Category: Research

Authors: Hugh F Davies, Casey Visintin, Brett P Murphy, Euan G Ritchie, Sam C Banks, Ian D Davies, and David MJS Bowman

Published in: Biological Conservation

Abstract

Maximising the spatiotemporal variability of prescribed fire (i.e. pyrodiversity) is often thought to benefit biodiversity. However, given mixed empirical support, the generality of the pyrodiversity hypothesis remains questionable.

Here, we use a simulation experiment to explore the effects of spatiotemporal fire patterns on the population trajectories of four mammal species in a northern Australian savanna: northern brown bandicoot (Isoodon macrourus), northern brushtail possum (Trichosurus vulpecula arnhemensis), grassland melomys (Melomys burtoni), and northern quoll (Dasyurus hallucatus). Underpinned by data from a landscape-scale fire experiment, we simulated mammal population trajectories under three scenarios of fire size (ambient, small/dispersed fires, large/clumped fires) and three levels of dispersal ability (low, moderate, high) over a 21-year period across the Kapalga area of Kakadu National Park.

The simulated population size of all four species declined markedly, regardless of fire spatial pattern and dispersal ability. However, the predicted final population size (i.e. number of individuals in the final timestep of the simulation) for the northern brown bandicoot, northern brushtail possum and grassland melomys were significantly influenced by fire size, with declines most severe under the small/dispersed fire scenario.

Our results suggest that maximising the dispersion of small fires at the expense of disturbance refugia (such as less-frequently burnt areas) may exacerbate the severity of mammal decline. This highlights the importance of considering trade-offs between spatial (i.e. fire dispersion) and temporal (i.e. fire frequency) aspects of pyrodiversity, and the potential risks when applying fire management for biodiversity conservation without a firm understanding of the requirements of the target species.

Davies HF, Visintin C, Murphy BP, Ritchie EG, Banks SC, Davies ID, Bowman DMJS (2023) Pyrodiversity trade-offs: A simulation study of the effects of fire size and dispersal ability on native mammal populations in northern Australian savannas. Biological Conservation PDF DOI

Authors: William L Geary, Ayesha IT Tulloch, Euan G Ritchie, Tim S Doherty, Dale G Nimmo, Marika A Maxwell, and Adrian F Wayne

Published in: Global Change Biology

Abstract

Ecosystem management in the face of global change requires understanding how co-occurring threats affect species and communities. Such an understanding allows for effective management strategies to be identified and implemented. An important component of this is differentiating between factors that are within (e.g. invasive predators) or outside (e.g. drought, large wildfires) of a local manager’s control.

In the global biodiversity hotspot of south-western Australia, small- and medium-sized mammal species are severely affected by anthropogenic threats and environmental disturbances, including invasive predators, fire, and declining rainfall. However, the relative importance of different drivers has not been quantified.

We used data from a long-term monitoring program to fit Bayesian state-space models that estimated spatial and temporal changes in the relative abundance of four threatened mammal species: the woylie (Bettongia penicillata), chuditch (Dasyurus geoffroii), koomal (Trichosurus vulpecula) and quenda (Isoodon fusciventor). We then use Bayesian structural equation modelling to identify the direct and indirect drivers of population changes, and scenario analysis to forecast population responses to future environmental change.

We found that habitat loss or conversion and reduced primary productivity (caused by rainfall declines) had greater effects on species’ spatial and temporal population change than the range of fire and invasive predator (the red fox Vulpes vulpes) management actions observed in the study area. Scenario analysis revealed that a greater extent of severe fire and further rainfall declines predicted under climate change, operating in concert are likely to further reduce the abundance of these species, but may be mitigated partially by invasive predator control.

Considering both historical and future drivers of population change is necessary to identify the factors that risk species recovery. Given that both anthropogenic pressures and environmental disturbances can undermine conservation efforts, managers must consider how the relative benefit of conservation actions will be shaped by ongoing global change.

Geary WL, Tulloch AIT, Ritchie EG, Doherty TS, Nimmo DG, Maxwell MA, Wayne AF (2023) Identifying historical and future global change drivers that place species recovery at risk. Global Change Biology PDF DOI

Authors: Justin P Suraci, Justine A Smith, Simon Chamaillé-Jammes, Kaitlyn M Gaynor, Menna Jones, Barney Luttbeg, Euan G Ritchie, Michael J Sheriff, and Andrew Sih

Published in: Oikos

Abstract

Predation risk, the probability that a prey animal will be killed by a predator, is fundamental to theoretical and applied ecology. Predation risk varies with animal behavior and environmental conditions, yet attempts to understand predation risk in natural systems often ignore important ecological and environmental complexities, relying instead on proxies for actual risk such as predator–prey spatial overlap.

