Forces structuring tree squirrel communities in landscapes fragmented by agriculture: species differences in perceptions of forest connectivity and carrying capacity

The North American red squirrel ( Tamiasciurus hudsonicus ) has expanded its range into the central hardwoods of the United States in conjunction with increasing forest fragmentation and declining gray squirrel ( Sciurus carolinensis ) populations. We used translocation experiments and patch occupancy data to test for interspecific differences in mobility and sensitivity to habitat loss and modification by agriculture. We released squirrels in fencerows to test the hypothesis that gray squirrels display inferior mobility relative to red and fox ( S. niger ) squirrels. Elapsed time to movement from fencerows for 76 individuals increased with distance to forest patches and harvesting of crops. Gray and red squirrels took longer to move from fencerows than fox squirrels, and gray squirrels were less successful at moving from fencerows than red and fox squirrels. Ecologically scaled landscape indices revealed the degree to which interspecific differences in mobility and individual area requirements accounted for the occurrence of these species across landscapes. Gray squirrel distribution was constrained both by individual area requirements and dispersal ability. Occurrence of red and fox squirrels was related to patch size but was unaffected by landscape connectivity.     

Experimental transmission of Eimeria confusa Joseph 1969 to the fox squirrel.

Eimeria confusa Joseph, 1969 from the gray squirrel Sciurus carolinensis was transmitted to the fox squirrel Sciurus niger rufiventer. This is the first report of the successful cross-transmission of a gray squirrel coccidium to the fox squirrel.     

赤狐线粒体全基因组及系统发育分析

测定了赤狐的线粒体基因组全序列,总长度为16 723 bp,碱基组成为：31.3% A、26.1% C、14.8% G、27.8% T。和大多数哺乳动物一样,赤狐的线粒体全基因组包含13个蛋白质编码基因、2个核糖体RNA基因、22个转运RNA基因和1个控制区。除ND3基因起始密码子为不常见的ATT外,赤狐与北极狐、狼、家犬、郊狼的线粒体蛋白质编码遵循相同模式。在控制区的保守序列区段1和2之间发现一段较长的富含AC的随机重复序列。为了验证赤狐与其他犬科动物的系统发育关系,利用12个重链蛋白质编码基因,分别通过邻接法和最大简约法构建了系统发育树。结果表明：赤狐与北极狐是姐妹群,它们在犬科中都属于赤狐型分支,而灰狼、家犬和郊狼则属于狼型分支,与现有的系统进化研究结果一致。     

Hair Snares for Noninvasive Sampling of Felids in North America: Do Gray Foxes Affect Success?

Abstract: Hair-snare sampling has become a popular technique to assess distribution and abundance of felids. Using standard hair-snaring protocols, we sampled for margays (Leopardus wiedii) in Mexico and mountain lions (Puma concolor) in California, USA, without success. However, we noted a preponderance of gray fox (Urocyon cinereoargenteus) hair at sampling stations. Our review of recent literature suggests a pattern of failure to detect target felids in hair-snare surveys conducted within the range of the gray fox. We propose, among several alternative explanations, that marking by gray foxes interferes with the tendency of felids to face-rub at sampling stations.     

Landscape-Genetic Analysis of Population Structure in the Texas Gray Fox Oral Rabies Vaccination Zone

ABSTRACT In west-central Texas, USA, abatement efforts for the gray fox (Urocyon cinereoargenteus) rabies epizootic illustrate the difficulties inherent in large-scale management of wildlife disease. The rabies epizootic has been managed through a cooperative oral rabies vaccination program (ORV) since 1996. Millions of edible baits containing a rabies vaccine have been distributed annually in a 16-km to 24-km zone around the perimeter of the epizootic, which encompasses a geographic area >4 × 10⁵ km². The ORV program successfully halted expansion of the epizootic into metropolitan areas but has not achieved the ultimate goal of eradication. Rabies activity in gray fox continues to occur periodically outside the ORV zone, preventing ORV zone contraction and dissipation of the epizootic. We employed a landscape-genetic approach to assess gray fox population structure and dispersal in the affected area, with the aim of assisting rabies management efforts. No unique genetic clusters or population boundaries were detected. Instead, foxes were weakly structured over the entire region in an isolation by distance pattern. Local subpopulations appeared to be genetically non-independent over distances >30 km, implying that long-distance movements or dispersal may have been common in the region. We concluded that gray foxes in west-central Texas have a high potential for long-distance rabies virus trafficking. Thus, a 16-km to 24-km ORV zone may be too narrow to contain the fox rabies epizootic. Continued expansion of the ORV zone, although costly, may be critical to the long-term goal of eliminating the Texas fox rabies virus variant from the United States.     

