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The native western gray squirrel (Sciurus griseus) and introduced fox squirrel (Sciurus niger) can be found occupying various locales in southern California (USA) either coexisting or living separa...

This study comparatively investigated gross features and osteometric variables in scapula of three rodents: tree squirrel (Funisciurus anerythrus ), house (Rattus Rattus ) and Wistar rats. A total of thirty three animals (11 per rodent species) were used for the study. The rodents were anaesthetized using ketamine and xylazine combination (80 mg/kg: 10 mg/kg body weight), sacrificed and processed for scapular bone extraction by burying method. Grossly, the scapular bones are flattened in all the rodents and have various shapes; semicircular in squirrel and roughly triangular in both Rattus rattus and Wistar rats. The scapula of the squirrel bears a hook-like acromion process and a distinct subscapular spine. Osteometric variables; scapular width and length of scapular neck are significantly reduced (p

This study examined the differences in cranial morphology of tree squirrel species (Heliosciuru srufobranchium) from four different locations in rainforest part of Nigeria. Locally fabricated live traps made of wire-mesh and steel were used to capture the squirrels. Trapped tree squirrels were immediately transferred to the laboratory in cages, where they were euthanized by placement in a bell-jar containing chloroform-soaked cotton wool. Individuals from two locations (33 from Ile Ife and 49 from Emure Ekiti) were then preliminarily identified to the generic level, using an identification key. Eighty-two (82) skulls were prepared from them, using Long Island Natural History Museum Guide. The sexes of the specimens were determined by visual inspection of the external genitalia. Twenty-seven (27) cranial and six (6) external body parameters were measured using digital Vernier caliper. One-way analysis of variance at p

In this chapter, enhanced tree squirrel search optimization algorithm (ETSS), enhanced salp swarm algorithm (ESS), and swim bladder operation-based shark algorithm (SBS) have been applied to solve the power loss reduction problem. Enhanced tree squirrel search optimization algorithm (ETSS) utilizes the jumping exploration method and progressive exploration technique—both possess winter search strategy—in order to preserve the population diversity and to perk up the convergence speed. A new-fangled winter exploration strategy is implemented in the jumping exploration technique. In enhanced salp swarm algorithm (ESS) an inertia weight ω∈ [0, 1] is applied, which picks up the pace of convergence during the period of exploration. Then swim bladder operation-based shark algorithm (SBS) is proposed to solve the problem. Based on contracting and expanding actions of the swim bladder in shark, SBS algorithm has been modelled.

Se conocen seis especies de chichimocos Neotamias spp. en México y para la Sierra Madre Oriental únicamente a Neotamias solivagus por ejemplares de dos localidades en las montañas del sureste del estado de Coahuila. Ningún registro de este sciúrido se ha publicado desde 1956. No se tiene registro de chichimocos del estado de Nuevo León. El 4 de Julio de 2020, en una caminata fotográfica de vida silvestre en la montaña Cerro El Escorpión, municipio de Santa Catarina, Nuevo León, se fotografió un pequeño roedor con bandas en la espalda típicas de un chichimoco en las ramas de un árbol caído. Una semana después, para mejor identificación de este roedor, se colocó una cámara trampa por dos semanas en el sitio. El roedor fotografiado con la cámara trampa presenta el mismo patrón de coloración al fotografiado durante la caminata, líneas dorsales blancas y negras intercaladas. Debido a su coloración típica como un chichimoco y a su distribución potencial es identificado como Neotamias solivagus; se registró también la presencia de la ardilla arbórea Sciurus alleni. Se identificaron a las especies arbóreas de la zona. Esta evidencia es el primer registro de un chichimoco en el estado de Nuevo León, dentro del Parque Nacional Cumbres de Monterrey en un bosque mixto de coníferas, así como el registro de menor altitud para la especie. Se documenta la coexistencia de N. solivagus con la ardilla arbórea S. alleni y se comenta la categoría de conservación de este chichimoco.

