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native and invasive squirrels show different behavioural responses to scent of a shared native predator.invasive species pose a serious threat to native species. in europe, invasive grey squirrels (sciurus carolinensis) have replaced native red squirrels (sciurus vulgaris) in locations across britain, ireland and italy. the european pine marten (martes martes) can reverse the replacement of red squirrels by grey squirrels, but the underlying mechanism of how pine martens suppress grey squirrels is little understood. research suggests the reversal process is driven by direct predation, but why the ...202032257340
seasonal expression of ngf and its cognate receptors in the ovaries of grey squirrels (sciurus carolinensis).the grey squirrel is an invasive alien species that seriously threatens the conservation of the native red squirrel species. with the aim of characterizing the reproductive physiology of this species due to its great reproductive success, the function of the ovarian nerve growth factor (ngf) system was analyzed in a grey squirrel population living in central italy. during the breeding and nonbreeding seasons, the ovarian presence, distribution, and gene expression of ngf, neurotrophic tyrosine k ...202032887345
a comparative study of intramuscular alfaxalone- or ketamine-based anesthetic mixtures in gray squirrels undergoing gonadectomy: clinical and physiologic findings.the gray squirrel is one of the most common invasive species in europe, whose presence is dangerous for the survival of the european red squirrel. to cope with this biological invasion and to safeguard biodiversity, the life+u-savereds project aims to protect the red squirrel, by limiting the growth of the current population of gray squirrels and simultaneously promoting their eradication with surgical sterilization. this study compares two different anesthetic protocols, including dexmedetomidi ...202032806590
prognostic indicators for survival of orphaned eastern gray squirrels (sciurus carolinensis).the eastern grey squirrel (egs), sciurus carolinensis, is a tree squirrel native to the eastern united states. this species commonly presents to wildlife medical clinics for a variety of human-related injuries including confrontations with road traffic and pet predation. the purpose of this study was to assess initial examination findings as prognostic indicators for survival in egs. the medical record database of the university of illinois wildlife medical clinic was searched from january 2012 ...202032549555
relationships between personality traits and the physiological stress response in a wild mammal.glucocorticoids (gcs) are involved in the regulation of an animal's energetic state. under stressful situations, they are part of the neuroendocrine response to cope with environmental challenges. animals react to aversive stimuli also through behavioral responses, defined as coping styles. both in captive and wild populations, individuals differ in their behavior along a proactive-reactive continuum. proactive animals exhibit a bold, active-explorative and social personality, whereas reactive o ...202032440278
reproductive traits of an invasive alien population of grey squirrel (sciurus carolinensis) in central italy.the reproductive cycle of an invasive alien italian grey squirrel population was studied to understand its adaptation and limit its spread, in order to conserve the autochthonous red squirrel. female and male genital traits were evaluated throughout the reproductive cycle, including the ovary, uterus, testicle, epididymis, seminiferous tubule morphometry, and germinative epithelium histology. moreover, individual female fecundity was determined by counting uterine scars. ovary width and uterus w ...202032344507
spillover of an alien parasite reduces expression of costly behaviour in native host species.understanding the effects of invasive alien species (ias) on native host-parasite relationships is of importance for enhancing ecological theory and ias management. when ias and their parasite(s) invade a guild, the effects of interspecific resource competition and/or parasite-mediated competition can alter existing native host-parasite relationships and the dependent biological traits such as native species' behaviour. we used a natural experiment of populations of native red squirrels sciurus ...202032291765
dispatches from the neighborhood watch: using citizen science and field survey data to document color morph frequency in space and time.heritable color polymorphisms have a long history of study in evolutionary biology, though they are less frequently examined today than in the past. these systems, where multiple discrete, visually identifiable color phenotypes co-occur in the same population, are valuable for tracking evolutionary change and ascertaining the relative importance of different evolutionary mechanisms. here, we use a combination of citizen science data and field surveys in the great lakes region of north america to ...202032076531
learning is negatively associated with strength of left/right paw preference in wild grey squirrels (sciurus carolinensis).cerebral laterality, via hemispheric specialisation, has been evidenced across the animal kingdom and linked to cognitive performance in a number of species. previously it has been suggested that cognitive processing is more efficient in brains with stronger hemispheric differences in processing, which may be the key fitness benefit driving the evolution of laterality. however, evidence supporting a positive association between cognitive performance and lateralization is mixed: data from studies ...202031965461
multilocus sequencing of hepatozoon cf. griseisciuri infections in ontario eastern gray squirrels (sciurus carolinensis) uncovers two genotypically distinct sympatric parasite species.intra-leukocytic gamonts consistent with the description of hepatozoon griseisciuri clark, 1958 are reported for the first time in canadian eastern gray squirrels (sciurus carolinensis gmelin, 1788). polymerase chain reaction (pcr) amplification and direct sanger sequencing identified a pair of distinct genotypes at both a nuclear and mitochondrial locus; two 18s ribosomal rna gene sequences (rdna; genotype a and genotype b: 1816 base pairs (bp); 98.8% pairwise identity) and 2 distinct complete ...202031912276
mechanisms underlying detection of seed dormancy by a scatter-hoarding rodent.the mechanism underlying detection of seed dormancy by scatter-hoarding rodents is unclear, although previous work suggests that the pericarp plays an important role in signaling dormancy status. eastern gray squirrels (sciurus carolinensis) consume early germinating seeds as they are more likely to perish immediately, whereas dormant seeds tend to be cached. to examine the mechanisms underlying dormancy detection, we characterized physical and chemical differences between germinating and dorman ...202031631524
landscape-scale differences among cities alter common species' responses to urbanization.understanding how biodiversity responds to urbanization is challenging, due in part to the single-city focus of most urban ecological research. here, we delineate continent-scale patterns in urban species assemblages by leveraging data from a multi-city camera trap survey and quantify how differences in greenspace availability and average housing density among ten north american cities relate to the distribution of eight widespread north american mammals. to do so, we deployed camera traps at 56 ...202033141996
