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Gray squirrels
\"Simple text and full-color photography introduce beginning readers to gray squirrels. Developed by literacy experts for students in kindergarten through third grade\"-- Provided by publisher.
Book
Squirrel Nation
A wide-ranging meditation on belonging and citizenship through the story of two squirrel species in Britain. Squirrel Nation is a history of Britain's two species of squirrel over the past two hundred years: the much-loved, though rare, red squirrel and the less-desirable, though more populous, grey squirrel. A common resident of British gardens and parks, the grey squirrel was introduced from North America in the late nineteenth century and remains something of a foreign interloper. By examining this species' rapid spread across Britain, Peter Coates explores timely issues of belonging, nationalism, and citizenship in Britain today. Ultimately, though people are swift to draw distinctions between British squirrels and squirrels in Britain, Squirrel Nation shows that Britain's two squirrel species have much more in common than at first appears.
eBook
Diets of Native and Introduced Tree Squirrels in Washington
Competition for food resources can be a primary mechanism for displacement of native species by introduced species. Investigation of dietary partitioning between potential competitors and spatiotemporal variability in food resources can reveal contested food items and intensity of competition. Introduced eastern gray squirrels (Sciurus carolinensis) have been implicated as competitors with western gray squirrels (S. griseus) and Douglas’ squirrels (Tamiasciurus douglasii), but little is known about interactions among these species. We collected foraging observations and fecal pellets of sympatric gray and Douglas’ squirrels trapped and radio-tracked in western Washington, USA, from 2007 to 2012. We compared food resources consumed across species, seasons, and years to evaluate dietary overlap and the potential for competitive interactions. All squirrel species ate hypogeous fungi throughout all seasons; spores of several genera were present in 272 of 275 fecal samples and observed in all months. Rhizopogon, Geopora, and Melanogaster spp. occurred in most fecal pellets for all squirrels, but the diet of the Douglas’ squirrels had slightly lower richness of hypogeous fungi than gray squirrels. Although foraging observations suggest that eastern and western gray squirrels shared important dietary items such as acorns, strong differences in consumption of seeds of a common conifer may facilitate their coexistence. Our results suggest that dietary overlap among arboreal squirrels could lead to competitive interactions during periods of food scarcity, but subtle differences may be sufficient to permit long-term coexistence. Tree squirrels in Washington would likely benefit from forest management practices that promote or sustain robust crops of hypogeous fungi.
Journal Article
Differential Resource Use between Native and Introduced Gray Squirrels
Differences in habitat requirements and the spatial distribution of habitat for native and introduced species can determine outcomes of biological invasions. Introduced eastern gray squirrels (Sciurus carolinensis) have displaced native red squirrels (S. vulgaris) in Europe and have been implicated as a contributing factor to the decline of western gray squirrels (S. griseus) in North America. Eastern and western gray squirrels are associated with oak (Quercus spp.), but little is known about how these species interact. From April 2007 to April 2012, we radio-tracked sympatric eastern and western gray squirrels in western Washington to compare habitat use and evaluate competitive interactions. We developed resource utilization functions for each species and evaluated distribution of habitat on Joint Base Lewis-McChord, Washington, USA. Both species shared affinity for closed canopy forests and oaks; however, important differences in relationships with riparian areas and shrub cover resulted in low overlap in habitat distribution, which likely limited potential competitive interactions. Eastern gray squirrels appeared restricted to areas around wetlands likely because they supported the deciduous tree species that comprise habitat for this species in its native range. Use by western gray squirrels, but not eastern gray squirrels, significantly decreased with increasing shrub cover. Forestry practices that promote mixed oak-conifer with little shrub cover in uplands can benefit western gray squirrels and minimize interactions with eastern gray squirrels.
Journal Article
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 weight, length, and width reached their highest values in the luteal and pregnancy phases. On conducting a histological evaluation of the testicular germinal epithelium, four morphotypes related to the different reproductive phases of the male squirrels were identified: immature, pubertal, spermatogenesis, and regressive. Testicle and epididymis weights and seminiferous tubule diameters reached their largest values during spermatogenesis. Uterine scar analysis showed that 69% of the females had given birth to one or two litters, while 31% had no uterine scars. Litters were larger in the first breeding period than in the second; annual fecundity was 4.52 ± 1.88 uterine scars/female. Umbrian grey squirrels have adapted to their non-native range, showing two annual mating periods at times similar to those in their native range, and high reproductive success.
