Eurasian Red Squirrel Sciurus Vulgaris Research Articles

Camera traps equipped with macro lenses as a tool for monitoring arboreal small mammals: a case study in an agroecosystem (NE Italy)

Despite their increasing use, camera traps as a monitoring tool for arboreal small mammals leave room for further improvements to increase their effectiveness. In the summer of 2023, we conducted a small mammal survey in a wooded area of a lowland agroecosystem in the Veneto region, using standard camera traps equipped with macro lenses for close-up shooting. This camera trap technique made it possible to contact three species of small mammals in the tree-shrub layer: Eurasian red squirrel Sciurus vulgaris, wood mouse Apodemus sylvaticus, and black rat Rattus rattus. The use of macro lenses combined with the standard camera trapping technique made it possible to obtain better quality images and more information even on smaller species compared to more traditional camera traps.

Aphid galls as a double food source for woodpeckers

An adult female and a young great spotted woodpecker Dendrocopos major were found exploiting galls of the elm balloon‐gall aphid Eriosoma lanuginosum by eating both the insects and their honeydew. Literature offers sparse and indirect information to explain this behavior. Taking both aphids and honeydew from within galls is reported here for the first time for a bird species. Only one other vertebrate, the Eurasian red squirrel Sciurus vulgaris, would show similar behavior. In contrast with the seeming rarity of such a feeding way, likely advantages in the double food source suggest it may have been overlooked.

Hepatozoon in Eurasian red squirrels Sciurus vulgaris, its taxonomic identity, and phylogenetic placement.

Adeleorid apicomplexan parasites of the genus Hepatozoon Miller, 1908 are broadly distributed among the rodents. Broader molecular data on Hepatozoon from Palaearctic squirrels are necessary for evaluation of diversity and origin of Hepatozoon in Eurasian red squirrel Sciurus vulgaris populations, considering ongoing invasion by Gray squirrel S. carolinensis. Our report brings a set of molecular data from a population of S. vulgaris in the Czech Republic, non-invaded by any invasive squirrel species. Cadavers of 41 Eurasian red squirrels were examined using nested PCR targeting 18S rRNA gene; 30 animals tested positive for the presence of Hepatozoon spp. DNA in at least one tissue. Phylogenetic analysis of obtained sequence types revealed relatedness to sequences of Hepatozoon sp. from S. vulgaris from Spain and the Netherlands, forming a sister clade to Hepatozoon isolates from other European rodents. The fact that all available 18S rRNA gene sequences form a monophyletic clade is interpreted as a presence of a single Hepatozoon species in S. vulgaris in continental Europe, most probably Hepatozoon sciuri. The presented molecular data on the Hepatozoon from European squirrels provides a basis for future studies on possible exchange of Hepatozoon species between Eurasian red and gray squirrels.

A systematic review into the suitability of urban refugia for the Eurasian red squirrel Sciurus vulgaris

Abstract Urban growth and intensification are projected to increase as the global human population increases. Historically, urban areas have been disregarded as suitable wildlife habitat, but it is now known that these areas can be biodiverse and that wildlife species can adapt to the environmental conditions. One such urban‐dwelling species is the Eurasian red squirrel Sciurus vulgaris, which has suffered population declines in several countries throughout its range in recent decades. The current published literature was systematically reviewed to determine whether or not urban habitats are suitable refugia for red squirrels, through identifying and discussing key topics regarding the urban ecology of red squirrels. Urban environments can support higher population densities of red squirrels than rural areas, probably due to the widespread and reliable provision of anthropogenic supplemental food alongside natural food sources. The availability and quality of urban greenspaces are important determinants of the suitability of urban habitats for red squirrels, as they provide natural food sources and nesting sites. Despite the barriers present in urban landscapes (e.g. roads), red squirrels can still disperse and maintain gene flow at the population level. Road traffic accidents appear to be a significant cause of mortality in some urban red squirrel populations, and seasonal peaks of mortality occur during the autumn months. Diseases (e.g. squirrelpox virus) can also be a significant cause of mortality, although effects differ between populations and depend on whether grey squirrels Sciurus carolinensis are present. Many of the predation events that affect red squirrels appear to be due to free‐ranging domestic and feral cats Felis catus, although there is currently little evidence to suggest that predation is a limiting factor for urban red squirrel populations. We conclude that urban areas can be suitable refugia for red squirrels, provided that high‐quality greenspaces are maintained. Mitigation measures may also be necessary to reduce population mortality and to prevent disease outbreaks.