A monitoring program for Patagonian foxes based on power analysis

Culpeo fox (Pseudalopex culpaeus) and gray fox (Pseudalopex griseus) are heavily culled in Patagonia. Fox populations seem to persist thanks to spatial refuges from which hunted areas are repopulated, following a source–sink dynamics. Sustainable use of Patagonian foxes warrants the design of a monitoring program in nature reserves and areas subjected to predator control. During 7 years, we used visitation indices to bait stations in a national park and neighboring sheep ranches of southern Argentina. We operated bait stations during three consecutive nights and calculated seven indices of relative abundance. For each fox species, we compared the power of different monitoring designs and scenarios that combined visitation indices, effort (number of bait station lines and survey frequency) while controlling for type I error, and magnitude of population change during a given period. We looked at the combinations that produced high power (β ≤ 0.24). The operation of bait stations during several nights markedly increased statistical power. Index 7 (recording visits 72 h after activation) exhibited the lowest variation and improved expected power to detect a population trend. Both fox species could be monitored simultaneously, with power >0.76 in the short term (5 years), activating 24 bait station lines. We conclude that monitoring programs for culpeo fox and gray fox based on bait stations are able to detect marked declines but are less useful to reliably detect moderate increases in abundance, especially in sheep ranches.

     

Mitochondrial Analysis of the Most Basal Canid Reveals Deep Divergence between Eastern and Western North American Gray Foxes (Urocyon spp.) and Ancient Roots in Pleistocene California

Pleistocene aridification in central North America caused many temperate forest-associated vertebrates to split into eastern and western lineages. Such divisions can be cryptic when Holocene expansions have closed the gaps between once-disjunct ranges or when local morphological variation obscures deeper regional divergences. We investigated such cryptic divergence in the gray fox (Urocyon cinereoargenteus), the most basal extant canid in the world. We also investigated the phylogeography of this species and its diminutive relative, the island fox (U. littoralis), in California. The California Floristic Province was a significant source of Pleistocene diversification for a wide range of taxa and, we hypothesized, for the gray fox as well. Alternatively, gray foxes in California potentially reflected a recent Holocene expansion from further south. We sequenced mitochondrial DNA from 169 gray foxes from the southeastern and southwestern United States and 11 island foxes from three of the Channel Islands. We estimated a 1.3% sequence divergence in the cytochrome b gene between eastern and western foxes and used coalescent simulations to date the divergence to approximately 500,000 years before present (YBP), which is comparable to that between recognized sister species within the Canidae. Gray fox samples collected from throughout California exhibited high haplotype diversity, phylogeographic structure, and genetic signatures of a late-Holocene population decline. Bayesian skyline analysis also indicated an earlier population increase dating to the early Wisconsin glaciation (~70,000 YBP) and a root height extending back to the previous interglacial (~100,000 YBP). Together these findings support California’s role as a long-term Pleistocene refugium for western Urocyon. Lastly, based both on our results and re-interpretation of those of another study, we conclude that island foxes of the Channel Islands trace their origins to at least 3 distinct female founders from the mainland rather than to a single matriline, as previously suggested.     

Susceptibility of red and gray foxes to infection by Ehrlichia chaffeensis

Red foxes (Vulpes vulpes) and gray foxes (Urocyon cinereoargenteus) were evaluated for their susceptibility to experimental infection with Ehrlichia chaffeensis, the causative agent of human monocytotropic ehrlichiosis. Two red foxes and three gray foxes were inoculated intravenously with E. chaffeensis (15B-WTD-GA strain) and were monitored at 7, 14, 21, and 28 days post inoculation (DPI) for evidence of infection using an indirect fluorescent antibody (IFA) assay, light microscopy, polymerase chain reaction (PCR), and cell culture methods. One red fox and one gray fox served as negative controls. Red foxes were susceptible to infection based on reisolation of E. chaffeensis from blood at 7 and 14 DPI, seroconversion by 7 DPI, and positive PCR assays on spleen and lymph nodes at 28 DPI. Morulae were not found in circulating leukocytes and clinical signs or lesions of ehrlichiosis were not observed. In contrast, gray foxes were refractory to infection based on negative results on all culture, PCR, serologic, and microscopic examinations. These findings imply that red foxes, but not gray foxes, are potential vertebrate reservoirs for E. chaffeensis. These findings also illustrate the need to verify serologic evidence of E. chaffeensis infection among wild animals.     