not all fine-branch locomotion is equal: grasping morphology determines locomotor performance on narrow supports.fine-branch models have long played a central role in primate evolutionary research. nevertheless, recent studies of positional behavior in nonprimate arboreal mammals have challenged the idea that synapomorphic primate features, such as grasping extremities, uniquely facilitated access to the fine-branch zone. we test the alternative hypothesis that grasping extremities specifically improve locomotor performance in a fine-branch environment by examining how support diameter influences locomotor ...202032240883
cross-sectional evaluation of multiple epidemiological cycles of leptospira species in peri-urban wildlife in california.to perform a cross-sectional survey to estimate prevalence of and potential risk factors for leptospira spp infection and exposure in peri-urban wildlife throughout california.202033021456
potential effects of blood meal host on bacterial community composition in ixodes scapularis nymphs.tick microbiomes may play an important role in pathogen transmission. however, the drivers of microbiome variation are poorly understood, and this limitation has impeded mechanistic understanding of the functions of microbial communities for pathogen acquisition. the goal of this research was to characterize the role of the blood meal host in structuring the microbiome of ixodes scapularis, the primary vector of lyme disease in the eastern united states, and to determine if ticks that fed from d ...201930660375
eavesdropping grey squirrels infer safety from bird chatter.when multiple species are vulnerable to a common set of predators, it is advantageous for individuals to recognize information about the environment provided by other species. eastern gray squirrels (sciurus carolinensis) and other small mammals have been shown to exploit heterospecific alarm calls as indicators of danger. however, many species-especially birds-emit non-alarm auditory cues such as contact calls when perceived predator threat is low, and such public information may serve as cues ...201931483829
interspecific competition affects the expression of personality-traits in natural populations.competition between animal species can cause niche partitioning and shape an individual's phenotype, including its behaviour. however, little is known about effects of interspecific competition on personality, the among-individual variation in behaviour that is consistent across different spatial and temporal contexts. we investigated whether alien grey squirrels (sciurus carolinensis) influenced the expression of personality traits in native red squirrels (sciurus vulgaris). in italy, alien gre ...201931371774
the drivers of squirrelpox virus dynamics in its grey squirrel reservoir host.many pathogens of conservation concern circulate endemically within natural wildlife reservoir hosts and it is imperative to understand the individual and ecological drivers of natural transmission dynamics, if any threat to a related endangered species is to be assessed. our study highlights the key drivers of infection and shedding dynamics of squirrelpox virus (sqpv) in its reservoir grey squirrel (sciurus carolinensis) population. to clarify sqpv dynamics in this population, longitudinal dat ...201931327730
multiple origins of melanism in two species of north american tree squirrel (sciurus).while our understanding of the genetic basis of convergent evolution has improved there are still many uncertainties. here we investigate the repeated evolution of dark colouration (melanism) in eastern fox squirrels (sciurus niger; hereafter "fox squirrels") and eastern gray squirrels (s. carolinensis; hereafter "gray squirrels").201931296164
conservation of genetic uniqueness in remaining populations of red squirrels (sciurus vulgaris l.) in the south of england.the eurasian red squirrel (sciurus vulgaris) is an emblematic species for conservation, and its decline in the british isles exemplifies the impact that alien introductions can have on native ecosystems. indeed, red squirrels in this region have declined dramatically over the last 60 years due to the spread of squirrelpox virus following the introduction of the gray squirrel (sciurus carolinensis). currently, red squirrel populations in britain are fragmented and need to be closely monitored in ...201931236243
a new species of eimeria schneider, 1885 (apicomplexa: eimeriidae) from the eastern gray squirrel, sciurus carolinensis (rodentia: sciuridae: sciurinae: sciurini) from oklahoma, usa.a new species of eimeria schneider, 1885 is described from an eastern gray squirrel (sciurus carolinensis) from mccurtain county, oklahoma, usa. oöcysts of eimeria lukfataensis n. sp. are ellipsoidal with a rough pitted bi-layered wall, measure 23.8 × 14.9 µm, and have a length/width (l/w) ratio of 1.6; a micropyle is absent but an oöcyst residuum and polar granule(s) are present. sporocysts are ellipsoidal and measure 12.5 × 6.1 µm, l/w 2.0; stieda and sub-stieda bodies are present, but para-st ...201931077062
inhibitory control and memory in the search process for a modified problem in grey squirrels, sciurus carolinensis.inhibiting learned behaviours when they become unproductive and searching for an alternative solution to solve a familiar but different problem are two indicators of flexibility in problem solving. a wide range of animals show these tendencies spontaneously, but what kind of search process is at play behind their problem-solving success? here, we investigated how eastern grey squirrels, sciurus carolinensis, solved a modified mechanical problem that required them to abandon their preferred and l ...201930976933
surgical sterilization of male and female grey squirrels (sciurus carolinensis) of an urban population introduced in italy.we report a successful surgical sterilization procedure for population control of 324 male and female free-ranging grey squirrels (sciurus carolinensis) in genoa (italy). we describe the clinical procedure from the trapping of the animals to their surgical sterilization and release in another part of the city. live-trapped squirrels were transported to the veterinary clinic within 1-2 hr of capture and maintained in a hospitalization room reserved for them. the waiting period before surgery was ...201930828030
british red squirrels remain the only known wild rodent host for leprosy bacilli.eurasian red squirrels (sciurus vulgaris) in the british isles are the most recently discovered animal reservoir for the leprosy bacteria mycobacterium leprae and mycobacterium lepromatosis. initial data suggest that prevalence of leprosy infection is variable and often low in different squirrel populations. nothing is known about the presence of leprosy bacilli in other wild squirrel species despite two others (siberian chipmunk [tamias sibiricus], and thirteen-lined ground squirrel [ictidomys ...201930775369
locomotor kinematics of tree squirrels (sciurus carolinensis) in free-ranging and laboratory environments: implications for primate locomotion and evolution.the grasping capabilities and gait kinematics characteristic of primates are often argued to be adaptations for safely moving on small terminal branches. the goal of this study was to identify whether eastern gray squirrels (sciurus carolinensis)-arboreal rodents that frequently move and forage on small branches, lack primate-like grasping and gait patterns, and arguably represent extant analogs of a stem primate ancestor-adjust gait kinematics to narrow and nonhorizontal branches. we studied lo ...201930369092
