Authors: Sarah J Maclagan, Terry Coates, Austin O’Malley, and Euan G Ritchie
Published in:Austral Ecology
Understanding how fundamental aspects of species’ ecology, such as diet, are affected in human‐dominated landscapes is vital for informing management and conserving biodiversity – particularly where species influence important ecosystem functions. Digging, mycophagous (‘fungus‐eating’) mammals play various such roles, including the dispersal of hypogeal (‘truffle‐like’) fungi.
The endangered, mycophagous southern brown bandicoot (Isoodon obesulus obesulus: Peramelidae) persists in a peri‐urban landscape south‐east of Melbourne, Australia, where it occupies both ‘novel’ habitats (linear strips of vegetation along roadsides, drains and railway lines) and ‘remnant’ habitats (larger blocks of native vegetation) within dedicated conservation areas. It remains unknown how bandicoot diet, including the diversity of hypogeal fungi, varies between these habitat types, yet this could have important conservation implications.
Our study aimed to (i) compare the diet of I. o. obesulus at novel and remnant sites; and (ii) attain knowledge of hypogeal fungal diversity in these different contexts. We collected 133 bandicoot scats over 23 months and examined both broad diet composition and diversity of fungi consumed.
Bandicoot diet differed between site types; in particular, ants were more prominent in scats from remnant sites, while millipedes and seeds were more prominent in scats from novel sites. All scats contained fungal spores, with hypogeal taxa comprising at least 35 of the 78 ‘morphotypes’ found at novel sites and 28 of the 59 detected at remnant sites. Fewer samples were collected at remnant sites, but they appeared to contain a greater richness of hypogeal fungi per scat. We did not detect any differences in fungal composition between site types. However, our sampling effort was insufficient to estimate true morphotype richness at either site type.
Our study highlights the adaptable generalist diet of the southern brown bandicoot, as well as the likely under‐appreciated diversity of hypogeal fungi that can occur in highly modified, novel ecosystems.
Maclagan SJ, Coates T, O’Malley A, Ritchie EG (2020) Dietary variation of an endangered mycophagous mammal in novel and remnant habitats in a peri‐urban landscape. Austral EcologyPDFDOI
Authors: Hayley M Geyle, Michael Stevens, Ryan Duffy, Leanne Greenwood, Dale G Nimmo, Derek Sandow, Ben Thomas, John White, and Euan G Ritchie
Published in:Ecological Solutions and Evidence
Introduced carnivores are often cryptic, making it difficult to quantify their presence in ecosystems, and assess how this varies in relation to management interventions. Survey design should thus seek to improve detectability and maximize statistical power to ensure sound inference regarding carnivore population trends. Roads may facilitate carnivore movements, possibly leading to high detectability. Therefore, targeting roads may improve inferences about carnivore populations.
We assessed our ability to monitor feral cats Felis catus and red foxes Vulpes vulpes on‐ and off‐road, with explicit consideration of the location of monitoring sites on our ability to detect population changes. We also assessed whether there was evidence of spatial or temporal interaction between these species that might influence their road‐use.
Surveys were conducted in a conservation reserve in south‐eastern Australia between 2016 and 2018. At each of 30 sites, we deployed two motion‐sensor cameras, one on‐road, and the other off‐road. Using occupancy models, we estimated cat and fox occupancy and detectability, and conducted a power analysis to assess our ability to detect declines in occupancy under three monitoring regimes (efforts targeted equally on‐ and off‐road, efforts targeted entirely off‐road and efforts targeted entirely on‐road).
On average, on‐road detectability was seven times higher for cats and three times higher for foxes. Targeting survey effort on‐road yielded the greatest power for detecting declines in both species, but our ability to detect smaller declines decreased with decreasing initial occupancy probability. No level of decline was detectable for cats when survey efforts were targeted off‐road, while only large declines (>50%) were detectable for foxes (assuming high initial occupancy probabilities). We found little evidence of spatial or temporal segregation, suggesting limited avoidance or suppression between the two species within this landscape.
Our results suggest that targeting monitoring on roads may be an effective approach for detecting declines in introduced carnivore populations, particularly following management intervention (e.g. lethal control), and in the face of resource limitations. We provide a framework that can help assist land managers to make informed decisions, which balance monitoring efforts and resource constraints with sufficient statistical power to assess management objectives.
Geyle HM, Stevens M, Duffy R, Greenwood L, Nimmo DG, Sandow D, Thomas B, White J, Ritchie EG (2020) Evaluation of camera placement for detection of free‐ranging carnivores; implications for assessing population changes. Ecological Solutions and EvidencePDFDOI
Authors: Grant D Linley, Annette Rypalski, Georgeanna Story, and Euan G Ritchie
Published in:Australian Mammalogy
Information about the ecological functional roles of native predators may help inform the conservation of wildlife and pest management.
If predators show preferences for certain prey, such as invasive species, this could potentially be used as a conservation tool to help restore degraded (e.g. overgrazed) ecosystems via the reintroduction of native predators and suppression of exotic prey (e.g. introduced herbivores).
The diet of spotted-tailed quolls was studied in a fenced reserve in south-eastern Australia where native mammals have been reintroduced, foxes and cats removed, but invasive European rabbits still persist.
A total of 80 scats were collected over 12 months and analysis of macroscopic prey remains was conducted to determine diet.
Rabbits were by far the most commonly consumed prey species by volume (~76%) and frequency (~60%), followed by brushtail possums (~11% for both volume and frequency), and other small and medium-sized native mammals in much smaller amounts. Quoll scat analysis revealed 10 mammal species in total, eight of which were native. Bird, reptile and invertebrate remains were uncommon in quoll scats.