Microbiota inhabiting the gastrointestinal (GI) tract of animals has important impacts on many host physiological processes. Although host diet is a major factor influencing the composition of the gut micro‐organismal community, few comparative studies have considered how differences in diet influence community composition across the length of the GI tract. We used 16S sequencing to compare the microbiota along the length of the GI tract in Abert's (Sciurus aberti) and fox squirrels (S. niger) living in the same habitat. While fox squirrels are generalist omnivores, the diet of Abert's squirrels is unusually high in plant fiber, particularly in winter when they extensively consume fiber‐rich inner bark of ponderosa pine (Pinus ponderosa). Consistent with previous studies, microbiota of the upper GI tract of both species consisted primarily of facultative anaerobes and was less diverse than that of the lower GI tract, which included mainly obligate anaerobes. While we found relatively little differentiation between the species in the microbiota of the upper GI tract, the community composition of the lower GI tract was clearly delineated. Notably, the Abert's squirrel lower GI community was more stable in composition and enriched for microbes that play a role in the degradation of plant fiber. In contrast, overall microbial diversity was higher in fox squirrels. We hypothesize that these disparities reflect differences in diet quality and diet breadth between the species.

Individual variation in behaviour can contribute to the heterogeneous distribution of parasites among hosts for example by affecting the probability of encountering infective stages (larvae). Here, we investigated the relationship between host boldness/exploration tendency and gastro-intestinal helminth infection in invasive Eastern grey squirrels (Sciurus carolinensis). We used direct helminth counts, data rarely available in host-parasite studies that often used less reliable indirect estimates of infection. We predicted that bolder animals with a strong exploration tendency will have higher parasite load than shy, less explorative hosts. We examined two parameters of parasite infection: infection status and intensity of infection. Individual personality of 207 grey squirrels was assessed by capture-mark-recapture (CMR), calculating the trappability and trap diversity indices as estimates of boldness and exploration, respectively. Since both indices were strongly correlated, we used PCA to derive a single score (first component) which had a high value for bold, exploring animals. At the end of the study, 77 individuals were euthanized and gastro-intestinal helminths were identified and counted. Overall 73% of grey squirrels were infected by Strongyloides robustus with the intensity of infection varying from 1 to 86 worms (mean ± SE = 10.7 ± 2.1 helminths per host). We found that bolder, more explorative animals were more likely to be infected by S. robustus. However, host personality was not related to parasite intensity, which was instead positively associated with host body mass. Our results confirm that differences in personality-related host behaviour can influence the distribution of infections within host populations and stimulate further questions on whether such personality-parasite relationships may affect the invasion process.

Acoustic signals are one of the reproductive isolation mechanisms that can be a driving force for speciation. Evidence that geographic variation in mating calls can cause reproductive isolation is abundant for birds and frogs, but not for mammals. In the Callosciurus genus of tree squirrels distributed in Southeast Asia, males emit mating calls to attract females and the sound properties are known to be distinctly different among coexisting congeneric species. We investigated whether mating calls emitted by males differ between ten populations of the widely distributed C. erythraeus/C. finlaysonii complex. Based on the acoustic properties, the populations were divided into four groups (South Vietnam, Taiwan, eastern China, and western areas including Thailand and western China), which resulted in a high discrimination rate of 94.7% by a discriminant function analysis. A playback experiment was also conducted to determine whether the mating calls from different localities were as effective in attracting conspecific individuals as those in the same locality. In Kanagawa, Japan, where squirrels were introduced from Taiwan in the 1950s, squirrels responded more frequently to the playback sounds recorded in Taiwan compared to those recorded in Thailand. In addition, the response of squirrels decreased with an increase in the difference in acoustic characteristics compared to that from the original habitat. These results suggest that local differences in acoustic characteristics could be one of the mechanisms that promote reproductive isolation of geographically distant populations of Callosciurus. Acoustic signals are one of the reproductive isolation mechanisms that can be a driving force for speciation. The tree squirrel genus Callosciurus (Sciuridae) is widely distributed in Southeast Asia and is one of the few suitable mammals for testing the premating isolation mechanism using acoustic signals. The mating calls of the C. erythraeus/C. finlaysonii complex were divided into four geographical groups (Taiwan, Vietnam, eastern China, and Thailand) by a discriminant function analysis. Playback experiments revealed that the squirrels responded more frequently to the sounds of their own group compared to those of other groups. In addition, the response of the squirrels decreased with an increase in the difference in acoustic characteristics compared to that from the original habitat. Local differences in acoustic characteristics could be one of the mechanisms that promote reproductive isolation of geographically distant populations of Callosciurus.