it's what's on the inside that counts: stress physiology and the bacterial microbiome of a wild urban mammal.the microbiome's capacity to shape the host phenotype and its mutability underlie theorization that the microbiome might facilitate host acclimation to rapid environmental change. however, when environmental change occurs, it is unclear whether resultant microbiome restructuring is proximately driven by this changing external environment or by the host's physiological response to this change. we leveraged urbanization to compare the ability of host environment (urban or forest) versus multi-scal ...201931640519
resource-area-dependence analysis: inferring animal resource needs from home-range and mapping data.an animal's home-range can be expected to encompass the resources it requires for surviving or reproducing. thus, animals inhabiting a heterogeneous landscape, where resource patches vary in size, shape and distribution, will naturally have home-ranges of varied sizes, so that each home-range encompasses a minimum required amount of a resource. home-range size can be estimated from telemetry data, and often key resources, or proxies for them such as the areas of important habitat types, can be m ...201830356319
widespread occurrence of squirrel adenovirus 1 in red and grey squirrels in scotland detected by a novel real-time pcr assay.the eurasian red squirrel (sciurus vulgaris) is distributed throughout large parts of europe and asia. however, its distribution in certain regions of europe is endangered by the invasive, non-native grey squirrel (sciurus carolinensis). adenoviruses were already described in squirrels in great britain almost two decades ago. in 2013, a squirrel adenovirus (sqadv-1) was additionally found in a red squirrel from germany, which suffered from acute diffuse catarrhal enteritis, and the complete geno ...201830237072
stress in biological invasions: introduced invasive grey squirrels increase physiological stress in native eurasian red squirrels.invasive alien species can cause extinction of native species through processes including predation, interspecific competition for resources or disease-mediated competition. increases in stress hormones in vertebrates may be associated with these processes and contribute to the decline in survival or reproduction of the native species. eurasian red squirrels (sciurus vulgaris) have gone extinct across much of the british isles and parts of northern italy following the introduction of north ameri ...201829790583
cortical projections to the superior colliculus in gray squirrels (sciurus carolinensis).the superior colliculus is an important midbrain structure involved with integrating information from varying sensory modalities and sending motor signals to produce orienting movements toward environmental stimuli. because of this role, the superior colliculus receives a multitude of sensory inputs from a wide variety of subcortical and cortical structures. proportionately, the superior colliculus of gray squirrels is among the largest in size of all studied mammals, suggesting the importance o ...201829450943
are tree squirrels involved in the circulation of flaviviruses in italy?west nile virus (wnv), usutu virus (usuv) and tick-borne encephalitis virus (tbev) are emerging zoonotic flaviviruses (family flaviviridae), which have circulated in europe in the past decade. a cross-sectional study was conducted to assess exposure to these antigenically related flaviviruses in eastern grey squirrels (sciurus carolinensis) in italy. seventeen out of 158 (10.8%; ci95% : 5.9-15.6) squirrels' sera tested through belisa had antibodies against flaviviruses. specific neutralizing ant ...201829635877
supplementing non-target taxa: bird feeding alters the local distribution of mammals.although the effects of bird feeding on avian species have been extensively examined, few studies evaluate the indirect effects of bird feeding on non-target taxa. bird seed could provide direct nourishment to several mammalian species (e.g., lagomorpha, rodentia, and cetartiodactyla), potentially altering their distribution and behavior with possible unintended consequences for some avian populations, particularly those not directly benefiting from the resource. to examine how bird feeders may ...201829509299
regulation of bone mineral density in the grey squirrel, sciurus carolinensis: bioavailability of calcium oxalate, and implications for bark stripping.the damage caused when grey squirrels strip the outer bark off trees and ingest the underlying phloem can result in reduced timber quality or tree death. this is extremely costly to the uk forestry industry and can alter woodland composition, hampering conservation efforts. the calcium hypothesis proposes that grey squirrels ingest phloem to ameliorate a seasonal calcium deficiency. calcium in the phloem predominantly takes the form of calcium oxalate (caox), however not all mammals can utilise ...201828603912
connections between the zona incerta and superior colliculus in the monkey and squirrel.the zona incerta contains gabaergic neurons that project to the superior colliculus in the cat and rat, suggesting that it plays a role in gaze changes. however, whether this incertal connection represents a general mammalian pattern remains to be determined. we used neuronal tracers to examine the zona incerta connections with the midbrain tectum in the gray squirrel and macaque monkey. collicular injections in both species revealed that most incertotectal neurons lay in the ventral layer, but ...201828852862
anophthalmia in a wild eastern gray squirrel (sciurus carolinensis).we describe bilateral true anophthalmia in a juvenile female eastern gray squirrel (sciurus carolinensis) with histologic confirmation that orbital contents lacked ocular tissues. additionally, the optic chiasm of the brain was absent and axon density in the optic tract adjacent to the lateral geniculate nucleus was reduced.201728753413
eastern gray squirrels are consistent shoppers of seed traits: insights from discrete choice experiments.seeds of many hardwood trees are dispersed by scatter-hoarding rodents, and this process is often mediated by the traits of seeds. although numerous studies have linked seed traits to seed preference by rodents, little is known about how rodents forage for seeds when multiple desirable and undesirable seed traits are available simultaneously. here, we adopt a novel method of designing choice experiments to study how eastern gray squirrels (sciurus carolinensis) select for 6 traits (caloric value ...201729168614
distribution and diversity of borrelia burgdorferi sensu lato group bacteria in sciurids of california.california has a remarkable diversity of squirrel and chipmunk species (sciurids), and five named and several unnamed genospecies in the borrelia burgdorferi sensu lato group (bbsl) of bacteria as well, many of which utilize sciurids as reservoirs. we investigated the prevalence, spatial distribution, and diversity of bbsl in sciurids of california by literature search, pcr of 585 ear tissue samples from 15 sciurid species prospectively collected across 19 california counties, and dna sequencing ...201728976820
native and introduced squirrels in italy host different cryptosporidium spp.the present study was undertaken to describe cryptosporidium spp. infection in tree squirrels from 17 locations in northern italy. a total of 357 squirrels were examined, including species native to europe (sciurus vulgaris; n=123), and species introduced from north america (sciurus carolinensis; n=162) and southeast asia (callosciurus erythraeus; n=72). faecal samples of all squirrels were examined for the presence of cryptosporidium infection by microscopy (flotation method) and pcr/sequence a ...201728992520
