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Animals change their daily activity patterns in response to season, food availability and the presence of competitors. Competition may be an important driver of a species' daily activity pattern, as animals manage conflict by avoiding each other temporally. We evaluated how vegetation structure and the presence of competitors changed the daily activity patterns of closely related fox squirrels, Sciurus niger, and grey squirrels, Sciurus carolinensis. We monitored squirrel activity in north and central Florida using passive game cameras at two spatial scales: local and point. To understand how seasonality and competition interact to drive behaviour, we compared squirrel activity during the leaf-off (1 January – 15 March) and leaf-on (16 March – 1 July) seasons. We tested for a relationship between squirrel activity and canopy cover by fitting a von Mises kernel distribution. To test how season and competition affected squirrel behaviour, we compared activity by computing a kernel density overlap function, ranging from 0 (no overlap: the squirrels are never active at the same time) to 1 (complete overlap: the squirrels have identical activity patterns). We found that daily squirrel behaviour was not influenced by canopy cover (P = 0.61). Fox squirrels had a single activity peak occurring around midday. In contrast, grey squirrels had a bimodal activity pattern with peaks shortly after sunrise and before sunset. The intensity of this partitioning existed on a gradient and changed with season and the presence of competitors. Fox and grey squirrel daily patterns overlapped the most when they were allopatric in the leaf-on season (overlap = 0.70, P < 0.001) and the least while sympatric in the leaf-on season (overlap = 0.24, P < 0.08). This ephemeral response to competition highlights that various axes of resource partitioning can promote coexistence between closely related species. Highlights • We examined daily activity patterns of competing grey and fox squirrels. • Squirrel behaviour was not influenced by canopy cover. • Fox squirrels had a single activity peak around midday. • Grey squirrel activity peaked shortly after sunrise and before sunset. • Temporal partitioning existed on a gradient and varied with season and competition. [ABSTRACT FROM AUTHOR]

We describe a new species of squirrel (Sciuridae, Callosciurus) from Hon Khoai Island, located off the coast of southern Vietnam (centered at ca. 8°26′08″N, 104°49′58″E) and discuss its phylogenetic position in the genus Callosciurus. Compared to other Callosciurus occurring on the Indochina Peninsula, the new species (Callosciurus honkhoaiensis) is strikingly small, especially head and body length, body mass, and hind foot length. Unlike other species of Callosciurus, the hairs at the tip of the tail are white with a black base, and the venter and feet are whitish cream. The new species at present is known only from the type locality, Hon Khoai Island. Phylogenetically, the new species is closely related to C. caniceps, suggesting that it evolved from C. caniceps or an ancestor in common with C. caniceps, possibly during the Pliocene. Genetic distances between the 2 species calculated from comparison of mitochondrial cytochrome b sequences are 10.1–10.3%. During both glaciations and interglaciations of the Pleistocene, the new species may have been isolated from other Callosciurus populations by rivers and sea, respectively. [ABSTRACT FROM AUTHOR]

The impacts of non-native, invasive grey squirrels ( Sciurus carolinensis ) on broadleaf woodlands and red squirrel population ( Sciurus vulgaris ) are well recognised among wildlife professionals, yet efforts to control the species across its expanding range require substantial time and resources. Through collaboration, wildlife professionals and communities can more effectively implement the population monitoring and control programmes necessary to conserve native species under threat. However, for such collaboration to be successful, wildlife professionals must first understand public attitudes towards grey squirrels, and the control methods available. Through a national level survey ( n  = 3758) we examine the UK public's attitudes to red and grey squirrels, and the acceptability of seven control methods. Results show that much of the public have little knowledge of the grey squirrel's negative impacts. In fact, contrary to the notion of a pest species, the presence of grey squirrels is often desirable. Furthermore, those control methods recommended by wildlife professionals are regarded by the public as some of the least acceptable. Those most accepting of controls include males, older generations, those most knowledgeable about squirrels and people who are aware of squirrel management being practiced in their local area. To foster more fruitful collaboration, wildlife professionals should raise awareness of why particular control methods are preferred, highlight the damage grey squirrels cause to other valued species, and offer local communities a variety of roles which contribute to the wider goal of native species conservation. [ABSTRACT FROM AUTHOR]