Environmental variability and allostatic load in the Eurasian red squirrel Sciurus vulgaris

The analysis of eco-physiological parameters in wildlife may represent a priority for their conservation and management, not only to establish causal relationships, obtaining a set of raw data, but also to monitor the effectiveness of management strategies. We studied Hair Cortisol concentration (HCC) in Eurasian red squirrels Sciurus vulgaris in four selected study areas in Italy. Areas differed from one another for vegetation type, degree of urbanization and anthropic disturbance, density of red squirrel populations and presence or absence of alien squirrel species. HCC measurements showed the highest values in a high-density population, subjected to a high predation pressure (i.e. in areas characterized by deciduous vegetation). Conversely, the lowest HCC levels have been observed in areas with the lowest squirrel density, i.e. in urbanized environments, where the species is established for a rather long time, and in areas with mixed vegetation and presence of conifers. Measuring HCC provides reliable information on the long-term activity of hypothalamic–pituitary–adrenal (HPA) axis and associated allostatic load. Furthermore, it constitutes a non-invasive method of investigation. The use of hair tubes further supports our non-invasive approach. Because of its simplicity and low costs, hair collection might be applied to monitor the long-term physiological response of wild species even in larger areas, besides focusing in the promotion of citizen-science data collection.

The Biodiversity of Demodecid Mites (Acariformes: Prostigmata), Specific Parasites of Mammals with a Global Checklist and a New Finding for Demodex sciurinus

Demodecidae are the most specialized parasitic mites of mammals; they typically inhabit the skin, but they have been found in other tissues and organs. They can cause demodecosis (a disease which is hazardous and difficult to cure) in humans, domestic animals and livestock. They are parasites with high host and topical specificity. They have been found for most orders of mammals, and they are common in the populations of numerous host species. Therefore, they not only constitute an important subject of veterinary and medical study, but also comprise an excellent model for faunistic and parasitological analyses concerning different aspects of functioning and evolution of the host–parasite relationship. The current level or knowledge of demodecid mites is irregular and fragmentary, and numerous questions require elaboration and ordering, from the taxonomic diversity to geographic distribution and relations with hosts. Such data may be of use i.a. for the development of more efficient and reliable diagnostic methods, as well as understanding the etiology and pathogenesis mechanisms of demodecosis, currently a contentious issue. The present paper lists all formally-described valid species of demodecid mites, together with other functioning specific names, verified and with comments on their status. This is significant for correct species identification and demodecosis diagnostics. The list has been drawn up on the basis of data acquired in the period 1842−2020. It contains 122 valid species of parasite, including their hosts and geographic distribution, data on parasitism, as well as only the second record of Demodex sciurinus in Eurasian red squirrel Sciurus vulgaris in over 100 years since its initial discovery.

Seasonal pelage color change of two sympatric arboreal squirrel species in the subarctic region

Some mammal species exhibit pelage color change with seasonal molt. Seasonal molt and pelage color change are beneficial to thermoregulation and concealment, associated with seasonal environmental change. The Eurasian red squirrel Sciurus vulgaris Linnaeus, 1758 and the Siberian flying squirrel Pteromys volans (Linnaeus, 1758) are arboreal and sympatrically distributed in the subarctic northern Eurasian Continent and Sakhalin and Hokkaido islands. We expect that diurnal S. vulgaris may demonstrate more conspicuous difference between summer and winter pelages than nocturnal P. volans, because of its protective coloration in each season. To test this conjecture, we investigated their seasonal pelage color change. To diminish the effect of geographic variation in pelage color, we chose S. vulgaris orientis Thomas, 1906 and P. volans orii (Kuroda, 1921), which are endemic subspecies of Hokkaido Island, Japan. We used skin and stuffed specimens and frozen materials and categorized them into two pelage groups (summer and winter pelages) based on collection date. Pelage color characteristics were measured with a spectrophotometer for lightness, redness and yellowness. Countershading was examined by comparing dorsal and ventral lightness. Both subspecies showed lighter winter pelage than summer pelage, suggesting their greyish-white winter pelage was beneficial to concealment from predators during winter. As we expected, seasonal changes of redness and yellowness were more clearly recognized in S. vulgaris than in P. volans. As S. vulgaris is diurnal and vulnerable to attack by diurnal avian predators, reddish and yellowish pelage patterns may be important for concealment. Because it is nocturnal, P. volans may not need this reddish and yellowish pelage. Sciurus vulgaris also had a remarkably counter-shaded body, indicating that its body may reduce predation risk from daytime visual predators. Differences in seasonal pelage color change of these two arboreal squirrels may be caused by their different circadian rhythms.

