Assessing the efficacy of electronic quail callers in attracting stubble quail and non-target predators

Hunting is a prominent feature of many human societies. Advancements in hunting technologies can challenge the ethics and sustainability of hunting globally. We investigated the efficacy of an electronic acoustic lure (‘quail caller’), in attracting the otherwise difficult-to hunt stubble quail Coturnix pectoralis in Victoria, Australia. Using distance sampling, the density and abundance of stubble quail was estimated at 79 sites across a range of habitat types in an agricultural setting, each with an active ‘quail caller’ station continuously broadcasting for 48 hours, and a control station (no broadcast). Quail detectability at the active stations (62.9%) far exceeded that at control stations (6.3%). Most (57%) detections occurred within 30 m of active ‘quail callers’. Stubble quail relative abundance was substantially greater when ‘quail callers’ were broadcasting. Cameras mounted near ‘quail callers’ identified the predatory red fox as a non-target predator, although rates of attraction appear similar between active and control sites. ‘Quail callers’ are highly effective at attracting stubble quail and concentrating them to a known area, raising questions in relation to sustainable hunting practices, indirect effects, and ethical implications. ‘Quail callers’ do, however, also offer a tool for estimating quail abundance and developing more accurate population size estimates.

Turning ghosts into dragons: improving camera monitoring outcomes for a cryptic low-density Komodo dragon population in eastern Indonesia

Abstract Context Detection probability is a key attribute influencing population-level wildlife estimates necessary for conservation inference. Increasingly, camera traps are used to monitor threatened reptile populations and communities. Komodo dragon (Varanus komodoensis) populations have been previously monitored using camera traps; however, considerations for improving detection probability estimates for very low-density populations have not been well investigated. Aims Here we compare the effects of baited versus non-baited camera monitoring protocols to influence Komodo dragon detection and occupancy estimates alongside monitoring survey design and cost considerations for ongoing population monitoring within the Wae Wuul Nature Reserve on Flores Island, Indonesia. Methods Twenty-six camera monitoring stations (CMS) were deployed throughout the study area with a minimum of 400 m among CMS to achieve independent sampling units. Each CMS was randomly assigned as a baited or non-baited camera monitoring station and deployed for 6 or 30 daily sampling events. Key results Baited camera monitoring produced higher site occupancy estimates with reduced variance. Komodo dragon detection probability estimates were 0.15 ± 0.092–0.22 (95% CI), 0.01 ± 0.001–0.03, and 0.03 ± 0.01–0.04 for baited (6 daily survey sampling events), unbaited (6 daily survey sampling events) and long-unbaited (30 daily survey sampling events) sampling durations respectively. Additionally, the provision of baited lures at cameras had additional benefits for Komodo detection, survey design and sampling effort costs. Conclusions Our study indicated that baited cameras provide the most effective monitoring method to survey low-density Komodo dragon populations in protected areas on Flores. Implications We believe our monitoring approach now lends itself to evaluating population responses to ecological and anthropogenic factors, hence informing conservation efforts in this nature reserve.

Two Methods of Monitoring Cats at a Landscape-Scale

Simple Summary

Feral cats are difficult to manage and harder to monitor. We report on the efficacy of Eradicat^® baiting and the cost and the efficacy of monitoring the activty of feral cats via camera-traps or track counts. Pre-baiting surveys for 2020 and 2021 suggested that the population of feral cats on Matuwa was very low, at 5.5 and 4.4 cats/100 km respectively, which is well below our target threshold of 10 cats/100 km. Post-baiting surveys then recorded 3.6 and 3.0 cats/100 km respectively, which still equates to a 35% and 32% reduction in cat activity despite initial low cat detection rate. Track counts recorded more feral cats than camera traps and were cheaper to implement.