Identifying and Controlling for Variation in Canid Harvest Data

An accurate understanding of harvest trends is required for effective wildlife management. Trapper harvest data represent valuable long-term data for evaluating patterns and trends for wildlife species at broad spatiotemporal scales. Inferring accurate trends from harvest data, however, first requires identifying and controlling for confounding factors that vary independent of abundance. We investigated trends in 43 years of trapper harvest data (1976–2018) from Illinois, USA, for red fox (Vulpes vulpes), gray fox (Urocyon cinereoargenteus), and coyote (Canis latrans) while controlling for factors that may affect trapper effort, including number of effective (i.e., successful) trappers, pelt price, gasoline price, winter unemployment, and winter weather conditions. Annual trapper harvest for red and gray foxes declined and was affected by gasoline price and winter unemployment, whereas annual trapper harvest for coyotes increased and was not strongly affected by other covariates. After adjusting for pelt price, harvest of red foxes was relatively stable, but harvest of gray foxes declined and harvest of coyotes increased. Effects of covariates on harvest per successful trapper varied by species; nevertheless, we detected an increasing trend for coyotes and decreasing trends for gray foxes and red foxes. Concordance across indices for gray foxes and coyotes was consistent with hypothesized declines for gray foxes and increases for coyotes in the midwestern United States. Trends for red foxes varied depending on how we accounted for potential confounding factors and it is unclear if these trends suggest population declines or distribution shifts to urban areas with reduced trapping susceptibility. Our results highlight the importance of understanding sources of variation in harvest data and that their effects can vary across species. © 2020 The Wildlife Society.     

Competition and intraguild predation among three sympatric carnivores

We examined the relative roles of dominance in agonistic interactions and energetic constraints related to body size in determining local abundances of coyotes (Canis latrans, 8-20 kg), gray foxes (Urocyon cinereoargenteus, 3-5 kg) and bobcats (Felis rufus, 5-15 kg) at three study sites (hereafter referred to as NP, CP, and SP) in the Santa Monica Mountains of California. We hypothesized that the largest and behaviorally dominant species, the coyote, would exploit a wider range of resources (i.e., a higher number of habitat and/or food types) and, consequently, would occur in higher density than the other two carnivores. We evaluated our hypotheses by quantifying their diets, food overlap, habitat-specific abundances, as well as their overall relative abundance at the three study sites. We identified behavioral dominance of coyotes over foxes and bobcats in Santa Monica because 7 of 12 recorded gray fox deaths and 2 of 5 recorded bobcat deaths were due to coyote predation, and no coyotes died as a result of their interactions with bobcats or foxes. Coyotes and bobcats were present in a variety of habitats types (8 out of 9), including both open and brushy habitats, whereas gray foxes were chiefly restricted to brushy habitats. There was a negative relationship between the abundances of coyotes and gray foxes (P=0.020) across habitats, suggesting that foxes avoided habitats of high coyote predation risk. Coyote abundance was low in NP, high in CP, and intermediate in SP. Bobcat abundance changed little across study sites, and gray foxes were very abundant in NP, absent in CP, and scarce in SP; this suggests a negative relationship between coyote and fox abundances across study sites, as well. Bobcats were solely carnivorous, relying on small mammals (lagomorphs and rodents) throughout the year and at all three sites. Coyotes and gray foxes also relied on small mammals year-round at all sites, though they also ate significant amounts of fruit. Though there were strong overall interspecific differences in food habits of carnivores (P<0.0001), average seasonal food overlaps were high due to the importance of small mammals in all carnivore diets [bobcat-gray fox: 0.79ǂ.09 (SD), n=4; bobcat-coyote: 0.69ǂ.16, n=6; coyote-gray fox: 0.52ǂ.05, n=4]. As hypothesized, coyotes used more food types and more habitat types than did bobcats and gray foxes and, overall, coyotes were the most abundant of the three species and ranged more widely than did gray foxes. We propose that coyotes limit the number and distribution of gray foxes in Santa Monica Mountains, and that those two carnivores exemplified a case in which the relationship between their body size and local abundance is governed by competitive dominance of the largest species rather than by energetic equivalences. However, in the case of the intermediate-sized bobcat no such a pattern emerged, likely due to rarity or inconsistency of agonistic interactions and/or behavioral avoidance of encounters by subordinate species.     

