The susceptibility of five species of wild animals to experimental infection with Leptospira grippotyphosa

Five species of wild animals including opossums, Didelphis marsupialis, striped skunks, Mephitis mephitis, red, Vulpes vulpes, and gray foxes, Urocyon cinereoargenteus and raccoons, Procyon lotor, were inoculated intraperitoneally with varying numbers of Leptospira grippotyphosa, organisms. Clinical signs were not detected, however, leptospiremia, leptospiruria and antibodies for the homologous organism, were demonstrated. Lesions attributed to leptospirosis were observed in liver and kidney tissue of infected animals. Infections were demonstrated in 5 of 9 opossums, 3 of 9 striped skunks, 3 of 9 red foxes, none of the gray foxes, and 9 of 9 raccoons. Therefore, it would appear that under conditions of this experiment that raccoons were most, opossums moderately, and skunks and red foxes least susceptible; gray foxes were not susceptible.     

Rotavirus-associated diarrhea in young raccoons (Procyon lotor), striped skunks (Mephitis mephitis) and red foxes (Vulpes vulpes)

Electron microscopy and a commercial ELISA test for rotavirus antigen were used to diagnose rotavirus infection in diarrheic raccoons (Procyon lotor), striped skunks (Mephitis mephitis) and red foxes (Vulpes vulpes). Gross and histopathological changes in two raccoons and two red foxes were found to be very similar to those described previously in rotavirus mediated diarrhea in other animals. While an etiology for the diarrhea is not definitively established, it would appear to involve rotavirus alone or possibly in concert with enteropathogenic coliform bacteria, overfeeding of a commercial kitten milk replacer and the stresses of captivity.     

When the Ghost of Predation has Passed: Do Rodents from Islands with and without Fox Predators Exhibit Aversion to Fox Cues?

Anti‐predator behavior can alter the dynamics of prey populations, but little is known about the rate at which anti‐predator behavior is lost from prey populations following predator removal. The Channel Islands differ in whether they have historically contained a top predator, the Island Fox (Urocyon littoralis), in evolutionary time (approximately 6200–10 000 yr). On a historically fox‐containing island and two historically fox‐free islands in 2007, I deployed live traps that contained olfactory cues of fox predators (fox feces), olfactory cues of an herbivore (horse feces) or a no‐feces control. Due to a captive breeding program, foxes on the historically fox‐containing island were effectively removed from 1998 to 2004. Rodents from one of the historically fox‐free islands did not respond to fox cues, whereas rodents on the historically fox‐containing island were more likely to be captured in a control trap and less likely to be captured in a fox‐cue trap. Results from the other historically fox‐free island that experienced a recent population bottleneck and period of captive rearing exhibited a preference for horse‐scented traps. These results suggest that, on islands where foxes are the primary predators, anti‐predator behavior in response to olfactory cues is not likely to be rapidly lost by short‐term removals of foxes, although the nature of anti‐predator behavior may depend upon founder events and recent population dynamics (e.g. population bottlenecks or several generations in captivity).     

Methods to mitigate human–wildlife conflicts involving common mesopredators: a meta-analysis

Conflicts between humans and mesopredators are frequent and widespread. Over the last decades, conflicts have led to the development and application of different mitigation methods to diminish the costs and damage caused by such conflicts. We conducted a systematic literature search and meta-analysis to assess the influence of different mitigation methods on 3 common nuisance species: raccoons (Procyon lotor), red foxes (Vulpes vulpes), and striped skunks (Mephitis mephitis). A majority of the studies, from 1963‒2022, were conducted in North America, followed by Australia and Europe. The predation of wildlife species of conservation concern by nuisance species is the main reported source of conflict in the published literature. Lethal control is the most commonly tested method and is generally effective at reducing conflicts based on the calculated effect size. Barriers have mixed effects, with electric fences and nest exclosures both being effective, whereas conventional fences seem to be less effective. Repellents mimicking predators (e.g., guard animal, predator smell) are also effective. Conditioned taste aversion is a promising approach, but no precise product or chemical has proven to be effective. Many interventions suffered from a lack of validation through experimental approach. Research on human–mesopredator conflict mitigation would benefit from repeated studies using the same methods in similar contexts, thus reducing heterogeneity in the results, and by testing new and innovative methods.     

