Olfactory Lures Research Articles

Trialling a new method to attract feral cats (Felis catus) in situ – the Mata Hari Judas queen

Context Feral cats are a significant threat to wildlife in Australia and globally. Current feral cat management techniques have limitations that can result in wary, remnant individuals persisting in the landscape and reducing overall pest control efficacy, thus there is a need for additional innovative management techniques. Aims This research aimed to identify whether the Mata Hari Judas technique could be applied to female cats (queens) in situ as a means of attracting and assisting the capture of feral cats. Methods Three queens were induced into prolonged oestrus and contained in enclosures (vennels) in situ with traps attached to capture attracted feral cats. Two vennel treatments were trialled, one housing a Mata Hari Judas queen (queen vennel) and another using auditory and olfactory lures from a Mata Hari Judas queen (faux queen vennel) to compare the attractiveness of the two treatments at three study sites. Camera traps and soil plots were used to monitor and compare cat activity surrounding the vennels prior to, during and after the presence of a Mata Hari Judas queen or her lures. Key results Both vennel treatments attracted multiple feral cats of both sexes, and each trapped one male cat, demonstrating proof of concept for this technique. The queen vennel was significantly more attractive than the faux queen vennel, as demonstrated by higher frequency of cat detections and the duration of time feral cats spent at this vennel. Comparisons between monitoring periods and when the vennels were active showed significant differences in the frequency of cats attracted to the area, further supporting that both the queen and her lures were attractive to cats. Conclusions This research is the first instance where Mata Hari Judas queens have been successfully used in situ to attract and capture feral cats. Future studies should aim to assess this technique in a controlled area with a known cat population to allow for a direct comparison of efficacy with more traditional feral cat management methods. Implications With further refinement, the use of Mata Hari Judas queens in situ could provide an efficient technique for removing remnant cats.

Olfactory lures in predator control do not increase predation risk to birds in areas of conservation concern

Abstract Context Lethal control of predators is often undertaken to protect species of conservation concern. Traps are frequently baited to increase capture efficacy, but baited traps can potentially increase predation risk by attracting predators to protected areas. This is especially important if targeted predators can escape capture due to low trap success. Snake traps using live mouse lures may be beneficial if traps effectively remove snakes in the presence of birds and do not attract additional snakes to the area. Aims The present study evaluated whether mouse-lure traps in areas occupied by birds (simulated by deploying bird-lure traps) could influence predation risk from an invasive snake on Guam. Methods Snake traps were used, with Japanese quail (Coturnix japonica) as a proxy for predation risk, to assess if an adjacent trap with a mouse (Mus musculus) would attract brown treesnakes (Boiga irregularis) to a focal area and increase contact between an invasive snake and avian prey. Catch per unit effort (CPUE) at stations containing either a bird-lure trap, mouse-lure trap or pair of traps (i.e. one bird-lure and one mouse-lure trap) was evaluated. Key results Bird-lure traps paired with mouse-lure traps did not differ in CPUE from isolated bird-lure traps. At paired stations, CPUE of snakes in mouse-lure traps was 2.3× higher than bird-lure traps, suggesting mouse lures were capable of drawing snakes away from avian prey. Bird-lure traps at paired stations experienced a decay in captures over time, whereas CPUE for isolated bird-lure traps increased after 9 weeks and exceeded mouse-lure traps after 7 weeks. Conclusions Mouse lures did not increase the risk of snakes being captured in bird-lure traps. Instead, mouse-lure traps may have locally suppressed snakes, whereas stations without mouse-lure traps still had snakes in the focal area, putting avian prey at greater risk. However, snakes caught with bird lures tended to be larger and in better body condition, suggesting preference for avian prey over mammalian prey in larger snakes. Implications Strategic placement of olfactory traps within areas of conservation concern may be beneficial for protecting birds of conservation concern from an invasive snake predator.