Poor Parasite Community of an Invasive Alien Species: Macroparasites of Pallas's Squirrel in Italy

The aim of the present study was to investigate the macroparasite fauna of Pallas's squirrel, Callosciurus erythraeus, native to SE Asia, recently introduced to Italy and co-occurring with the native Eurasian red squirrel Sciurus vulgaris. A total of 161 Pallas's squirrels harboured a poor macroparasite fauna, characterized by two main ectoparasite species, the flea Ceratophyllus (M.) sciurorum sciurorum (prevalence 50%, mean intensity 1.0 ± 0.1) and the tick Ixodes ricinus (prevalence 47%, mean intensity 3.0 ± 0.7), and a few helminths (Rodentoxyuris sciuri, Trichuris muris, Strongyloides callosciureus) all with prevalence below 10%. All parasites, except S. callosciureus, are native to Europe and were acquired in the invaded range. The loss of native parasites might have contributed to their successful invasion. The acquisition of local parasites C. sciurorum and Trichuris sciuri, and the introduction of the Asiatic nematode S. callosciureus may lead to spill-back and spill-over processes towards red sq...

Effects of habitat quality on parasite abundance: do forest fragmentation and food availability affect helminth infection in the Eurasian red squirrel?

AbstractHabitat quality affects demography, population genetics, space use and phenotypic characteristics of mammals. However, little is known about the effects of habitat quality, fragmentation and/or food abundance, on host–parasite interactions. Here we present a first study on the relationships between the abundance of the dominant gastrointestinal helminth, Trypanoxyuris (Rodentoxyuris) sciuri, infecting the Eurasian red squirrel Sciurus vulgaris and three environmental factors: habitat type (mountain conifer forests vs. lowland mixed deciduous forests), fragmentation (fragmented woodlands vs. continuous forests) and food availability. Abundance of T. (R.) sciuri increased in fragmented woods. Furthermore, in mountain conifer forests, squirrels were more heavily infected after a poor Norway spruce seed crop than in years with medium or high seed production, indicating that squirrels are less capable of reducing parasite load when food availability is low. Hence, we suggest that T. (R.) sciuri abundance in red squirrels may be determined mainly by changes in host susceptibility induced by higher stress levels and/or poorer nutritional status, while in fragments, reduced genetic diversity may also increase host susceptibility to parasite infection. Although our data do not shed light on the mechanisms generating the observed patterns, results from other field studies highlighted the effect of stress and nutritional status on parasite infection, thus suggesting their implication in the changes in the abundance of T. (R.) sciuri.

Comparing pellet and stable isotope analyses of nestling Bonelli's Eagle Aquila fasciata diet

Diet analyses are central to the study of avian trophic ecology, and stable isotope analyses have made an increasing contribution in the last two decades. Few isotopic studies have assessed the diet of raptor species, which are more frequently analysed by conventional diet methods such as pellet analysis. In this study, we compare prey consumption estimates of nestling Bonelli's Eagles Aquila fasciata from conventional pellet analysis (in terms of items and biomass) and stable isotopic mixing models (SIAR) using δ13C, δ15N and δ34S of feathers. The pellet analysis showed that European Rabbits Oryctolagus cuniculus, pigeons (mainly Common Wood Pigeons Columba palumbus and Domestic Pigeons Columba livia dom.), Red‐legged Partridges Alectoris rufa, passerines, Yellow‐legged Gulls Larus michahellis and Eurasian Red Squirrels Sciurus vulgaris were the main prey, so they were selected for diet reconstructions in SIAR. At the population level, mean prey consumption estimates were similar for pellets (both items and biomass) and SIAR. At the territory level, the weighted kappa statistic showed good ordinal scale agreement in main prey consumption between items or biomass and SIAR. Although the intraclass correlation coefficient showed poor method agreement when considering all prey in the same analysis, the intraclass correlation coefficients for each prey category showed significant agreement between pellets and SIAR when estimating the consumption of Rabbits, pigeons and Gulls, with lower agreement for passerines and Squirrels. Lastly, there was poor method agreement for estimates of Partridges. Our results suggest an overall agreement between the pellet analysis and SIAR when estimating nestling Bonelli's Eagle diet at both the population and, to a lesser extent, the territory level, supporting the usefulness of isotopic mixing models when identifying the terrestrial and marine components of raptor diets.

