBooks, Aug 17, 2006
Appendix A. Predator manipulation studies included in the meta-analysis
Predator manipulation studies included in the meta-analysis.
Dry, drier, driest: An Australian story of extreme years and potential ecosystem collapse
Returning the rat-kangaroos: translocation attempts in the family Potoroidae (superfamily Macropodoidea) and recommendations for conservation
Desert Channels: The Impulse to Conserve
Transactions of the Royal Society of South Africa, 2011
2010. Collingwood (Victoria), CSIRO Publishing. Price: AU$59.95 (~R400) (hardback). Pp. 300. ISBN... more 2010. Collingwood (Victoria), CSIRO Publishing. Price: AU$59.95 (~R400) (hardback). Pp. 300. ISBN 978 0 6430 9749 0.
Australian Journal of Zoology, Jan 1, 2003
This paper evaluates the systematic status of the Antechinus populations of northern New South Wa... more This paper evaluates the systematic status of the Antechinus populations of northern New South Wales and southern Queensland, using a combined morphological and molecular (allozymes and mitochondrial DNA) approach. Analysis of the d-loop section of the mitochondrial DNA control region revealed two highly supported clades within A. stuartii sensu lato that were sympatric in the Border Ranges of northern New South Wales. However, genetic distances between these clades were small (approximately 3%), indicating that time of divergence was probably relatively recent. Allozyme electrophoresis also showed very small differences between clades/species. Analyses of cranial and dental characters showed that the members of each of these clades differed morphologically and that the clades corresponded to A. stuartii and the recently described A. subtropicus. The combined results support the species status of A. stuartii and A. subtropicus, and suggest that speciation was likely a result of a recent vicariant event. Z O 0 2 0 0 9 M o l e c u l a r a n d m o r p h o l o g i c a l d i v i s i o n w i t h i n A n t e c h i n u s s t u a r t i i M . S . C r o w t h e r e t a l .
Australian Journal of Zoology, Jan 1, 1999
Molecular Ecology, Jan 1, 2006
Mating in the marsupial genus Antechinus is a synchronous annual event that is characterized by m... more Mating in the marsupial genus Antechinus is a synchronous annual event that is characterized by monoestry in females and abrupt postmating mortality in males. Male semelparity (multiple copulations during a single breeding season per lifetime) is often assumed to occur as a consequence of the intense mating effort expended by males in the rut, but the forces selecting for this remain elusive. Here, we investigate selection in male brown antechinus, Antechinus stuartii, and test two hypotheses for the evolution of semelparity: intermale competition and sperm competition. If intermale competition drives semelparity, we predicted that males would be under strong selection for large body size. If sperm competition is important, we predicted that selection would be strongest on scrotal size, a surrogate for testes volume. Using microsatellite markers, we found that 92% of females in free-living conditions mated with multiple males, producing litters of eight that had up to four fathers. These observations confirm the potential for sperm competition. Using selection analysis, we then found paternity success in 119 males to be related most strongly to body mass and scrotal size, thus providing support for both hypotheses. Large males presumably experience increased paternity success by gaining more matings or prolonged copulations via mate guarding, while large testes may allow increased sperm investment per copulation. Increased levels of free corticosteroid hormones in males facilitate the extreme mating effort during the short period of rut, but lead to immune suppression and consequently to the phenomenon of postmating mortality.
Biological Journal of The Linnean Society, Jan 1, 2008
The house mouse (Mus musculus domesticus) was introduced into Australia two centuries ago and is ... more The house mouse (Mus musculus domesticus) was introduced into Australia two centuries ago and is now succeeding in a wide range of habitats and climatic regions. To explore how mice exploit such extreme environments, we compared growth rate, morphology and reproductive success of animals reared under differing thermal regimes (13 °C ‘cool’, 22 °C ‘moderate’ and 30 °C ‘warm’) in laboratory mice derived from wild stock. ‘Warm’ group young were smaller and grew more slowly than those from other groups. At 6 weeks of age, body mass was less in ‘warm’ than in ‘cool’ treatment individuals; and liver mass/body mass also was less in ‘warm’ than in ‘cool’ treatment individuals. Paired kidney mass/body mass and paired adrenal mass/body mass were less in ‘warm’ than in ‘cool’ and ‘moderate’ treatment mice. Low heritability values indicate that these effects were from the temperature treatments rather than genetic influences. Irrespective of temperature treatment, females were more likely to produce a litter from post-partum matings if they were experienced, rather than young or reproductively naïve, and also bore more young from post-partum matings. These observations contribute to understanding of the sudden plague activities of mice in some parts of Australia and also their sparse distribution in the interior of the continent. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 21–30.
