An invasive human commensal and a native marsupial maintain tick populations at the urban fringe.

Ticks (Acari: Ixodidae) are major disease vectors globally making it increasingly important to understand how altered vertebrate communities in urban areas shape tick population dynamics. In urban landscapes of Australia, little is known about which native and introduced small mammals maintain tick populations preventing host-targeted tick management and leading to human-wildlife conflict. Here, we determined (1) larval, nymphal, and adult tick burdens on host species and potential drivers, (2) the number of ticks supported by the different host populations, and (3) the proportion of medically significant tick species feeding on the different host species in Northern Sydney. We counted 3551 ticks on 241 mammals at 15 sites and found that long-nosed bandicoots (Perameles nasuta) hosted more ticks of all life stages than other small mammals but introduced black rats (Rattus rattus) were more abundant at most sites (33%-100%) and therefore important in supporting larval and nymphal ticks in our study areas. Black rats and bandicoots hosted a greater proportion of medically significant tick species including Ixodes holocyclus than other hosts. Our results show that an introduced human commensal contributes to maintaining urban tick populations and suggests ticks could be managed by controlling rat populations on urban fringes.

A new conceptual and quantitative approach to exploring and defining potential open-access olfactory information.

All organisms emit odour, providing 'open-access' olfactory information for any receiver with the right sensory apparatus. Characterizing open-access information emitted by groups of organisms, such as plant species, provides the means to answer significant questions about ecological interactions and their evolution. We present a new conceptual framework defining information reliability and a practical method to characterize and recover information from amongst olfactory noise. We quantified odour emissions from two tree species, one focal group and one outgroup, to demonstrate our approach using two new R statistical functions. We explore the consequences of relaxing or tightening criteria defining information and, from thousands of odour combinations, we identify and quantify those few likely to be informative. Our method uses core general principles characterizing information while incorporating knowledge of how receivers detect and discriminate odours. We can now map information in consistency-precision reliability space, explore the concept of information, and test information-noise boundaries, and between cues and signals.

Testing transgenerational transfer of personality in managed wildlife populations: a house mouse control experiment.

Pest species control operations are most effective if every individual in a population is targeted. Yet, individual personality drives variation in animal responses to devices such as traps and baits. Failing to account for differences in behavior during control operations may drive a selective removal, resulting in residual animals with biased expressions of personality. If these biased traits are passed onto offspring, control operations would become increasingly problematic. To test if biased trait expressions in founding populations are passed on to offspring, we quantified personality traits in wild-caught house mice (Mus musculus) and created founder populations selected for biased (high, low) or intermediate expressions of activity. We released the behaviorally biased populations into outdoor yards to breed to the F1 generation and, 10 weeks later, removed the mice and quantified the personality traits of the offspring. Despite the strong personality bias in founder populations, we observed no transgenerational transfer of personality and detected no personality bias in the F1 generation. Our results provide reassuring evidence that a single intensive control operation that selects for survivors with a personality bias is unlikely to lead to a recovering population inherently more difficult to eradicate, at least for house mice.

Behavioural drivers of survey bias: interactive effects of personality, the perceived risk and device properties.

Detecting small mammal species for wildlife research and management typically depends on animals deciding to engage with a device, for instance, by entering a trap. While some animals engage and are detected, others do not, and we often lack a mechanistic understanding of what drives these decisions. As trappability can be influenced by traits of personality, personality has high potential to similarly influence detection success for non-capture devices (chew-track cards, tracking tunnels, etc.). We present a conceptual model of the detection process where animal behaviours which are detected by different devices are grouped into tiers based on the degree of intimacy with a device (e.g., approach, interact, enter). Each tier is associated with an increase in the perceived danger of engaging with a device, and an increase in the potential for personality bias. To test this model, we first surveyed 36 populations of free-living black rats (Rattus rattus), a global pest species, to uniquely mark individuals (n = 128) and quantify personality traits. We then filmed rat behaviour at novel tracking tunnels with different risk-reward treatments. As predicted, detection biases were driven by personality, the bias increased with each tier and differed between the risk treatments. Our findings suggest that personality biases are not limited to live-capture traps but are widespread across devices which detect specific animal behaviours. In showing that biases can be predictable, we also show biases can be managed. We recommend that studies involving small mammal sampling report on steps taken to manage a personality-driven bias.