Abstract

Feral cats are difficult to manage and harder to monitor. We analysed the cost and the efficacy of monitoring the pre- and post-bait abundance of feral cats via camera-traps or track counts using four years of data from the Matuwa Indigenous Protected Area. Additionally, we report on the recovery of the feral cat population and the efficacy of subsequent Eradicat^® aerial baiting programs following 12 months of intensive feral cat control in 2019. Significantly fewer cats were captured in 2020 (n = 8) compared to 2019 (n = 126). Pre-baiting surveys for 2020 and 2021 suggested that the population of feral cats on Matuwa was very low, at 5.5 and 4.4 cats/100 km, respectively, which is well below our target threshold of 10 cats/100 km. Post-baiting surveys then recorded 3.6 and 3.0 cats/100 km, respectively, which still equates to a 35% and 32% reduction in cat activity. Track counts recorded significantly more feral cats than camera traps and were cheaper to implement. We recommend that at least two methods of monitoring cats be implemented to prevent erroneous conclusions.

Does aerial baiting for controlling feral cats in a heterogeneous landscape confer benefits to a threatened native meso-predator?

Introduced mammalian predators can have devastating impacts on recipient ecosystems and disrupt native predator–prey relationships. Feral cats (Felis catus) have been implicated in the decline and extinction of many Australian native species and developing effective and affordable methods to control them is a national priority. While there has been considerable progress in the lethal control of feral cats, effective management at landscape scales has proved challenging. Justification of the allocation of resources to feral cat control programs requires demonstration of the conservation benefit baiting provides to native species susceptible to cat predation. Here, we examined the effectiveness of a landscape-scale Eradicat® baiting program to protect threatened northern quolls (Dasyurus hallucatus) from feral cat predation in a heterogeneous rocky landscape in the Pilbara region of Western Australia. We used camera traps and GPS collars fitted to feral cats to monitor changes in activity patterns of feral cats and northern quolls at a baited treatment site and unbaited reference site over four years. Feral cat populations appeared to be naturally sparse in our study area, and camera trap monitoring showed no significant effect of baiting on cat detections. However, mortality rates of collared feral cats ranged from 18–33% after baiting, indicating that the program was reducing cat numbers. Our study demonstrated that feral cat baiting had a positive effect on northern quoll populations, with evidence of range expansion at the treatment site. We suggest that the rugged rocky habitat preferred by northern quolls in the Pilbara buffered them to some extent from feral cat predation, and baiting was sufficient to demonstrate a positive effect in this relatively short-term project. A more strategic approach to feral cat management is likely to be required in the longer-term to maximise the efficacy of control programs and thereby improve the conservation outlook for susceptible threatened fauna.

Zooming in on mechanistic predator-prey ecology: Integrating camera traps with experimental methods to reveal the drivers of ecological interactions

Camera trap technology has galvanized the study of predator-prey ecology in wild animal communities by expanding the scale and diversity of predator-prey interactions that can be analysed. While observational data from systematic camera arrays have informed inferences on the spatiotemporal outcomes of predator-prey interactions, the capacity for observational studies to identify mechanistic drivers of species interactions is limited. Experimental study designs that utilize camera traps uniquely allow for testing hypothesized mechanisms that drive predator and prey behaviour, incorporating environmental realism not possible in the laboratory while benefiting from the distinct capacity of camera traps to generate large datasets from multiple species with minimal observer interference. However, such pairings of camera traps with experimental methods remain underutilized. We review recent advances in the experimental application of camera traps to investigate fundamental mechanisms underlying predator-prey ecology and present a conceptual guide for designing experimental camera trap studies. Only 9% of camera trap studies on predator-prey ecology in our review use experimental methods, but the application of experimental approaches is increasing. To illustrate the utility of camera trap-based experiments using a case study, we propose a study design that integrates observational and experimental techniques to test a perennial question in predator-prey ecology: how prey balance foraging and safety, as formalized by the risk allocation hypothesis. We discuss applications of camera trap-based experiments to evaluate the diversity of anthropogenic influences on wildlife communities globally. Finally, we review challenges to conducting experimental camera trap studies. Experimental camera trap studies have already begun to play an important role in understanding the predator-prey ecology of free-living animals, and such methods will become increasingly critical to quantifying drivers of community interactions in a rapidly changing world. We recommend increased application of experimental methods in the study of predator and prey responses to humans, synanthropic and invasive species, and other anthropogenic disturbances.