The eastern grey squirrel (Sciurus carolinensis) is a North American tree squirrel species which has been introduced to several countries outside its native range. We made use of squirrels culled in Italy within control activities to establish hematological reference intervals for this invasive species, with the aim to broaden the current knowledge about its physiology. Blood from 104 individuals was analysed through a laser analyser. Manual leukocyte differential counts on blood films from a subset of 77 animals were used for validation of the automated counts, resulting in a fairly good agreement between the two methods for all variables excluding monocytes. Reference intervals and the 90% confidence interval of their limits were estimated for 19 hematological variables, partitioning by sex when statistically significant differences were detected. For most variables, our results were comparable with the few data available on the grey squirrel and on related species. An exception was represented by the hematocrit and mean corpuscular volume which were higher than values reported by other authors, and by the mean corpuscular hemoglobin concentration, which was instead lower. This study gathered valuable reference information for studies aimed at disclosing the mechanisms underlying grey squirrels’ invasiveness and for future research on tree squirrels’ physiology.

Background 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”). Results We show that convergent evolution of melanism has arisen by independent genetic mechanisms in two populations of the fox squirrel. In a western population, melanism is associated with a 24 bp deletion in the melanocortin-1-receptor gene (MC1RΔ24 allele), whereas in a south-eastern population, melanism is associated with a point substitution in the agouti signalling protein gene causing a Gly121Cys mutation. The MC1R∆24 allele is also associated with melanism in gray squirrels, and, remarkably, all the MC1R∆24 haplotypes are identical in the two species. Evolutionary analyses show that the MC1R∆24 haplotype is more closely related to other MC1R haplotypes in the fox squirrel than in the gray squirrel. Modelling supports the possibility of gene flow between the two species. Conclusions The presence of the MC1R∆24 allele and melanism in gray squirrels is likely due to introgression from fox squirrels, although we cannot completely rule out alternative hypotheses including introgression from gray squirrels to fox squirrels, or an ancestral polymorphism. Convergent melanism in these two species of tree squirrels has evolved by at least two and probably three different evolutionary routes. Electronic supplementary material The online version of this article (10.1186/s12862-019-1471-7) contains supplementary material, which is available to authorized users.

Knowledge of which population parameters and mortality risks contribute most to population decline and endangerment is necessary to develop informed and actionable conservation plans for threatened and endangered species (Rushton et al., 2006). The federally endangered Mount Graham red squirrel (Tamiasciurus fremonti grahamensis) is restricted to the Pinaleno Mountains, in southeastern Arizona, USA. The population is critically threatened with extensive habitat loss from fire as well as by an introduced non-native squirrel species, the Abert's squirrel (Sciurus aberti). Recovery is challenged by low survival and poor reproduction, such that the subspecies is functionally semelparous. We calculate survival rates and cause-specific mortality hazards from known-fate individuals to understand the impact of predation on survival and demography in this peripheral population. We document the lowest survival and highest rates of mortality in any population of North American red squirrels in both adult and juvenile age classes (mean annual survival: adults = 0.32, juveniles = 0.26). We attributed the majority of confirmed deaths to avian predation (adults 65%, juveniles 75%), and the daily hazard rate for avian predation was 15 times higher than for mammalian predation and 2 times higher than death from unknown causes. It is likely that the presence of an ecologically similar, non-native tree squirrel subsidizes a diverse avian predator guild, which includes two raptor species of conservation concern. In addition to efforts to remove the non-native Abert's squirrel, we recommend immediate forest restoration efforts in the long term, and habitat augmentation to increase structural complexity, cover, shelter, and food resources in the short term.