Invasive mammalian predators habituate to and generalize avian prey cues: a mechanism for conserving native prey.

Invasive mammalian predators can cause the decline and extinction of vulnerable native species. Many invasive mammalian predators are dietary generalists that hunt a variety of prey. These predators often rely upon olfaction when foraging, particularly at night. Little is understood about how prey odor cues are used to inform foraging decisions. Prey cues can vary spatially and temporally in their association with prey and can either reveal the location of prey or lead to unsuccessful foraging. Here we examine how two wild-caught invasive mammalian bird predator species (European hedgehogs Erinaceus europaeus and ferrets Mustela putorius furo) respond to unrewarded bird odors over successive exposures, first demonstrating that the odors are perceptually different using house mice (Mus musculus) as a biological olfactometer. We aim to test if introduced predators categorize odor cues of similar prey together, a tactic that could increase foraging efficiency. We exposed house mice to the odors using a standard habituation/dishabituation test in a laboratory setting, and wild-caught European hedgehogs and ferrets in an outdoor enclosure using a similar procedure. Mice discriminated among all bird odors presented, showing more interest in chicken odor than quail or gull odor. Both predator species showed a decline in interest toward unrewarded prey odor (i.e., habituation), but only ferrets generalized their response from one unrewarded bird odor to another bird odor. Hedgehog responses to unrewarded bird odors were highly variable between individuals. Taken together, our results reveal interspecific and intraspecific differences in response to prey odors, which we argue are a consequence of different diet breadth, life and evolutionary histories, and the conditions in each experiment. Generalization of prey odors may have enabled some species of invasive predators to efficiently hunt a range of intraguild prey species, for example, ground-nesting shorebirds. Olfactory manipulation of predators may be a useful conservation tool for threatened prey if it reduces the conspicuousness of vulnerable prey.

Molecular identification of the Trypanosoma (Herpetosoma) lewisi clade in black rats (Rattus rattus) from Australia.

Invasive rodent species are known hosts for a diverse range of infectious microorganisms and have long been associated with the spread of disease globally. The present study describes molecular evidence for the presence of a Trypanosoma sp. from black rats (Rattus rattus) in northern Sydney, Australia. Sequences of the 18S ribosomal RNA (rRNA) locus were obtained in two out of eleven (18%) blood samples with subsequent phylogenetic analysis confirming the identity within the Trypanosoma lewisi clade.

Overcoming prey naiveté: Free-living marsupials develop recognition and effective behavioral responses to alien predators in Australia.

Naiveté in prey arises from novel ecological mismatches in cue recognition systems and antipredator responses following the arrival of alien predators. The multilevel naiveté framework suggests that animals can progress through levels of naiveté toward predator awareness. Alternatively, native prey may be preadapted to recognize novel predators via common constituents in predator odors or familiar predator archetypes. We tested predictions of these competing hypotheses on the mechanisms driving behavioral responses of native species to alien predators by measuring responses of native free-living northern brown bandicoots (Isoodon macrourus) to alien red fox (Vulpes vulpes) odor. We compared multiple bandicoot populations either sympatric or allopatric with foxes. Bandicoots sympatric with foxes showed recognition and appropriate antipredator behavior toward fox odor via avoidance. On the few occasions bandicoots did visit, their vigilance significantly increased, and their foraging decreased. In contrast, bandicoots allopatric with foxes showed no recognition of this predator cue. Our results suggest that vulnerable Australian mammals were likely naïve to foxes when they first arrived, which explains why so many native mammals declined soon after fox arrival. Our results also suggest such naiveté can be overcome within a relatively short time frame, driven by experience with predators, thus supporting the multilevel naiveté framework.