Preliminary Survey of Habitat Use bySciurus vulgaris orientisin a Natural Forest of Hokkaido Island, Japan

The Eurasian red squirrel Sciurus vulgaris Linnaeus, 1758 is widely distributed in the northern part of Eurasian Continents, Sakhalin Island (Russia), and Hokkaido Island (Japan) (Gurnell and Wauters 1999; Wilson and Reeder 2005). The distribution area of this squirrel is widest of all the world’s squirrel species (Gurnell 1987). In Russia, this squirrel occurs in boreal coniferous forests consisting of larch (Larix), pine (Pinus), and spruce (Picea) (Lurz et al. 2005). The Hokkaido population of the Eurasian red squirrel is regarded as an endemic subspecies: S. vulgaris orientis (e.g., Imaizumi 1960). This subspecies occurs from lowlands to mountains (1,650 m) in Hokkaido (Takaragawa 1996). Ecological characteristics of S. vulgaris orientis living in forests isolated by agricultural and urban areas are reported (Lee and Fukuda 1999; Lee 2001, 2002). In urban areas, this squirrel frequently feeds cones of Pinus koraiensis (Lee 2002), which was introduced to Hokkaido by human activity (Maeda 1970; Miyaki and Miyaki 1980). In Hokkaido’s original environments, however, the ecological characteristics of S. vulgaris orientis are little known. Therefore, this subspecies should be studied in its original habitats, such as the natural and mountainous forests of Hokkaido. Vegetation of Hokkaido’s natural forests mainly contains Abies sachalinensis, Picea jezoensis, Quercus mongolica, Betula spp., and Tilia japonica (Tatewaki 1958; Horikawa 1976; Okitsu 2002). This is different from forests of northern Eurasia where S. vulgaris populations are extensive. Abies sachalinensis, which is confined to Hokkaido Island, the southern parts of Sakhalin Island, and the Kuril Islands (Satake 1989), is the most abundant conifer tree in Hokkaido’s natural forests. Unlike the coniferous forests of northern Eurasia, several kinds of hardwoods account for 60% of the trees in Hokkaido’s forests (Okitsu 2002). In this unique vegetation structure, there may be an association between S. vulgaris orientis distribution and forest type. Ognev (1966) described S. vulgaris in Russia as inhabiting coniferous forests containing spruce and pine. In south-central Sweden, this squirrel inhabits Norway spruce-dominated forests (Andren and Delin 1994). In the natural forests of Hokkaido, therefore, this subspecies should prefer coniferous forests, even though hardwoods are more dominant. Here, we present preliminary results of microhabitat use by S. vulgaris orientis in the mountainous natural forests of Hokkaido.

Effects of spatio‐temporal variation in food supply on red squirrel Sciurus vulgaris body size and body mass and its consequences for some fitness components

Food availability is likely to influence body condition and, in turn, fitness. The intensity of this response may vary between populations of the same species on a small spatial and temporal scale. We used 5 yr of data from 6 Eurasian red squirrel Sciurus vulgaris populations from the southern Alps to explore differences in body size and body mass among neighbouring populations, in relation to habitat type and variation in food supply. We also investigated sexual dimorphism in these traits and whether phenotypic variation affects local survival and female reproductive success. Mean hind foot length, a measure of body size, did not differ between sexes but differed between areas. Seasonal variation in body mass was small with no evidence for fattening in autumn. Females were slightly heavier than males, but this difference was largely explained by mass gain of females during reproduction. The size of conifer seed crops, the major food supply, varied strongly over years and between habitats, but this variation corresponded only weakly with autumn body mass. Differences in size and mass between populations were partially explained by habitat‐related differences in body size and variability of seed‐crops, suggesting differential selection for smaller squirrels in spruce‐larch forests against selection for larger and heavier animals in mixed broadleaves and conifer forests and in Scots pine forests with more stable seed production. The probability of reproduction by females increased with body mass, but varied strongly between habitats and years, with more females reproducing in years with rich seed‐crops. In both sexes, body mass positively affected probability of settlement and length of residency. Our results suggest that in temporally variable environments that differ in overall amount of food resources, individual variation in body mass is related to habitat type, and that having a relatively high body mass, within each population, positively affects male and female settlement success and local survival, and female reproductive success.