Wildfires occur almost every year at the end of the dry season in some dry dipterocarp forests (or dry deciduous forests) of northeastern Thailand. This study assessed the effects of a wildfire on the occurrence of variable squirrels (Callosciurus finlaysonii), gray-bellied squirrels (C. caniceps), and Indochinese ground squirrels (Menetes berdmorei). Route census surveys before and after the wildfire revealed that the frequency of occurrence of the two tree squirrels (Callosciurus spp.) did not change, whereas that of the Indochinese ground squirrel decreased. The wildfire burned bushes and grasses but did not destroy the trees, leaving the food and resting sites for the tree squirrel species intact. Therefore, wildfires in this area may have no clear effects on tree squirrel species, but negative ones on ground squirrels. The probable reasons for these findings may be the nature and extent of the wildfire, as well as the space utilization of the squirrel species.

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 analysis of the Cryptosporidium 18S rRNA, actin, and gp60 genes. Despite the overlapping ranges of native and introduced tree squirrel species in the study area, they host different Cryptosporidium spp. Sciurus vulgaris were exclusively infected with Cryptosporidium ferret genotype (n = 13) belonging to three novel gp60 subtypes, VIIIb–VIIId. Sciurus carolinensis hosted C. ubiquitum subtype XIIb (n = 2), Cryptosporidium skunk genotype subtype XVIa (n = 3), and chipmunk genotype I subtype XIVa (n = 1). Cryptosporidium chipmunk genotype I subtype XIVa was also found in two C. erythraeus. Comparing data from this and previous studies, we propose that Cryptosporidium skunk genotype and possibly C. ubiquitum subtype XIIb were introduced to Europe with eastern grey squirrels. Cryptosporidium chipmunk genotype I and ferret genotype were associated with high intensity infections, but there was no association with diarrhoea.

Changes in the composition of biological communities can be elicited by competitive exclusion, wherein a species is excluded from viable habitat by a superior competitor. Yet less is known about the role of environmental change in facilitating or mitigating exclusion in the context of invasive species. In these situations, decline in a native species can be due to the effects of habitat change, or due to direct effects from invasive species themselves. This is summarized by the “driver-passenger” concept of native species loss. We present a multi-year study of tree squirrels that tested the hypothesis that tree canopy fragmentation, often a result of human development, influenced the replacement of native western gray tree squirrels (Sciurus griseus) by non-native eastern gray tree squirrels (Sciurus carolinensis). We tested this hypothesis along a continuum of invasion across three study sites in central California. We found that within the developed areas of the University of California at Santa Cruz campus and city of Santa Cruz, S. carolinensis excluded S. griseus from viable habitat. The competitive advantage of S. carolinensis may be due to morphological and/or behavioral adaptation to terrestrial life in fragmented hardwood forests. We classify S. carolinensis as a “driver” of the decline of native S. griseus in areas with high tree canopy fragmentation. Future habitat fragmentation in western North America may result in similar invasion dynamics between these species. Our study warrants consideration of existing and predicted interactions between potentially invasive species that co-occur with native species where land use change is proposed.

The American red squirrel (Tamiasciurus hudsonicus Exrleben) and northern flying squirrel (Glaucomys sabrinus Shaw) are important mammal species in coniferous forests that are widely distributed across temperate and boreal ecological zones. Although T. hudsonicus and G. sabrinus apparently prefer late-successional forests, their population dynamics show no clear pattern in young second-growth and old-growth conifer forests. We used a compilation of study results that had standardized methodology and sampling effort to compare tree squirrel responses across a range of forest conditions. We tested the hypotheses (H) that abundance, reproduction, recruitment, and survival would be higher in (H1) old-growth than second-growth stands, (H2) unthinned than thinned second-growth stands, and (H3) lightly than heavily thinned stands. Tree squirrel populations in old-growth stands were considered the “standard” treatment to which other treatments in second-growth stands (unthinned and variously thinned) were compared. Thinned stands were grouped into low, medium, and high densities of trees. Datasets from seven published studies included 2804 Tamiasciurus and 837 G. sabrinus individuals, 25 study years, and 158 trapping periods. Mean abundance of Tamiasciurus was similar among treatment stands, ranging from 0.62 to 1.29·ha−1. Mean numbers of G. sabrinus were highest in old-growth stands at 0.65·ha−1, followed by the low- and medium-density stands at 0.50·ha−1, the high-density stands at 0.25·ha−1, and finally the unthinned second-growth stands at a low of 0.12·ha−1. In terms of effect size, mean proportional change in abundance, relative to that within old-growth stands, of both squirrel species in the three thinned stands were within the range of natural fluctuations in old-growth stands. Populations of Tamiasciurus in the unthinned stands were not within the range of fluctuations in the old-growth stands. Mean number of successful pregnancies and total recruits were similar among stands for Tamiasciurus, with variability in female breeding and winter survival. Mean number of recruits of G. sabrinus was highest in old-growth stands with no other differences in demographic attributes among stands. The biological significance of these differences in demographic variables was small in terms of effect sizes. Tamiasciurus and G. sabrinus seem to persist in a relatively broad range of young managed forest habitats, as well as in old-growth stands.