This suggests that spotted-tailed quolls may show a preference for preying on invasive European rabbits in certain contexts, and this could potentially be used as part of quoll reintroductions to aid rabbit population suppression and ecosystem restoration.
Linley GD, Rypalski A, Story G, Ritchie EG (2020) Run rabbit run: spotted-tailed quoll diet reveals invasive prey is top of the menu. Australian MammalogyPDFDOI
Feral and pet cats are responsible for a huge part of Australia’s shameful mammal extinction record. Small and medium-sized ground-dwelling mammals are most susceptible.
But we’ve found one mammal in particular that can outsmart cats and live alongside them: the long-nosed potoroo.
These miniature kangaroo-like marsupials are officially listed as vulnerable. And after the recent devastating fires, extensive swathes of their habitat in southeastern Australia were severely burnt, leaving them more exposed to predators such as foxes and cats. But the true extent of the impact on their numbers remains unclear.
Using motion-sensing camera traps on the wildlife haven of French Island – which is free of foxes, but not cats – we found potoroos may have developed strategies to avoid prowling cats, such as hiding in dense vegetation.
If these long-nosed potoroos can co-exist with one of the world’s most deadly predators, then it’s time we rethink our conservation strategies.
Surviving cats with a deadly game of hide and seek
We conservatively estimated that between five and 14 cats lived in our study area (but it takes only one cat to eradicate a population of native animals).
Although cats were common here, we detected them less often in areas of dense vegetation. By contrast, this was where we found potoroos more often.
Long-nosed potoroos are nocturnal foragers that mainly, but not exclusively, feed in more open habitat before sheltering in dense vegetation during the day. But we found potoroos rarely ventured out of their thick vegetation shelter.
This may be because they’re trading off potentially higher quality foraging habitat in more open areas against higher predation risk. In other words, it appears they’ve effectively learnt to hide from the cats.
Another intriguing result from our study was that although potoroos and feral cats shared more than half of their activity time, the times of peak activity for each species differed.
Cats were active earlier in the night, while potoroo activity peaked three to four hours later. This might be another potoroo strategy to avoid becoming a cat’s evening meal.
Still, completely avoiding cats isn’t possible. Our study site was in the national park on French Island, and it’s likely cats saturate this remnant patch of long-nosed potoroo habitat.
It’s also possible cats may be actively searching for potoroos as prey, and indeed some of our camera images showed cats carrying young long-nosed potoroos in their mouths. These potoroos were more likely killed by these cats, rather than scavenged.
Cats are expert hunters
Cats are exceedingly difficult to manage effectively. They’re adaptable, elusive and have a preference for live prey.
The two most common management practices for feral cats are lethal control and exclusion fencing. Lethal control needs to be intensive and conducted over large areas to benefit threatened species.
“Safe havens” – created through the use of exclusion fencing or predator-free islands – can overcome some of these challenges. But while exclusion fencing is highly effective, it can create other bad outcomes, including an over-abundance of herbivores, leading to excessive grazing of vegetation.
In any case, removing introduced predators might not be really necessary in places native species can co-exist. If long-nosed potoroos have learnt to live with feral cats, we should instead focus on how to maintain their survival strategies.
Why cat eradication isn’t always the best option
It’s clear cats are here to stay, so we shouldn’t simply fall back largely on predator eradication or predator-free havens as the only way to ensure our wildlife have a fighting chance at long-term survival.
But perhaps most important is having predator-savvy insurance populations, such as long-nosed potoroos on French Island. This is incredibly valuable for one day moving them to other areas where predators – native or feral – are present, such as nearby Phillip Island.
In the absence of predators, native wildlife can rapidly lose their ability to recognise predator danger. Programs aimed at eradicating introduced predators where they’re co-existing with native species need to pay careful attention to this.
Authors: Vivianna Miritis, Anthony R Rendall, Tim S Doherty, Amy L Coetsee, and Euan G Ritchie
Published in:Wildlife Research
Feral domestic cats (Felis catus) have contributed to substantial loss of Australian wildlife, particularly small- and medium-sized terrestrial mammals. However, mitigating cat impacts remains challenging.
Understanding the factors that facilitate coexistence between native prey and their alien predators could aid better pest management and conservation actions.
We estimated feral cat density, examined the impact of habitat cover on long-nosed potoroos (Potorous tridactylus tridactylus), and assessed the spatial and temporal interactions between cats and potoroos in the ‘Bluegums’ area of French Island, south-eastern Australia.
Materials and methods
We operated 31 camera stations across Bluegums for 99 consecutive nights in each of winter 2018 and summer 2018/19. We used a spatially explicit capture–recapture model to estimate cat density, and two-species single-season occupancy models to assess spatial co-occurrence of cats and potoroos.
We assessed the influence of vegetation cover and cat activity on potoroo activity by using a dynamic occupancy model. We also used image timestamps to describe and compare the temporal activities of the two species.
Bluegums had a density of 0.77 cats per km² across both seasons, although this is a conservative estimate because of the presence of unidentified cats.
Cats and long-nosed potoroos were detected at 94% and 77% of camera stations, respectively.
Long-nosed potoroo detectability was higher in denser vegetation and this pattern was stronger at sites with high cat activity.
Cats and potoroos overlapped in their temporal activity, but their peak activity times differed.
Feral cat density at Bluegums, French Island, is higher than has been reported for mainland Australian sites, but generally lower than in other islands.
Long-nosed potoroos were positively associated with cats, potentially indicating cats tracking potoroos as prey or other prey species that co-occur with potoroos.
Temporal activity of each species differed, and potoroos sought more complex habitat, highlighting possible mechanisms potoroos may use to reduce their predation risk when co-occurring with cats.