Effectiveness of the Felixer grooming trap for the control of feral cats: a field trial in arid South Australia

Abstract ContextFeral cats pose a significant threat to wildlife in Australia and internationally. Controlling feral cats can be problematic because of their tendency to hunt live prey rather than be attracted to food-based lures. The Felixer grooming trap was developed as a targeted and automated poisoning device that sprays poison onto the fur of a passing cat, relying on compulsive grooming for ingestion. AimsWe conducted a field trial to test the effectiveness of Felixers in the control of feral cats in northern South Australia where feral cats were present within a 2600-ha predator-proof fenced paddock. MethodsTwenty Felixers were set to fire across vehicle tracks and dune crossings for 6 weeks. Cat activity was recorded using track counts and grids of remote camera traps set within the Felixer Paddock and an adjacent 3700-ha Control Paddock where feral cats were not controlled. Radio-collars were placed on six cats and spatial mark–resight models were used to estimate population density before and after Felixer deployment. Key resultsNone of the 1024 non-target objects (bettongs, bilbies, birds, lizards, humans, vehicles) that passed a Felixer during the trial was fired on, confirming high target specificity. Thirty-three Felixer firings were recorded over the 6-week trial, all being triggered by feral cats. The only two radio-collared cats that triggered Felixers during the trial, died. Two other radio-collared cats appeared to avoid Felixer traps possibly as a reaction to previous catching and handling rendering them neophobic. None of the 22 individually distinguishable cats targeted by Felixers was subsequently observed on cameras, suggesting death after firing. Felixer data, activity and density estimates consistently indicated that nearly two-thirds of the cat population was killed by the Felixers during the 6-week trial. ConclusionsResults suggest that Felixers are an effective, target-specific method of controlling feral cats, at least in areas in which immigration is prevented. The firing rate of Felixers did not decline significantly over time, suggesting that a longer trial would have resulted in a higher number of kills. ImplicationsFuture studies should aim to determine the trade-off between Felixer density and the efficacy relative to reinvasion.

On the right track: placement of camera traps on roads improves detection of predators and shows non-target impacts of feral cat baiting

Abstract ContextTo 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. AimsWe 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. MethodsWe deployed 80 remotely triggered camera traps over the 2410-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 resultsCameras 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. ConclusionsCamera 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. ImplicationsManagement 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).

Feral cat abundance, density and activity in tropical island rainforests

Abstract ContextIntroduced predators, especially cats, are a major cause of extinction globally. Accordingly, an extensive body of literature has focussed on the ecology and management of feral cats in continental and island systems alike. However, geographic and climatic gaps remain, with few studies focusing on rainforests or tropical islands of the south-western Pacific. AimsWe aimed to estimate cat densities and elucidate activity patterns of cats and sympatric birds and mammals in tropical island rainforests. We hypothesised that cat activity would be most influenced by the activity of introduced rodents and ground-dwelling birds that are predominant prey on islands. MethodsWe used camera traps to detect feral cats, pigs, rodents and birds on four tropical islands in the south-western Pacific. We used spatial capture–recapture models to estimate the abundance and density of feral cats. Relative abundance indices, and temporal overlaps in activity were calculated for feral cats, pigs, rodents, and birds. We used a generalised linear model to test for the influence of pig, rodent, and bird abundance on feral cat abundance. Key resultsThe species most commonly detected by our camera traps was feral cat, with estimated densities between 0.31 and 2.65 individuals km−2. Pigs and introduced rodents were the second- and third-most commonly detected fauna respectively. Cat activity was bimodal, with peaks in the hours before dawn and after dusk. Cat abundance varied with site and the abundance of rodents. ConclusionsFeral cats are abundant in the tropical rainforests of our study islands, where one bird and two mammal species are now presumed extinct. Introduced rodents possibly amplify the abundance and impacts of feral cats at our sites. Peak cat activity following dusk did not clearly overlap with other species detected by our camera traps. We postulate cats may be partly focussed on hunting frogs during this period. ImplicationsCats are likely to be a major threat to the highly endemic fauna of our study region. Management of feral cats will benefit from further consideration of introduced prey such as rodents, and their role in hyperpredation. Island archipelagos offer suitable opportunities to experimentally test predator–prey dynamics involving feral cats.