functional characterization and spatial clustering of visual cortical neurons in the predatory grasshopper mouse onychomys arenicola.mammalian neocortical circuits are functionally organized such that the selectivity of individual neurons systematically shifts across the cortical surface, forming a continuous map. maps of the sensory space exist in cortex, such as retinotopic maps in the visual system or tonotopic maps in the auditory system, but other functional response properties also may be similarly organized. for example, many carnivores and primates possess a map for orientation selectivity in primary visual cortex (v1 ...201727927787
deciphering the effects of disperser assemblages and seed mass on patterns of seed dispersal in a rodent community.the sizes of both seed dispersers and seeds are traits that are likely to interact to influence seed fate in many synzoochoric plant species. here, we examined whether members of a granivorous rodent community consisting of species of different body size vary in their effectiveness as seed dispersers, and how this relationship may be altered by seed size. we marked northern red oak (quercus rubra) acorns with plastic tags and placed them in size-selective rodent exclosures. the exclosures allowe ...201728488781
accessible areas in ecological niche comparisons of invasive species: recognized but still overlooked.understanding biological invasions is crucial for their control and prevention. specially, establishing whether invasive species operate within the constraint of conservative ecological niches, or if niche shifts occur at all commonly as part of the invasion process, is indispensable to identifying and anticipating potential areas of invasion. ecological niche modeling (enm) has been used to address such questions, but improvements and debate in study design, model evaluation, and methods are st ...201728450747
touch screen assays of behavioural flexibility and error characteristics in eastern grey squirrels (sciurus carolinensis).behavioural flexibility allows animals to adjust their behaviours according to changing environmental demands. such flexibility is frequently assessed by the discrimination-reversal learning task. we examined grey squirrels' behavioural flexibility, using a simultaneous colour discrimination-reversal learning task on a touch screen. squirrels were trained to select their non-preferred colour in the discrimination phase, and their preferred colour was rewarded in a subsequent reversal phase. we u ...201728130606
eradicating the grey squirrel sciurus carolinensis from urban areas: an innovative decision-making approach based on lessons learnt in italy.eradication of invasive alien species supports the recovery of native biodiversity. a new european union regulation introduces obligations to eradicate the most harmful invasive species. however, eradications of charismatic mammals may encounter strong opposition. considering the case study of the eastern grey squirrel (sciurus carolinensis gmelin, 1788) in central italy, we developed a structured decision-making technique based on a bayesian decision network model and explicitly considering the ...201727367228
parallelisms and contrasts in the diverse ecologies of the anaplasma phagocytophilum and borrelia burgdorferi complexes of bacteria in the far western united states.anaplasma phagocytophilum and borrelia burgdorferi are two tick-borne bacteria that cause disease in people and animals. for each of these bacteria, there is a complex of closely related genospecies and/or strains that are genetically distinct and have been shown through both observational and experimental studies to have different host tropisms. in this review we compare the known ecologies of these two bacterial complexes in the far western usa and find remarkable similarities, which will help ...201629056734
insights on the host associations and geographic distribution of hymenolepis folkertsi (cestoda: hymenolepididae) among rodents across temperate latitudes of north america.synoptic data and an understanding of helminth parasite diversity among diverse rodent assemblages across temperate latitudes of north america remain remarkably incomplete. renewed attention to comprehensive survey and inventory to establish the structure of biodiverse faunas is essential in providing indicators and proxies for identifying the outcomes of accelerating change linked to climate warming and anthropogenic forcing. subsequent to the description of hymenolepis folkertsi in the oldfiel ...201627630100
pelvic sexual dimorphism among species monomorphic in body size: relationship to relative newborn body mass.females have larger pelves than males among eutherians to mitigate obstetrical difficulty. this study addresses 3 issues concerning pelvic sexual dimorphism using 8 species that are sexually monomorphic in nonpelvic size: aotus azarae , castor canadensis , dasypus novemcinctus , hylobates lar , saguinus geoffroyi , sciurus carolinensis , sylvilagus floridanus , and urocyon cinereoargenteus . using published data to compute the index of relative newborn body mass (rnbm = [newborn body mass/adult ...201630302031
total alopecia in a grey squirrel (sciurus carolinensis). 20164810214
diversity and host specificity of coccidia (apicomplexa: eimeriidae) in native and introduced squirrel species.introduction of alien species into new areas can have detrimental effects on native ecosystems and impact the native species. the present study aims to identify coccidia infecting native and introduced squirrels in italy, to gain insight into possible transmission patterns and role of monoxenous coccidia in mediating the competition between alien and native hosts. we collected 540 faecal samples of native red squirrels, sciurus vulgaris, invasive alien grey squirrels, s. carolinensis, and introd ...201627268408
no safety in the trees: local and species-level adaptation of an arboreal squirrel to the venom of sympatric rattlesnakes.within some species, squirrels respond to variable selection from venomous snake predators by showing population-level variation in resistance, while between species, some rattlesnakes possess venom that is more effective at overcoming venom resistance in different species of squirrels. a functional evaluation of resistance variation to venom within and between species of squirrels and snakes can link resistance variation to its evolutionary causes across these different evolutionary scales. to ...201627158112
data from camera surveys identifying co-occurrence and occupancy linkages between fishers (pekania pennanti), rodent prey, mesocarnivores, and larger predators in mixed-conifer forests.these data provide additional information relevant to the frequency of fisher detections by camera traps, and single-season occupancy and local persistence of fishers in small patches of forest habitats detailed elsewhere, "landscape fuel reduction, forest fire, and biophysical linkages to local habitat use and local persistence of fishers (pekania pennanti) in sierra nevada mixed-conifer forests" [10]. the data provides insight on camera trap detections of 3 fisher predators (bobcat [lynx rufus ...201626937448
quantifying dilution and amplification in a community of hosts for tick-borne pathogens.recent controversy over whether biodiversity reduces disease risk (dilution effect) has focused on the ecology of lyme disease, a tick-borne zoonosis. a criticism of the dilution effect is that increasing host species richness might amplify disease risk, assuming that total host abundance, and therefore feeding opportunities for ticks, increase with species richness. in contrast, a dilution effect is expected when poor quality hosts for ticks and pathogens (dilution hosts) divert tick blood meal ...201627209790