Our study highlighted how predator and prey spatial and temporal interactions, and habitat cover and complexity (ecological refuges), may influence the ability for native prey to coexist with invasive predators.
We encourage more consideration and investigation of these factors, with the aim of facilitating more native species to persist with invasive predators or be reintroduced outside of predator-free sanctuaries, exclosures and island safe havens.
Miritis V, Rendall AR, Doherty TS, Coetsee AL, Ritchie EG (2020) Living with the enemy: a threatened prey species coexisting with feral cats on a fox-free island. Wildlife ResearchPDFDOI
Authors: Grant D Linley, Yvette Pauligk, Courtney Marneweck, and Euan G Ritchie
Published in: Australian Mammology
Moon phase and variation in ambient light conditions can influence predator and prey behaviour. Nocturnal predators locate prey visually, and prey may adjust their activity to minimise their predation risk. Understanding how native mammals in Australia respond to varying phases of the moon and cloud cover (light) enhances knowledge of factors affecting species’ survival and inference regarding ecological and population survey data.
Over a two-year period within a fenced conservation reserve, in south-eastern Australia, with reintroduced native marsupial predator and prey species (eastern barred bandicoot, southern brown bandicoot, long-nosed potoroo, rufous bettong, Tasmanian pademelon, brush-tailed rock-wallaby, red-necked wallaby, eastern quoll, spotted-tailed quoll, and naturally occurring swamp wallaby, common brushtail possum, common ringtail possum), we conducted monthly spotlight surveys during different moon phases (full, half and new moon).
We found an interaction between cloud cover and moon phase, and an interaction of the two depending on the mammal size and class. Increased activity of prey species corresponded with periods of increasing cloud cover. Predators and medium-sized herbivores were more active during times of low illumination.
Our findings suggest that moon phase affects the nocturnal activity of mammal species and that, for prey species, there might be trade-offs between predation risk and foraging. Our findings have implications for: ecological survey design and interpretation of results for mammal populations across moon phases, understanding predator and prey behaviour and interactions in natural and modified (artificial lighting) ecosystems, and potential nocturnal niche partitioning of species.
Linley GD, Pauligk Y, Marneweck C, Ritchie EG (2020) Moon phase and nocturnal activity of native Australian mammals. Australian MammalogyPDFDOI
Authors: Michael L Wysong, Gwenllian D Iacona, Leonie E Valentine, Keith Morris, and Euan G Ritchie
Published in:Wildlife Research
To understand the ecological consequences of predator management, reliable and accurate methods are needed to survey and detect predators and the species with which they interact.
Recently, poison baits have been developed specifically for lethal and broad-scale control of feral cats in Australia. However, the potential non-target effects of these baits on other predators, including native apex predators (dingoes), and, in turn, cascading effects on lower trophic levels (large herbivores), are poorly understood.
We examined the effect that variation in camera trapping-survey design has on detecting dingoes, feral cats and macropodids, and how different habitat types affect species occurrences. We then examined how a feral cat poison baiting event influences the occupancy of these sympatric species.
We deployed 80 remotely triggered camera traps over the 2,410-km² Matuwa Indigenous Protected Area, in the semiarid rangelands of Western Australia, and used single-season site-occupancy models to calculate detection probabilities and occupancy for our target species before and after baiting.
Cameras placed on roads were ~60 times more likely to detect dingoes and feral cats than were off-road cameras, whereas audio lures designed to attract feral cats had only a slight positive effect on detection for all target species.
Habitat was a significant factor affecting the occupancy of dingoes and macropodids, but not feral cats, with both species being positively associated with open woodlands.
Poison baiting to control feral cats did not significantly reduce their occupancy but did so for dingoes, whereas macropodid occupancy increased following baiting and reduced dingo occupancy.
Camera traps on roads greatly increase the detection probabilities for predators, whereas audio lures appear to add little or no value to increasing detection for any of the species we targeted.
Poison baiting of an invasive mesopredator appeared to negatively affect a non-target, native apex predator, and, in turn, may have resulted in increased activity of large herbivores.
Management and monitoring of predators must pay careful attention to survey design, and lethal control of invasive mesopredators should be approached cautiously so as to avoid potential unintended negative ecological consequences (apex-predator suppression and herbivore release).
Wysong ML, Iacona GD, Valentine LE, Morris K, Ritchie EG (2020) On the right track: placement of camera traps on roads improves detection of predators and shows non-target impacts of feral cat baiting. Wildlife ResearchPDFDOI
Authors: Michael L Wysong, Bronwyn A Hradsky, Gwenllian D Iacona, Leonie E Valentine, Keith Morris, and Euan G Ritchie
Published in: Movement Ecology
Where mesopredators co-exist with dominant apex predators, an understanding of the factors that influence their habitat and space use can provide insights that help guide wildlife conservation and pest management actions.
A predator’s habitat use is defined by its home range, which is influenced by its selection or avoidance of habitat features and intra- and inter-specific interactions within the landscape. These are driven by both innate and learned behaviour, operating at different spatial scales.
We examined the seasonal home ranges and habitat selection of actively-managed populations of a native apex predator (dingo Canis dingo) and invasive mesopredator (feral cat Felis catus) in semi-arid Western Australia to better understanding their sympatric landscape use, potential interactions, and to help guide their management.
We used kernel density estimates to characterise the seasonal space use of dingoes and feral cats, investigate inter- and intra-species variation in their home range extent and composition, and examine second-order habitat selection for each predator. Further, we used discrete choice modelling and step selection functions to examine the difference in third-order habitat selection across several habitat features.
The seasonal home ranges of dingoes were on average 19.5 times larger than feral cats. Feral cat seasonal home ranges typically included a larger proportion of grasslands than expected relative to availability in the study site, indicating second-order habitat selection for grasslands.