Eastern fox squirrels (Sciurus niger), reddish-brown tree squirrels native to the eastern and southeastern United States, were introduced to and now thrive in suburban/urban California. As a result, many residents in the greater Los Angeles region are grappling with living amongst tree squirrels, particularly because the state’s native western gray squirrel (Sciurus griseus) is less tolerant of human beings and, as a result, has historically been absent from most sections of the greater Los Angeles area. ‘Easties,’ as they are colloquially referred to in the popular press, are willing to feed on trash and have an ‘appetite for everything.’ Given that the shift in tree squirrel demographics is a relatively recent phenomenon, this case presents a unique opportunity to question and re-theorize the ontological given of ‘otherness’ that manifests, in part, through a politics whereby animal food choices ‘[come] to stand in for both compliance and resistance to the dominant forces in [human] culture’. I,...

Intraspecific variation in home range size has important implications for the distribution of animals across landscapes and the spatial structuring of population, community, and ecosystem processes. Among species of similar trophic guild and body mass, differences in home range size can reflect extrinsic variables that exert divergent selective forces upon spacing behavior and social organization. We tested predictions about how resource availability and timing influence social system, home range size, and territoriality in two tree squirrel species of similar size and ecological niches but that differ in foraging strategy and social organization. We estimated home range size and intraspecific home range core overlap in the Mt. Graham red squirrel (Tamiasciurus fremonti grahamensis; Arizona USA; MGRS) and the Eurasian red squirrel (Sciurus vulgaris; Alps, Italy; ERS) as functions of species, sex, season, and individual’s body mass. However, body mass did not explain differences found between the two species. We found MGRS home ranges being three times smaller with higher core area exclusivity compared to ERS in all seasons. In fact, territorial MGRS evolved in a system of brief resource pulses and are larder hoarders, whereas ERS experience prolonged resource availability and are non-territorial. Only male MGRSs increased their home range during the breeding season, reflecting interspecific differences in social organization and mating behavior. Male ERS home ranges always overlap with several females to enhance mating success although male and female MGRS maintain nearly exclusive territories throughout the year. Only during spring and summer do males temporarily leave their food-based territory to increase mating opportunities with neighboring estrus females. Home range comparisons between ecologically similar species emphasize the importance of divergent extrinsic factors in shaping variability in body size–home range size scaling relationships. Timing in resource availability influenced the social structure and space use in tree squirrels of similar body size, highlighting how the coevolution of arboreal squirrels with conifer tree species has shaped their natural history.

Short-term elevation of glucocorticoids (GCs) is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors (stressors). However, when exposure to stressors occurs repeatedly or over a prolonged period of time, animals may experience chronic elevation of GCs, which reduces the immune response efficiency and can lead to higher intensity of parasitic infection. Here, we used invasive gray squirrels Sciurus carolinensis introduced in Northern Italy and their 2 most prevalent gastrointestinal parasites, the nematode Strongyloides robustus and coccidia of the genus Eimeria, as a model to investigate relationships among macroparasite infection and concentrations of fecal glucocorticoid metabolites (FGMs), an integrated measure of circulating GCs. Our results revealed an association of FGMs with infection by St. robustus, but not with coccidia. Individuals with higher FGMs appear to be responsible for the greatest St. robustus egg shedding within gray squirrel populations, thus possibly acting as superspreaders. However, FGMs were negatively associated with adult St. robustus, suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs, but is only affected by it through immune-mediated effects on its fecundity. Finally, the relationship between St. robustus (both eggs and adult parasites) and FGMs was not linear, suggesting that only high levels of physiological stress influence parasite infection. Our findings highlight that the direction and magnitude of the stress–infection relationship may depend not only on the specific host–parasite system, but also on the different life stages of the same parasite.