comparative morphology and histology of the nasal fossa in four mammals: gray squirrel, bobcat, coyote, and white-tailed deer.although the anatomy of the nasal fossa is broadly similar among terrestrial mammals, differences are evident in the intricacies of nasal turbinal architecture, which varies from simple scroll-like to complex branching forms, and in the extent of nonsensory and olfactory epithelium covering the turbinals. in this study, detailed morphological and immunohistochemical examinations and quantitative measurements of the turbinals and epithelial lining of the nasal fossa were conducted in an array of ...201627090617
biodiversity threats from outside to inside: effects of alien grey squirrel (sciurus carolinensis) on helminth community of native red squirrel (sciurus vulgaris).biological invasions are among the major causes of biodiversity loss worldwide, and parasites carried or acquired by invaders may represent an added threat to native species. we compared gastrointestinal helminth communities of native eurasian red squirrels (sciurus vulgaris) in the presence and absence of introduced eastern grey squirrels (sciurus carolinensis) to detect alterations induced by the alien species. in particular, we investigated whether spillover of a north american nematode stron ...201525877391
north american tree squirrels and ground squirrels with overlapping ranges host different cryptosporidium species and genotypes.wildlife-associated cryptosporidium are an emerging cause of cryptosporidiosis in humans. the present study was undertaken to determine the extent to which north american tree squirrels and ground squirrels host zoonotic cryptosporidium species and genotypes. fragments of the cryptosporidium 18s rrna and actin genes were amplified and sequenced from fecal samples obtained from three tree squirrel and three ground squirrel species. in tree squirrels, cryptosporidium was identified in 40.5% (17/42 ...201526437239
an invasive mammal (the gray squirrel, sciurus carolinensis) commonly hosts diverse and atypical genotypes of the zoonotic pathogen borrelia burgdorferi sensu lato.invasive vertebrate species can act as hosts for endemic pathogens and may alter pathogen community composition and dynamics. for the zoonotic pathogen borrelia burgdorferi sensu lato, the agent of lyme borreliosis, recent work shows invasive rodent species can be of high epidemiological importance and may support host-specific strains. this study examined the role of gray squirrels (sciurus carolinensis) (n = 679), an invasive species in the united kingdom, as b. burgdorferi sensu lato hosts. w ...201525888168
association between body size and reservoir competence of mammals bearing borrelia burgdorferi at an endemic site in the northeastern united states.the reservoirs for the lyme disease agent, borrelia burgdorferi, are dominated by several different small to medium sized mammals in eastern north america.201526024881
evidence for west nile virus spillover into the squirrel population in atlanta, georgia.in the united states, spillover of west nile virus (wnv) into wild mammal populations has been reported since the introduction of the virus into the new world in 1999. eastern gray squirrels (sciurus carolinensis) exhibit a high seroprevalence for wnv in urban settings where high virus circulation and human spillover have been reported. in atlanta, georgia, human cases of wnv are uncommon despite high infection rates in birds and mosquitoes. in this study, we evaluated wnv exposure of eastern gr ...201525988439
radiation therapy of a presumptive urethral transitional cell carcinoma in an eastern gray squirrel (sciurus carolinensis).an adult female eastern gray squirrel (sciurus carolinensis), with a previous history of primary renal transitional cell carcinoma treated by nephrectomy, was diagnosed with a metastatic urethral transitional cell carcinoma (tcc) utilizing the veterinary bladder tumor antigen test in combination with other noninvasive diagnostic tests. the squirrel was treated with piroxicam and external beam radiation therapy given in 18 treatments over 30 days to achieve a total of 54 gray. mild to moderate si ...201526667551
serial reversal learning in gray squirrels: learning efficiency as a function of learning and change of tactics.learning allows individuals to adapt their behaviors flexibly to a changing environment. when the same change recurs repeatedly, acquiring relevant tactics may increase learning efficiency. we examined this relationship, along with the effects of proactive interference and other interference information, in a serial spatial reversal task with 5 gray squirrels (sciurus carolinensis). squirrels completed an acquisition and 11 reversal phases with a poke box in which 2 of 4 possible reward location ...201526147602
segregating the effects of seed traits and common ancestry of hardwood trees on eastern gray squirrel foraging decisions.the evolution of specific seed traits in scatter-hoarded tree species often has been attributed to granivore foraging behavior. however, the degree to which foraging investments and seed traits correlate with phylogenetic relationships among trees remains unexplored. we presented seeds of 23 different hardwood tree species (families betulaceae, fagaceae, juglandaceae) to eastern gray squirrels (sciurus carolinensis), and measured the time and distance travelled by squirrels that consumed or cach ...201526110828
behavioural responses of eastern grey squirrels, sciurus carolinensis, to cues of risk while foraging.previous studies have shown that eastern grey squirrels modify their behaviour while foraging to offset risks of social and predatory costs, but none have simultaneously compared whether such modifications are performed at a cost to foraging. the present study directly compares how grey squirrels respond to cues of these risks while foraging. we simulated social risk and predatory risk using acoustic playbacks of stimuli that grey squirrels might be exposed to at a foraging patch: calls of consp ...201525957953
scatterhoarding rodents favor higher predation risks for cache sites: the potential for predators to influence the seed dispersal process.scatterhoarding rodents often place caches in the open where pilferage rates are reduced, suggesting that they tradeoff higher risks of predation for more secure cache sites. we tested this hypothesis in two study systems by measuring predation risks inferred from measures of giving-up densities (guds) at known cache sites and other sites for comparison. rodent guds were measured with small trays containing 3 l of fine sand mixed with sunflower seeds. in the first experiment, we relied on a 2-ye ...201525827710
subtyping novel zoonotic pathogen cryptosporidium chipmunk genotype i.cryptosporidium chipmunk genotype i is an emerging zoonotic pathogen in humans. the lack of subtyping tools makes it impossible to determine the role of zoonotic transmission in epidemiology. to identify potential subtyping markers, we sequenced the genome of a human chipmunk genotype i isolate. altogether, 9,509,783 bp of assembled sequences in 853 contigs were obtained, with an n50 of 117,886 bp and >200-fold coverage. based on the whole-genome sequence data, two genetic markers encoding the 6 ...201525762767