Australian Journal of Zoology, Jan 1, 2002
This paper uses a combined morphological, molecular and ecological approach to assess the taxonom... more This paper uses a combined morphological, molecular and ecological approach to assess the taxonomic status of Antechinus flavipes leucogaster from Western Australia, and its relationship to A. flavipes flavipes from eastern Australia. Morphological analyses show that A. flavipes leucogaster is smaller and finer than its eastern Australian counterpart in both cranial and dental dimensions. Phylogenetic analyses of partial cytochrome-b sequences showed that A. flavipes flavipes and A. flavipes leucogaster form reciprocally monophyletic clades that have a relatively high level of divergence (approximately 6%). Analysis of the timing of reproduction indicates that the two subspecies show opposite responses to latitude, with A. flavipes leucogaster ovulating later at high latitudes and A. flavipes flavipes ovulating later in more northerly parts of its range. The combined data and the entirely allopatric distributions of the two subspecies confirm their distinctive status. Bioclimatic analysis suggests further that A. flavipes leucogaster occupies wetter but seasonally more variable environments than its eastern relative. It is clear from the level of morphological, molecular, reproductive and distributional differences that A. flavipes flavipes and A. flavipes leucogaster should be regarded as separate taxa for the purposes of conservation management, and their current subspecific status should be maintained. Z O 0 2 0 3 0 T a x o n o m i c s t a t u s o f t h e m a r d o M . S . C r o w t h e r e t a l .
Current zoology, Jan 1, 2011
The roles that top predators play in regulating the structure and function of ecosystems have lon... more The roles that top predators play in regulating the structure and function of ecosystems have long been controversial. This is particularly the case when predators pose adverse risks for human life and/or economic interests. The critique of literature on dingoes and their ecological roles in Australia provided by shows that top predators remain a potentially polarising issue. In opposition to Allen et al. we argue that these widespread patterns of species' abundances, attributed to the effects of dingoes and evident at scales ranging from the foraging behaviour of individuals through to continental scale patterns of species abundances, constitute strong support for the mesopredator release hypothesis and provide evidence that dingoes benefit biodiversity conservation by inducing community wide trophic cascades. Harnessing the positive ecological effects of dingoes while at the same time minimising their impacts on agriculture is a major socio-political challenge in Australia [Current Zoology 57 (5): 668670].
Austral Ecology
Australia has a range of native and introduced large herbivores that could affect the abundance o... more Australia has a range of native and introduced large herbivores that could affect the abundance of small mammals through direct and indirect effects. Here we study the relationship between occurrence of the introduced rusa deer (Rusa timorensis) and the native swamp wallaby (Wallabia bicolor), and the abundance of four species of native small mammals in coastal heath vegetation with varying fire history.The abundance of two species, the brown antechinus (Antechinus stuartii) and bush rat (Rattus fuscipes), was related to occurrence of large herbivores and was dependent also on fire history. Abundance of swamp rats (R. lutreolus) and New Holland mice (Pseudomys novaehollandiae) was not related to the occurrence of any of the large herbivores, and did not depend on fire history. At sites burned within the last 9 years, captures of brown antechinus were negatively related to both deer and wallaby occurrence, and captures of bush rats were negatively related to deer occurrence. However, at sites that burned more than 15 years ago, captures of brown antechinus and bush rats were not related to large herbivore occurrence. Overall there was either no relationship, or a negative one, between small mammals and the large herbivores.This mensurative study has demonstrated relationships between deer and wallabies and small mammals, with fire as an additional important factor. From the results of the current study we put forward a series of hypotheses that need to be tested by future experiments.
… wader studies/Wader …, Jan 1, 2012
Biological Conservation, Jan 1, 2008
Information-theory Patch size Persistence Rodents A B S T R A C T Many species that exist patchil... more Information-theory Patch size Persistence Rodents A B S T R A C T Many species that exist patchily across the landscape are declining due to incremental losses of their constituent sub-populations and increasing isolation of those that remain.