Quantifying resource partitioning is central to community and food web ecology and of increasing interest in an era of rapid global change disrupting biotic interactions. Multichannel feeding – consuming resources from both green and brown food webs – can be a stabilizing force in communities. While multichannel feeding has been well-documented in invertebrate and aquatic systems, it has been relatively under-studied in terrestrial vertebrate populations. Applied ecologists are seeking approaches to assess niche partitioning and cryptic trophic pathways, like multichannel feeding, which have been difficult to quantify, especially among vertebrates. Using both bulk (δ13C and δ15N) and compound specific stable isotope ratios (δ15N glutamic acid and phenylalanine), we tested how three common and competing tree squirrel partition resources. Our complementary analyses revealed that squirrels partitioned niche space and, because of differences in multichannel foraging, possessed different trophic identities. While all squirrels consumed food items from green and brown food webs, their dependence on each differed, revealing an important, yet cryptic, mechanism behind apparent stable co-occurrence of these competitors. Our work supports multichannel feeding as a potential mechanism promoting coexistence in this guild of terrestrial vertebrates, and provides a framework to quantify resource partitioning in other ecological communities.

Microsciurus flaviventer ([Gray, 1867][1]) is a Neotropical tree squirrel commonly known as the Amazon dwarf squirrel. Small bodied with dark brown dorsal pelage contrasted with a gray or yellowish gray venter, and a faintly banded tail. M. flaviventer is 1 of 4 species in the genus Microsciurus . The geographic range of M. flaviventer extends from the Amazon basin of South America throughout western and southeastern Colombia, Ecuador, southern Peru, Brazil west of Rio Negro, and Madeira. It is most commonly associated with evergreen lowland tropical rainforest. Status of M. flaviventer is “Data Deficient” under the International Union for Conservation of Nature and Natural Resources Red List of Threatened Species ; however, loss of habitat is a major concern. [1]: #ref-18

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 through December 2018 for records of EGS weighing

Southeast Asia contains a diverse array of squirrels, with several species living sympatrically. However, limited data are available on how the squirrels coexist and share resources in the same habitat. Here, we examined resource-use variation between sympatric Callosciurus finlaysonii and C. caniceps in two habitats of northeastern Thailand: dry dipterocarp forest (DDF) and dry evergreen forest (DEF). Both species were bimodally crepuscular and did not differ in daily activity patterns. Callosciuruscaniceps was fewer in number than C. finlaysonii in DDF, but they had similar frequencies in DEF. The two species generally consumed different plant species, though some preferred fruits overlapped. Callosciurus finlaysonii from DEF remained higher in the trees than C. caniceps; all nests at elevated locations belonged to C. finlaysonii. When feeding, the preferred height of both species varied depending on food availability. In DEF, C. caniceps dominated C. finlaysonii during interactions. Together, our observations indicate that sympatry is possible because the two species differ in food choice and/or engage in vertical zonation.

Microsciurus santanderensis (Hernandez-Camacho, 1957) is a sciurid commonly called the Santander dwarf squirrel. M. santanderensis is a small tree squirrel with orange and black mixed fur and is 1 of 4 species in the genus Microsciurus. Endemic to Colombia, South America, in forests at elevations up to 3,800 m, M. santanderensis is listed as “Data Deficient” by the International Union for Conservation of Nature and Natural Resources, and more research is needed to determine its conservation needs.

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) of American red squirrels (Tamiasciurus hudsonicus), 40.4% (55/136) of eastern gray squirrels (Sciurus carolinensis), and 28.6% (2/7) of fox squirrels (Sciurus niger). Human-pathogenic Cryptosporidium ubiquitum and Cryptosporidium skunk genotype were the most prevalent species/genotypes in tree squirrels. Because tree squirrels live in close proximity to humans and are frequently infected with potentially zoonotic Cryptosporidium species/genotypes, they may be a significant reservoir of infection in humans. In ground squirrels, Cryptosporidium was detected in 70.2% (33/47) of 13-lined ground squirrels (Ictidomys tridecemlineatus), 35.1% (27/77) of black-tailed prairie dogs (Cynomys ludovicianus), and the only golden-mantled ground squirrel (Callospermophilus lateralis) that was sampled. Cryptosporidium rubeyi and ground squirrel genotypes I, II, and III were identified in isolates from these ground squirrel species. In contrast to the Cryptosporidium infecting tree squirrels, these species/genotypes appear to be specific for ground squirrels and are not associated with human disease.