A Case of Letting the Cat out of The Bag-Why Trap-Neuter-Return Is Not an Ethical Solution for Stray Cat (Felis catus) Management

Trap-Neuter-Return (TNR) programs, in which stray cats are captured, neutered and returned to the environment are advocated as a humane, ethical alternative to euthanasia. We review the TNR literature in light of current debate over whether or not there should be further TNR trials in Australia. We revisit the problems arising from stray cats living in association with human habitation and estimate how many stray cats would have to be processed through a scientifically-guided TNR program to avoid high euthanasia rates. We also identify 10 ethical and welfare challenges that have to be addressed: we consider the quality of life for stray cats, where they would live, whether the TNR process itself is stressful, whether TNR cats are vulnerable to injury, parasites and disease, can be medically treated, stray cats' body condition and diet, and their impacts on people, pet cats, and urban wildlife, especially endemic fauna. We conclude that TNR is unsuitable for Australia in almost all situations because it is unlikely to resolve problems caused by stray cats or meet ethical and welfare challenges. Targeted adoption, early-age desexing, community education initiatives and responsible pet ownership have greater promise to minimize euthanasia, reduce numbers rapidly, and address the identified issues.

Designing a camera trap monitoring program to measure efficacy of invasive predator management

Context Evaluating predator management efficacy is difficult, especially when resources are limited. Carefully designing monitoring programs in advance is critical for data collection that is sufficient to evaluate management success and to inform decisions. Aims The aim was to investigate how the design of camera trap studies can affect the ability to reliably detect changes in red fox (Vulpes vulpes) activity over space and time. Specifically, to examine the effect of study duration, camera cost and detection zone under various environmental and management scenarios, including different fox densities, management impacts, monitoring budgets and levels of spatial and temporal variation. Methods A generalised linear mixed model was used to analyse simulated datasets from control sites and sites with predator management actions implemented, following a before–after or control–impact sampling design. Statistical power analyses were conducted to evaluate whether a change in fox abundance could be detected across various environmental and management scenarios. Key results Results showed that a before–after sampling design is less sensitive than a control–impact sampling design to the number of cameras used for monitoring. However, a before–after sampling design requires a longer monitoring period to achieve a satisfactory level of power, due to higher sensitivity to study duration. Given a fixed budget, there can be a trade-off between purchasing a small number of high quality cameras with large detection zones, or a larger number of cameras with smaller detection zones. In a control-impact design we found that if spatial heterogeneity was high, a larger number of cameras with smaller detection zones provided more power to detect a difference in fox abundance. Conclusion This simulation-based approach demonstrates the importance of exploring various monitoring designs to detect the effect of predator management across plausible environmental and budgetary scenarios. Implications The present study informs the monitoring design of an adaptive management program that aims to understand the role of managing fox predation on malleefowl (Leipoa ocellata), a threatened Australian bird. Furthermore, this approach provides a useful guide for developing cost-effective camera trap monitoring studies to assess efficacy of conservation management programs. Power analyses are an essential step for designing efficient monitoring, and indicate the strength of ecological signals that can realistically be detected through the noise of spatial and temporal heterogeneity under various budgetary constraints.