Sooner, closer, or longer: detectability of mesocarnivores at camera traps

AbstractCamera trapping, paired with analytical methods for estimating species occurrence, population size or density, can yield information with direct consequences for wildlife management and conservation. Detectability, the ability to detect a species or individual if it is present, affects the reliability and efficiency of camera trap surveys and, in turn, varies across species, space and time. Greater detectability means greater sample size, and a common approach to boost detectability of wildlife by camera traps involves the application of olfactory lures. Using a camera trap study on sympatric mesocarnivores (European badger Meles meles, red fox Vulpes vulpes, pine marten Martes martes and domestic cat Felis catus), we quantified three elements of detectability: (1) the time until first detection (‘sooner’, conditional on being present), (2) the proximity to a focal point in front of the camera (‘closer’, conditional on being detected) and (3) the duration of exposure to the camera (‘longer’, conditional on being detected). A hierarchical analytical approach and a quasi‐experimental setup allowed us to test for and quantify the species‐specific effect of olfactory lures on these aspects of detectability. Depending on species, average median time to first detection ranged from 4 to 28 days, distance to the focal point from 0.3 to 0.8 body lengths, and median time to departure from 2 to 6 seconds. Credible intervals overlapped substantially between most species in all three measures, and variation between observations was extensive. We detected effects of lures on time to first detection for cats (castoreum; American beaver Castor canadensis scent), distance to focal point for badgers (striped skunk Mephitis mephitis scent) and martens (castoreum, fox and skunk scents), and the duration of exposure for foxes (fox and skunk scents). We discuss how a multifaceted perspective on detectability in camera trap studies, linked with species biology, can give investigators a more structured approach to selecting and testing measures intended to boost detection probability.

What evidence exists on the effectiveness of different types of olfactory lures as attractants for invasive mammalian predators? A systematic map protocol

BackgroundAlien mammalian predators are a major cause of species extinction and decline globally. Baits and lures, usually human-food based (for example meat, nuts or oils), are widely deployed in trapping programs to attract target species, but their effectiveness compared to other types of olfactory lures, for example social odours or prey odours, has never been systematically examined. Depending on the context, there can be high proportions of non-target captures, for example when targeting feral cats using cage traps, or low capture success, for example, when targeting introduced rats on tropical islands. Here we use a systematic process to map evidence on the effectiveness of different categories of olfactory attractants for invasive mammalian predators within different ecological contexts. We aim to look for where evidence clusters and knowledge gaps occur, for example, across different lure types or across different habitat-types, and highlight opportunities for future research into behaviourally-relevant olfactory lures.MethodsWe will compile evidence from bibliographic databases, online search engines, government websites, specialist sites and expert contacts, and include ‘grey’ literature. Where possible, a Boolean-style full search string will be used, including Population, Intervention and Outcome search terms. Searches will be conducted in English, but a public request to the IUCN SSC Invasive Species Specialist Group (ISSG) will be made for literature including in languages other than English. Search comprehensiveness will be evaluated against 25 benchmark articles known to the authors. We will base inclusion of articles on presence of quantitative data, subject identity (invasive mammalian predator species), comparator (more than one type of olfactory lure assessed or lure compared to a control) and outcome (quantified attraction to lures or controls). Inclusion consistency checks will be performed with 10% of the titles and abstracts and 10% of the full texts. We will critically appraise the literature only on the basis of study design (e.g. appropriate controls) and sample size, rather than interpret the results. Finally, we will develop a searchable literature database accompanied by systematic ‘heat’ maps to visually represent knowledge clusters and gaps within different subsets of evidence, and a narrative synthesis of the evidence.

Measuring the Welfare Impact of Soft-Catch Leg-Hold Trapping for Feral Cats on Non-Target By-Catch.