Journal Article
Fearing the feline: domestic cats reduce avian fecundity through trait-mediated indirect effects that increase nest predation by other species
1. Urban areas contain high densities of non-native species, which in the UK include the domestic cat Felis catus (Linnaeus 1758) and the grey squirrel Sciurus carolinensis (Gmelin 1788). The direct predation effects of domestic cats on prey populations attract intense debate, and such influences of the nest-predatory grey squirrel are receiving increasing attention. In contrast, theory predicts that sublethal and indirect effects are more important, but empirical evidence is currently lacking. 2. We conducted controlled model presentation experiments at active urban blackbird Turdus merula (Linnaeus 1758) nests to provide the first empirical evidence that quantifies the potential sublethal and indirect effects of predators (domestic cat and grey squirrel) on avian reproductive success. 3. Domestic cat models reduced subsequent parental provisioning rates, a strong indicator of sublethal effects, by one-third relative to a nonpredatory rabbit Oryctolagus cuniculus (Linnaeus 1758) control. There was no compensatory increase in food load size. Previous experiments demonstrate that this magnitude of reduced food delivery will reduce nestling growth rates by c. 40%. The grey squirrel model induced similar but weaker effects. 4. Following the brief presence of the domestic cat model, subsequent daily nest predation rates, chiefly by corvids, increased by an order of magnitude relative to the squirrel and rabbit models. The intensity of parental nest defence elicited in response to model presentations predicts the probability of such third-party predator predation events, and the domestic cat model generated significant increases in nest defence behaviour. 5. Synthesis and applications. The brief presence of a domestic cat at avian nest sites reduces subsequent provisioning rates and induces lethal trait-mediated indirect effects. We provide the first robust evidence for these latter effects in any avian predator—prey system, although they are likely to be common in many avian assemblages with high predator densities. It is imperative that future assessments of the impact of predatory species on avian prey species take lethal trait-mediated indirect effects into account, as so doing will prevent biased estimates of predator effects and facilitate the design of more effective control strategies. Full mitigation of the sublethal and indirect effects of domestic cats would problematically require permanent indoor housing.
Journal Article
Future Range Dynamics Suggest Increasing Threats of Grey Squirrels in Europe: A Perspective on Climatic Suitability
Interactions between the introduced gray squirrel (Sciurus carolinensis) and the native red squirrel (S. vulgaris) play an important role in the ecological equilibrium of European forest ecosystems. However, the range dynamics of the grey squirrel and red squirrel under future climate change scenarios remain unknown. The present study examined the range dynamics of grey squirrels and red squirrels in Europe and their range overlap now and in the future based on climate change. Under the most optimistic climate change scenario (SSP126), expansion of the grey squirrel’s range was mainly predicted in Germany, France, Croatia, Serbia, and Bulgaria. Under the most pessimistic climate change scenario (SSP585), expansion of the grey squirrel’s range was predicted in vast and scattered regions. Additionally, France, Italy, and Germany were overlapping ranges for the grey squirrel and red squirrel in the future under the SSP126 scenario but not under the current conditions, suggesting that there will be new regions where grey squirrels may threaten red squirrels in the future under SSP126. The range overlaps under the SSP585 scenario but not under the current conditions were vast and scattered, suggesting that there will be new regions in the future where grey squirrel may displace red squirrels under SSP585. Despite considerable variation, we detected expansions in the grey squirrel and red squirrel ranges and an increase in overlapping ranges between grey squirrels and red squirrels in the future. Therefore, our prediction suggests increasing threats of grey squirrels toward red squirrels in Europe in the future under climate change, which may impact the ecological equilibrium of European forest ecosystems.
Journal Article
Patterns in tree squirrel co-occurrence vary with responses to local land cover in US cities
Urbanization has important effects on the distribution and persistence of wildlife communities. Urbanization may alter not just the distributions of individual species, but also co-occurrence patterns and thus the potential for interspecific interactions (e.g., competition, predation) that structure wildlife communities. Little is currently known about how urbanization alters species co-occurrence or how these changes shape urban species assemblages. Using tree squirrels as a model functional group, we quantified how urbanization alters species occurrence and co-occurrence patterns to shape species assemblages, and how these effects vary within and among cities. We constructed a multi-species, multi-season occupancy model to identify relationships between tree squirrel occupancy and co-occurrence and local land and tree canopy cover and examined variation in these relationships within and among nine US cities. Species’ responses to canopy cover were highly variable among, but less variable within cities, suggesting that even common urban wildlife species may respond differently to urban intensity in different landscape contexts. Species co-occurrence was also highly variable among cities and weakly related to canopy cover within a city. These findings provide important evidence that both environmental attributes and species interactions shape urban wildlife communities. Important for management and conservation, they suggest that tree-canopy cover can particularly support forest species co-occurrence and that managing urban forests to provide high canopy cover could contribute to the diversity of urban wildlife communities in forested ecoregions.
Journal Article
Supplementing non-target taxa
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 influence the presence and behavior of mammals, we used camera traps to quantify differences in the distribution and richness of mammal species frequenting sites with bird feeders and control sites (lacking feeders) in Ithaca, New York, USA. We recorded 15,684 images capturing 12 mammal species with gray squirrel (Sciurus carolinensis) and raccoon (Procyon lotor) detected significantly more often at feeder sites than at control sites. Detections of white-tailed deer (Odocoileus virginianus) marginally increased near feeders whereas detections of several carnivorous species were unrelated to the presence of bird feeders. We recorded larger gray squirrel and raccoon group sizes and greater mammal richness at feeder sites than at nearby control sites. We detected squirrels and raccoons less when snow covered the ground than on snow-free days. Ambient temperature was not a strong predictor of mammal detections. Camera trapping revealed strong, species-specific patterns in the timing of daily visitation to areas with feeders. Because many mammals depredate bird nests, the local increases in mammal richness and activity near bird feeders may create an ecological trap for avian species nesting in close proximity to supplemental feeding stations.
Journal Article