The value of camera traps in monitoring a feral-cat and fox reduction program

Abstract ContextWe examined the effectiveness of camera traps to monitor the success of a feral-cat (Felis catus) and fox (Vulpes vulpes) reduction program near Ravensthorpe, Western Australia. AimsTo determine whether camera traps are an effective tool to measure a reduction in the abundance of F. catus and V. vulpes at a local scale. MethodsIn all, 201 Foxoff® baits (i.e. 1080) were laid along the edge of unsealed tracks for each of three periods (i.e. opened 13–15 May 2017, Period 1 closed 29–31 May 2017, Period 2 closed 12–13 June 2017, Period 3 closed 25–26 June 2017), and 98 bait sites were monitored by camera traps during each period. In addition, 150 baited cage traps were deployed to catch F. catus for the same three periods. Vulpes vulpes and F. catus were also shot in the adjacent paddocks before traps were opened and during the laying of traps and bait replacement. We used the first 13 days of camera-trapping data for each period to examine whether there was a significant reduction in V. vulpes and F. catus. Key resultsCamera traps recorded a significant reduction in V. vulpes images, but knock-down with Foxoff® baits was not as effective as in other programs, and there was no change in the measured abundance of F. catus. Numerous baits were taken and not recorded by camera traps. Multiple V. vulpes moved past or investigated, but did not take baits and a V. vulpes was recorded regurgitating a bait. ConclusionsCamera traps were not effective for recording bait-take events. Vulpes vulpes knock-down was low and slow compared with other studies, did not reflect the number of baits taken and Foxoff® baits appeared unpalatable or unattractive to many V. vulpes. ImplicationsCamera traps did not record a high proportion of bait-take, appeared to be insensitive to small changes in fox and cat abundance and Foxoff® baits were less effective in reducing the abundance of V. vulpes than in other studies.

Evidence of significantly higher island feral cat abundance compared with the adjacent mainland

Context Feral cats (Felis catus) impact the health and welfare of wildlife, livestock and humans worldwide. They are particularly damaging where they have been introduced into island countries such as Australia and New Zealand, where native prey species evolved without feline predators. Kangaroo Island, in South Australia, is Australia’s third largest island and supports several threatened and endemic species. Cat densities on Kangaroo Island are thought to be greater than those on the adjacent South Australian mainland, based on one cat density estimate on the island that is higher than most estimates from the mainland. The prevalence of cat-borne disease in cats and sheep is also higher on Kangaroo Island than the mainland, suggesting higher cat densities. A recent continental-scale spatial model of cat density predicted that cat density on Kangaroo Island should be about double that of the adjacent mainland. However, although cats are believed to have severe impacts on some native species on the island, other species that are generally considered vulnerable to cat predation have relatively secure populations on the island compared with the mainland. Aims The present study aimed to compare feral cat abundance between Kangaroo Island and the adjacent South Australian mainland using simultaneous standardised methods. Based on previous findings, we predicted that the relative abundance of feral cats on Kangaroo Island would be approximately double that on the South Australian mainland. Methods Standardised camera trap surveys were used to simultaneously estimate the relative abundance of feral cats on Kangaroo Island and the adjacent South Australian mainland. Survey data were analysed using the Royle–Nichols abundance-induced heterogeneity model to estimate feral cat relative abundance at each site. Key results Cat abundance on the island was estimated to be over 10 times greater than that on the adjacent mainland. Conclusions Consistent with predictions, cat abundance on the island was greater than on the adjacent mainland. However, the magnitude of this difference was much greater than expected. Implications The findings show that the actual densities of cats at local sites can vary substantially from predictions generated by continental-scale models. The study also demonstrates the value of estimating abundance or density simultaneously across sites using standardised methods.