Molecular …, 2006
Mating in the marsupial genus Antechinus is a synchronous annual event that is characterized by m... more Mating in the marsupial genus Antechinus is a synchronous annual event that is characterized by monoestry in females and abrupt postmating mortality in males. Male semelparity (multiple copulations during a single breeding season per lifetime) is often assumed to occur as a consequence of the intense mating effort expended by males in the rut, but the forces selecting for this remain elusive. Here, we investigate selection in male brown antechinus, Antechinus stuartii , and test two hypotheses for the evolution of semelparity: intermale competition and sperm competition. If intermale competition drives semelparity, we predicted that males would be under strong selection for large body size. If sperm competition is important, we predicted that selection would be strongest on scrotal size, a surrogate for testes volume. Using microsatellite markers, we found that 92% of females in free-living conditions mated with multiple males, producing litters of eight that had up to four fathers. These observations confirm the potential for sperm competition. Using selection analysis, we then found paternity success in 119 males to be related most strongly to body mass and scrotal size, thus providing support for both hypotheses. Large males presumably experience increased paternity success by gaining more matings or prolonged copulations via mate guarding, while large testes may allow increased sperm investment per copulation. Increased levels of free corticosteroid hormones in males facilitate the extreme mating effort during the short period of rut, but lead to immune suppression and consequently to the phenomenon of postmating mortality.
The success of GPS collar deployments on mammals in Australia
Australian Mammalogy, 2013
Abstract Global Positioning System (GPS) wildlife telemetry collars are being used increasingly t... more Abstract Global Positioning System (GPS) wildlife telemetry collars are being used increasingly to understand the movement patterns of wild mammals. However, there are few published studies on which to gauge their general utility and success. This paper highlights issues faced by some of the first researchers to use GPS technology for terrestrial mammal tracking in Australia. Our collated data cover 24 studies where GPS collars were used in 280 deployments on 13 species, including dingoes or other wild dogs (Canis lupus dingo and ...
Wildlife Research, Jan 1, 2007
Detailed studies of how endangered species use their environments at varied habitat scales are cr... more Detailed studies of how endangered species use their environments at varied habitat scales are crucial if they are to be conserved and managed effectively. In this study, we used spool-and-line tracking to investigate the microhabitats used by the brush-tailed bettong (Bettongia penicillata) and the burrowing bettong (B. lesueur), two species with geographical ranges that have been dramatically reduced since European settlement in Australia. The study was carried out at Scotia Sanctuary, in semiarid western New South Wales, where both species have been recently reintroduced. The nocturnal movements and foraging of bettongs were associated with sites containing more canopy cover (mean 10-25%) than was available on average (0-10%). Models generated to predict the probability of bettong movements or activity points showed positive correlations with ground vegetation cover and ground vegetation height. Other microhabitat components of varying importance, including sand cover, litter cover, litter depth, crust cover, and distance to shrub/tree, were incorporated into these models. Species comparisons indicated that, although slight differences occurred in the way each species moved through the habitat, both species foraged in areas with similar microhabitat characteristics. While the models should have broad utility for the selection of favourable habitat for future release sites for B. penicillata and B. lesueur, further studies of diet and food availability are recommended to refine them further.
Journal of …, 2004
Aim To determine whether latitudinal and longitudinal gradients in seed mass are related to varia... more Aim To determine whether latitudinal and longitudinal gradients in seed mass are related to variation in climatic features including temperature, solar radiation and rainfall.