Behavioural flexibility has been argued to be an evolutionarily favourable trait that helps invasive species to establish themselves in non-native environments. Few studies, however, have compared the level of flexibility (whether considered as an outcome or as a process) in mammalian invaders and related native species. Here, we tested whether flexibility differs between groups of free-ranging invasive eastern grey squirrels, Sciurus carolinensis , and native Eurasian red squirrels, Sciurus vulgaris , in the U.K., using an easy and a difficult food extraction task. All individuals of both species showed flexibility, at the outcome level, in solving the easy task and solution time was comparable between species across a series of successes. A higher proportion of grey squirrels than red squirrels solved the difficult task. However, for those squirrels that did solve the task, solving efficiency was comparable between species on their first success, and a few red squirrels outperformed the grey squirrels in subsequent successes. Between-species analysis showed that instantaneous flexibility, flexibility at the process level that was measured as the rate of switching between tactics after a failed attempt, was higher in red squirrels than in grey squirrels. Within-species analysis also revealed that red squirrel problem solvers showed higher flexibility at the process level than their nonsolver counterparts. Nonsolvers also failed to make ‘productive’ switches (switching from ineffective to effective tactics). Together, the results suggest that problem-solving ability overlaps in the two species, but is less variable, and on average higher, in grey squirrels than in red squirrels. The superior behavioural flexibility of the grey squirrels, shown here by success at problem solving, may have facilitated their invasion success, but it may also have resulted from selective pressures during the invasion process. [ABSTRACT FROM AUTHOR]

ABSTRACT: Habitat loss and fragmentation can have detrimental effects on wildlife populations and where pervasive can create population isolates that may experience reduced genetic diversity and lower persistence. Diseases that cause epizootics also can reduce wildlife populations and may have disproportionate effects on small populations. We studied survival of radio‐marked western gray squirrels (Sciurus griseus) using known‐fate models in Program MARK and we quantified annual reproductive success by following females through the breeding season and counting young at natal nests. We used data on survival and productivity to model population growth rate and associated parameters using deterministic and stochastic approaches. Populations of western gray squirrels that we studied in an extensive, forested landscape and in a highly fragmented, urbanizing landscape in Washington, USA differed in their modeled growth rate. Adult survival was similar between populations although both were strongly affected by different endemic diseases with high epizootic potential. The demographic parameters that differed most between these 2 populations were related to productivity; litter size was marginally smaller and reproductive success was significantly lower in the urbanizing Puget Trough compared to rural Klickitat County. Results of our demographic modeling suggest that the larger Klickitat population is robust to immediate threats, whereas the smaller Puget Trough population is at risk because of its small size and low fecundity. Periodic outbreaks of notoedric mange in the Klickitat population reduce adult survival, although our models suggest that these epizootics would need to occur more frequently than observed to be of significant risk to the population. Continued degradation and fragmentation of western gray squirrel habitat in the Klickitat region along with mild winters resulting from climate change could increase the frequency and severity of mange epizootics and further threaten this population. Actions to retain and improve habitat resources may help ameliorate the effects of future mange epizootics and maintaining quality habitat should be a management priority in this region. The insular Puget Trough population experienced mortality due to tularemia each year of our study with infection rates ≥14%. Lack of characteristic histological indications in some affected squirrels may lead to underreporting of tularemia in animals submitted for routine necropsy and could complicate assessment of mortality risks in wildlife population studies. Given its small size and isolation, the Puget Trough population should be monitored closely for indications of decline in number or occupancy; this small population may need periodic augmentation to maintain genetic diversity. Increasing suitable habitat and maintaining connectivity between currently occupied range and potential habitat in the surrounding landscape will be crucial to the long‐term viability of this population but will be challenging in the urbanizing landscape of the Puget Trough. © 2017 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Male reproductive success in most mammals is determined by their success in direct inter-male competition through aggression and conflict, resulting in female-defense mating systems being predominant. This is linked to male testosterone levels and its dynamics. However, in certain environments, a scramble-competition mating system has evolved, where female reproductive behavior takes precedence and male testosterone dynamics are unlikely to be related to inter-male competition. We studied the North American red squirrel ( Tamiasciurus hudsonicus ), a species with a well-established scramble-competition system. Using an ACTH hormonal challenge protocol as a proxy for competitive interactions, we compared the testosterone dynamics in breeding males in late winter with that in nonbreeding males in late spring in the Yukon. To gain an integrated picture of their physiological state, we also assessed changes in their stress response, body mass, energy mobilization, and indices of immune function. Testosterone levels at the base bleed were high in breeding males (2.72 ng/mL) and virtually absent in non-breeding males (0.04 ng/mL). Breeding males were in better condition (heavier body mass, higher hematocrit, and higher erythrocytes), had higher indices of immune function (neutrophil:lymphocyte ratio), but a similar ability to mobilize energy (glucose) compared with non-breeding males. Though total cortisol was higher in non-breeding males, free cortisol was twice as high in breeding males as their corticosteroid binding globulin levels were half as high. In response to the ACTH challenge, testosterone levels in breeding males declined 49% over the first hour and increased 36% over the next hour; in non-breeding males levels showed no change. Free cortisol increased only modestly (26% in breeding males; 23% in non-breeding males). Glucose levels changed similarly in breeding and nonbreeding males, declining for the first 30 min and then increasing for the next 60 min. Thus, testosterone and components of the stress axis function in a profoundly different manner in male red squirrels than in males of mammals with female-defense mating systems. There are four probable interrelated reasons for these adaptations in male red squirrels: the marginal benefits of each mating, the constraints of mate searching away from their own resource-based territories, energy mobilization in a harsh environment, and a long life span. [ABSTRACT FROM AUTHOR]