Here we detail the ecological and environmental complexities driving disconnects between three stages of the predation sequence that are often assumed to be tightly linked: spatial overlap, encounters and prey capture. Our review highlights several major sources of variability in natural predator–prey systems that lead to the decoupling of spatial overlap estimates from actual encounter rates (e.g. temporal activity patterns, predator and prey movement capacity, resource limitations) and that affect the probability of prey capture given encounter (e.g. predator hunger levels, temporal, topographic and other environmental influences on capture success). Emerging technologies and statistical methods are facilitating a transition to a more spatiotemporally detailed, mechanistic understanding of predator–prey interactions, allowing for the concurrent examination of multiple stages of the predation sequence in mobile, free-ranging animals.

We describe crucial applications of this new understanding to fundamental and applied ecology, highlighting opportunities to better integrate ecological contingencies into dynamic predator–prey models and to harness a mechanistic understanding of predator–prey interactions to improve targeting and effectiveness of conservation interventions.

Suraci JP, Smith JA, Chamaillé‐Jammes S, Gaynor KM, Jones M, Luttbeg B, Ritchie EG, Sheriff MJ, Sih A (2022) Beyond spatial overlap: harnessing new technologies to resolve the complexities of predator–prey interactions. Oikos PDF DOI

Authors: Alyson M Stobo-Wilson, Brett P Murphy, Heather M Crawford, Stuart J Dawson, Chris R Dickman, Tim S Doherty, Patricia A Fleming, Matthew N Gentle, Sarah M Legge, Thomas M Newsome, Russell Palmer, Matthew W Rees, Euan G Ritchie, James Speed, John-Michael Stuart, Eilysh Thompson, Jeff Turpin, and John C Z Woinarski

Published in: Biological Conservation

Abstract

Two introduced carnivores, the European red fox Vulpes vulpes and domestic cat Felis catus, have had, and continue to have, major impacts on wildlife, particularly mammals, across Australia. Based mainly on the contents of almost 50,000 fox dietary samples, we provide the first comprehensive inventory of Australian mammal species known to be consumed by foxes, and compare this with a similar assessment for cats.

We recorded consumption by foxes of 114 species of Australian land mammal (40% of extant species), fewer than consumed by cats (173 species). Foxes are known to consume 42 threatened mammal species (50% of Australia’s threatened land mammals and 66% of those within the fox’s Australian range). Reflecting the importance of mammals in their diet, foxes are known to consume a far higher proportion of Australian mammal species (40%) than of Australian birds (24%) and reptiles (16%).

Both foxes and cats were most likely to consume medium-sized mammals, with the likelihood of predation by foxes peaking for mammals of ca. 280 g and by cats at ca. 130 g. For non-flying mammals, threatened species had a higher relative likelihood of predation by foxes than non-threatened species. Using trait-based modelling, we estimate that many now-extinct Australian mammal species had very high likelihoods of predation by foxes and cats, although we note that for some of these species, extinction likely pre-dated the arrival of foxes. These two predators continue to have compounding and complementary impacts on Australian mammals. Targeted and integrated management of foxes and cats is required to help maintain and recover the Australian mammal fauna.

Stobo-Wilson AM, Murphy BP, Crawford HM, Dawson SJ, Dickman CR, Doherty TS, Fleming PA, Gentle MN, Legge SM, Newsome TM, Palmer R, Rees MW, Ritchie EG, Speed J, Stuart J-M, Thompson E, Turpin J, Woinarski JCZ (2021) Sharing meals: Predation on Australian mammals by the introduced European red fox compounds and complements predation by feral cats. Biological Conservation PDF DOI

Authors: Alyson M Stobo-Wilson, Brett P Murphy, Sarah M Legge, David G Chapple, Heather M Crawford, Stuart J Dawson, Chris R Dickman, Tim S Doherty, Patricia A Fleming, Matthew Gentle, Thomas M Newsome, Russell Palmer, Matthew W Rees, Euan G Ritchie, James Speed, John-Michael Stuart, Eilysh Thompson, Jeff Turpin, and and John C Z Woinarski

Published in: Wildlife Research

Abstract

Context: Invasive species are a major cause of biodiversity loss across much of the world, and a key threat to Australia’s diverse reptile fauna. There has been no previous comprehensive analysis of the potential impact of the introduced European red fox, Vulpes vulpes, on Australian reptiles.