Induced changes in island fox (Urocyon littoralis) activity do not mitigate the extinction threat posed by a novel predator

Prey response to novel predators influences the impacts on prey populations of introduced predators, bio-control efforts, and predator range expansion. Predicting the impacts of novel predators on native prey requires an understanding of both predator avoidance strategies and their potential to reduce predation risk. We examine the response of island foxes (Urocyon littoralis) to invasion by golden eagles (Aquila chrysaetos). Foxes reduced daytime activity and increased night time activity relative to eagle-na?ve foxes. Individual foxes reverted toward diurnal tendencies following eagle removal efforts. We quantified the potential population impact of reduced diurnality by modeling island fox population dynamics. Our model predicted an annual population decline similar to what was observed following golden eagle invasion and predicted that the observed 11% reduction in daytime activity would not reduce predation risk sufficiently to reduce extinction risk. The limited effect of this behaviorally plastic predator avoidance strategy highlights the importance of linking behavioral change to population dynamics for predicting the impact of novel predators on resident prey populations.     

Nesting Habitat Creation Enhances Recruitment in a Predator‐Free Environment: Malaclemys Nesting at the Paul S. Sarbanes Ecosystem Restoration Project

Aquatic turtles worldwide are plagued with habitat loss due to development and shoreline alteration that destroys the terrestrial–aquatic linkage which they must cross to reproduce successfully. Furthermore, nesting habitat loss can concentrate nesting, increasing nest predator efficiency. We describe how the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island created nesting habitat for Malaclemys terrapin (Diamondback Terrapin), and document nesting success in response to construction progress and the absence of raccoons and foxes, the primary nest predators. We monitored terrapin nests throughout the nesting seasons from 2002 to 2011 to determine overall and within‐nest survivorship. Female terrapins began nesting on the restoration project within 1 year but planned construction during the study eliminated some nesting areas and opened previously inaccessible areas. Overall, nest survivorship was considerably higher than mainland nesting areas due to the absence of raccoons and foxes on the island and within‐nest survivorship was similar. Egg size, hatchling size, and the frequency of shell scute anomalies were similar to other terrapin populations, suggesting normal developmental conditions on the island. We documented annual variation in hatchling size that correlated negatively with mean air temperature during the incubation season. Our results indicate that restored or created isolated island habitat can be located rapidly by terrapins and can become an important source of recruitment in regions where nesting habitat is limited and predation is high. Poplar Island illustrates how habitat loss and restoration can affect turtle populations by revealing the changes in nesting patterns and success in newly created, predator‐free habitat.     

Dietary breadth and overlap among five sympatric prairie carnivores

Ecological communities are shaped, in part, by the manner in which similar species consume and partition food resources. To better understand the structure of a mammalian carnivore community from a prairie habitat in central North America, we determined the dietary breadth and overlap of sympatric American badgers Taxidea taxus , coyotes Canis latrans , red foxes Vulpes vulpes , raccoons Procyon lotor and striped skunks Mephitis mephitis , via stomach content analysis of 411 carcasses salvaged as part of a predator control program in southern Saskatchewan, Canada (2000–2001). Carnivores consumed a total of 25 separate food items; for all species except raccoons, the majority of stomachs contained mammals, whereas other foods such as amphibians, bird remains and insects were also recovered. Raccoon stomachs tended to contain wheat seed, eggshells and birds. Dietary breadth varied among the five carnivore species, being narrowest for raccoons and widest for skunks. Overall, dietary overlap tended to be highest for species pairings associated with the highest level of presumed niche similarity, which included raccoon–skunk and coyote–fox dyads. Yet, levels of dietary overlap exhibited notable interannual variability for most species pairings. The assessment of a larger assemblage of carnivores within a North American prairie community shows that marked interspecific and temporal variation in dietary breadth and overlap may characterize a guild of sympatric species occupying similar habitat.     

