Christopher R. Dickman

The University of Sydney · School of Biological Sciences

Sex ratios in wild populations of mammals often differ from parity. Here, we describe variation in offspring sex ratios in a population of quenda (Isoodon fusciventer, Marsupialia: Peramelidae), along with observations of maternal body mass and home range size. We evaluate whether the Local Resource Competition (LRC) or Trivers–Willard hypothesis b...

Camera traps are widely used in wildlife research and monitoring, so it is imperative to understand their strengths, limitations, and potential for increasing impact. We investigated a decade of use of wildlife cameras (2012–2022) with a case study on Australian terrestrial vertebrates using a multifaceted approach. We (i) synthesised information...

Understanding the factors driving species' range and niche contractions can help us identify how and where threats to those species are being mediated or tolerated. Here, we used the 'niche reduction hypothesis' to investigate changes in the geographic range and realised niche of the greater bilby (Macrotis lagotis). We compiled bilby occurrence re...

Megafires are becoming increasingly common in regions across the globe due to climate change and human activities. This rapid departure from historical fire regimes is creating novel challenges for animal populations, and their ability to persist may depend on fire-driven adaptations. Understanding how species respond and adapt to altered fire regi...

Co‐evolutionary relationships associated with biogeographical context mediate the response of native prey to introduced predators, but this effect has not yet been demonstrated for domestic cats. We investigated the main factors influencing the vulnerability of prey species to domestic cat Felis catus predation across Australia, Europe and North Am...

With large wildfires becoming more frequent1,2, we must rapidly learn how megafires impact biodiversity to prioritize mitigation and improve policy. A key challenge is to discover how interactions among fire-regime components, drought and land tenure shape wildfire impacts. The globally unprecedented3,4 2019–2020 Australian megafires burnt more tha...

Rewilding is the deliberate (re)introduction of animal species into local or regional areas with the joint aims to assist the conservation of those species and promote the re-establishment of lost or degraded ecological processes. In Australia and Aotearoa New Zealand rewilding is particularly important in reversing losses of species and ecological...

Brushtail possums (Trichosurus vulpecula) are becoming increasingly recognized as key members of local scavenger guilds in Australia. Yet, our understanding of the spatiotemporal scavenging dynamics of this mainly herbivorous marsupial species remains limited. We investigated abiotic and biotic factors influencing possum carcass use across an alpin...

The bidirectional relationship between plant species richness and community biomass is often variable and poorly resolved in natural grassland ecosystems1–3, impeding progress in predicting impacts of environmental changes. In contrast, most biological communities have lognormal species abundance distributions (e.g., biomass, cover, number of indiv...

Carcass scavenging by vertebrates is a critical ecosystem service that is influenced by environmental factors such as season and habitat. However, there is limited understanding of the role that these factors play in shaping scavenging patterns across different bioregions. We used camera traps to monitor vertebrate scavengers at 120 kangaroo (Famil...

Global change is associated with variable shifts in the annual production of aboveground plant biomass, suggesting localized sensitivities with unclear causal origins. Combining remotely sensed normalized difference vegetation index data since the 1980s with contemporary field data from 84 grasslands on 6 continents, we show a widening divergence i...

Mineral-associated organic carbon (MAOC) constitutes a major fraction of global soil carbon and is assumed less sensitive to climate than particulate organic carbon (POC) due to protection by minerals. Despite its importance for long-term carbon storage, the response of MAOC to changing climates in drylands, which cover more than 40% of the global...

Forbs (“wildflowers”) are important contributors to grassland biodiversity and services, but they are vulnerable to environmental changes that affect their coexistence with grasses. In a factorial experiment at 94 sites on 6 continents, we tested the global generality of several broad predictions arising from previous studies: (1) Forb cover and ri...

Context Introduced predators pose a significant threat to biodiversity. Understanding how predators interact with other threats such as fire is crucial to developing effective conservation strategies. Aims We investigated interactions between the greater bilby (Macrotis lagotis) and two introduced predators, the European red fox (Vulpes vulpes) and...

Increasing environmental threats and more extreme environmental perturbations place species at risk of population declines, with associated loss of genetic diversity and evolutionary potential. While theory shows that rapid population declines can cause loss of genetic diversity, populations in some environments, like Australia’s arid zone, are rep...

Scavenging dynamics are influenced by many abiotic and biotic factors, but there is little knowledge of how scavengers respond to extreme weather events. As carrion is a major driver of the organisation and structure of food webs within ecological communities, understanding the response of scavengers to extreme weather events is critical in a world...

The 2019–2020 Australian bushfire season had a devastating impact on native wildlife. It was estimated that 3 billion native animals were impacted by the fires, yet there are few estimates of the number of animals that were rescued and rehabilitated post-fire. Focusing on the state of New South Wales (NSW) and Kangaroo Island, South Australia, we u...

Plant diversity decline under nutrient addition in local grassland communities is typically ascribed to the loss of rare species, species with particular traits ill-suited for high nutrient levels, and displacement of many localized species with a few widespread species. Whether these changes result in stronger diversity decline and vegetation homo...