Aims: We seek to provide an inventory of all Australian reptile species known to be consumed by the fox, and identify characteristics of squamate species associated with such predation. We also compare these tallies and characteristics with reptile species known to be consumed by the domestic cat, Felis catus, to examine whether predation by these two introduced species is compounded (i.e. affecting much the same set of species) or complementary (affecting different groups of species).

Methods: We collated records of Australian reptiles consumed by foxes in Australia, with most records deriving from fox dietary studies (tallying >35 000 samples). We modelled presence or absence of fox predation records against a set of biological and other traits, and population trends, for squamate species.

Key results: In total, 108 reptile species (~11% of Australia’s terrestrial reptile fauna) have been recorded as consumed by foxes, fewer than that reported for cats (263 species). Eighty-six species have been reported to be eaten by both predators. More Australian turtle species have been reported as consumed by foxes than by cats, including many that suffer high levels of predation on egg clutches. Twenty threatened reptile species have been reported as consumed by foxes, and 15 by cats. Squamate species consumed by foxes are more likely to be undergoing population decline than those not known to be consumed by foxes. The likelihood of predation by foxes increased with squamate species’ adult body mass, in contrast to the relationship for predation by cats, which peaked at ~217 g. Foxes, but not cats, were also less likely to consume venomous snakes.

Conclusions: The two introduced, and now widespread, predators have both compounding and complementary impacts on the Australian reptile fauna.

Implications: Enhanced and integrated management of the two introduced predators is likely to provide substantial conservation benefits to much of the Australian reptile fauna.

Stobo-Wilson AM, Murphy BP, Legge SM, Chapple DG, Crawford HM, Dawson SJ, Dickman CR, Doherty TS, Fleming PA, Gentle M, Newsome TM, Palmer R, Rees MW, Ritchie EG, Speed J, Stuart J-M, Thompson E, Turpin J, Woinarski JCZ (2021) Reptiles as food: predation of Australian reptiles by introduced red foxes compounds and complements predation by cats. Wildlife Research PDF DOI

Authors: Michael F Clarke, Luke T Kelly, Sarah C Avitabile, Joe Benshemesh, Kate E Callister, Don A Driscoll, Peter Ewin, Katherine Giljohann, Angie Haslem, Sally A Kenny, Steve Leonard, Euan G Ritchie, Dale G Nimmo, Natasha Schedvin, Kathryn Schneider, Simon J Watson, Martin Westbrooke, Matt White, Michael A Wouters, and Andrew F Bennett

Published in: Frontiers in Ecology and Evolution

Abstract

Fire shapes ecosystems globally, including semi-arid ecosystems. In Australia, semi-arid ‘mallee’ ecosystems occur primarily across the southern part of the continent, forming an interface between the arid interior and temperate south. Mallee vegetation is characterized by short, multi-stemmed eucalypts that grow from a basal lignotuber. Fire shapes the structure and functioning of mallee ecosystems.

Using the Murray Mallee region in south-eastern Australia as a case study, we examine the characteristics and role of fire, the consequences for biota, and the interaction of fire with other drivers.

Wildfires in mallee ecosystems typically are large (1000s ha), burn with high severity, commonly cause top-kill of eucalypts, and create coarse-grained mosaics at a regional scale. Wildfires can occur in late spring and summer in both dry and wet years. Recovery of plant and animal communities is predictable and slow, with regeneration of eucalypts and many habitat components extending over decades. Time since the last fire strongly influences the distribution and abundance of many species and the structure of plant and animal communities.

Animal species display a discrete set of generalized responses to time since fire. Systematic field studies and modeling are beginning to reveal how spatial variation in fire regimes (‘pyrodiversity’) at different scales shapes biodiversity. Pyrodiversity includes variation in the extent of post-fire habitats, the diversity of post-fire age-classes and their configuration.

At regional scales, a desirable mix of fire histories for biodiversity conservation includes a combination of early, mid and late post-fire age-classes, weighted toward later seral stages that provide critical habitat for threatened species. Biodiversity is also influenced by interactions between fire and other drivers, including land clearing, rainfall, herbivory and predation.

Extensive clearing for agriculture has altered the nature and impact of fire, and facilitated invasion by pest species that modify fuels, fire regimes and post-fire recovery.