Paragonimus kellicotti infection in wild carnivores in southwestern Ontario: II. Histopathologic features.

Pulmonary lesions associated with naturally acquired Paragonimus kellicotti infection were studied in mink (Mustela vison), striped skunks (Mephitis mephitis), red foxes (Vulpes vulpes) and a coyote (Canis latrans). In ,ink a fibrous capsule was formed around mature flukes in dilated bronchioles or bronchi, and there was mild focal interstitial pneumonitis adjacent to fluke eggs in alveoli and migrating parasites. A thick wall, infiltrated heavily with mononuclear cells and eosinophils, surrounded mature P. kellicotti in skunks and an extensive inflammatory reaction was found around fluke eggs. In red foxes the wall was thin, hemorrhagic and contained little collagen; necrosis was associated with migrating parasites. Thick capsules formed by marked fibroplastic changes in the lamina propria of affected bronchi were found in the coyote. In raccoons with pleural adhesions massive fibroplasia with eosinophil infiltration beneath the pulmonary pleura suggested a reaction to a migrating parasite entering the lung from the thoracic cavity. It was thought that immature P. kellicotti may have caused the lesion.     

Does Weather or Site Characteristics Influence the Ability of Scavengers to Locate Food?

Olfactory predators and scavengers rely on odors to locate food, and they forage primarily at night. We hypothesized that weather (e.g. wind speed, humidity, and temperature), vegetation, and landscape features affect the dissipation of odors in the atmosphere and, thus, impact the foraging efficiency of olfactory predators. We tested this hypothesis by assessing what conditions were correlated with the persistence of bait along the dike surrounding Willard Bay Reservoir, Utah. We distributed 124 chicken eggs and 199 dead European starlings (Sturnus vulgaris) as bait over 21 separate occasions spanning from May 21, 2009, to August 18, 2009. We used timers to record the time of consumption and cameras to identify which species ate the bait. Sixty‐six eggs and 87 dead European starlings were consumed. The bait was consumed mostly at night (83%) and by striped skunks (Mephitis mephitis), raccoons (Procyon lotor), and red foxes (Vulpes vulpes). We used nest survival models in program MARK to determine which covariates influenced bait persistence. We tested nine variables and found that bait persistence was influenced by section of the dike, time since study initiation, temperature, humidity, and wind speed but not bait type (egg or dead European starling), terrain, or visual cover. How quickly scavengers were able to locate food, which was inversely related to rates of bait persistence, decreased with higher temperatures and wind speeds and increased with higher humidity. Our results support the hypothesis that weather and micro‐habitat characteristics impact the ability of olfactory predators and scavengers to locate food.     

Natal Dispersal and Philopatry of Red Foxes in Urban and Agricultural Areas of Illinois