weak orientation and direction selectivity in lateral geniculate nucleus representing central vision in the gray squirrel sciurus carolinensis.classic studies of lateral geniculate nucleus (lgn) and visual cortex (v1) in carnivores and primates have found that a majority of neurons in lgn exhibit a center-surround organization, while v1 neurons exhibit strong orientation selectivity and, in many species, direction selectivity. recent work in the mouse and the monkey has discovered previously unknown classes of orientation- and direction-selective neurons in lgn. furthermore, some recent studies in the mouse report that many lgn cells e ...201525717157
european red squirrel population dynamics driven by squirrelpox at a gray squirrel invasion interface.infectious disease introduced by non-native species is increasingly cited as a facilitator of native population declines, but direct evidence may be lacking due to inadequate population and disease prevalence data surrounding an outbreak. previous indirect evidence and theoretical models support squirrelpox virus (sqpv) as being potentially involved in the decline of red squirrels (sciurus vulgaris) following the introduction of the non-native gray squirrel (sciurus carolinensis) to the united k ...201425614793
relative roles of grey squirrels, supplementary feeding, and habitat in shaping urban bird assemblages.non-native species are frequently considered to influence urban assemblages. the grey squirrel sciurus carolinensis is one such species that is widespread in the uk and is starting to spread across europe; it predates birds' nests and can compete with birds for supplementary food. using distance sampling across the urbanisation intensity gradient in sheffield (uk) we test whether urban grey squirrels influence avian species richness and density through nest predation and competition for suppleme ...201425338062
novel host-related virulence factors are encoded by squirrelpox virus, the main causative agent of epidemic disease in red squirrels in the uk.squirrelpox virus (sqpv) shows little evidence for morbidity or mortality in north american grey squirrels (sciurus carolinensis), in which the virus is endemic. however, more recently the virus has emerged to cause epidemics with high mortality in eurasian red squirrels (s. vulgaris) in great britain, which are now threatened. here we report the genome sequence of sqpv. comparison with other poxviridae revealed a core set of poxvirus genes, the phylogeny of which showed sqpv to be in a new chor ...201424983354
agouti signalling protein is an inverse agonist to the wildtype and agonist to the melanic variant of the melanocortin-1 receptor in the grey squirrel (sciurus carolinensis).the melanocortin-1 receptor (mc1r) is a key regulator of mammalian pigmentation. melanism in the grey squirrel is associated with an eight amino acid deletion in the mutant melanocortin-1 receptor with 24 base pair deletion (mc1rδ24) variant. we demonstrate that the mc1rδ24 exhibits a higher basal activity than the wildtype mc1r (mc1r-wt). we demonstrate that agouti signalling protein (asip) is an inverse agonist to the mc1r-wt but is an agonist to the mc1rδ24. we conclude that the deletion in t ...201424879893
melanocortin 1 receptor (mc1r) gene sequence variation and melanism in the gray (sciurus carolinensis), fox (sciurus niger), and red (sciurus vulgaris) squirrel.sequence variations in the melanocortin 1 receptor (mc1r) gene are associated with melanism in many different species of mammals, birds, and reptiles. the gray squirrel (sciurus carolinensis), found in the british isles, was introduced from north america in the late 19th century. melanism in the british gray squirrel is associated with a 24-bp deletion in the mc1r. to investigate the origin of this mutation, we sequenced the mc1r of 95 individuals including 44 melanic gray squirrels from both th ...201424534267
flotac for diagnosis of endo-parasites in pet squirrels in southern italy.the present study investigated the occurrence of endoparasites in pet squirrels in southern italy. fresh fecal samples were collected from 50 asymptomatic pet squirrels belonging to five different species (callosciurus finlaysonii, n=6, c. prevosti, n=6; tamias striatus, n=26, t. sibiricus, n=10; sciurus carolinensis, n=2) housed both in pet shops and/or in private residences. all fecal samples were processed using the flotac pellet technique to identify and count helminth eggs/larvae and protoz ...201424389007
an experimental study of vertebrate scavenging behavior in a northwest european woodland context.vertebrate scavengers can modify surface deposited human remains which can hinder forensic investigations. the effects of such scavenging vary between species and regions. published research into the effects of the scavenging of human remains is dominated by work from north america with few studies covering northwestern europe. forensic scientists, investigators, and police search officers in northwestern europe are often left questioning on a basic level as to which scavengers are active and ho ...201424611615
squirrelpox virus: assessing prevalence, transmission and environmental degradation.red squirrels (sciurus vulgaris) declined in great britain and ireland during the last century, due to habitat loss and the introduction of grey squirrels (sciurus carolinensis), which competitively exclude the red squirrel and act as a reservoir for squirrelpox virus (sqpv). the disease is generally fatal to red squirrels and their ecological replacement by grey squirrels is up to 25 times faster where the virus is present. we aimed to determine: (1) the seropositivity and prevalence of sqpv dn ...201424586845
effects of parasitism and morphology on squirrelpox virus seroprevalence in grey squirrels (sciurus carolinensis).invasive species have been cited as major causes of population extinctions in several animal and plant classes worldwide. the north american grey squirrel (sciurus carolinensis) has a major detrimental effect on native red squirrel (sciurus vulgaris) populations across britain and ireland, in part because it can be a reservoir host for the deadly squirrelpox virus (sqpv). whilst various researchers have investigated the epizootiology of sqpv disease in grey squirrels and have modelled the conseq ...201424416155
macroparasite fauna of alien grey squirrels (sciurus carolinensis): composition, variability and implications for native species.introduced hosts populations may benefit of an "enemy release" through impoverishment of parasite communities made of both few imported species and few acquired local ones. moreover, closely related competing native hosts can be affected by acquiring introduced taxa (spillover) and by increased transmission risk of native parasites (spillback). we determined the macroparasite fauna of invasive grey squirrels (sciurus carolinensis) in italy to detect any diversity loss, introduction of novel para ...201424505348
francisella tularensis infection without lesions in gray tree squirrels (sciurus griseus): a diagnostic challenge.fifteen cases of francisella tularensis infection (tularemia) were identified in western gray (sciurus griseus) and eastern gray (sciurus carolinensis) squirrels submitted to the washington animal disease diagnostic laboratory between 2008 and 2011. all of the squirrels originated in washington state, a geographical area with endemic tularemia in wildlife. nine of the 15 squirrels with f. tularensis infection had gross (2/15) or microscopic (9/15) multifocal necrotizing lesions in the spleen, li ...201424557750
ljungan virus and an adenovirus in italian squirrel populations.we report ljungan virus infection in eurasian red squirrels (sciurus vulgaris) for the first time, and extend the known distribution of adenoviruses in both native red squirrels and alien gray squirrels (sciurus carolinensis) to southern europe.201424484493