In their fine-scale movements (third-order habitat selection), both predators selected for roads, hydrological features (seasonal intermittent streams, seasonal lakes and wetlands), and high vegetation cover. Dingoes also selected strongly for open woodlands, whereas feral cats used open woodlands and grasslands in proportion to availability.
Based on these results, and in order to avoid unintended negative ecological consequences (e.g. mesopredator release) that may stem from non-selective predator management, we recommend that feral cat control focuses on techniques such as trapping and shooting that are specific to feral cats in areas where they overlap with apex predators (dingoes), and more general techniques such as poison baiting where they are segregated.
Wysong ML, Hradsky BA, Iacona GD, Valentine LE, Morris K, Ritchie EG (2020) Space use and habitat selection of an invasive mesopredator and sympatric, native apex predator. Movement Ecology PDFDOI
Authors: William L Geary, Tim S Doherty, Dale G Nimmo, Ayesha I T Tulloch, and Euan G Ritchie
Published in: Journal of Animal Ecology
Knowledge of how disturbances such as fire shape habitat structure and composition, and affect animal interactions, is fundamental to ecology and ecosystem management. Predators also exert strong effects on ecological communities, through top‐down regulation of prey and competitors, which can result in trophic cascades. Despite their ubiquity, ecological importance and potential to interact with fire, our general understanding of how predators respond to fire remains poor, hampering ecosystem management.
To address this important knowledge gap, we conducted a systematic review and meta‐analysis of the effects of fire on terrestrial, vertebrate predators worldwide. We found 160 studies spanning 1978–2018. There were 36 studies with sufficient information for meta‐analysis, from which we extracted 96 effect sizes (Hedge’s g) for 67 predator species relating to changes in abundance indices, occupancy or resource selection in burned and unburned areas, or before and after fire.
Studies spanned geographic locations, taxonomic families, and study designs, but most were located in North America and Oceania (59% and 24%, respectively), and largely focussed on felids (24%) and canids (25%). Half (50%) of the studies reported responses to wildfire, and nearly one third concerned prescribed (management) fires.
There were no clear, general responses of predators to fire, nor relationships with geographic area, biome or life history traits (e.g. body mass, hunting strategy and diet). Responses varied considerably between species. Analysis of species for which at least three effect sizes had been reported in the literature revealed that red foxes (Vulpes vulpes) mostly responded positively to fire (e.g. higher abundance in burned compared to unburned areas) and eastern racers (Coluber constrictor) negatively, with variances overlapping zero only slightly for both species.
Our systematic review and meta‐analysis revealed strong variation in predator responses to fire, and major geographic and taxonomic knowledge gaps. Varied responses of predator species to fire likely depend on ecosystem context. Consistent reporting of ongoing monitoring and management experiments is required to improve understanding of the mechanisms driving predator responses to fire, and any broader effects (e.g. trophic interactions). The divergent responses of species in our study suggest that adaptive, context‐specific management of predator‐fire relationships is required.
Geary WL, Doherty TS, Nimmo DG, Tulloch AIT, Ritchie EG (2019) Predator responses to fire: A global systematic review and meta‐analysis. Journal of Animal EcologyPDFDOI
Authors: Lauren M Halstead, Duncan R Sutherland, Leonie E Valentine, Anthony R Rendall, Amy L Coetsee, and Euan G Ritchie
Published in:Austral Ecology
Digging mammals are often considered ecosystem engineers, as they affect important properties of soils and in turn nutrient exchange, vegetation dynamics and habitat quality. Returning such species, and their functions, to areas from where they have been extirpated could help restore degraded landscapes and is increasingly being trialled as a conservation tool.
Studies examining the effects of digging mammals have largely been from arid and semi‐arid environments, with little known about their impacts and importance in mesic systems. To address this knowledge gap, we investigated the ecological role of a recently introduced population of eastern barred bandicoots (Perameles gunnii) on Churchill Island, Victoria, south‐eastern Australia, from which all digging mammals have been lost.
We quantified the annual rate of soil turnover by estimating the number of foraging pits bandicoots created in 100‐m² plots over a 24‐hour period. Foraging pit counts could not be completed in each season, and the overall turnover estimate assumes that autumn/winter months represent turnover rates for the entire year; however, this is likely to fluctuate between seasons. Ten fresh and ten old pits were compared to paired undug control sites to quantify the effect soil disturbance had on soil hydrophobicity, moisture content and soil strength. Plots contained between zero and 64 new foraging pits each day. We estimated that an individual eastern barred bandicoot digs ~487 (95% CI = 416–526) small foraging pits per night, displacing ~13.15 kg (95% CI = 11.2–14.2 kg) of soil, equating to ~400 kg (95% CI = 341–431 kg) of soil in a winter month. Foraging pits were associated with decreased soil compaction and increased soil moisture along the foraging pit profile.
Eastern barred bandicoots likely play an important role in ecosystems through their effects on soil, which adds to an increasing body of knowledge suggesting restoration of ecosystems, via the return of ecosystem engineers and their functions, holds much promise for conserving biodiversity and ecological function.
Halstead LM, Sutherland DR, Valentine LE, Rendall AR, Coetsee AL, Ritchie EG (2019) Digging up the dirt: Quantifying the effects on soil of a translocated ecosystem engineer. Austral Ecology PDFDOI
Authors: Harry A Moore, Judy A Dunlop, Leonie E Valentine, John C Z Woinarski, Euan G Ritchie, David M Watson, and Dale G Nimmo
Published in:Diversity and Distributions
Aim: Species range contractions are increasingly common globally. The niche reduction hypothesis posits that geographic range contractions are often patterned across space owing to heterogeneity in threat impacts and tolerance. We applied the niche reduction hypothesis to the decline of a threatened marsupial predator across northern Australia, the northern quoll (Dasyurus hallucatus).