Improving mesocarnivore detectability with lures in camera-trapping studies

Context Camera trapping is commonly employed for studying carnivores because it provides better data than do other methods, and with lower costs. Increasing the probability of detecting the target species can reduce parameter uncertainty and survey effort required to estimate density and occurrence. Different methods, including attractants and baits, can be used to increase detectability. However, their efficacy has rarely been quantitatively assessed. Aims To quantify the efficacy of scent and bait attractants to increase the detection probability of mesocarnivores by camera trapping. Methods We tested two scent lures, valerian extract (Val) and lynx urine (LU), their combination (Val–LU), and a non-reward bait (i.e. not accessible to the animal), raw chicken, as carnivore attractants in two protected areas of central Spain. We used camera-trapping records under an occupancy-modelling framework to estimate attractant-specific detection probabilities for six mesocarnivore species, and quantified their effects by comparing these estimates with the baseline (i.e. no attractant) detectability. Key results The weekly detection probability of four mesocarnivore species (red fox, Vulpes vulpes, stone marten, Martes foina, common genet, Genetta genetta, and Eurasian badger, Meles meles) significantly increased when Val–LU (between 0.11 ± 0.07 and 0.67 ± 0.05) or chicken (between 0.31 ± 0.02 and 0.77 ± 0.22) were used as attractant, when compared with baseline detectability (between 0.01 ± 0.02 and 0.29 ± 0.05). Although rarely, wildcats (Felis silvestris) were mostly detected with Val–LU. The probability of detecting a species after k sampling occasions (7 days each) where it was present was highly improved with both Val–LU and chicken for all species (e.g. from 0.20 to 0.98 after four sampling occasions with chicken for the stone marten). Both attractants reduced the sampling time required to ascertain that a species was absent to between 42% and 15% of baseline values. Conclusions The tested attractants greatly improved the detectability of most Iberian mesocarnivores. Although chicken was preferable for some species such as stone marten, Val–LU is most efficient for detecting the whole mesocarnivore community, including rare species such as wildcats. Implications Attractant selection in studies using non-invasive detection methods must be supported by quantitative assessment of the detection probability associated to each attractant. Researchers must choose those attractants best fitting target species and study aims.

Fate of dried meat baits aimed at wild dog (Canis familiaris) control

Context Livestock predation is a worldwide phenomenon, causing financial losses and emotional strain on producers. Wild dogs (Canis familiaris) cause millions of dollars of damage to cattle, sheep and goat production in Australia every year, and despite on-going control (baiting, trapping, shooting, and fencing), they remain a significant problem for livestock producers across many pastoral and agricultural regions of Australia. Aims We aimed to quantify the uptake of dried meat baits by wild dogs and determine whether an olfactory lure (fish oil) could increase uptake. Methods Camera traps and sand pads were used to monitor bait uptake for three baiting events on two pastoral properties in the southern rangelands of Western Australia in 2016 and 2017. Key results Of the 337 monitored baits with a known outcome, young wild dogs (<8 months old) removed only four, three of which were covered in a fish-oil lure. In warmer months, baits were largely consumed by varanids, and in cooler months, when baits were taken it was predominantly by corvids. Varanids and corvids took more baits than expected on the basis of activity indices. Kangaroos, feral cats and wild dogs consumed significantly fewer baits than expected from their activity on camera. Conclusions We have no evidence that adult wild dogs removed baits, despite many opportunities to do so (wild dogs passing cameras), and fewer wild dogs took baits than expected on the basis of activity events seen on camera. Olfactory lures may have the potential to increase bait uptake by naïve individuals (i.e. young dogs), but the sample size was small. Implications Increasing the number of baiting events per year, trialling novel baits, and baiting during low non-target activity are some of the recommended methods that may increase bait persistence and uptake by wild dogs.