Research Square (Research Square), Dec 15, 2021
An important but understudied modality for eavesdropping between predators and prey is olfaction,... more An important but understudied modality for eavesdropping between predators and prey is olfaction, especially between non-mammalian vertebrate predators and their prey. Here we test three olfactory eavesdropping predictions involving an apex reptilian predator, the sand goanna Varanus gouldii, and several species of its small mammalian prey in arid central Australia: 1) small mammals will recognise and avoid the odour of V. gouldii; 2) V. gouldii will be attracted to the odour of small mammals, especially of species that maximise its energetic returns; and 3) small mammals will be less mobile and will show higher burrow delity where V. gouldii is absent compared with where it is present. As expected, we found that small mammals recognised and avoided faecal odour of this goanna, feeding less intensively at food patches where the odour of V. gouldii was present than at patches with no odour or a pungency control odour. Varanus gouldii also was attracted to the odour of small mammals in arti cial burrows, and dug more frequently at burrows containing the odour of species that were energetically pro table than at those of species likely to yield diminished returns. Our third prediction received mixed support. Rates of movement of three species of small mammals were no different where V. gouldii was present or absent, but burrow delity in two of these species increased as expected where V. gouldii had been removed. We conclude that olfaction plays a key role in the dynamic interaction between V. gouldii and its mammalian prey, with the interactants using olfaction to balance their respective costs of foraging and reducing predation risk. We speculate that the risk of predation from this apex reptilian predator drives the highly unusual burrow-shifting behaviour that characterises many of Australia's small desert mammals.
Animal mortality during fire
Global Change Biology, Jan 6, 2022
Earth's rapidly warming climate is propelling us towards an increasingly fire‐prone future. C... more Earth's rapidly warming climate is propelling us towards an increasingly fire‐prone future. Currently, knowledge of the extent and characteristics of animal mortality rates during fire remains rudimentary, hindering our ability to predict how animal populations may be impacted in the future. To address this knowledge gap, we conducted a global systematic review of the direct effects of fire on animal mortality rates, based on studies that unequivocally determined the fate of animals during fire. From 31 studies spanning 1984–2020, we extracted data on the direct impacts of fire on the mortality of 31 species from 23 families. From these studies, there were 43 instances where direct effects were measured by reporting animal survival from pre‐ to post‐fire. Most studies were conducted in North America (52%) and Oceania (42%), focused largely on mammals (53%) and reptiles (30%), and reported mostly on animal survival in planned (82%) and/or low severity (70%) fires. We found no studies from Asia, Europe or South America. Although there were insufficient data to conduct a formal meta‐analysis, we tested the effect of fire type, fire severity, fire regime, animal body mass, ecological attributes and class on survival. Only fire severity affected animal mortality, with a higher proportion of animals being killed by high than low severity fires. Recent catastrophic fires across the globe have drawn attention to the plight of animals exposed to wildfire. Yet, our systematic review suggests that a relatively low proportion of animals (mean predicted mortality [95% CI] = 3% [1%–9%]) are killed during fire. However, our review also underscores how little we currently know about the direct effects of fire on animal mortality, and highlights the critical need to understand the effects of high severity fire on animal populations.
The evolution and classification of marsupials
Cambridge University Press eBooks, Aug 17, 2006
Appendix A. Predator manipulation studies included in the meta-analysis
Predator manipulation studies included in the meta-analysis.
Dry, drier, driest: An Australian story of extreme years and potential ecosystem collapse
Returning the rat-kangaroos: translocation attempts in the family Potoroidae (superfamily Macropodoidea) and recommendations for conservation
Desert Channels: The Impulse to Conserve
Transactions of the Royal Society of South Africa, 2011
2010. Collingwood (Victoria), CSIRO Publishing. Price: AU$59.95 (~R400) (hardback). Pp. 300. ISBN... more 2010. Collingwood (Victoria), CSIRO Publishing. Price: AU$59.95 (~R400) (hardback). Pp. 300. ISBN 978 0 6430 9749 0.
Australian Journal of Zoology, Jan 1, 2003
This paper evaluates the systematic status of the Antechinus populations of northern New South Wa... more This paper evaluates the systematic status of the Antechinus populations of northern New South Wales and southern Queensland, using a combined morphological and molecular (allozymes and mitochondrial DNA) approach. Analysis of the d-loop section of the mitochondrial DNA control region revealed two highly supported clades within A. stuartii sensu lato that were sympatric in the Border Ranges of northern New South Wales. However, genetic distances between these clades were small (approximately 3%), indicating that time of divergence was probably relatively recent. Allozyme electrophoresis also showed very small differences between clades/species. Analyses of cranial and dental characters showed that the members of each of these clades differed morphologically and that the clades corresponded to A. stuartii and the recently described A. subtropicus. The combined results support the species status of A. stuartii and A. subtropicus, and suggest that speciation was likely a result of a recent vicariant event. Z O 0 2 0 0 9 M o l e c u l a r a n d m o r p h o l o g i c a l d i v i s i o n w i t h i n A n t e c h i n u s s t u a r t i i M . S . C r o w t h e r e t a l .