faecal egg counts from field experiment reveal density dependence in helminth fecundity: strongyloides robustus infecting grey squirrels (sciurus carolinensis).investigation of endo-macroparasite infections in living animals relies mostly on indirect methods aimed to detect parasite eggs in hosts' faeces. however, faecal flotation does not provide quantitative information on parasite loads, whereas faecal egg count (fec) techniques may not give reliable estimates of parasite intensity, since egg production may be affected by density-dependent effects on helminth fecundity. we addressed this issue using eastern grey squirrels (sciurus carolinensis) and ...201424974093
preliminary characterisation of pentlands paramyxovirus-1, -2 and -3, three new paramyxoviruses of rodents.a paramyxovirus was discovered by chance during the primary culture of grey squirrel (sciurus carolinensis) kidney cells from the uk. amplification, sequencing and phylogenetic analysis of part of the genome encoding a region of the rna polymerase (l gene) confirmed that the virus was a member of the paramyxovirinae subfamily, but that it did not partition with any of the currently recognised paramyxovirus genera and instead segregated with the unclassified rodent viruses, j-virus, beilong virus ...201424613080
an experimental test of competition among mice, chipmunks, and squirrels in deciduous forest fragments.mixed hardwood forests of the northeast united states support a guild of granivorous/omnivorous rodents including gray squirrels (sciurus carolinensis), eastern chipmunks (tamias striatus), and white-footed mice (peromyscus leucopus). these species coincide geographically, co-occur locally, and consume similar food resources. despite their idiosyncratic responses to landscape and patch variables, patch occupancy models suggest that competition may influence their respective distributions and abu ...201323824654
pathologic findings in western gray squirrels (sciurus griseus) from a notoedric mange epidemic in the san bernardino mountains, california.notoedric mange, caused by the contagious, burrowing mite notoedres centrifera, has been associated with several large-scale population declines of western gray squirrels (sciurus griseus) and has been a significant obstacle to population recovery in washington state where the species is listed as threatened. in 2009, residents and wildlife rehabilitators in the isolated san bernardino mountains of southern california reported a dramatic die-off of western gray squirrels, in what had been a prev ...201324533345
using gps telemetry to validate least-cost modeling of gray squirrel (sciurus carolinensis) movement within a fragmented landscape.in britain, the population of native red squirrels sciurus vulgaris has suffered population declines and local extinctions. interspecific resource competition and disease spread by the invasive gray squirrel sciurus carolinensis are the main factors behind the decline. gray squirrels have adapted to the british landscape so efficiently that they are widely distributed. knowledge on how gray squirrels are using the landscape matrix and being able to predict their movements will aid management. th ...201323919175
the use of climatic niches in screening procedures for introduced species to evaluate risk of spread: a case with the american eastern grey squirrel.species introduction represents one of the most serious threats for biodiversity. the realized climatic niche of an invasive species can be used to predict its potential distribution in new areas, providing a basis for screening procedures in the compilation of black and white lists to prevent new introductions. we tested this assertion by modeling the realized climatic niche of the eastern grey squirrel sciurus carolinensis. maxent was used to develop three models: one considering only records ...201323843957
changes in the impact and control of an invasive alien: the grey squirrel (sciurus carolinensis) in great britain, as determined from regional surveys.the grey squirrel, sciurus carolinensis gmelin, was introduced into sites in england, wales, scotland and ireland from the united states and canada between 1876 and 1929. soon after its introduction there were reports of damage to trees by seasonal bark stripping activity. surveys in state and private forests since 1954 have monitored their distribution and impacts. two surveys also gathered information on control efforts used to minimise damage. grey squirrel population range has expanded signi ...201323417829
the use of diazacon™ to limit fertility by reducing serum cholesterol in female grey squirrels, sciurus carolinensis.the grey squirrel, sciurus carolinensis gmelin, is an invasive alien species introduced into great britain in the late nineteenth century and into northern italy during the early twentieth century. grey squirrels have displaced the native european red squirrel, sciurus vulgaris l., throughout much of great britain and have a significant impact on trees and woodlands through bark-stripping activity. in britain, eradication is no longer an option at a regional scale, but fertility control offers a ...201322791583
molecular compartmentalization of lateral geniculate nucleus in the gray squirrel (sciurus carolinensis).previous research has suggested that the three physiologically defined relay cell-types in mammalian lateral geniculate nucleus (lgn)-called parvocellular (p), magnocellular (m), and koniocellular (k) cells in primates and x, y, and w cells in other mammals-each express a unique combination of cell-type marker proteins. however, some of the relationships among physiological classification and protein expression found in primates, prosimians, and tree shrews do not apply to carnivores and murid r ...201222514523
scale-dependent neighborhood effects: shared doom and associational refuge.a resource's susceptibility to predation may be influenced by its own palatability and the palatability of its neighbors. we tested for effects of plant chemical defenses on seed survival by manipulating the frequency of palatable and less palatable sunflower seeds in food patches subject to harvest by fox squirrels (sciurus niger) and gray squirrels (sciurus carolinensis). we varied resource distributions at three scales: among stations (aggregates of patches ca. 50 m apart), among patches imme ...201221987268
development of a mitochondrial 12s rdna analysis for distinguishing sciuridae species with potential to transmit ehrlichia and borrelia species to feeding amblyomma americanum (acari: ixodidae).unique oligonucleotide probes were synthesized to distinguish among closely related vertebrate mitochondrial rdna sequences present in residual bloodmeals in emergent amblyomma americanum (l.) (acari: ixodidae) nymph life-stage ticks. use of these probes enabled the identification of the eastern gray squirrel as an important bloodmeal source in nymphs harboring ehrlichia and borrelia species. these results were confirmed by identifying these same bacterial genera in eastern gray squirrel tissues ...201222679888
the nature and properties of squirrel lens yellow pigment.the low molecular weight yellow pigment in the gray squirrel lens is confirmed to be n-acetyl-3-oh-kynurenine (nak). this conclusion is based upon the results of studies of the compound's optical, chromatographic, and mass spectroscopic properties. the original tentative identification of this compound was reported by van heyningen (1971, 1973). the pigment is distributed equivalently throughout the lens. its absorbance increases with age, but the increase is related to the growth of the lens an ...20113215294