Simple SummaryFeral cats are linked to fauna extinctions and declines globally through predation, disease transmission, and hybridisation. Soft-catch leg-hold trapping, with or without olfactory lures, is used to capture feral cats; however, by-catch may occur, including species of conservation concern. Using data from 431 non-target animals trapped at six Western Australian sites over 18 years, we demonstrate that birds are at greatest risk of serious injury. Appropriate placement of traps, careful choice of lures depending on the non-target species known to be in the study area, adjustment of traps to minimize the chance of closing on small animals, and training of all personnel associated with trapping will minimize the risk to birds and other non-target fauna.To inform trapping protocols to reduce by-catch while trapping feral cats by-catch welfare costs should be quantified. During cat trapping programs at six Western Australian sites from 1997–2015, 431 non-target individuals, including 232 individuals from native species (132 mammals, 52 birds and 42 reptiles) were captured. Among the native fauna; birds were more likely to be severely injured (33%, compared to 12% in mammals and 21% in reptiles). Amongst other vertebrates, larger individuals were less likely to be injured. Olfactory lures used in these studies attracted reptiles, but repelled mammals. By-catch varied with climate and landscape. Trap injury to by-catch species poses ethical concerns, especially for threatened species that can least afford an additional threat. Future trapping should consider the timing of trapping, trap placement, trap settings (especially the treadle pressure needed to close the trap) and new innovations sending immediate capture alerts to minimise by-catch and potential injury associated with prolonged restraint. By-catch welfare data should be analysed to identify best practice and on-going improvement.

Phloem-feeding herbivory on flowering melon plants enhances attraction of parasitoids by shifting floral to defensive volatiles

Emission of herbivore-induced plant volatiles (HIPVs) can differ according to the type of herbivory and the plant development stage, ultimately affecting recruitment of the natural enemy. Little is known about plant defenses induced at the flowering stage by phloem-feeding insects. We investigated the olfactory preference of Encarsia desantisi parasitoids and the chemical profile of flowering melon plants induced or not by the phloem-feeding of Bemisia tabaci whiteflies. In addition, we tested whether the parasitoids were attracted to synthetic defensive HIPVs, which mimicked whitefly-infested flowering melons. The parasitoids recognized volatiles from undamaged melons but preferred the scent of host-infested melons in olfactometry assays. Amounts of most individual volatiles did not differ between plant treatments; however, only whitefly-induced melons released methyl salicylate and tetradecane, compounds known to attract parasitoids. Interestingly, grouping volatiles by chemical classes revealed that whitefly-infested melon released larger amounts of monoterpenes and smaller amounts of benzenoids than undamaged melons, which might underlying the parasitoid attraction and indicate a possible trade-off between defensive and reproductive defenses at the melon flowering stage. Additionally, E. desantisi preferred the mix of synthetic and defensive HIPVs over hexane (control), opening a new avenue for further investigations in using olfactory lures for B. tabaci biological control. This study is the first report of induced defenses in melon plants and their mediation in a tritrophic interaction, as well as the first record of E. desantisi behavioral preference for HIPVs.

New Long-Life Semiochemical Lures for Rats

Author(s): Jackson, Michael D.; Linklater, Wayne L.; Keyzers, Robert A. | Abstract: Olfactory lures are important pest control tools, being widely used to attract animals to detection devices, traps, and poisons. For small mammals, like commensal rodents, almost all lures are foods. For invertebrates, however, semiochemical lures predominate and have done so for decades. Semiochemical lures overcome the inherent limitations of food-based lures, such as their perishability and inconsistent odour properties, and poor performance when foods are abundant. They can also provide benefits like low cost, ease of handling, and in-field longevity. Semiochemical lures for rodents would be a major advance, like that achieved for invertebrate monitoring and control, but their discovery has been constrained by the complexity of the challenge. Our research group is the first to achieve animal response-guided semiochemical lure discovery. We statistically integrated rapid field-based bioassays with scent chemical profiling and partial least squares regression to identify and test a suite of new single- and multi-compound rat lures. Field trials identified a tetrad and dyad mixture as the best performing lures, with an attraction rate of 0.61 and 0.60, respectively, compared to an attraction rate of 0.55 for the peanut butter standard. In total, 17 compound-based lures performed statistically as well as the peanut butter standard. We are currently working with an industry partner to encapsulate the lures as consumable, cost-effective pest-control products. Semiochemical lures will be particularly useful for multi-kill traps, toxic bait delivery devices, and remote monitoring devices that could operate for long periods without intervention. These devices offer substantial control program cost reductions but require long-life lures to realise their full potential.