Location: Northern Australia.
Methods: We assembled a database containing 3,178 historic and contemporary records for northern quolls across the extent of their distribution dating between 1778 and 2019. Based on these records, we estimated changes in the geographic range of the northern quoll using α‐hulls across four main populations. We then examined how range contractions related to factors likely to mediate the exposure, susceptibility, or tolerance of northern quolls to threats.
Result: The extent of range contractions showed an east–west gradient, most likely reflecting the timing of spread of introduced cane toads (Rhinella marina). There were clear changes in environmental characteristics within the contemporary compared to the historic geographic range, with the most substantial occurring in populations that have suffered the greatest range contractions. The contemporary range is comprised of higher quality habitats (measured using environmental niche models), characterized by higher topographical ruggedness and annual rainfall, and reduced distance to water, compared to the historic range.
Main conclusions: Changes to range and niche likely reflect the capacity of complex habitats to ameliorate threats (namely predation and altered fire regimes), and access to resources that increase threat tolerance. This study highlights the multivariate nature of ecological refuges and the importance of high‐quality habitats for the persistence of species exposed to multiple threats. Our methods provide a useful framework which can be applied across taxa in providing valuable insight to management.
Moore HA, Dunlop JA, Valentine LE, Woinarski JCZ, Ritchie EG, Watson DM, Nimmo DG (2019) Topographic ruggedness and rainfall mediate geographic range contraction of a threatened marsupial predator. Diversity and Distributions PDFDOI
Authors: Sarah J Maclagan, Terry Coates, Bronwyn A Hradsky, Ryan Butryn, and Euan G Ritchie
Published in:Animal Conservation
Animal movement can be significantly altered in human‐dominated landscapes such as urban and peri‐urban areas, where habitat is often fragmented and/or linear. Knowledge regarding how wildlife respond to anthropogenic change is vital for informing conservation efforts in such landscapes, including the design of nature reserves and wildlife corridors.
To better understand how threatened species persist and behave within human‐dominated landscapes, we examined the home range and space use of the nationally endangered southern brown bandicoot Isoodon obesulus obesulus in peri‐urban Melbourne, Australia’s second‐largest city. Specifically, we examined whether:
bandicoots were confined to linear strips of remnant vegetation or also made use of the broader highly modified landscape matrix;
the configuration of the linear vegetated strips affected home range shape; and
home range area differed between bandicoots living in linear strips and those in larger remnant habitat patches.
We found that:
71% of adult males and 33% of adult females used the matrix, but non‐dispersing juveniles were entirely confined to the linear strips; males also travelled greater distances into the matrix (away from the vegetated strips) than females;
bandicoots had longer home ranges in narrower strips and males had longer home ranges than females; and
home range area for both sexes was smaller in linear strips than has been recorded in other studies in larger remnant habitats.
Our study highlights the importance of retaining narrow, fragmented and modified vegetation to accommodate threatened biodiversity within human‐dominated landscapes, but suggests the surrounding matrix may also offer important resources for adaptable species, such as bandicoots.
Supporting off‐reserve conservation of biodiversity in novel ecosystems is increasingly pertinent in our rapidly urbanizing world.
Maclagan SJ, Coates T, Hradsky BA, Butryn R, Ritchie EG (2019) Life in linear habitats: the movement ecology of an endangered mammal in a peri‐urban landscape. Animal Conservation PDFDOI
Authors: Jim‐Lino Kämmerle, Euan G Ritchie, and Ilse Storch
Published in:Conservation Science and Practice
Predators are often culled to benefit prey, but in many cases this conservation goal is not achieved or results remain unknown.
The red fox (Vulpes vulpes) is a predator of global significance, and an invasive species in some regions. Red fox culls intended to benefit prey are often restricted to small areas, and effectiveness is rarely sufficiently evaluated.
Given the economic, ecological, social, and welfare issues associated with lethal predator control, there is a strong need to assess the effects of spatiotemporal variation in culling intensity on red fox abundance.
We surveyed red fox populations in fragmented forests of south‐western Germany and related indices of local fox abundance to culling data, predicted landscape‐scale fox abundance, and other covariates. We tested whether restricted‐area culling was associated with local reductions in fox abundance, and examined how this relationship changed over time.
Local fox abundance was temporarily reduced in spring, following winter culls. However, the effect was minor and fox populations had compensated for the reductions at the latest by autumn. Restricted‐area culling therefore likely failed to sustain effects on fox abundance throughout the period most relevant for conservation (i.e., the reproductive period of the target prey species).
To be effective as a conservation tool, culling will therefore require explicit spatiotemporal coordination matching the biology of predators and target prey.
Kämmerle J, Ritchie EG, Storch I (2019) Restricted‐area culls and red fox abundance: Are effects a matter of time and place? Conservation Science and Practice PDFDOI
Without significant tree cover, dry and dusty landscapes can result. Image credit: Don Driscoll
By Martine Maron (The University of Queensland), Andrea Griffin (University of Newcastle), April Reside (The University of Queensland), Bill Laurance (James Cook University), Don Driscoll (Deakin University), Euan Ritchie (Deakin University), and Steve Turton (CQUniversity Australia).
Australia’s high rates of forest loss and weakening land clearing laws are increasing bushfire risk, and undermining our ability to meet national targets aimed at curbing climate change.
This dire situation is why we are among the more than 300 scientists and practitioners who have signed a declaration calling for governments to restore, or better strengthen regulations to protect native vegetation.