Eastern gray squirrels produce moans for aerial predators and quaas for terrestrial threats. One commonly-supported hypothesis for such predator-associated signals is that they elicit predatorspecific escape responses in conspecifics. With simulated aerial predators, squirrels ran to the far side of tree trunks. In response to simulated terrestrial predators, squirrels frequently ran to where they could see the predator but could quickly flee to the far side of the tree trunk. Playbacks of quaas and moans elicited flight behaviour, but without association between escape location and alarm call type. Locations elicited by alarm calls differed from those elicited by simulated predators, with squirrels pausing on the side facing the call's source. While grey squirrel alarms and escape strategies differ by predator type, the vocalizations do not function to elicit divergent escape strategies in conspecifics. This result stands in contrast to observed functions in other species with calls differing by predator type. [ABSTRACT FROM AUTHOR]

The aim of the present study was to elucidate the regulatory role of cell proliferation and apoptosis in testicular development of wild Daurian ground squirrels during the breeding season (April), the non-breeding season (June) and before hibernation (September). Gross mass and hormonal analysis showed that the testis : body mass ratio and plasma testosterone concentration fluctuated seasonally, with a peak in April and lowest values in June. Similarly, spermatogenesis was fully developed in April but suppressed in June and September. Testicular decellularisation and vacuolisation was seen during the transition from the breeding to the non-breeding season. Furthermore, testicular levels of proliferating cell nuclear antigen, cyclin D2 and caspase-3 protein were significantly increased in June and September. Intriguingly, positive terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling staining and nuclear translocation of caspase-3 in testicular germ cells appeared only during the prehibernation period, whereas accumulation of cyclin D2 in spermatocyte nuclei occurred in September. These findings demonstrate, for the first time, that both cell proliferation and apoptosis are stimulated during the prehibernation period, indicating that a hormonal-regulated balance of testicular germ cell proliferation and apoptosis may play a pivotal role in preparing for testicular recrudescence of wild Daurian ground squirrels. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

During hibernation, thirteen-lined ground squirrels (Ictidomys tridecemlineatus) regularly cycle between bouts of torpor and interbout arousal (IBA). Most of the brain is electrically quiescent during torpor but regains activity quickly upon arousal to IBA, resulting in extreme oscillations in energy demand during hibernation. We predicted increased functional capacity of brain mitochondria during hibernation compared with spring to accommodate the variable energy demands of hibernation. To address this hypothesis, we examined mitochondrial bioenergetics in the ground squirrel brain across three time points: spring (SP), torpor (TOR), and IBA. Respiration rates of isolated brain mitochondria through complex I of the electron transport chain were more than twofold higher in TOR and IBA than in SP (P < 0.05). We also found a 10% increase in membrane potential between hibernation and spring (P < 0.05), and that proton leak was lower in TOR and IBA than in SP. Finally, there was a 30% increase in calcium loading in SP brain mitochondria compared with TOR and IBA (P < 0.01). To analyze brain mitochondrial abundance between spring and hibernation, we measured the ratio of copy number in a mitochondrial gene (ND1) vs. a nuclear gene (B2M) in frozen cerebral cortex samples. No significant differences were observed in DNA copies between SP and IBA. These data show that brain mitochondrial bioenergetics are not static across the year and suggest that brain mitochondria function more effectively during the hibernation season, allowing for rapid production of energy to meet demand when extreme physiological changes are occurring. [ABSTRACT FROM AUTHOR]