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.

Detection of Iberian terrestrial mammals employing olfactory, visual and auditory attractants

Whereas high lure specificity for mammal monitoring is often sought, little effort has been put into identifying general-purpose attractants for multispecies mammal surveys. We examined whether the olfactory lures ‘fatty acid scent’ (FAS) and catnip oil differ in their ability to detect Iberian larger mammals (body mass > 800 g, i.e. lagomorphs, ungulates and most carnivores); whether the addition of visual and acoustic stimuli increases detection efficiency; and whether environmental variables interact with lures to influence detection. Three treatments were randomly assigned to 192 detection plots: olfactory lures only, visual lures (a combination of olfactory and visual stimuli) and auditory lures (all three types of stimuli). The design was balanced across two detection methods and three landscapes. Out of 13 target species, two were absent in the study plots and six (three common and three rare species) were detected with low frequency. The two olfactory attractants produced similar detection rates for species allowing analysis. The addition of visual and auditory stimuli did not increase detection and apparently induced repulsion for some species. Environmental variables associated with scent diffusion and lure visibility did not significantly influence mammal detection. Monitoring of mammal communities over large areas may gain efficiency by selecting lures that are simple, have a constant chemical composition, require short handling times and allow detection of all occurring species. A single olfactory attractant (FAS) could be suitable for designing large-scale monitoring programmes at least for five common mammal species, provided that passive detection methods and lure use are chosen.

The Development of Semiochemical Lures for Invasive Rats: An Integrated Chemical Image and Response-Guided Approach

Author(s): Jackson, Michael D.; Linklater, Wayne L.; Keyzers, Robert A. | Abstract: Olfactory lures are important tools in pest-species management, being widely used to monitor and trap populations. For vertebrates like rats, lures are most commonly foods such as peanut butter. However, these are perishable and require frequent replenishment; factors that decrease control operation efficacy and increase costs. Synthetic semiochemical-based lures might address these limitations, but their identification and use for vertebrate population management remains an underexploited opportunity. We used headspace solid-phase microextraction and gas chromatography-mass spectrometry to characterise the volatile chemical profiles of 19 food products previously presented to wild, free-ranging rats and assessed for attraction. Partial least squares regression identified 10 of the 111 compounds found in two or more analysed products to be statistically significant predictors of attraction. The identity of nine of the compounds was verified using authentic samples, while one was not commercially available. Field trials used tracking tunnels to present compounds at seven different concentrations from 10,000 ppm to 0.01 ppm. Inked cards inside tracking tunnels were used to quantify visitations using species tracking marks, with the presence of rat tracks on inked cards scored to provide a tracking rate. Five compounds outperformed peanut butter while eight individual semiochemical-based lures each statistically outperformed peanut butter. Nearly half of all confirmed visits to compounds were with lures presented at 0.1 and 0.01 ppm. A trend of increasing tracking rates with decreasing lure concentration was identified for aggregated compound data. Our results suggest a number of compounds have the potential for onward development as synthetic attractants for rats. Further, the results support our integrated chemical image and response-guided approach that statistically associated behavioural responses to a range of products with the volatile compounds in those products. This approach has the potential to identify semiochemical compounds, either allelochemical or pheromone, for use as olfactory lures for managing and monitoring a range of vertebrate pest species.