Land clearing laws have been contentious in several states for years. New South Wales relaxed its land clearing controls in 2017, triggering concerns over irreversible environmental damage. Although it is too early to know the impact of those changes, a recent analysis found that land clearing has increased sharply in some areas since the laws changed.
The Queensland Labor government’s 2018 strengthening of land clearing laws came after years of systematic weakening of these protections. Yet the issue has remained politically divisive. While discussing a federal inquiry into the impact of these policies on farmers, federal agriculture minister David Littleproud suggested that the strenthening of regulations may have worsened Queensland’s December bushfires.
We argue such an assertion is at odds with scientific evidence. And, while the conservation issues associated with widespread land clearing are generally well understood by the public, the consequences for farmers and fire risks are much less so.
Tree loss can increase fire risk
During December’s heatwave in northern Queensland, some regions were at “catastrophic” bushfire risk for the first time since ratings began. Even normally wet rainforests, such as at Eungella National Park inland from Mackay, sustained burns in some areas during “unprecedented” fire conditions.
There is no evidence to support the suggestion that 2018’s land clearing law changes contributed to the fires. No changes were made to how vegetation can be managed to reduce fire risk. This is governed under separate laws, which remained unaltered.
In fact, shortly after the fires, Queensland’s land clearing figures were released. They showed that in the three years to June 2018, an area equivalent to roughly 570,000 Melbourne Cricket Grounds (1,138,000 hectares) of bushland was cleared, including 284,000 hectares of remnant (old-growth) ecosystems.
Tree clearing can worsen fire risk in several ways. It can affect the regional climate. In parts of eastern Australia, tree cover reductions are estimated to have increased summer surface temperatures by up to 2℃ and southwest Western Australia by 0.4–0.8℃, reduced rainfall in southeast Australia, and made droughts hotter and longer.
Removing forest vegetation depletes soil moisture. Large, intact areas of forest typically have cooler, wetter microclimates buffered from extreme temperatures. Over time, some forest types can even become fire-resistant, but smaller patches of trees are typically drier and more flammable.
Trees also form a natural windbreak that can slow the spread of bushfires. An analysis of the 2005 Wangary fire in South Australia found that fires spread most rapidly through paddocks, rather than through areas lined with native trees.
Extensive tree clearing also leads to problems for farmers, including rising salinity, reduced water quality, and soil erosion. Governments and rural communities spend significant money and labour redressing the aftermath of excessive clearing.
Sensible regulation of native vegetation removal does not restrict existing agriculture, but rather seeks to support sustainable production. Retained trees can help deal with many environmental risks that hamper agricultural productivity, including animal health, long-term pasture productivity, risks to the water cycle, pest control, and human well-being.
Rampant tree clearing is undoing climate policy too. Much of the federal government’s A$2.55 billion Emissions Reduction Fund has gone towards tree planting. But it would take almost this entire sum just to replace the trees cleared in Queensland since 2012.
In 2019, Australians might reasonably expect that our relatively wealthy and well-educated country has moved beyond a frontier-style reliance on continued deforestation, and we would do well to better acknowledge and learn lessons from Indigenous Australians with respect to their land management practices.
Yet the periodic weakening of land clearing laws in many parts of Australia has accelerated the problem. The negative impacts on industry, society and wildlife are numerous and well established. They should not be ignored.
Authors: April E Reside, Natalie J Briscoe, Chris R Dickman, Aaron C Greenville, Bronwyn A Hradsky, Salit Kark, Michael R Kearney, Alex S Kutt, Dale G Nimmo, Chris R Pavey, John L Read, Euan G Ritchie, David Roshier, Anja Skroblin, Zoe Stone, Matt West, and Diana O Fisher
Published in:Biodiversity and Conservation
It may be possible to avert threatened species declines by protecting refuges that promote species persistence during times of stress. To do this, we need to know where refuges are located, and when and which management actions are required to preserve, enhance or replicate them.
Here we use a niche-based perspective to characterise refuges that are either fixed or shifting in location over ecological time scales (hours to centuries). We synthesise current knowledge of the role of fixed and shifting refuges, using threatened species examples where possible, and examine their relationships with stressors including drought, fire, introduced species, disease, and their interactions.
Refuges often provide greater cover, water, food availability or protection from predators than other areas within the same landscapes. In many cases, landscape features provide refuge, but refuges can also arise through dynamic and shifting species interactions (e.g., mesopredator suppression). Elucidating the mechanisms by which species benefit from refuges can help guide the creation of new or artificial refuges. Importantly, we also need to recognise when refuges alone are insufficient to halt the decline of species, and where more intensive conservation intervention may be required.
We argue that understanding the role of ecological refuges is an important part of strategies to stem further global biodiversity loss.
Reside AE, Briscoe NJ, Dickman CR, Greenville AC, Hradsky BA, Kark S, Kearney MR, Kutt AS, Nimmo DG, Pavey CR, Read JL, Ritchie EG, Roshier D, Skroblin A, Stone Z, West M, Fisher DO (2019) Persistence through tough times: fixed and shifting refuges in threatened species conservation. Biodiversity and ConservationPDFDOI
Authors: Michael L Wysong, Ayesha IT Tulloch, Leonie E Valentine, Richard J Hobbs, Keith Morris, and Euan G Ritchie
Published in:Jornal of Mammalogy
Dietary (scat) analysis is a key tool for assessing the potential effects of predators on prey and for comparing resource use between predators, information that is crucial for effective wildlife management. However, misidentification of the species from which scats originate could result in inaccurate conclusions regarding predator–prey interactions and their consequences for ecosystems, which may ultimately compromise conservation and management actions.
To address this issue, we developed a framework for decision-making in the face of uncertain scat species origin by incorporating field, laboratory, and molecular identification techniques.