epizootiology and pathologic findings associated with a newly described adenovirus in the red squirrel, sciurus vulgaris.an infectious disease caused by squirrelpox virus has contributed to the decline of red squirrels, sciurus vulgaris, in the british isles. because of the heightened disease surveillance activity in red squirrels, adenovirus infection with associated mortality has been detected. adenoviral disease is described in other rodent species usually associated with stressors. here we 1) describe the pathologic findings in red squirrels found dead with adenoviral infection and gastrointestinal disease, an ...201121441198
novel hepatozoon in vertebrates from the southern united states.abstract novel hepatozoon spp. sequences collected from previously unrecognized vertebrate hosts in north america were compared with documented hepatozoon 18s rrna sequences in an effort to examine phylogenetic relationships between the different hepatozoon organisms found cycling in nature. an approximately 500 base pair fragment of 18s rdna common to hepatozoon spp. and some other apicomplexans was amplified and sequenced from the tissues or blood of 16 vertebrate host species from the souther ...201121506825
The Functional Organization and Cortical Connections of Motor Cortex in Squirrels.Despite extraordinary diversity in the rodent order, studies of motor cortex have been limited to only 2 species, rats and mice. Here, we examine the topographic organization of motor cortex in the Eastern gray squirrel (Sciurus carolinensis) and cortical connections of motor cortex in the California ground squirrel (Spermophilus beecheyi). We distinguish a primary motor area, M1, based on intracortical microstimulation (ICMS), myeloarchitecture, and patterns of connectivity. A sensorimotor area ...201122021916
the narrow niche hypothesis: gray squirrels shed new light on primate origins.current hypotheses for primate origins propose that nails and primate-like grasping hands and feet were important early adaptations for feeding in fine branches. comparative research in this area has focused on instances of convergence in extant animals, showing that species with primate-like morphology feed predominantly from terminal branches. little has been done to test whether animals without primate-like morphology engage in similar behavior. we tested the fine-branch niche hypothesis for ...201121404237
superior colliculus connections with visual thalamus in gray squirrels (sciurus carolinensis): evidence for four subdivisions within the pulvinar complex.as diurnal rodents with a well-developed visual system, squirrels provide a useful comparison of visual system organization with other highly visual mammals such as tree shrews and primates. here, we describe the projection pattern of gray squirrel superior colliculus (sc) with the large and well-differentiated pulvinar complex. our anatomical results support the conclusion that the pulvinar complex of squirrels consists of four distinct nuclei. the caudal (c) nucleus, distinct in cytochrome oxi ...201121344403
immunocontraception in eastern gray squirrels (sciurus carolinensis): morphologic changes in reproductive organs.eastern gray squirrels (egs) (sciurus carolinensis) damage trees through bark stripping or gnawing due to territorial marking or agonistic gnawing behavior in concert with higher densities. this study was conducted to determine the effects of a contraceptive vaccine on egs and its reproductive organ histology. free-ranging urban egs were vaccinated with the immunocontraceptive gonacon. all egs were > or = 6 mo of age as determined by a combination of pelage characteristics and body weights. the ...201122204069
feeding of grey squirrels (sciurus carolinensis) with the contraceptive agent diazacon™: effect on cholesterol, hematology, and blood chemistry.grey squirrels (sciurus carolinensis) are an invasive species in britain and italy. they have replaced native red squirrels (sciurus vulgaris) throughout most of britain, and cause damage to trees. currently, lethal control is used to manage grey squirrel populations in britain, but nonlethal methods might be more acceptable to the public. one such method is contraception with 20,25-diazacholesterol dihydrochloride (diazacon™). diazacon™ inhibits the conversion of desmosterol to cholesterol, res ...201122182332
grey squirrels (sciurus carolinensis) show a feature-negative effect specific to social learning.previous laboratory studies on social learning suggest that some animals can learn more readily if they first observe a conspecific demonstrator perform the task unsuccessfully and so fail to obtain a food reward than if they observe a successful demonstrator that obtains the food. this effect may indicate a difference in how easily animals are able to associate different outcomes with the conspecific or could simply be the result of having food present in only some of the demonstrations. to inv ...201019588175
comparative studies of diurnal and nocturnal rodents: differences in lifestyle result in alterations in cortical field size and number.in this study we examine and describe the neuroanatomical organization of sensory cortex in four rodents: laboratory norway rats (long evans; rattus norvegicus), wild-caught norway rats (rattus norvegicus), wild-caught california ground squirrels (spermophilus beecheyi), and wild-caught eastern gray squirrels (sciurus carolinensis). specifically, we examined the myeloarchitecture and cytochrome oxidase reactivity for several well-identified areas in visual cortex (areas 17, 18, and 19), somatose ...201020886618
distribution of the lyme disease spirochete borrelia burgdorferi in naturally and experimentally infected western gray squirrels (sciurus griseus).the dynamics of borrelia burgdorferi infections within its natural hosts are poorly understood. we necropsied four wild-caught western gray squirrels (sciurus griseus) that were acquired during a previous study that evaluated the reservoir competence of this rodent for the lyme disease spirochete. one animal was infected experimentally, whereas the others were infected in the wild before capture. to investigate dissemination of b. burgdorferi and concurrent histopathologic lesions in different t ...201020017717
divergent patterns of breakpoint reuse in muroid rodents.multiple genome rearrangement (mgr) analysis was used to define the trajectory and pattern of chromosome rearrangement within muroid rodents. mgr was applied using 107 chromosome homologies between mus, rattus, peromyscus, the muroid sister taxon cricetulus griseus, and sciurus carolinensis as a non-muroidea outgroup, with specific attention paid to breakpoint reuse and centromere evolution. this analysis revealed a high level of chromosome breakpoint conservation between rattus and peromyscus a ...201020033182
coinfection of western gray squirrel (sciurus griseus) and other sciurid rodents with borrelia burgdorferi sensu stricto and anaplasma phagocytophilum in california.overlapping geographic distributions of tick-borne disease agents utilizing the same tick vectors are common, and coinfection of humans, domestic animals, wildlife, and ticks with both borrelia burgdorferi and anaplasma phagocytophilum has been frequently reported. this study was undertaken in order to evaluate the prevalence of both b. burgdorferi sensu stricto (hereinafter referred to as b. burgdorferi) and a. phagocytophilum in several species of sciurid rodents from northern california, usa. ...201020090047
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