Abstract: Dispersal and philopatry may be influenced by habitat, intraspecific and interspecific interactions, and resource quality. Dispersal may vary substantially between urban and rural wildlife populations due to differences in urban-rural habitat and trophic relationships. We examined effects of environmental, body condition, and social influences on dispersal and philopatry of urban and rural red foxes (Vulpes vulpes) in east-central Illinois and western Indiana, USA. We recorded 96 dispersal events and 66 cases of philopatry in juvenile foxes. We used Akaike's Information Criterion to evaluate regression models of dispersal probability, initiation date, distance, and days spent dispersing. Habitat (i.e., urban-rural), sex, row-crop percentage in natal home ranges, family home-range overlap, and social interactions with family members all influenced dispersal probability. Juvenile foxes with fewer row crops in their home ranges, individuals with high intra-familial overlap of summer range, females, and urban foxes were associated with philopatry. Dispersals began mid-September and ended in March. Rural juveniles dispersed 23 days earlier than did urban conspecifics. Heavier foxes (capture wt) and those with heavily row-cropped home ranges dispersed earlier. Littermates dispersed at similar times, although in different directions. Dispersal distances averaged 44.8 km for all foxes (range = 1–478 km). Male and urban foxes dispersed farther than female and rural foxes, respectively. Time between dispersal and settlement averaged 41.2 days (range = 2–114 days), with urban foxes dispersing over longer time periods. Dispersal direction between the sexes had different directional distributions, though mean vectors for both were oriented north. Dispersing foxes selected cropland in proportion to availability, whereas grassland was selected preferentially. We demonstrate influences of habitat, resource availability, familial social interactions, and interspecific interactions on dispersal and philopatry of juvenile red foxes in an intensively row-cropped region of the Midwest. Our findings demonstrate red fox dispersal ecology differences in urban and rural environments. In intensively row-cropped regions of the Midwest where landscape crop harvest alters dispersal timing, minimizing seasonal habitat changes with permanent vegetative structure (e.g., crop food plots, native grass fields) would likely delay dispersal activity, and increase survival.     

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.     

Resource utilization by two insular endemic mammalian carnivores,the island fox and island spotted skunk

We compared resource utilization of two insular endemic mammalian carnivores, the island spotted skunk and island fox, along niche dimensions of space, food, and time on Santa Cruz Island. We predicted that resource use by foxes and skunks would differ along one or more niche dimensions, and that both species would have broader niches or higher densities compared with mainland relatives. Island foxes and island spotted skunks differed to some extent in habitat use, diets, and circadian activity, which may account for their long-term coexistence. Nonetheless, substantial overlap between skunks and foxes in spatial, dietary, and temporal dimensions suggests that competition between the two species does occur. Moreover, competition may be asymmetric, affecting skunks more than foxes. Compared with mainland foxes, island foxes have smaller body size, smaller home range, increased population density, increased diurnal activity, and behavior that is more highly inquisitive and less flightprone all common features of insular faunas. Island skunks, however, apparently have not developed these changes, perhaps due to asymmetric competition with foxes in conjunction with severe ecosystem disturbances caused by feral sheep.     

Landscape genetics of the nonnative red fox of California

Invasive mammalian carnivores contribute disproportionately to declines in global biodiversity. In California, nonnative red foxes (Vulpes vulpes) have significantly impacted endangered ground‐nesting birds and native canids. These foxes derive primarily from captive‐reared animals associated with the fur‐farming industry. Over the past five decades, the cumulative area occupied by nonnative red fox increased to cover much of central and southern California. We used a landscape‐genetic approach involving mitochondrial DNA (mtDNA) sequences and 13 microsatellites of 402 nonnative red foxes removed in predator control programs to investigate source populations, contemporary connectivity, and metapopulation dynamics. Both markers indicated high population structuring consistent with origins from multiple introductions and low subsequent gene flow. Landscape‐genetic modeling indicated that population connectivity was especially low among coastal sampling sites surrounded by mountainous wildlands but somewhat higher through topographically flat, urban and agricultural landscapes. The genetic composition of populations tended to be stable for multiple generations, indicating a degree of demographic resilience to predator removal programs. However, in two sites where intensive predator control reduced fox abundance, we observed increases in immigration, suggesting potential for recolonization to counter eradication attempts. These findings, along with continued genetic monitoring, can help guide localized management of foxes by identifying points of introductions and routes of spread and evaluating the relative importance of reproduction and immigration in maintaining populations. More generally, the study illustrates the utility of a landscape‐genetic approach for understanding invasion dynamics and metapopulation structure of one of the world's most destructive invasive mammals, the red fox.     

