Explore the vast range of titles available.

Paraxerus cepapi (A. Smith, 1836) is a rodent commonly called Smith's bush squirrel. Pelage color varies throughout its distribution, with grayer individuals in the western reaches of its distribution and more brown individuals in eastern areas. Paraxerus cepapi is 1 of 11 species in the genus Paraxerus and is found throughout sub-Saharan Africa. The International Union for the Conservation of Nature (IUCN) considers P. cepapi to be a species of “Least Concern” (LC), listing no major threats.

Vocal communication is an important method squirrels (Sciuridae) use to transfer information from one individual to others. While behaviors associated with vocal communication have been explored in individual species or single call‐types in specific groups of squirrels, no comprehensive review of these behaviors exists for Sciuridae. Herein, I review the current literature to describe behaviors associated with vocal communication in three groups of squirrels: ground squirrels, tree squirrels, and flying squirrels. I discuss the behavioral functions of squirrel vocalizations. A wide variety of behaviors are associated with particular call‐types produced by squirrels, including alarm, agonistic, discomfort, affiliative, mating, and neonatal calls. There are large knowledge gaps in cataloging the vocal repertoires and associated behaviors of many species of squirrels, including commonly studied species such as marmots and ground squirrels, as alarm calls are typically focused on and other call‐types are understudied or ignored. Since vocal communication is important to the development, reproduction, and survival of squirrels, further understanding the biological and ecological drivers behind vocal repertoires is critical to evaluating the ethology of this family as a whole.

Squirrels are diurnal rodents with high visual acuity including unique properties well-suited for their natural environment. This study was conducted to explore some ocular microscopic features of tree-harbouring squirrels in the University of Ibadan, Ibadan, Nigeria. Two male squirrels were cage-trapped within the University premises. Light microscopic analysis was carried on paraffin-embedded eye samples harvested from the animals. The densely compacted stromal fibres, 351 ± 52.5 µm thick, formed the thickest part of the cornea, and the basement membrane of the corneal epithelium, 63.8 ± 13.0 µm thick, was notably positive with Periodic Acid Schiff (PAS) stain. Strong pigmentation was present at the choroid as well as the iridal and ciliary epithelia. The multiple layering of the retinal structure exhibited densely packed ganglion cells at the ganglion cell layer which together with the nerve fibre layer was observed to be thinnest at the more peripheral portion but becomes thicker towards the optic disc. Strongly positive glia fibrillary acidic protein (GFAP+) cells with their abundant fibrous processes were demonstrated immunohistochemically at the retinal nerve fibre layer and the optic nerve. Histological features of the retinal cellular components of the tree squirrels investigated has thus highlighted the structural adaptation of these animal species to their environmental arboreal habitat and diurnal lifestyle. Findings from this study, while further noted to be similar to that in human, showed that African tree squirrels represent promising rodent model for human retinal/ocular research.

It is widely assumed that spillover of alien parasites to native host species severely impacts naïve populations, ultimately conferring a competitive advantage to invading hosts that introduced them. Despite such host-switching events occurring in biological invasions, studies demonstrating the impact of alien macroparasites on native animal hosts are surprisingly few. In Europe, native red squirrels (Sciurus vulgaris) are replaced by introduced North American grey squirrels (S. carolinensis) mainly through resource competition, and, only in the United Kingdom and Ireland, by competition mediated by a viral disease. In Italy such disease is absent, but spillover of an introduced North American nematode (Strongyloides robustus) from grey to red squirrels is known to occur. Here, we used long-term (9 years) capture-mark-recapture and parasitological data of red squirrels in areas co-inhabited by grey squirrels in Northern Italy to investigate the impact of this alien helminth on naïve native squirrels’ body mass, local survival, and reproduction of females. We found no negative effect of the alien parasite on body mass or reproductive success, but intensity of infection by S. robustus reduced survival of both male and female squirrels. Significantly, survival of squirrels co-infected by their native nematode, Trypanoxyuris sciuri, was less affected by S. robustus, suggesting a protective effect of the native helminth against the new infection. Hence, we demonstrate that alien S. robustus spillover adds to the detrimental effects of resource competition and stress induced by grey squirrels, further reducing the fitness of the native species in the presence of the invasive competitor.

According to producer–consumer models, consumers should follow pulsed resources with a time lag. This view has been challenged by studies demonstrating that individuals may anticipate future resource pulses by increasing reproduction just before the pulse. We studied population fluctuations and reproduction in European red squirrels, Sciurus vulgaris, in relation to seed masting of the main food resource (the Norway spruce) in boreal coniferous forests between 1979 and 2013. Red squirrels are pre-dispersal seed predators, and previous studies have shown that they can anticipate the coming seed mast. We did not find any indication that anticipation of masting (year ₜ) increased red squirrel reproduction in the preceding spring to early summer. Instead, the reproductive output of the squirrels was highest in the spring following the mast, indicating that the population had to be at its largest size in the autumn after the mast (year ₜ₊₁), when lots of subadults were around. However, we surmised, based on snow tracks and squirrel nest data, that the population crashed during the following winter (year ₜ₊₁). These data reflected the adult population during winter, which peaked at the same time as the resource pulse. We can therefore conclude that the time lag between the resource pulse and the attainment of the peak number of squirrels was less than one year, and that the resource crash affected more juveniles and subadults than adults. The population increase overlapped with the occurrence of masting, but there was also a lagged response, supporting the classical view of producer–consumer models.