Modeling habituation of introduced predators to unrewarding bird odors for conservation of ground-nesting shorebirds.

Foraging mammalian predators face a myriad of odors from potential prey. To be efficient, they must focus on rewarding odors while ignoring consistently unrewarding ones. This may be exploited as a nonlethal conservation tool if predators can be deceived into ignoring odors of vulnerable secondary prey. To explore critical design components and assess the potential gains to prey survival of this technique, we created an individual-based model that simulated the hunting behavior of three introduced mammalian predators on one of their secondary prey (a migratory shorebird) in the South Island of New Zealand. Within this model, we heuristically assessed the outcome of habituating the predators to human-deployed unrewarding bird odors before the bird's arrival at their breeding grounds, i.e., the predators were "primed." Using known home range sizes and probabilities of predators interacting with food lures, our model suggests that wide-ranging predators should encounter a relatively large number of odor points (between 10 and 115) during 27 d of priming when odor is deployed within high-resolution grids (100-150 m). Using this information, we then modeled the effect of different habituation curves (exponential and sigmoidal) on the probability of predators depredating shorebird nests. Our results show that important gains in nest survival can be achieved regardless of the shape of the habituation curve, but particularly if predators are fast olfactory learners (exponential curve), and even if some level of dishabituation occurs after prey become available. Predictions from our model can inform the amount and pattern in which olfactory stimuli need to be deployed in the field to optimize encounters by predators, and the relative gains that can be expected from reduced predation pressure on secondary prey under different scenarios of predator learning. Habituating predators to odors of threatened secondary prey may have particular efficacy as a conservation tool in areas where lethal predator control is not possible or ethical, or where even low predator densities can be detrimental to prey survival. Our approach is also relevant for determining interaction probabilities for devices other than odor points, such as bait stations and camera traps.

Australian native mammals recognize and respond to alien predators: a meta-analysis.

Prey naiveté is a failure to recognize novel predators and thought to cause exaggerated impacts of alien predators on native wildlife. Yet there is equivocal evidence in the literature for native prey naiveté towards aliens. To address this, we conducted a meta-analysis of Australian mammal responses to native and alien predators. Australia has the world's worst record of extinction and declines of native mammals, largely owing to two alien predators introduced more than 150 years ago: the feral cat, Felis catus, and European red fox, Vulpes vulpes Analysis of 94 responses to predator cues shows that Australian mammals consistently recognize alien foxes as a predation threat, possibly because of thousands of years of experience with another canid predator, the dingo, Canis lupus dingo We also found recognition responses towards cats; however, in four of the seven studies available, these responses were of risk-taking behaviour rather than antipredator behaviour. Our results suggest that a simple failure to recognize alien predators is not behind the ongoing exaggerated impacts of alien predators in Australia. Instead, our results highlight an urgent need to better understand the appropriateness of antipredator responses in prey towards alien predators in order to understand native prey vulnerability.

Food quality and conspicuousness shape improvements in olfactory discrimination by mice.

How animals locate nutritious but camouflaged prey items with increasing accuracy is not well understood. Olfactory foraging is common in vertebrates and the nutritional desirability of food should influence the salience of odour cues. We used signal detection analysis to test the effect of nutritional value relative to the conspicuousness of food patches on rates of foraging improvement of wild house mice Mus musculus searching for buried food (preferred peanuts or non-preferred barley). Olfactory cues were arranged to make food patches conspicuous or difficult to distinguish using a novel form of olfactory camouflage. Regardless of food type or abundance, mice searching for conspicuous food patches performed significantly better than mice searching for camouflaged patches. However, food type influenced how mice responded to different levels of conspicuousness. Mice searching for peanuts improved by similar rates regardless of whether food was easy or hard to find, but mice searching for barley showed significant differences, improving rapidly when food was conspicuous but declining in accuracy when food was camouflaged. Our results demonstrate a fundamental tenet of olfactory foraging that nutritional desirability influences rates of improvement in odour discrimination, enabling nutritious but camouflaged prey to be located with increasing efficiency.