In order to test how flexibly animals are able to behave when making trade-offs that involve assessing constantly changing risks, we examined whether wild Eastern grey squirrels showed flexibility of behavioral responses in the face of variation in 2 conflicting risks, cache pilferage, and predation. We established that cache pilferage risk decreased with distance from cover and was thus negatively correlated with long-term predation risk. We then measured changes in foraging and food-caching behavior in the face of changes in the risk of predation and food theft over a short time-scale. We found that, overall, squirrels move further away from the safety of cover when they cache, compared to when they forage, as predicted by pilferage risk. However, there was no effect of immediate pilferage or predation risk (i.e., the presence of potential predators or pilferers) on the distance from cover at which they cached, and only a slight increase in forage distance when predation risk increased. These results suggest that "rules of thumb" based on static cues may be more cost-effective for assessing risk than closely tracking changes over time in the way suggested by a number of models of risk assessment. [ABSTRACT FROM AUTHOR]

The optimal prey selection hypothesis, a part of Optimal Foraging Theory, uses prey energy content and forager searching and handling times to predict when a forager will choose only the most profitable prey and when it will include less profitable prey in its diet. I tested the hypothesis using eastern gray squirrels as foragers and pairs of prey--sunflower fruits and seeds, and pumpkin seeds and embryos-- that differed in handling time. In all foraging trials, the squirrels consumed both prey types, but showed a partial preference for the less profitable prey (sunflower fruit and pumpkin seed). For squirrels foraging on pumpkin seeds and embryos, the hypothesis, which predicts that the more profitable prey (embryos) alone would be selected, was not supported by a partial preference value significantly greater than 0.5 which would indicate that both prey types were consumed. The hypothesis may be limited to laboratory conditions in which prey are presented sequentially, a condition not met in the experiments described here where prey types were offered together and were constantly mixed as the squirrels searched for prey in a sand-containing dish. Instead, squirrels showed a slight preference for larger prey which may result from higher encounter rates or may result from squirrels using a "rule of thumb:" when hungry, consume prey as they are encountered. [ABSTRACT FROM AUTHOR]

Matrilineal kin groups are common in social mammals and often exhibit cooperative behaviors. Social interactions in such groups may have varying consequences on fitness depending on the number of kin present. We used social network analysis to study which factors (including individual spatial distribution, sex, age, and kinship) affected patterns of aggressive interactions in Columbian ground squirrels during the important breeding period of lactation. In addition, we studied how patterns of aggressive interactions affected female reproduction and fitness. Received aggressions lessened as ground squirrels aged, likely reflecting greater dominance in older individuals. Outwards aggression peaked at prime reproductive age, but decreased in older individuals. In females, outwards aggressiveness was positively related to energy allocated to reproduction and annual fitness, suggesting that highly aggressive females were either of high intrinsic quality or were able to defend high-quality territories. Finally, female-female aggression was primarily targeted toward non-kin individuals, revealing the advantage for breeding adult females of having close kin neighbors that were also breeding. Thus, breeding females that were close kin appeared to be "genial neighbors" that benefited from increased fitness, highlighting the role of kin selection in mitigating the costs (e.g., injuries, stress) of aggression. [ABSTRACT FROM AUTHOR]

For food caching to be adaptive, the benefits of recovery must outweigh the costs of storing an item. One of the costs to cachers is the risk of theft, and therefore, it is predicted that individuals may be sensitive to this theft and show various behavioural strategies to minimise it. In this study, we gave wild Cape ground squirrels ( Xerus inauris) a choice between two different coloured items of the same food type: one item with a specific colour that was always artificially removed when cached and the other item with a different colour that was not removed when cached. During the choice presentations, subjects reduced the amount they consumed and cached of the food items with the colour that was experimentally removed when cached, despite the two items only differing in caching pay-off. This avoidance to choose the food with the colour that was removed occurred over time, which suggests that subjects were using information about the item's pay-off during cache recovery and this then impacted on successive decisions. This study highlights how the sensitivity to a food item's pay-off can affect an individual's choice towards items that offer the greater overall reward. [ABSTRACT FROM AUTHOR]