Lack of Response to Olfactory Lures Among Mammals in Riparian Habitat in Southern Wisconsin

Non-invasive mammal surveys often employ olfactory stimuli on the assumption that they will attract mammals and increase the success of monitoring projects. However, information on the effectiveness of scent lures is variable and often relies on data generated from mammal tracks or sign, which can be challenging to quantify. Therefore, we sought to determine whether certain olfactory stimuli are more effective than others at eliciting a response from mammals along riparian corridors in Southern Wisconsin, using camera traps to monitor response to four scents and a control of de-ionized water. We recorded the number of times each species responded as well as the length of time spent investigating scents (Muskrat gland, mink gland, Red fox urine, crayfish oil) and the control. We recorded 2812 passes by 16 mammal species during our 12-month study, with Virginia Opossum (Didelphis virginiana), Woodchuck (Marmota monax), Eastern Gray Squirrel (Sciurus carolinensis), Eastern Fox Squirrel (Sciurus niger), Raccoon (Procyon lotor), Coyote (Canis latrans), and White-tailed Deer (Odocoileus virginianus)observed on cameras most frequently. However, 72% of observations involved mammals passing through without investigating any scents or the control, and among the 28% of observations where mammals did investigate, we found no significant differences in their response to specific scents or the control or in response by season. Further analysis revealed no significant differences in the time mammals spent investigating individual scents or the control. The lack of response suggests that factors other than scent may have attracted wildlife to our stations. Although under some circumstances olfactory attractants may increase the level of response to monitoring stations, we suggest that attraction to our stations was largely a behavioural response to novel stimuli in the environment.

Progressing the Possum Pied Piper Project

Author(s): Kavermann, Matt; Ross, James; Paterson, Adrian; Eason, Charles | Abstract: Improving vertebrate pest control operations relies on increasing pest animal interactions with control devices (e.g., bait stations, bait bags, and/or traps). Interactions are encouraged using a variety of baits and lures that stimulate an animal’s visual, olfactory, or auditory sense, orientating the target species towards a control device. On a generalised spatial scale of conspicuousness, an auditory lure will function over a greater distance for mammals in forested ecosystems than both visual and olfactory lures, suggesting auditory lures could have the greatest luring potential. In New Zealand, there is an overabundance of the introduced Australian brushtail possum that is the subject of ongoing control. Ground-based control operations typically use visual (e.g., a flour blaze), and to a lesser extent olfactory (e.g., cinnamon) lures for attracting possums to control devices. However, the potential for an auditory stimulus remains largely unexamined and underutilised. Research presented here expands on previous studies with captive animals and examines the development and field testing of an audio lure for possum control. The results from three preliminary field trials show that possums found audio-lured devices sooner than un-lured devices, and that a greater proportion of lured devices were located over time. In addition, possums were recorded investigating lured sites at a higher rate compared to un-lured sites, suggesting that possums were more likely to interact with a control device if it has an audio-lure than if it does not.

The use of poison baits to control feral cats and red foxes in arid South Australia II. Bait type, placement, lures and non-target uptake

Context Poison baits are often used to control both foxes and feral cats but success varies considerably. Aims This study investigated the influence of bait type, placement and lures on bait uptake by the feral cat, red fox and non-target species to improve baiting success and reduce non-target uptake. Methods Six short field trials were implemented during autumn and winter over a five-year period in northern South Australia. Key results Results suggest that poison baiting with Eradicat or dried kangaroo meat baits was inefficient for feral cats due to both low rates of bait detection and poor ingestion rates for baits that were encountered. Cats consumed more baits on dunes than swales and uptake was higher under bushes than in open areas. The use of auditory or olfactory lures adjacent to baits did not increase ingestion rates. Foxes consumed more baits encountered than cats and exhibited no preference between Eradicat and kangaroo meat baits. Bait uptake by native non-target species averaged between 14 and 57% of baits during the six trials, accounting for up to 90% of total bait uptake. Corvid species were primarily responsible for non-target uptake. Threatened mammal species investigated and nibbled baits but rarely consumed them; however, corvids and some common rodent species ingested enough poison to potentially receive a lethal dose. Conclusions It is likely that several factors contributed to poor bait uptake by cats including the presence of alternative prey, a preference for live prey, an aversion to scavenging or eating unfamiliar foods and a stronger reliance on visual rather than olfactory cues for locating food. Implications Further trials for control of feral cats should concentrate on increasing ingestion rates without the requirement for hunger through either involuntary ingestion via grooming or development of a highly palatable bait.