Southern California is home to one native and one introduced species of tree squirrel. The native Western Gray Squirrel (Sciurus griseus; here on gray squirrel), is a highly arboreal tree squirrel that can be found inhabiting mixed oak and pine forest habitats and tree dominated parks and gardens in suburban areas within California (King 2004; Muchlinski et al. 2009). Gray squirrels feed primarily on fungi, pine nuts, acorns, and bay fruit. They have also been documented to feed on Eucalyptus seeds, samaras, and berries (Morus and Phoradendron spp.) along with bird eggs and nestlings (Carraway and Verts 1994). Fungi are one of the gray squirrel’s most highly utilized food items. By consuming fungi, gray squirrels assist in providing a healthy soil environment for the development and growth of oak-woodland communities (Maser et al. 1981). The introduced Eastern Fox squirrel (Sciurus niger; here on fox squirrel) is an invasive generalist species (Tatina 2007) typically found in upland areas, open forests, or areas neighboring open spaces such as agricultural lands and pastures (Sexton 1990). The presence of the fox squirrel in California has been a concern of the general public, land managers, and researchers. The Los Angeles County Agricultural Commission considers the fox squirrel a pest species and potentially aggressive. In their native range, the fox squirrel has been important ecologically in the succession of grasslands to forests by caching their food within open grasslands (Stapanian and Smith 1986). Seeds cached and fed on by the fox squirrel come from persimmon, blue gum Eucalyptus, cottonwood, pines, and many others (Koprowski 1994). Fox squirrels incorporate animal foods in their diet such as insects, butterflies, ants, birds, and bird eggs (Koprowski 1994). It is reported that the fox squirrel takes advantage of fruits found within backyards such as avocados, oranges, and strawberries, an activity often disliked by human occupants (Becker and Kimball 1947; Salmon et al. 2005). Very little is known regarding food preferences of the two species within Southern California and detailed information is limited. This study sought to gain information on what foods each species selects, and which food items overlap and differ between gray and fox squirrels. Knowledge of food preferences among species promotes making management decisions that sustain their populations. For example, improving habitat by adding particular plants or trees preferred by the gray squirrel can aid in the recovery of its population (Linders and Stinson 2006). Information on food selection may also reveal a high degree of overlap such that competition is possible in years of food shortage. Competition could lead to extirpation of the gray squirrel where food selection is limited. Muchlinski et al. (2009) established that fox squirrels replace gray squirrels at locations

Restoration of the functionally extirpated American chestnut (Castanea dentata) to landscapes of the eastern United States is planned with the successful propagation of a blight-resistant hybrid tree. Predicting the response of rodent seed consumers to this novel source of mast will be critical to restoration success, as rodents are important seed predators and dispersers in forests that once included chestnut. In particular, frequency-dependent foraging responses by rodents could affect the rate of spread of rare chestnuts following reintroductions. We conducted field trials to test for seed preferences and frequency-dependent selection by fox squirrels (Sciurus niger) when combinations of American chestnut and two common associates [northern red oak (Quercus rubra) and white oak (Q. alba)] were available in varying frequencies. Fox squirrels tended toward positive frequency-dependent seed predation when combinations of white oak and chestnuts were available, consuming more common mast items at a higher rate than expected based on availability. No preferences were observed between American chestnut and either red or white oak independent of frequency, but red oak was preferred over white oak. Frequency-dependent consumption of more common white oak acorns could benefit rarer chestnut during restoration, as squirrels would feed disproportionately on established white oak; however, this management strategy should only be considered following larger-scale and longer-term studies that consider impacts on white oak regeneration. Lack of preference or frequency dependence for chestnut when paired with red oak suggests that negative impacts of fox squirrel consumption on restoration will vary with the relative availability of the two seed types.