The eastern gray squirrel (Sciurus carolinensis) is known to gnaw on bone and thus has the potential to affect terrestrial surface remains in forensic scenes throughout its extensive geographic range in North America and other places in the world where it has been introduced. To determine the timing, extent, and characteristics of gnawing of this rodent species within an urban environment, an initial sample of 305 dry postcranial bones of white-tailed deer (Odocoileus virginianus) were wired to trees for a period of 8 weeks and observed every 2 weeks in multiple sites in Boston, Massachusetts. Squirrel gnawing damage included the typical parallel striations noted for rodents and the loss of epiphyses of long bones, marrow cavity exposure, and sculpting of bone margins, with a cumulative total of 58 out of the original sample of 305 bones (19.0%) having gnawing damage of some kind. When subtracting the bones lost during the experiment without previous gnawing, the cumulative total is 58 out of 271 bones (21.4%). Rodent gnawing can advance rapidly, potentially causing the loss of diagnostic bone features and obscuring previous trauma sites, and researchers should be aware of its effects on exposed skeletal remains. [ABSTRACT FROM AUTHOR]

This study identifies techniques to maximize trap efficiency and minimize trapping effort when using live traps to capture the invasive alien Pallas's squirrel ( Callosciurus erythraeus), which was introduced in Italy near the Swiss borders. We explored the effects of time of day, season, number of checks in the capture session and type of live trap (single or multi-capture). Moreover, the vegetation around traps (characteristics of the tree supporting the trap, vegetation growth, vegetation cover, vegetation richness and similarity index) was tested. Squirrels were caught more frequently in the morning, but trapping success was not affected by the type of trap used. Squirrel trap response varied significantly in relation to the season, and a higher trapping success in the first days of the trapping session suggests the importance of prebaiting. We reject the hypothesis that vegetation around traps affected the capture success of Pallas's squirrel in deciduous forests. Thus, recommendations to improve the trapping efficiency of this species are to (1) use single capture live traps with at least one week of prebaiting, (2) increase the capture effort in winter and (3) set traps where access is easy and where there are signs of high activity of individuals of the alien species. [ABSTRACT FROM AUTHOR]

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Gliding squirrels occur globally and many are of conservation concern due to habitat fragmentation and degradation. Information on their ability to cover the distance between two trees by gliding is lacking in many species which might be vital for habitat management and conservation. The aim of the study was to present the field observations on gliding behaviour of the red giant gliding squirrel Petaurista petaurista observed within tropical rain-forest of Namdapha National Park, Arunachal Pradesh, Indian eastern Himalaya. The data were collected on 71 glides observed at nights. The mean height of launching and landing trees were 28.5 ± 1.0 m and 16.4 ± 0.9 m, respectively. Gliding variables calculated were vertical drop (mean = 13.4 ± 1.0 m), horizontal distance (mean = 36.3 ± 2.7 m), air speed (mean = 8.9 ± 0.2 m s-1), ground speed (mean = 7.9 ± 0.2 m s-1), glide ratio (mean = 3.1 ± 0.2), glide angle (mean = 19.0 ± 0.9°), GBH of launching tree (mean = 156.8 ± 8.5 cm) and GBH of landing tree (mean = 195.2 ± 9.5 cm). Gliding distance was categorized in four types. The highest glides in a 26-50 m glide-class (44% (n = 31)) were the most frequently observed. Gliding squirrels preferred top canopy (56%, n = 40) for distant glides. Forest structure has an influence on the gliding habits of gliding squirrels and thus our data on gliding parameters should be used when planning forest management actions. [ABSTRACT FROM AUTHOR]

This study evaluated the normal haematological profile of apparently healthy African grey squirrels ( Sciurus carolinensis) trapped in Nsukka, Southeast Nigeria. A total of 20 squirrels comprising 8 males and 12 females were used and determination of haematological profile followed standard procedures. Results obtained for the parameters assessed are summarized as follows (mean ± standard error): packed cell volume, 37.54 ± 0.76 %; haemoglobin concentration, 14.79 ± 0.18 g/dl; red blood cell count, 7.27 ± 0.27 × 10/μl; mean corpuscular volume, 54.33 ± 1.09 fl; mean corpuscular haemoglobin, 21.74 ± 0.55 pg; mean corpuscular haemoglobin concentration, 37.39 ± 0.50 g/dl; white blood cell count, 4.77 ± 0.19 × 10/μl; neutrophil counts, 27.93 ± 1.36 %; lymphocyte counts, 67.80 ± 1.38 %; monocyte counts, 2.33 ± 0.29 %; eosinophil counts, 1.80 ± 0.26 %; basophil counts, 0.13 ± 0.09 % and body weight, 176.67 ± 3.55 g. There were no significant differences ( p > 0.05) between the sexes in all the haematological parameters assessed. Results from this study was considered important as deviations in the normal haematology have a predictive value for general pathological changes in the body and may be useful in wildlife quarantine services and in active disease surveillance. [ABSTRACT FROM AUTHOR]