Considering several logistical limitations associated with live trapping in arid environments, owl pellet analysis provides a potentially useful alternative to estimate small mammal diversity. Owl pellet analysis has been used to estimate local small mammal diversity under the assumption that the method can reliably reflect the composition of local...

Deserts are often highly biodiverse and provide important habitats for many threatened species. Fire is a dominant disturbance in deserts, and prescribed burning is increasingly being used by conservation managers and Indigenous peoples to mitigate the damaging effects of climate change, invasive plants, and land‐use change. The size, severity, and...

Software for realistically simulating complex population genomic processes is revolutionizing our understanding of evolutionary processes, and providing novel opportunities for integrating empirical data with simulations. However, the integration between standalone simulation software and R is currently not well developed. Here, we present slimr, a...

Co-occurring species often overlap in their use of resources and can interact in complex ways. However, shifts in environmental conditions or resource availability can lead to changes in patterns of species co-occurrence, which may be exacerbated by global escalation of human disturbances to ecosystems, including conservation-directed interventions...

1. Climate change and human activities have disrupted historical fire regimes, leading to complex and far-reaching impacts on global ecosystems. Despite extensive research in fire ecology, studies exploring vertebrate responses to megafires, and to nuanced fire characteristics, remain limited. 2. We collected camera trap data 3-27 months followin...

In episodic environments like deserts, populations of some animal species exhibit irregular fluctuations such that populations are alternately large and connected or small and isolated. Such dynamics are typically driven by periodic resource pulses due, for example, to large but infrequent rainfall events. The repeated population bottlenecks result...

Herbivore exclusion is implemented globally to recover ecosystems from grazing by introduced and native herbivores, but evidence for large‐scale biodiversity benefits is inconsistent in arid ecosystems. We examined the effects of livestock exclusion on dryland plant richness and reproductive capacity. We collected data on plant species richness and...

Previous studies have suggested that mammal life history varies along the fast-slow continuum and that, in eutherians, this continuum is linked to variation in the potential contribution of survival and reproduction to population growth rate (λ). Fast eutherians mature early, have large litters and short lifespans, and exhibit high potential contri...

Species interactions play a fundamental role in ecosystems. However, few ecological communities have complete data describing such interactions, which is an obstacle to understanding how ecosystems function and respond to perturbations. Because it is often impractical to collect empirical data for all interactions in a community, various methods ha...

Human activities are altering ecological communities around the globe. Understanding the implications of these changes requires that we consider the composition of those communities. However, composition can be summarized by many metrics which in turn are influenced by different ecological processes. For example, incidence-based metrics strongly re...

Catastrophic megafires can increase extinction risks; identifying species priorities for management and policy support is critical for preparing and responding to future fires. However, empirical data on population loss and recovery post-fire, especially megafire, are limited and taxonomically biased. These gaps could be bridged if species' morphol...

Simple Summary Rodents in Australia’s central deserts face highly unpredictable climatic conditions, with long dry ‘bust’ periods, when resources are sparse, punctuated by brief ‘boom’ periods, after heavy rainfall, when resources are abundant. We studied the diet of an Australian desert-dwelling rodent species, the sandy inland mouse Pseudomys her...

This is the introductory article to the Research Topic "Drivers of Small-mammal Community Structure in Tropical Savannas", in the journals Conservation and Restoration Ecology section. The editorial provides background from previously published studies and a brief synopsis of each newly published article in the Research Topic. This collection will...

Plant productivity varies due to environmental heterogeneity, and theory suggests that plant diversity can reduce this variation. While there is strong evidence of diversity effects on temporal variability of productivity, whether this mechanism extends to variability across space remains elusive. Here we determine the relationship between plant di...

Abstract While almost half of all mammal species are rodents, records of albinism in free‐ranging rodents are very rare. Australia has a large and diverse assemblage of native rodent species, but there are no records of free‐ranging albino rodents in the published literature. In this study, we aim to improve our understanding of the occurrence of a...

Effective conservation of Australasian marsupials requires detailed knowledge of their food habits and activity patterns. Ancestral marsupials were probably nocturnal insectivores. Food habits of extant fauna are studied by techniques such as direct observations, analysis of prey remains in stomach contents or feces, field experiments, eDNA, stable...

This chapter introduces the book by telling how the history of research on American and Australasian marsupials has developed up to now. It focuses on the main disciplines that aim to study the diversity of marsupials and other metatherians, from the past to today. These disciplines are taxonomy, systematics, biogeography, ecology, and conservation...

Predation by feral cats ( Felis catus ) has caused the extinction of many native species in Australia and globally. There is growing evidence that the impacts of feral cats can be amplified in post‐fire environments, as cats are drawn to hunt in or around recently burnt areas and are also more effective hunters in open habitats. In 2018–2019, we es...

Roaming domestic cats (Felis catus) are recognised as a threat to wildlife globally. Yet management of pet cats in urbanised areas is not regularly mandated, and management of feral cats in urbanised areas is rarely implemented. Mounting evidence emphasises the value of urban environments as hot spots of wildlife activity, which as the human popula...