Toxoplasma gondii antibodies in naturally exposed wild coyotes, red foxes, and gray foxes and serologic diagnosis of Toxoplasmosis in red foxes fed T. gondii oocysts and tissue cysts

Antibodies to Toxoplasma gondii were determined in sera from 222 coyotes (Canis latrans), 283 red foxes (Vulpes vulpes), and 97 gray foxes (Urocyon cinereoargenteus) from Indiana, Kentucky, Michigan, and Ohio during 1990-1993. Sera were examined in 1:25, 1:100, and 1:500 dilutions by the modified direct agglutination test (MAT) with formalinized whole tachyzoites plus mercaptoethanol. Antibodies were found in 131 (59.0%) of 222 coyotes, 243 (85.9%) of 283 red foxes, and 73 (75.3%) of 97 gray foxes. Antibodies were also measured by different serologic tests in 4 littermate T. gondii-free red foxes fed T. gondii tissue cysts or oocysts; the fifth littermate fox was not fed T. gondii. Antibodies were measured in fox sera obtained 0, 14, and 36-55 days after infection with T. gondii. All 4 foxes fed T. gondii developed MAT and dye test antibody titers of 1:200 or more 14 days later. The latex agglutination test (LAT) and indirect hemagglutination test (IHAT) were less sensitive than MAT for the diagnosis of T. gondii infection in foxes. Antibodies were not detected by LAT (titer 1:64) in the 2 foxes fed tissue cysts nor by IHAT in 1 of the foxes fed tissue cysts. Toxoplasma gondii was isolated by bioassay in mice from tissues of all 4 foxes fed T. gondii. The control fox had no T. gondii antibodies detectable by any of the serologic tests.     

Diagnostic Genetic Marker That Differentiates Eastern Fox Squirrels From Eastern Gray Squirrels

Abstract The Delmarva fox squirrel (Sciurus niger cinereus) has been listed as endangered by the United States Department of Interior since 1967. A high-priority task for the recovery of this taxon is to determine its current geographic distribution. Toward this end, we have identified a microsatellite locus that unambiguously differentiates Delmarva fox squirrels from eastern gray squirrels (S. carolinensis), which frequently co-occur with Delmarva fox squirrels. Analysis of this marker in noninvasively collected hair samples will allow unequivocal identification of localities occupied by Delmarva fox squirrels with a minimum investment of funds, time, and effort because handling individuals will be unnecessary. This protocol will expedite site review in connection with the Endangered Species Act consultation process.     

Asymmetrical intraguild interactions with coyotes,red foxes,and domestic dogs may contribute to competitive exclusion of declining gray foxes

Species coexistence is governed by availability of resources and intraguild interactions including strategies to reduce ecological overlap. Gray foxes are dietary generalist mesopredators expected to benefit from anthropogenic disturbance, but populations have declined across the midwestern USA, including severe local extirpation rates coinciding with high coyote and domestic dog occurrence and low red fox occurrence. We used data from a large‐scale camera trap survey in southern Illinois, USA to quantify intraguild spatial and temporal interactions among the canid guild including domestic dogs. We used a two‐species co‐occurrence model to make pairwise assessments of conditional occupancy and detection rates. We also estimated temporal activity overlap among species and fit a fixed‐effects hierarchical community occupancy model with the four canid species. We partitioned the posterior distributions to compare gray fox occupancy probabilities conditional on estimated state of combinations of other species to assess support for hypothesized interactions. We found no evidence of broadscale avoidance among native canids and conclude that spatial and temporal segregation were limited by ubiquitous human disturbance. Mean guild richness was two canid species at a site and gray fox occupancy was greater when any combination of sympatric canids was also present, setting the stage for competitive exclusion over time. Domestic dogs may amplify competitive interactions by increasing canid guild size to the detriment of gray foxes. Our results suggest that while human activities can benefit some mesopredators, other species such as gray foxes may serve as bellwethers for habitat degradation with trophic downgrading and continued anthropogenic homogenization.     