Attraction of auditory and olfactory lures to Feral Cats, Red Foxes, European Rabbits and Burrowing Bettongs

Attraction of auditory and olfactory lures to Feral Cats, Red Foxes, European Rabbits and Burrowing Bettongs

Trapping and demographics of feral cats (Felis catus) in central New South Wales

A total of 76 feral cats (Felis catus) (29 individuals; 47 recaptures) was trapped during 6027 trap-nights using both cage and leg-hold traps from November 1994 to August 1996 at Lake Burrendong in central New South Wales. No significant difference was found in the relative capture efficiency between cage and leg-hold traps (P > 0.05). Overall capture efficiency was 1.3 cats per 100 trap-nights, although this varied seasonally, being higher in late autumn and early winter. Most cats were caught with rabbit as bait, and visual and olfactory lures added to baits did not appear to increase capture efficiency, although the power of the test was limited. Most captured cats were adult males weighing 4.37 0.14 kg; these were larger than the females (3.34 0.06 kg). Litters, comprising 2–5 kittens, were born between September and March.

Visual and olfactory stimuli and fruit maturity affect trap captures of Oriental fruit flies (Diptera: Tephritidae).

An effective lure-and-kill trap is a potentially important instrument in monitoring and controlling oriental fruit flies, Bactrocera dorsalis (Hendel). A number of experiments were performed in an orchard of commercial guava, Psydium guajava L., to determine how fly captures are affected by combining visual and olfactory stimuli, and by the timing of trap deployment relative to host phenology. Baiting sticky Ladd traps with hydrolyzed liquid protein significantly increased the number of captured flies. Mostly male flies were caught in the absence of mature guava fruit, whereas mostly female flies were caught when ripe fruit was abundant. These results suggest that an effective oriental fruit fly trap should include both visual and olfactory lures, and that proper timing of trap deployment can be an important factor in monitoring female abundance in oriental fruit fly populations.

Field Evaluation of Olfactory Lures for Feral Cats (Felis catus L.) in Central Australia

Field trials were conducted in central Australia to evaluate the ability of various olfactory lures to attract feral cats (Felis catus L.). Ten food-based lures, one plant extract and two scent-based lures (anal-gland preparations from male and female cats) were evaluated on the basis of visitation rates and elicited behavioural responses. A visual lure composed of bird feathers was also tested in conjunction with the scent-based lures. One food-based lure (sun-rendered prawn) and both of the scent-based lures were found to attract feral cats. The visual lure did not enhance the attractiveness of the scent-based lures. The possible uses and relative advantages of these lures in control programmes and in ecological studies of cats are discussed.

Development of chemosensory attractants for white-tailed deer ( Odocoileus virginianus)

White-tailed deer ( Odocoileus spp.) overpopulate many areas of the United States. Browse damage to agricultural crops, forest regeneration and landscaping can be severe. Human and animal health also are threatened by Lyme disease, which is spread by the deer tick ( Ixodes dammini). Although sterilants to reduce and/or slow the growth of deer populations and vaccines against Lyme disease may soon become available, efficient and economical techniques to inoculate large numbers of deer have not been developed. Oral baits represent one promising possibility. In experiment 1, salt blocks and several olfactory lures were evaluated as potential lures for use in deer baits. Plain salt blocks were attractive and odour stimuli such as acorn, apple and peanut butter significantly enhanced effectiveness. Apple was the best stimulus in an old field; peanut butter and acorn were the best stimuli in a bottomland habitat. In experiment 2, blocks of minerals, salt, molasses, and mineral-molasses were presented; all were scented with apple extract. Mineral blocks were the most attractive, followed by salt blocks and mineral-molasses blocks; molasses blocks were the least attractive. In experiment 3, mixtures of apple, acorn and peanut butter extracts were presented with mineral blocks. None of the combinations was more attractive than the others and none was more attractive than mineral blocks presented with apple extract only.