Effects of spatio-temporal variation in food supply on red squirrel Sciurus vulgaris body size and body mass and its consequences for some fitness components

Food availability is likely to influence body condition and, in turn, fitness. The intensity of this response may vary between populations of the same species on a small spatial and temporal scale. We used 5 yr of data from 6 Eurasian red squirrel Sciurus vulgaris populations from the southern Alps to explore differences in body size and body mass among neighbouring populations, in relation to habitat type and variation in food supply. We also investigated sexual dimorphism in these traits and whether phenotypic variation affects local survival and female reproductive success. Mean hind foot length, a measure of body size, did not differ between sexes but differed between areas. Seasonal variation in body mass was small with no evidence for fattening in autumn. Females were slightly heavier than males, but this difference was largely explained by mass gain of females during reproduction. The size of conifer seed crops, the major food supply, varied strongly over years and between habitats, but this variation corresponded only weakly with autumn body mass. Differences in size and mass between populations were partially explained by habitat-related differences in body size and variability of seed-crops, suggesting differential selection for smaller squirrels in spruce-larch forests against selection for larger and heavier animals in mixed broadleaves and conifer forests and in Scots pine forests with more stable seed production. The probability of reproduction by females increased with body mass, but varied strongly between habitats and years, with more females reproducing in years with rich seed-crops. In both sexes, body mass positively affected probability of settlement and length of residency. Our results suggest that in temporally variable environments that differ in overall amount of food resources, individual variation in body mass is related to habitat type, and that having a relatively high body mass, within each population, positively affects male and female settlement success and local survival, and female reproductive success.

Feeding and hoarding behaviour of the Eurasian red squirrelSciurus vulgaris during autumn in Hokkaido, Japan

The feeding habits and hoarding behaviour of the Eurasian red squirrelSciurus vulgaris Linnaeus, 1758 were examined during autumn in Nopporo Forest Park (43°20’N, 141°30’E), in western Hokkaido, Japan. The diet consisted of 32 plant species. Twelve species were both eaten and hoarded (the two most common of which wereAbies sachalinensis andPinus koraiensis), and 20 species were eaten but not hoarded. The distance from where a food item was found to the hoarding spot averaged 50 m and differed significantly according to food type. WalnutsJuglans regia were transported farthest, and chestnutsCastanea crenata to the second farthest from the site of origin. Most food was hoarded beneath the ground surface (95%), but some were hoarded in forks of trees and in small tree holes. Squirrels selected food items of high energy content for hoarding, in preparation for winter and the breeding season.

The distribution and habitat use of the Eurasian red squinel Sciurus vulgaris L. during summer, in Nopporo Forest Park, Hokkaido.

The distribution and habitat use of the Eurasian red squirrel Sciurus vulgaris L. was studied in Nopporo Forest Park (43°20'N, 141°30'E), Hokkaido, Japan where a study area consisting of a total of 401, 200 m by 200 m, grid squares was established. Observations were made of individuals, their dreys, their feeding signs, and their footprints (after dusting with wheat flour). Squirrels were found to be widely distributed throughout the study area, and to inhabit 45 of the 401 squares (11.2%). Squirrels occurred at high frequencies in three areas within the forest. The percentages of squares in which squirrels lived, differed significantly between different forest types, with 28.2% of squares in evergreen coniferous forest used, 5.3% in deciduous coniferous forest; 5.2% in mixed forest; 3.9% in deciduous broad-leaved forest, and 0% in other areas. We concluded that dusting with flour was a useful method for revealing footprints, and that this facilitated the ease study of squirrel distribution. The distribution of the red squirrel clearly depends on the forest type. Coniferous forest areas were selected as habitat by squirrels during summer because they provided good sources of food and ideal sites for building dreys.

Population fluctuations and habitat selection in the Eurasian red squirrel Sciurus vulgaris

The population fluctuations of Eurasian red squirrel Sciurus vulgaris during ten winters showed a strong relation to Norway spruce Picea abres cone crop one year before Neither, Scots pme Pinus sylvestris cone crop nor mean temperature in December and January had an additional significant effect on the fluctuations The one‐year time‐lag between the good spruce cone crop and mcreased red squirrel density suggests that the rich food supply first mcrease the winter survival and then the reproductive successThe highest density‐index of red squirrels was found m old forest dominated by Norway spruce (mean density‐index 34 km−2) This habitat was also occupied in all 10 winters Other habitats with lower densities were occupied in fewer winters The vanation in density‐index was also highest in this habitat indicating that the dispersion of red squirrel individuals in different habitats follow the food supply