Australian Journal of Zoology, Jan 1, 1999
Molecular Ecology, Jan 1, 2006
Mating in the marsupial genus Antechinus is a synchronous annual event that is characterized by m... more Mating in the marsupial genus Antechinus is a synchronous annual event that is characterized by monoestry in females and abrupt postmating mortality in males. Male semelparity (multiple copulations during a single breeding season per lifetime) is often assumed to occur as a consequence of the intense mating effort expended by males in the rut, but the forces selecting for this remain elusive. Here, we investigate selection in male brown antechinus, Antechinus stuartii, and test two hypotheses for the evolution of semelparity: intermale competition and sperm competition. If intermale competition drives semelparity, we predicted that males would be under strong selection for large body size. If sperm competition is important, we predicted that selection would be strongest on scrotal size, a surrogate for testes volume. Using microsatellite markers, we found that 92% of females in free-living conditions mated with multiple males, producing litters of eight that had up to four fathers. These observations confirm the potential for sperm competition. Using selection analysis, we then found paternity success in 119 males to be related most strongly to body mass and scrotal size, thus providing support for both hypotheses. Large males presumably experience increased paternity success by gaining more matings or prolonged copulations via mate guarding, while large testes may allow increased sperm investment per copulation. Increased levels of free corticosteroid hormones in males facilitate the extreme mating effort during the short period of rut, but lead to immune suppression and consequently to the phenomenon of postmating mortality.
Biological Journal of The Linnean Society, Jan 1, 2008
The house mouse (Mus musculus domesticus) was introduced into Australia two centuries ago and is ... more The house mouse (Mus musculus domesticus) was introduced into Australia two centuries ago and is now succeeding in a wide range of habitats and climatic regions. To explore how mice exploit such extreme environments, we compared growth rate, morphology and reproductive success of animals reared under differing thermal regimes (13 °C ‘cool’, 22 °C ‘moderate’ and 30 °C ‘warm’) in laboratory mice derived from wild stock. ‘Warm’ group young were smaller and grew more slowly than those from other groups. At 6 weeks of age, body mass was less in ‘warm’ than in ‘cool’ treatment individuals; and liver mass/body mass also was less in ‘warm’ than in ‘cool’ treatment individuals. Paired kidney mass/body mass and paired adrenal mass/body mass were less in ‘warm’ than in ‘cool’ and ‘moderate’ treatment mice. Low heritability values indicate that these effects were from the temperature treatments rather than genetic influences. Irrespective of temperature treatment, females were more likely to produce a litter from post-partum matings if they were experienced, rather than young or reproductively naïve, and also bore more young from post-partum matings. These observations contribute to understanding of the sudden plague activities of mice in some parts of Australia and also their sparse distribution in the interior of the continent. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 21–30.
Australian Journal of Zoology, Jan 1, 2002
This paper uses a combined morphological, molecular and ecological approach to assess the taxonom... more This paper uses a combined morphological, molecular and ecological approach to assess the taxonomic status of Antechinus flavipes leucogaster from Western Australia, and its relationship to A. flavipes flavipes from eastern Australia. Morphological analyses show that A. flavipes leucogaster is smaller and finer than its eastern Australian counterpart in both cranial and dental dimensions. Phylogenetic analyses of partial cytochrome-b sequences showed that A. flavipes flavipes and A. flavipes leucogaster form reciprocally monophyletic clades that have a relatively high level of divergence (approximately 6%). Analysis of the timing of reproduction indicates that the two subspecies show opposite responses to latitude, with A. flavipes leucogaster ovulating later at high latitudes and A. flavipes flavipes ovulating later in more northerly parts of its range. The combined data and the entirely allopatric distributions of the two subspecies confirm their distinctive status. Bioclimatic analysis suggests further that A. flavipes leucogaster occupies wetter but seasonally more variable environments than its eastern relative. It is clear from the level of morphological, molecular, reproductive and distributional differences that A. flavipes flavipes and A. flavipes leucogaster should be regarded as separate taxa for the purposes of conservation management, and their current subspecific status should be maintained. Z O 0 2 0 3 0 T a x o n o m i c s t a t u s o f t h e m a r d o M . S . C r o w t h e r e t a l .