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.

Knowledge of the spatiotemporal variability of abundance and vital rates is essential to the conservation of wildlife populations. In Pacific Northwest forests, previous small mammal research has focused on estimating abundance; few studies have focused on vital rates. We used robust design temporal symmetry models and live-trapping data collected 2011–2016 at nine sites to estimate apparent annual survival, population growth rate, and recruitment of Humboldt's flying squirrels (Glaucomys oregonensis) and Townsend's chipmunks (Neotamias townsendii) in a late-successional forest of the Cascade Mountains of Oregon, United States. We also estimated the proportional contribution of apparent annual survival and recruitment to population growth rate. Covariates previously associated with abundance were also associated with vital rates for Townsend's chipmunks, but less so for Humboldt's flying squirrels. Apparent annual survival was nearly constant (range = 0.47 to 0.51) among years and sites for Humboldt's flying squirrels but was consistently lower and more variable among years for Townsend's chipmunks (range = 0.13 to 0.31). Recruitment was variable among years for both species. Apparent annual survival generally contributed more than recruitment to the population growth rate of Humboldt's flying squirrels. For Townsend's chipmunks, recruitment consistently contributed more than apparent annual survival to population growth rate. These findings suggest that life history strategies differed for these co-occurring species. This study demonstrates substantial temporal variation in vital rates and some differences in abundance and vital rate habitat associations, suggesting that habitat suitability inferences based on short time series or variation in abundance could be misleading.

In an ever more urbanized world, animals have to cope with different challenging conditions that may shape the individual’s phenotype in the urban environment. Since body mass and body size are found to be related to fitness in many species, investigating the variation in these two morphological traits along the rural-urban gradient, is a first step to understand how animals adapt to urbanization. Here we studied two tree squirrels, the native Eurasian red squirrel (Sciurus vulgaris) and the invasive Eastern grey squirrel (Sciurus carolinensis), using a pseudo-experimental design with replicated study sites (2 rural, 2 suburban and 2 urban sites for each species). We investigated whether squirrels differed in body size and body mass along the urbanization gradient and whether the invasive alien squirrels had more marked differences along the gradient, showing a higher adaptation capacity. We did not find variation in body size in red squirrels along the gradient, but invasive grey squirrels were slightly larger in urban than in other area-types. In both species, animals of either sex were heavier in the urban than in the rural sites, while the difference between urban and suburban areas depends on species and sex. Hence, morphologically both native and invasive species showed similar changes, with higher body mass in urban habitat, which could result in higher fitness, since body mass in squirrels species is positively related to reproductive success.

Sciurus anomalus Güldenstädt, 1785 is a rodent commonly called the Caucasian squirrel. S. anomalus is a medium-sized squirrel with chestnut gray to grizzled buff dorsum, buff eye rings, and chestnut to buff-yellow underparts. S. anomalus is 1 of 28 species in the genus Sciurus and is found in forests of the Middle East and extreme southwestern Asia. The International Union for Conservation of Nature and Natural Resources considers S. anomalus to be a species of “Least Concern;” habitat destruction is the main threat.

Cryptosporidium spp. are opportunistic pathogens that cause diarrhea in a variety of animal hosts. Although they have been reported in many animals, no information has been published on the occurrence of Cryptosporidium spp. in red-bellied tree squirrels ( Callosciurus erythraeus ). A total of 287 fecal specimens were collected from Sichuan province in China; the prevalence of Cryptosporidium spp . , measured by nested-PCR amplification of the partial small-subunit (SSU) rRNA gene, was 1.4% (4/287). Three different Cryptosporidium species or genotypes were identified: Cryptosporidium parvum ( n  = 1), Cryptosporidium wrairi ( n  = 1), and Cryptosporidium rat genotype II ( n  = 2). The present study is the first report of Cryptosporidium infection in red-bellied tree squirrels in China. Although there is a relatively low occurrence of Cryptosporidium , the presence of C. parvum and C. wrairi , which were previously reported in humans, indicates that red-bellied tree squirrels may be a source of zoonotic cryptosporidiosis in China. Les Cryptosporidium spp. sont des agents pathogènes opportunistes qui provoquent une diarrhée chez divers animaux hôtes. Bien qu’ils aient été signalés chez de nombreux animaux, aucune information n’a été publiée sur la présence de Cryptosporidium spp. chez les écureuils à ventre rouge ( Callosciurus erythraeus ). Au total, 287 spécimens fécaux ont été recueillis dans la province du Sichuan en Chine. La prévalence de Cryptosporidium spp., mesurée par amplification par PCR imbriquée du gène partiel de la petite sous-unité de l’ARNr (SSU), était de 1,4 % (4/287). Trois espèces ou génotypes différents de Cryptosporidium ont été identifiés :  Cryptosporidium parvum ( n  = 1), Cryptosporidium wrairi ( n  = 1) et le génotype II de Cryptosporidium du rat ( n  = 2). La présente étude est le premier signalement d’infection à Cryptosporidium chez des écureuils à ventre rouge en Chine. Cryptosporidium est relativement peu présent, mais la présence de C. parvum et de C. wrairi , déjà signalés chez l’homme, indique que les écureuils à ventre rouge peuvent être une source de cryptosporidiose zoonotique en Chine.