Limits to predator regulation of rabbits in Australia: evidence from predator-removal experiments

Summary Predator-prey studies in semi-arid eastern Australia demonstrated that populations of rabbits (Oryctolagus cuniculus) could be regulated by predators. The functional, numerical and total responses of foxes (Vulpes vulpes) to rabbits and the numerical response of feral cats (Felis catus) to rabbits, are described. Measurement of the rabbit component of foxes' stomach contents indicates a Type III functional response. The size of the fox population in summer was dependent on the availability of rabbits over the immediately preceding rabbit breeding season but there appeared to be no density-dependent aggregation of young foxes in areas of surplus food. The total response of foxes, estimated using the short-term numerical response of dispersing foxes, was directly density-dependent for low rabbit densities and inversely density-dependent for high rabbit densities. Two states are possible with this form of total response: a state with low rabbit densities regulated by predators and a state with high rabbit densities which occurs when rabbits escape predator regulation. The boundary between regulation and non-regulation by predators was demonstrated by a predator-removal experiment. In the treated areas, predators were initially culled and rabbits increased to higher densities than in an untreated area where predators were always present. When predators were allowed back into the treated areas, rabbit populations continued to increase and did not decline to the density in the untreated area. This is the critical evidence for a two-state system. When predators were present, rabbits could be maintained at low densities which were in the density-dependent part of the total response curve for foxes. Exceptionally high rabbit recruitment, or artificially reduced predation, could result in rabbits escaping predator-regulation. Under these circumstances, rabbits could move into the inversely density-dependent region of the total response curve for foxes.     

Not all predators are equal: a continent‐scale analysis of the effects of predator control on Australian mammals

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Effects of Coyote Population Reduction on Swift Fox Demographics in Southeastern Colorado

ABSTRACT The distribution and abundance of swift foxes (Vulpes velox) has declined from historic levels. Causes for the decline include habitat loss and fragmentation, incidental poisoning, changing land use practices, trapping, and predation by other carnivores. Coyotes (Canis latrans) overlap the geographical distribution of swift foxes, compete for similar resources, and are a significant source of mortality amongst many swift fox populations. Current swift fox conservation and management plans to bolster declining or recovering fox populations may include coyote population reduction to decrease predation. However, the role of coyote predation in swift fox population dynamics is not well-understood. To better understand the interactions of swift foxes and coyotes, we compared swift fox population demographics (survival rates, dispersal rates, reproduction, density) between areas with and without coyote population reduction. On the Piñon Canyon Maneuver Site, Colorado, USA, we monitored 141 swift foxes for 65,226 radio-days from 15 December 1998 to 14 December 2000 with 18,035 total telemetry locations collected. Juvenile swift fox survival rate was increased and survival was temporarily prolonged in the coyote removal area. Adult fox survival patterns were also altered by coyote removal, but only following late-summer coyote removals and, again, only temporarily. Coyote predation remained the main cause of juvenile and adult fox mortality in both areas. The increase in juvenile fox survival in the coyote removal area resulted in a compensatory increase in the juvenile dispersal rate and an earlier pulse in dispersal movements. Adult fox dispersal rate was more consistent throughout the year in the coyote removal area. Coyote removal did not influence the reproductive parameters of the swift foxes. Even though juvenile survival increased, swift fox density remained similar between the areas due to the compensatory dispersal rate among juvenile foxes. We concluded that the swift fox population in the area was saturated. Although coyote predation appeared additive in the juvenile cohort, it was compensatory with dispersal.     

Different colour morphs of the poison frog Andinobates bombetes (Dendrobatidae) are similarly effective visual predator deterrents

Aposematism is the use of warning signals to advertise unpleasant or dangerous defences to potential predators. As the effectiveness of this strategy depends on predator learning, little variation is expected in aposematic warning signals, as similar signals facilitate predator learning. However, warning signals are frequently variable in aposematic species. Such variability could arise as a result of geographic variation in the interpretation that local predators give warning signals. We tested this divergent learning hypothesis in the polytypic poison frog Andinobates bombetes (Anura: Dendrobatidae), focusing on visual predators. Our study was conducted in two populations of this species located in the Western Andes of Colombia, where individuals at some localities exhibit red dorsolateral stripes, while those in others exhibit yellow dorsolateral stripes. We deployed paraffin models imitating both forms of A. bombetes in size and colouration, as well as dull‐coloured controls, at sites inhabited by either red‐striped or yellow‐striped frogs. Red and yellow models were attacked at similar rates at both sites, and brown models were attacked more frequently at one of the sites. These results suggest that red and yellow colourations function as similarly effective aposematic signals for primarily visual predators, regardless of the form previously experienced by these predators. Therefore, our results do not support the hypothesis of divergent predator learning as a driver of the polytypism present in this species. Finally, we discuss other mechanisms that may be involved in the evolution and maintenance of this polytypism.     