Given the natural and anthropogenic drivers of fire and the consequences of their interactions, we highlight opportunities for conserving mallee ecosystems. These include learning from and fostering Indigenous knowledge of fire, implementing actions that consider synergies between fire and other processes, and strategic monitoring of fire, biodiversity and other drivers to guide place-based, adaptive management under climate change.

Clarke MF, Kelly LT, Avitabile SC, Benshemesh J, Callister KE, Driscoll DA, Ewin P, Giljohann K, Haslem A, Kenny SA, Leonard S, Ritchie EG, Nimmo DG, Schedvin N, Schneider K, Watson SJ, Westbrooke M, White M, Wouters MA, Bennett AF (2021) Fire and its interactions with other drivers shape a distinctive, semi-arid ‘mallee’ ecosystem, Frontiers in Ecology and Evolution PDF DOI

Authors: Tim S Jessop, Ben Holmes, Arvel Sendjojo, Mary O Thorpe, and Euan G Ritchie

Published in: Restoration Ecology

Abstract

Increasingly threatened species and their habitats require multiple successful management actions to ensure persistence. Introduced predator exclusion and suppression programs are key conservation actions used to retain or restore Australian ecosystems. Nevertheless, few direct comparisons are made to ascertain the individual and combined efficacy of multiple introduced predator conservation actions to benefit biodiversity. When colocated, both management actions could generate additive conservation benefits that greatly assist the recovery or persistence of threatened native species.

Varanid lizards are key functional components in Australian predator guilds and could benefit, via ecological release, when introduced predator management actions are successful. Here we tested the effects of a colocated predator-exclusion fence and lethal fox baiting on varanid site occupancy in a semiarid protected area.

Varanid site occupancy was higher at sites inside (Ψ = 0.90 ± 0.26) compared to sites outside (Ψ = 0.61 ± 0.28) the introduced predator-proof fenced enclosure. There was only weak evidence of increased varanid site occupancy at fox baited sites (Ψ = 0.037 ± 0.024) compared to nonfox baited (Ψ = 0.00) sites.

Overall, colocated introduced predator management actions achieved some additive benefits via possible spillover fencing effects for native mesopredator populations. However, most potential benefits to varanid populations outside of the predator-proof fenced enclosure were absent due to unsuccessful lethal-baiting effects on fox populations. The predator-proof fenced enclosure nevertheless provides important habitat refugia for future source populations for reintroduction once adjacent protected areas become suitable.

Jessop TS, Holmes B, Sendjojo A, Thorpe MO, Ritchie EG (2021) Assessing the benefits of integrated introduced predator management for recovery of native predators. Restoration Ecology PDF DOI

Authors: Sarah J Maclagan, Terry Coates, Austin O’Malley, and Euan G Ritchie

Published in: Austral Ecology

Abstract

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 Ecology PDF DOI

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

Abstract

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 Evidence PDF DOI

Authors: Grant D Linley, Annette Rypalski, Georgeanna Story, and Euan G Ritchie

Published in: Australian Mammalogy

Abstract

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 Mammalogy PDF DOI

Authors: Vivianna Miritis, Anthony R Rendall, Tim S Doherty, Amy L Coetsee, and Euan G Ritchie

Published in: Wildlife Research

Abstract

Context: 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.

Aims: 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.

Key results

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.

Conclusions: 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.

Implications: 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 Research PDF DOI

Authors: Grant D Linley, Yvette Pauligk, Courtney Marneweck, and Euan G Ritchie

Published in: Australian Mammology

Abstract

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 Mammalogy PDF DOI

Authors: Michael L Wysong, Gwenllian D Iacona, Leonie E Valentine, Keith Morris, and Euan G Ritchie

Published in: Wildlife Research

Abstract

Context: 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.

Aims: 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.

Method: 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.

Key results: 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.

Conclusions: 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.

Implications: 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 Research PDF DOI

Authors: Michael L Wysong, Bronwyn A Hradsky, Gwenllian D Iacona, Leonie E Valentine, Keith Morris, and Euan G Ritchie

Published in: Movement Ecology

Abstract

Background: 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.

Methods: 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.

Results: 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.

Management recommendations: 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 PDF DOI

Authors: William L Geary, Tim S Doherty, Dale G Nimmo, Ayesha I T Tulloch, and Euan G Ritchie

Published in: Journal of Animal Ecology

Abstract

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 Ecology PDF DOI 

Authors: Lauren M Halstead, Duncan R Sutherland, Leonie E Valentine, Anthony R Rendall, Amy L Coetsee, and Euan G Ritchie

Published in: Austral Ecology

Abstract

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 PDF DOI