Prevalence of selected pathogenic microbial agents in the red fox (Vulpes fulva) and gray fox (Urocyon cinereoargenteus) of southwestern Wisconsin

Free-ranging red foxes (Vulpes fulva) and gray foxes (Urocyon cinereoargenteus) were trapped in southwestern Wisconsin. Fox sera were tested to determine the prevalence of antibody for five different Leptospira interrogans serovars, canine distemper virus (CDV), infectious canine hepatitis virus (ICHV), and Franciscella tularensis infections. Grippotyphosa was the most prevalent leptospiral serovar antibody observed. Twenty-five of 53 (47%) red foxes and 11 of 36 (31%) gray foxes had specific antibodies to grippotyphosa. Juvenile foxes had geometric mean antibody titers to grippotyphosa significantly higher (P less than 0.05) than those of the adults of both species. CDV antibody was detected in sera of red foxes only. Six of 57 (11%) red foxes had CDV antibody. ICHV antibody was detected in 2 of 57 (3%) red foxes and 3 of 32 (9%) gray foxes. Antibody to F. tularensis was not detected in any fox sera.     

Endozoochorous dispersal of forest seeds by carnivorous mammals in Sierra Fría,Aguascalientes, Mexico

Some carnivorous mammals ingest fruit and disperse seeds of forest plant species capable of colonizing disturbed areas in ecosystems. The objective of the present study was to evaluate the dissemination of Arctostaphylos pungens and Juniperus deppeana seeds by the gray fox (Urocyon cinereoargenteus), coyote (Canis latrans), and other carnivores in the Protected Natural Area Sierra Fría, in Aguascalientes, Mexico. Scat collection was undertaken via transects using the direct search method, while the seasonal phenology of A. pungens and J. deppeana was evaluated by recording flower and fruit abundance on both the plant and the surrounding forest floor ground. Seed viability was assessed by optical densitometry via X‐ray and a germination test. It was found that the gray fox, coyote, ringtail (Bassariscus astutus), and bobcat (Lynx rufus) disseminated seeds of A. pungens (212 ± 48.9 seeds/scat) and J. deppeana (23.6 ± 4.9 seeds/scat), since a large proportion of the collected scat of these species contained seeds (28/30 = 93.33%, 12/43 = 27.9%, 6/12 = 50% and 7/25 = 28% respectively). The gray fox, coyote, ringtail, and bobcat presented an average of seed dispersion of both plant species of 185.4 ± 228.7, 4.0 ± 20.0, 12.1 ± 30.4, and 0.8 ± 1.5 per scat; the seed proportions in the gray fox, coyote, ringtail, and bobcat were 89.6/10.4%, 82.3/17.7%, 90.4/9.6%, and 38.1/61.9% for A. pungens and J. deppeana, respectively. The phenology indicated a finding related to the greater abundance of ripe fruit in autumn and winter (p < .01). This coincided with the greater abundance of seeds found in scats during these seasons. Endozoochory and diploendozoochory enhanced the viability and germination of the seeds (p > .05), except in those of A. pungens dispersed by coyote. These results suggest that carnivores, particularly the gray fox, the coyote, and the bobcat, play an important role in forest seed dissemination, and thus forest regeneration, by making both a quantitative and qualitative contribution to the dispersal of the two pioneer species under study.     