Current zoology, Jan 1, 2011
The roles that top predators play in regulating the structure and function of ecosystems have lon... more The roles that top predators play in regulating the structure and function of ecosystems have long been controversial. This is particularly the case when predators pose adverse risks for human life and/or economic interests. The critique of literature on dingoes and their ecological roles in Australia provided by shows that top predators remain a potentially polarising issue. In opposition to Allen et al. we argue that these widespread patterns of species' abundances, attributed to the effects of dingoes and evident at scales ranging from the foraging behaviour of individuals through to continental scale patterns of species abundances, constitute strong support for the mesopredator release hypothesis and provide evidence that dingoes benefit biodiversity conservation by inducing community wide trophic cascades. Harnessing the positive ecological effects of dingoes while at the same time minimising their impacts on agriculture is a major socio-political challenge in Australia [Current Zoology 57 (5): 668670].
Austral Ecology
Australia has a range of native and introduced large herbivores that could affect the abundance o... more Australia has a range of native and introduced large herbivores that could affect the abundance of small mammals through direct and indirect effects. Here we study the relationship between occurrence of the introduced rusa deer (Rusa timorensis) and the native swamp wallaby (Wallabia bicolor), and the abundance of four species of native small mammals in coastal heath vegetation with varying fire history.The abundance of two species, the brown antechinus (Antechinus stuartii) and bush rat (Rattus fuscipes), was related to occurrence of large herbivores and was dependent also on fire history. Abundance of swamp rats (R. lutreolus) and New Holland mice (Pseudomys novaehollandiae) was not related to the occurrence of any of the large herbivores, and did not depend on fire history. At sites burned within the last 9 years, captures of brown antechinus were negatively related to both deer and wallaby occurrence, and captures of bush rats were negatively related to deer occurrence. However, at sites that burned more than 15 years ago, captures of brown antechinus and bush rats were not related to large herbivore occurrence. Overall there was either no relationship, or a negative one, between small mammals and the large herbivores.This mensurative study has demonstrated relationships between deer and wallabies and small mammals, with fire as an additional important factor. From the results of the current study we put forward a series of hypotheses that need to be tested by future experiments.
… wader studies/Wader …, Jan 1, 2012
Biological Conservation, Jan 1, 2008
Information-theory Patch size Persistence Rodents A B S T R A C T Many species that exist patchil... more Information-theory Patch size Persistence Rodents A B S T R A C T Many species that exist patchily across the landscape are declining due to incremental losses of their constituent sub-populations and increasing isolation of those that remain.
Molecular …, 2006
Mating in the marsupial genus Antechinus is a synchronous annual event that is characterized by m... more Mating in the marsupial genus Antechinus is a synchronous annual event that is characterized by monoestry in females and abrupt postmating mortality in males. Male semelparity (multiple copulations during a single breeding season per lifetime) is often assumed to occur as a consequence of the intense mating effort expended by males in the rut, but the forces selecting for this remain elusive. Here, we investigate selection in male brown antechinus, Antechinus stuartii , and test two hypotheses for the evolution of semelparity: intermale competition and sperm competition. If intermale competition drives semelparity, we predicted that males would be under strong selection for large body size. If sperm competition is important, we predicted that selection would be strongest on scrotal size, a surrogate for testes volume. Using microsatellite markers, we found that 92% of females in free-living conditions mated with multiple males, producing litters of eight that had up to four fathers. These observations confirm the potential for sperm competition. Using selection analysis, we then found paternity success in 119 males to be related most strongly to body mass and scrotal size, thus providing support for both hypotheses. Large males presumably experience increased paternity success by gaining more matings or prolonged copulations via mate guarding, while large testes may allow increased sperm investment per copulation. Increased levels of free corticosteroid hormones in males facilitate the extreme mating effort during the short period of rut, but lead to immune suppression and consequently to the phenomenon of postmating mortality.