We used the framework to examine the diets of two predators, a native apex predator (dingo, Canis lupus dingo) and an invasive mesopredator (feral cat, Felis catus), from 696 field-collected scats in the arid zone of Australia.
We examined how uncertainty regarding scat species origin changed perceptions of the nature of the relationship between coexisting predators and their prey.
The extent of dietary overlap between dingoes and cats varied with the method used to identify scat species origin. Dietary overlap assessed by laboratory identifications was twice as high as when uncertainty in scat species origin was resolved through our decision framework.
If uncertainty in scat species origin is not resolved in dietary studies, practitioners and decision-makers relying on this information run the risk of making misinformed conclusions regarding the ecological function of predators (including potential impacts on threatened species), which could have perverse outcomes if the wrong predators are targeted for management.
With uncertainty in scat species origin resolved through our decision framework, a low level of dietary overlap between the two predators was demonstrated, and medium-sized mammals most threatened with extinction were shown to be more at risk of impact from feral cat than from dingo depredations.
Wysong ML, Tulloch AIT, Valentine LE, Hobbs RJ, Morris K, Ritchie EG (2019) The truth about cats and dogs: assessment of apex- and mesopredator diets improves with reduced observer uncertainty. Journal of MammalogyPDFDOI
Authors: Michalis Hadjikakou, Euan G Ritchie, Kate E Watermeyer, and Brett A Bryan
Published in:The Lancet – Planetary Health
The global food system is causing unsustainable pressures on the environment, leading to widespread land use change, increased greenhouse gas emissions, disruption of the nitrogen and phosphorus cycles, biodiversity loss, and freshwater depletion and pollution. Environmental pressures are mounting as populations grow and diets change, escalating the need to make food production and consumption more sustainable. Yet, there are limitations in the current analysis of global food system sustainability. We believe there are four main areas that could be improved to make such analysis more comprehensive and insightful. These improvements could have important repercussions on the development of effective evidence-based policy that ultimately promotes production efficiencies and sustainable diets.
One set of opportunities for improvement in the analysis of food system sustainability relates to the robustness of the dietary scenarios that are modelled. First, these scenarios need to be made more plausible. Although assessment of radical shifts in human diets might be useful in highlighting the effects of animal-based versus plant-based foods, we question the benefit of emphasising the most extreme of scenarios (ie, a complete switch from omnivore to vegetarian or vegan diets), when the foreseeable global trend is heading strongly in the opposite direction. In addition, analyses of these extreme diet substitution scenarios tend to focus on greenhouse gas emissions, but in such scenarios, trade-offs between sustainability indicators are highly likely—aptly highlighted by the increased use of water in scenarios that model shifts from grass-fed livestock towards water-intensive crops. We argue that it is more insightful to model ambitious yet achievable, context-specific reductions in animal products, overconsumption (particularly of discretionary foods), and food waste, in line with those recently recommended by the EAT-Lancet Commission on sustainable food systems for overall planetary health.
Secondly, more granular and dynamic analyses are needed. Estimates of environmental effects underpinning global food system analyses are typically based on life cycle assessment, an environmental accounting framework that captures effects from farm-to-fork. While the rigour and comprehensiveness of available life cycle assessment data and associated meta-analyses are improving and encompassing important trade-offs between sustainability objectives,5 significant shortcomings remain, notably in terms of low commodity-level detail and the use of global averages to infer region-specific or nation-specific environmental intensities (defined in life cycle assessments as the impact per functional unit of production). In addition, most life cycle assessments are static, and therefore do not represent system feedbacks that incorporate changes in demand because of production efficiency enhancements, or marginal changes in environmental effects involved in large-scale dietary shifts—such as when animal-based products are completely eliminated. The quantification of these dynamics and their system-wide environmental impacts is an opportunity to greatly improve sustainability assessments of different food products and proposed substitutions.
Thirdly, protein sources beyond conventional livestock need greater consideration. In many parts of the world, alternative animal protein sources such as abundant native species that are better adapted to local conditions (eg, kangaroo in Australia and deer in the northern hemisphere) can contribute to human nutrition, with such sourcing having considerably lower environmental effects than farming of conventional livestock. Many countries are also host to introduced feral animal populations that could serve as alternative protein sources—for example, Australia has substantial feral deer, goat, rabbit, pig, horse, and camel populations. Partly replacing existing mainstream protein sources with wild harvests of these alternative sources could achieve co-benefits for the environment (eg, through reducing emissions, land degradation, and the effects on native biodiversity), and improve human health, since game meat is typically leaner than lamb and beef. Conventional analyses also fail to account for other transformative shifts in animal-sourced protein, such as those towards laboratory-grown meat, insect-derived protein, and feeding animals on ecological leftovers such as food waste or grass from pastures. Including potential shifts to novel low-impact protein sources would ensure more comprehensive modelling of the associated environmental effects.
Finally, analyses should better quantify the diverse effects of food production on biodiversity and ecosystems. Food production contributes considerably to species extinction, which has detrimental effects on many ecosystems and plant and animal communities that are essential for supporting human life. Yet, there is an overreliance on proxy indicators such as land use when assessing terrestrial food systems. Previous research has highlighted how the extent of agricultural land area is not a good proxy for biodiversity impact, because of differences in production intensity and heterogeneity in biodiversity values. This limited analysis also extends to marine and freshwater food production. Stock depletion, bycatch, and habitat modification or loss, resulting from intensive aquaculture and fishing practices such as trawling, have substantial effects on the biodiversity of coastal and oceanic ecosystems. However, although some studies have considered the environmental intensities of aggregate categories such as farmed fish and crustaceans, the effect of fishing on wild stocks is typically not encompassed in life cycle assessments, despite appropriate data being available. Integration of a more diverse range of biodiversity indicators into the assessment of food system sustainability would allow for more meaningful analyses.