A comparison of camera trap and permanent recording video camera efficiency in wildlife underpasses

In the current context of biodiversity loss through habitat fragmentation, the effectiveness of wildlife crossings, installed at great expense as compensatory measures, is of vital importance for ecological and socio‐economic actors. The evaluation of these structures is directly impacted by the efficiency of monitoring tools (camera traps…), which are used to assess the effectiveness of these crossings by observing the animals that use them. The aim of this study was to quantify the efficiency of camera traps in a wildlife crossing evaluation. Six permanent recording video systems sharing the same field of view as six Reconyx HC600 camera traps installed in three wildlife underpasses were used to assess the exact proportion of missed events (event being the presence of an animal within the field of view), and the error rate concerning underpass crossing behavior (defined as either Entry or Refusal). A sequence of photographs was triggered by either animals (true trigger) or artefacts (false trigger). We quantified the number of false triggers that had actually been caused by animals that were not visible on the images (“false” false triggers). Camera traps failed to record 43.6% of small mammal events (voles, mice, shrews, etc.) and 17% of medium‐sized mammal events. The type of crossing behavior (Entry or Refusal) was incorrectly assessed in 40.1% of events, with a higher error rate for entries than for refusals. Among the 3.8% of false triggers, 85% of them were “false” false triggers. This study indicates a global underestimation of the effectiveness of wildlife crossings for small mammals. Means to improve the efficiency are discussed.

Multiple cameras required to reliably detect feral cats in northern Australian tropical savanna: an evaluation of sampling design when using camera traps

Context Feral cats are a major cause of mammal declines and extinctions in Australia. However, cats are elusive and obtaining reliable ecological data is challenging. Although camera traps are increasingly being used to study feral cats, their successful use in northern Australia has been limited. Aims We evaluated the efficacy of camera-trap sampling designs for detecting cats in the tropical savanna of northern Australia. We aimed to develop a camera-trapping method that would yield detection probabilities adequate for precise occupancy estimates. Methods First, we assessed the influence of two micro-habitat placements and three lure types on camera-trap detection rates of feral cats. Second, using multiple camera traps at each site, we examined the relationship between sampling effort and detection probability by using a multi-method occupancy model. Key results We found no significant difference in detection rates of feral cats using a variety of lures and micro-habitat placement. The mean probability of detecting a cat on one camera during one week of sampling was very low (p = 0.15) and had high uncertainty. However, the probability of detecting a cat on at least one of five cameras deployed concurrently on a site was 48% higher (p = 0.22) and had a greater precision. Conclusions The sampling effort required to achieve detection rates adequate to infer occupancy of feral cats by camera trap is considerably higher in northern Australia than has been observed elsewhere in Australia. Adequate detection of feral cats in the tropical savanna of northern Australia will necessitate inclusion of more camera traps and a longer survey duration. Implications Sampling designs using camera traps need to be rigorously trialled and assessed to optimise detection of the target species for different Australian biomes. A standard approach is suggested for detecting feral cats in northern Australian savannas.

Toxic Trojans: can feral cat predation be mitigated by making their prey poisonous?

Predation, along with competition and disease transmission from feral domestic cats (Felis catus), poses the key threat to many in situ and reintroduced populations of threatened species globally. Feral cats are more challenging to control than pest canids because cats seldom consume poison baits or enter baited traps when live prey are readily available. Novel strategies for sustainably protecting threatened wildlife from feral cats are urgently required. Emerging evidence suggests that once they have successfully killed a challenging species, individual feral cats can systematically eradicate threatened prey populations. Here we propose to exploit this selective predation through three targeted strategies to improve the efficacy of feral cat control. Toxic collars and toxic implants, fitted or inserted during monitoring or reintroduction programs for threatened species, could poison the offending cat before it can effect multiple kills of the target species. A third strategy is informed by evidence that consumption of prey species that are relatively tolerant to natural plant toxins, can be lethal to more sensitive cats. Within key habitats of wildlife species susceptible to cat predation, we advocate increasing the accessibility of these toxins in the food chain, provided negative risks can be mediated. Deliberate poisoning using live and unaffected ‘toxic Trojan prey’ enables ethical feral cat management that takes advantage of cats’ physiological and behavioural predilection for hunting live prey while minimising risks to many non-targets, compared with conventional baiting.