The arid and semiarid regions of Australia encompass about three quarters of the continent. This vast area – the arid zone – is characterized by very varied habitats and landscapes and inter-annual extremes of rainfall that drive dramatic shifts in primary productivity. Arid zone marsupials use morphological, behavioral, and physiological adaptatio...

Expert elicitation can be valuable for informing decision-makers on conservation and wildlife management issues. To date, studies eliciting expert opinions have primarily focused on identifying and building consensus on key issues. Nonetheless , there are drawbacks of a strict focus on consensus, and it is important to understand and emphasize diss...

The availability of natural habitats is decreasing due to increases in the human population and inexorable urban spread. Although many marsupials cannot live in urban environments and others occur in areas removed from intensive human activity, some marsupials persist and even fare well in towns and cities or in disturbed habitats within the built...

Australasia is home to many iconic species of marsupials, most found nowhere else. The region also leads the world in marsupial declines and extinctions. There are many causes of marsupial decline with focus in this chapter on habitat loss and habitat fragmentation. While habitat loss and habitat fragmentation are typically considered together, the...

Global change drivers, such as anthropogenic nutrient inputs, are increasing globally. Nutrient deposition simultaneously alters plant biodiversity, species composition and ecosystem processes like aboveground biomass production. These changes are underpinned by species extinction, colonisation and shifting relative abundance. Here, we use the Pric...

Introduction of the domestic cat and red fox has devastated Australian native fauna. We synthesized Australian diet analyses to identify traits of prey species in cat, fox and dingo diets, which prey were more frequent or distinctive to the diet of each predator, and quantified dietary overlap. Nearly half (45%) of all Australian terrestrial mammal...

Under the Ecosystem Exploitation Hypothesis ecosystem productivity predicts trophic complexity, but it is unclear if spatial and temporal drivers of productivity have similar impacts. Long-term studies are necessary to capture temporal impacts on trophic structure in variable ecosystems such as deserts. We sampled ants and measured plant resources...

Species interactions play a fundamental role in ecosystems. They affect where species can live, how their population sizes fluctuate through time, and how environmental perturbations cascade through communities. But few ecological communities have complete data describing such interactions, which is an obstacle to understanding how ecosystems funct...

The 2021 annual forum of the Royal Zoological Society of NSW raked over the ashes of the unprecedented “Black Summer” bushfires of 2019–2020 in eastern and southern Australia to assess how forest ecosystems and their constituent fauna had fared. This paper provides an overview of the 21 studies that were presented at the forum, now as papers in thi...

Free-roaming domestic cats (i.e., cats that are owned or unowned and are considered ‘at large’) are globally distributed non-native species that have marked impacts on biodiversity and human health. Despite clear scientific evidence of these impacts, free-roaming cats are either unmanaged or managed using scientifically unsupported and ineffective...

Australia’s 2019–20 mega-fires burnt 79% of the Greater Blue Mountains World Heritage Area, prompting an urgent need for rapid on-ground post-fire assessments of flora and fauna to aid in post-fire recovery. This project aimed to determine spatial patterns in populations and assemblages of vertebrates, vertebrate temporal activity, and the diet of...

Carrion is an ubiquitous resource that drives the dynamics of scavenger populations and shapes the structure and composition of their communities. Corvids (Family: Corvidae) are among the most common scavengers globally, facilitating carcass discovery by other species and contributing to carcass biomass removal. Here, we examine how environmental f...

Ecological models predict that the effects of mammalian herbivore exclusion on plant diversity depend on resource availability and plant exposure to ungulate grazing over evolutionary time. Using an experiment replicated in 57 grasslands on six continents, with contrasting evolutionary history of grazing, we tested how resources (mean annual precip...

Global change drivers such as anthropogenic nutrient inputs simultaneously alter biodiversity, species composition, and ecosystem functions such as aboveground biomass. These changes are interconnected by complex feedbacks among extinction, colonization, and shifting relative abundance. Here, we use a novel temporal application of the Price equatio...

Populations of many animal species decline after fire, with some individuals killed during the fire and others succumbing to impoverished conditions in the post-fire environment. For individuals that survive a fire, an ability to exploit scarce resources in the burnt landscape is particularly important. In this study, we compared the numbers, survi...

Australia has suffered more modern mammal extinctions than any nation. Among the list of extinct species is the blue-grey mouse (Pseudomys glaucus), a rodent known from just three specimens (two from southern Queensland and one from northern New South Wales). We investigated circumstances of collection for the three specimens referred to this speci...

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...

Ecosystem engineers are typically seen as organisms whose activities modulate the availability of resources for other species. A new study shows that Brandt's vole engineers its local environment specifically to reduce its own risk of being killed by predatory birds.

Urban environments provide the only or best habitats that are left for wildlife in many areas, promoting increased interest in urban conservation and a need to understand how wildlife cope with urban stressors, such as altered predator activity and human disturbance. Here, we used filmed giving-up density experiments to investigate behavioral copin...