Seasonal food habits of corsac and red foxes in Mongolia and the potential for competition

Competition often occurs between sympatric species that exploit similar ecological niches. Among canids, competition may be reduced by partitioning resources such as food, time, and habitat, but the mechanisms of coexistence remain poorly understood, particularly among fox species. We described the food habits of two foxes that live sympatrically across northern and central Asia, the corsac fox (Vulpes corsac) and red fox (V. vulpes), by analyzing scats collected during a field study in Mongolia. We analyzed 829 corsac and 995 red fox scats collected from April 2005 to August 2007 and tested the extent to which food partitioning occurred. The diets of both species consisted mainly of insects followed by rodents, but also included birds, reptiles, large mammal remains (carrion), plant material (including fruits and seeds), and garbage. Despite high overlap in the proportion of food items consumed, differences existed between species in overall diet with corsacs more frequently consuming beetles, but proportionally fewer crickets and large mammal remains than red foxes. We detected interspecific differences during the pup rearing and dispersal seasons, when prey was abundant, but not during the breeding season, when prey was scarce and diet overlap highest. Each species’ diet also differed seasonally and exhibited moderate overall breadth. Corsacs consumed proportionally more beetles and rodents during pup rearing and crickets during dispersal relative to other seasons, whereas red foxes consumed proportionally more crickets during pup rearing and dispersal and more rodents and large mammals during pup rearing and breeding relative to other seasons. Our results suggest that partitioning of food resources during most of the year facilitates coexistence, and that the potential for competition is highest during winter months.     

Intramuscular vaccination of skunks and raccoons against rabies

Live-captured striped skunks (Mephitis mephitis) and raccoons (Procyon lotor) were immunized with inactivated rabies vaccine by intramuscular injection and released at the point of capture during a rabies control program in Metropolitan Toronto (Ontario, Canada). Serum samples collected prior to and following vaccination revealed that 100% of the skunks and 98% of the raccoons seroconverted. Rabies antibody was still detectable 314 to 757 days postvaccination. Five of six skunks vaccinated in the laboratory survived challenge with rabies virus 90 days postvaccination. To our knowledge, this is the first documentation of the successful seroconversion of skunks and raccoons vaccinated against rabies in the field.     

Recent invasion of European red foxes (Vulpes vulpes) on to Fraser Island (K'gari) and South Stradbroke Island

Invasive predators are globally significant drivers of threatened fauna population decline and extinction, and the early detection of new incursions is critical to the chances of successful predator eradication and fauna conservation. Here, we provide evidence of the recent invasion of European red foxes (Vulpes vulpes) on to two large and internationally significant islands off the southeast coast of Queensland, Australia – Fraser Island (K'gari) and South Stradbroke Island. From camera trap footage collected on Fraser Island since 2009, foxes have now been observed on seven different occasions between 2012 and 2016. Two scats collected on South Stradbroke Island in 2013 and 2014 tested positive for fox DNA (and negative for Canis spp. DNA), with fox presence confirmed by subsequent camera trap footage in 2016. These data confirm the recent incursion of foxes on to these islands and suggest that small populations now exist there. Fraser Island and South Stradbroke Island represent key RAMSAR wetland areas of refuge for populations of multiple threatened fauna that have never been previously been exposed to foxes. Fox impacts on these fauna can only be expected to increase without management intervention to eradicate them before they become widespread.