The success of GPS collar deployments on mammals in Australia
Australian Mammalogy, 2013
Abstract Global Positioning System (GPS) wildlife telemetry collars are being used increasingly t... more Abstract Global Positioning System (GPS) wildlife telemetry collars are being used increasingly to understand the movement patterns of wild mammals. However, there are few published studies on which to gauge their general utility and success. This paper highlights issues faced by some of the first researchers to use GPS technology for terrestrial mammal tracking in Australia. Our collated data cover 24 studies where GPS collars were used in 280 deployments on 13 species, including dingoes or other wild dogs (Canis lupus dingo and ...
Wildlife Research, Jan 1, 2007
Detailed studies of how endangered species use their environments at varied habitat scales are cr... more Detailed studies of how endangered species use their environments at varied habitat scales are crucial if they are to be conserved and managed effectively. In this study, we used spool-and-line tracking to investigate the microhabitats used by the brush-tailed bettong (Bettongia penicillata) and the burrowing bettong (B. lesueur), two species with geographical ranges that have been dramatically reduced since European settlement in Australia. The study was carried out at Scotia Sanctuary, in semiarid western New South Wales, where both species have been recently reintroduced. The nocturnal movements and foraging of bettongs were associated with sites containing more canopy cover (mean 10-25%) than was available on average (0-10%). Models generated to predict the probability of bettong movements or activity points showed positive correlations with ground vegetation cover and ground vegetation height. Other microhabitat components of varying importance, including sand cover, litter cover, litter depth, crust cover, and distance to shrub/tree, were incorporated into these models. Species comparisons indicated that, although slight differences occurred in the way each species moved through the habitat, both species foraged in areas with similar microhabitat characteristics. While the models should have broad utility for the selection of favourable habitat for future release sites for B. penicillata and B. lesueur, further studies of diet and food availability are recommended to refine them further.
Journal of …, 2004
Aim To determine whether latitudinal and longitudinal gradients in seed mass are related to varia... more Aim To determine whether latitudinal and longitudinal gradients in seed mass are related to variation in climatic features including temperature, solar radiation and rainfall.
Following a bush fire, wire mesh refuges were installed at Ethabuka Station, Queensland to provid... more Following a bush fire, wire mesh refuges were installed at Ethabuka Station, Queensland to provide refuge (from the invasive predators) to the small mammals and reptiles. We monitored the habitat selection of dunnarts, small dasyurid marsupials on two grids, one with shelters and one without. The dunnarts showed use of the shleters however, only in combination with median spinifex density (13 bushes per M^2) and at a subsection 10-30 meters from the dune crest.
Journal of Mammalogy, 2020
Disturbances such as fire reduce the structural complexity of terrestrial habitats, increasing th... more Disturbances such as fire reduce the structural complexity of terrestrial habitats, increasing the risk of predation for small prey species. The postfire effect of predation has especially deleterious effects in Australian habitats owing to the presence of invasive mammalian predators, the red fox (Vulpes vulpes) and feral cat (Felis catus), that rapidly exploit burned habitats. Here, we investigated whether the provision of artificial shelter could alleviate the risk of predation perceived by two species of small marsupial, the dunnarts Sminthopsis hirtipes and S. youngsoni, in open postfire habitat in the sandridge system of the Simpson Desert, central Australia. We installed artificial shelters constructed from wire mesh that allowed passage of the dunnarts but not of their predators at one site, and measured and compared the perceived risk of predation by the dunnarts there with those on a control site using optimal patch-use theory (giving-up densities, GUDs). GUDs were lower near artificial shelters than away from them, and near dune crests where dunnarts typically forage, suggesting that the shelters acted as corridors for dunnarts to move up to the crests from burrows in the swales. Foraging was lower near the crest in the control plot. Two-day foraging bouts were observed in dunnart activity, with recruitment to GUD stations occurring a day earlier in the augmented shelter plot. Despite these results, the effects of the shelters were localized and not evident at the landscape scale, with GUDs reduced also in proximity to sparse natural cover in the form of regenerating spinifex grass hummocks. Mapping dunnart habitat use using the landscape of fear (LOF) framework confirmed that animals perceived safety near shelter and risk away from it. We concluded that the LOF framework can usefully assess real-time behavioral responses of animals to management interventions in situations where demographic responses take longer to occur.