Taking advantage of the opportunities outlined here could facilitate a more complete understanding of the environmental effects of food production and consumption. Embracing these advances is a key prerequisite for developing effective policy recommendations. Our recommendations aim to foster a more comprehensive and nuanced debate on sustainable diets and the food system within the context of global environmental limits.
We declare no competing interests. We thank D Driscoll and BG Ridoutt for their insightful comments on the manuscript.
Hadjikakou M, Ritchie EG, Watermeyer KE, Bryan BA (2019) Improving the assessment of food system sustainability. The Lancet – Planetary HealthPDFDOI
Authors: Rebecca C Cherubin, Susanna E Venn, Don A Driscoll, Tim S Doherty, and Euan G Ritchie
Published in:Ecological Management & Restoration
Feral herbivores are a major driver of biodiversity loss globally and can alter the structure, composition and functioning of ecosystems. The direct impacts of feral herbivores on plant communities are well studied, but the direct and indirect effect they have on wildlife is not well understood.
In Victoria (south‐eastern Australia), a large feral Horse (Equus caballus) population coincides with highly sensitive and nationally endangered Alpine Sphagnum Bogs and Associated Fens communities, and several threatened animal species.
We assessed the impact of feral horses on this ecological community and the Alpine Water Skink (Eulamprus kosciuskoi) and the Broad‐toothed Rat (Mastacomys fuscus) at 20 sites with varying levels of horse disturbance. We used scat counts to determine an index of feral horse abundance and quantified impacts associated with their presence in the landscape. Active searches were used for Alpine Water Skink and scat and runway surveys for Broad‐toothed Rat. We also measured the vegetation structure and the abundance of different vegetation types (life forms).
Our results suggest that feral horses are associated with vegetation types and characteristics that negatively influence the presence or abundance of Alpine Water Skink and Broad‐toothed Rat. Sites with high horse activity had more low‐growing forbs, and the abundance of Alpine Water Skink was negatively related to this vegetation type. Grasses, sedges, rushes and shrubs were also less dense and lower in height in high horse activity sites, and Broad‐toothed Rat was less likely to be present in areas with these habitat attributes.
We recommend that feral horses are controlled to protect these threatened vertebrate species and their Sphagnum bog habitat.
Cherubin RC, Venn SE, Driscoll DA, Doherty TS, Ritchie EG (2019) Feral horse impacts on threatened plants and animals in sub-alpine and montane environments in Victoria, Australia. Ecological Management & RestorationPDFDOI
Authors: Don A Driscoll, Graeme L Worboys, Hugh Allan, Sam C Banks, Nicholas J Beeton, Rebecca C Cherubin, Tim S Doherty, C Max Finlayson, Ken Green, Renée Hartley, Geoffrey Hope, Chris N Johnson, Mark Lintermans, Brendan Mackey, David J Paull, Jamie Pittock, Luciana L Porfirio, Euan G Ritchie, Chloe F Sato, Ben C Scheele, Deirdre A Slattery, Susanna Venn, David Watson, Maggie Watson, and Richard M Williams
Published in:Ecological Management & Restoration
New evidence of impacts by feral horses in Australia’s alpine parks systems confirms they endanger threatened species and extensively damage critically endangered bog communities that could take millennia to recover. These impacts are not confounded by effects of deer and accumulate over time, even when only a small number of feral horses (∼100) are present.
With protected areas representing only a small proportion of the area of the Australian states of New South Wales (9.3%) and Victoria (17%), allowing feral horses to degrade reserves is not a reasonable management compromise, is contrary to the purpose of the protected area system and conflicts with international obligations.
Modelling and decades of management experience indicate that trapping alone does not control feral horse numbers. Trapping and fertility control can work in small populations, but not when there are several thousand horses in remote areas. Aerial culling is needed to cost‐effectively and humanely control feral horse populations.
The relatively small amount of suffering feral horses experience during a cull is outweighed by
avoiding suffering and death of horses from starvation and thirst,
avoiding the suffering of native animals displaced by horses, and
avoiding the ethical concerns of driving threatened species towards extinction.
Objections to aerial culling on welfare and cultural grounds are contradicted by evidence.
Improving knowledge in the general community about what is at stake is long overdue because without this knowledge, small groups with vested interests and unfounded claims have been able to dominate debate and dictate management actions.
As a result of ineffective management, horse populations are now expanding and causing well‐documented damage to Australia’s alpine parks, placing at risk almost $10M spent on restoration after livestock grazing ended. The costs of horse control and restoration escalate the longer large horse populations remain in the alpine parks.
It is crucial that feral horse numbers are rapidly reduced to levels where ecosystems begin to recover. Aerial culling is needed as part of the toolbox to achieve that reduction.
Driscoll DA, Worboys GL, Allan H, Banks SC, Beeton NJ, Cherubin RC, Doherty TS, Finlayson CM, Green K, Hartley R, Hope G, Johnson CN, Lintermans M, Mackey B, Paull DJ, Pittock J, Porfirio LL, Ritchie EG, Sato CF, Scheele BC, Slattery DA, Venn S, Watson D, Watson M, Williams RM (2019) Impacts of feral horses in the Australian Alps and evidence-based solutions. Ecological Management & RestorationPDFDOI
We’re living in the middle of an extinction crisis, on par with what wiped out the dinosaurs 65 million years ago. But an asteroid isn’t responsible this time; we are.
Imagine walking into the most beautiful museum, taking all the artworks off the shelves and burning them or throwing them in the bin. That’s what we’re doing. We’re losing species every day all over the world.
De-extinction science can never replicate the wonder of evolution, nor how long it takes for species to evolve…