Bovine tuberculosis in free-ranging carnivores from Michigan

During a survey of carnivores and omnivores for bovine tuberculosis conducted in Michigan (USA) since 1996, Mycobacterium bovis was cultured from lymph nodes pooled from six coyotes (Canis latrans) (four adult female, two adult male), two adult male raccoons (Procyon lotor), one adult male red fox (Vulpes vulpes), and one 1.5-yr-old male black bear (Ursus americanus). One adult, male bobcat (Felis rufus) with histologic lesions suggestive of tuberculosis was negative on culture but positive for organisms belonging to the Mycobacterium tuberculosis complex when tested by polymerase chain reaction. All the tuberculous animals were taken from three adjoining counties where M. bovis is known to be endemic in the free-ranging white-tailed deer (Odocoileus virginianus) population. There were two coyotes, one raccoon, one red fox, and one bobcat infected in Alpena county. Montmorency County had two coyotes and one raccoon with M. bovis. Two coyotes and a bear were infected from Alcona County. These free-ranging carnivores/omnivores probably became infected with M. bovis through consumption of tuberculous deer. Other species included in the survey were opossum (Didelphis virginiana), gray fox (Urocyon cinereoargenteus), and badger (Taxidea taxus); these were negative for M. bovis.     

Morbidity and mortality of red foxes (Vulpes vulpes) and gray foxes (Urocyon cinereoargenteus) admitted to the Wildlife Center of Virginia, 1993-2001

The medical records of 48 red foxes (Vulpes vulpes) and 35 gray foxes (Urocyon cinereoargenteus) examined at the Wildlife Center of Virginia (Waynesboro, Virginia, USA) from 1993 to 2001 were reviewed. The most common diagnosis in red foxes was orphaned (33%), followed by trauma (27%), undetermined diagnosis (23%), and sarcoptic mange (17%). Trauma (46%) was the most frequent cause of morbidity and mortality in gray foxes followed by orphaned (23%), undetermined (20%), toxoplasmosis (6%), presumptive canine distemper (3%), and rabies (3%). One gray fox had concurrent toxoplasmosis and presumptive canine distemper (3%). Similar diseases were detected in previous studies at a diagnostic laboratory; however in this study, trauma and orphaned animals were more common than infectious diseases. The lack of diagnostic information on some cases limited the usefulness of this study, and more emphasis should be placed on performing postmortem examinations of wildlife presented to wildlife rehabilitation centers.     

A noninvasive method for distinguishing among canid species: amplification and enzyme restriction of DNA from dung

Endangered San Joaquin kit foxes Vulpes macrotis mutica can be sympatrically distributed with as many as four other canids: red fox, gray fox, coyote and domestic dog. Canid scats are often found during routine fieldwork, but cannot be reliably identified to species. To detect and study the endangered kit fox, we developed mitochondrial DNA markers that can be amplified from small amounts of DNA extracted from scats. We amplified a 412-bp fragment of the mitochondrial cytochrome- b gene from scat samples and digested it with three restriction enzymes. The resulting restriction profiles discriminated among all five canid species and correctly identified 10 'unknown' fox scats to species in blind tests. We have applied our technique to identify canids species for an environmental management study and a conservation study. We envision that our protocol, and similar ones developed for other endangered species will be greatly used for conservation management in the future.     

Yersinia enterocolitica and related species isolated from wildlife in New York State

Fecal specimens for Yersinia screening were obtained from a variety of wild mammals, birds, reptiles, fish, and invertebrates throughout New York State. One specimen from each of 1,426 animals was examined. A total of 148 isolates of Yersinia enterocolitica and related species were obtained from 133 (9.3%) of the animals. Y. enterocolitica was isolated from 100 (7%) of the animals tested, including 81 (10%) of 812 mammals and 19 (3.3%) of 573 birds. Y. intermedia, Y. frederiksenii, and Y. kristensenii were isolated from 39 (2.7%), 5 (0.35%), and 4 (0.28%) animals, respectively. The 81 Y. enterocolitica isolates from mammals belonged to 15 serogroups and included three pathogens: two isolates of typical serogroup 0:8, the "American strain," one from a gray fox (Urocyon cinereoargenteus) and one from a porcupine (Erethizon dorsatum); and one isolate of serogroup 0:3, bacteriophage type IXb, the "Canadian strain," from a gray fox. The most prevalent serogroups recovered from mammals were 0:6,31 (16 isolates) and 0:5,27 (6 isolates). The 19 isolates of Y. enterocolitica from birds belonged to nine serogroups and included one serogroup 0:6,31 isolate from a common grackle (Quiscalus quiscula) and two serogroup 0:5,27 isolates from great horned owls (Bubo virginianus).