We described the relationship between relatedness as full or maternal half siblings and expression of social play and other social behaviors in juvenile Belding's ground squirrel ( Urocitellus beldingi) litters and evaluated the possible role of play in establishing social bonds between juvenile females. We used microsatellite analysis to determine relatedness. Juvenile females did not interact preferentially with full over half siblings, suggesting that they may form bonds equally with full and half sisters. The probability that females will have a surviving full sister beyond the juvenile period may be low in U. beldingi, and establishing a cooperative relationship with a half sister may sometimes be the best available option in adulthood. As the proportion of females within litters increased, rates of play decreased, suggesting that low social play may be adequate for social bonding among females. Among juvenile male U. beldingi, play bouts lasted longer between full than half brothers; however, juvenile males did not interact preferentially with full brothers in play or other social interactions. Body mass differences were smaller between full than half brothers, and in both full and half brother pairings, play bouts lasted longest when body mass differences were small. Because male U. beldingi do not ordinarily interact with littermate siblings after emigrating from the natal area, it is unlikely that play behavior functions to establish long-term social bonds between full brothers. Rather, young males may favor play interactions with phenotypically similar partners who can provide optimal challenges in interactions that promote motor development. [ABSTRACT FROM AUTHOR]

Animals often exhibit consistent individual differences in behavior (i.e., animal personality) and correlations between behaviors (i.e., behavioral syndromes), yet the causes of those patterns of behavioral variation remain insufficiently understood. Many authors hypothesize that state-dependent behavior produces animal personality and behavioral syndromes. However, empirical studies assessing patterns of covariation among behavioral traits and state variables have produced mixed results. New statistical methods that partition correlations into between-individual and residual within-individual correlations offer an opportunity to more sufficiently quantify relationships among behaviors and state variables to assess hypotheses of animal personality and behavioral syndromes. In a population of wild Belding's ground squirrels ( Urocitellus beldingi), we repeatedly measured activity, exploration, and response to restraint behaviors alongside glucocorticoids and nutritional condition. We used multivariate mixed models to determine whether between-individual or within-individual correlations drive phenotypic relationships among traits. Squirrels had consistent individual differences for all five traits. At the between-individual level, activity and exploration were positively correlated whereas both traits negatively correlated with response to restraint, demonstrating a behavioral syndrome. At the within-individual level, condition negatively correlated with cortisol, activity, and exploration. Importantly, this indicates that although behavior is state-dependent, which may play a role in animal personality and behavioral syndromes, feedback mechanisms between condition and behavior appear not to produce consistent individual differences in behavior and correlations between them. [ABSTRACT FROM AUTHOR]

In ecosystems with seasonal fluctuations in food supply many species use two strategies to store food: larder hoarding and scatter hoarding. However, because species at different geographic locations may experience distinct environmental conditions, differences in hoarding behavior may occur. Tree squirrels in the genus Tamiasciurus display variation in hoarding behavior. Whereas red ( Tamiasciurus hudsonicus) and Douglas's ( Tamiasciurus douglasii) squirrels in mesic coniferous forests defend territories centered around larder hoards maintaining non-overlapping home ranges, red squirrels in deciduous forests defend small scatter-hoarded caches of cones maintaining overlapping home ranges. As in other rodent species, variation in hoarding behavior appears to influence the spacing behavior of red and Douglas's squirrels. In contrast, Mearns's squirrels ( Tamiasciurus mearnsi) in xeric coniferous forests neither rely on larder hoards nor appear to display territorial behavior. Unfortunately, little is known about the ecology of this southernmost Tamiasciurus. Using radiotelemetry, we estimated home-range size, overlap, and maximum distance traveled from nest to examine the spacing behavior of Mearns's squirrels. Similar to scatter-hoarding rodents, maximum distance traveled from nest was greater for males during mating season, whereas those of females were similar year round. Although no seasonal differences were detected, male home ranges were three times larger during mating season, whereas those of females were smaller and displayed a minor variation between seasons. Home ranges were overlapped year round but contrary to our expectations, overlap was greater during mating season for both sexes, with no detectable relationship between male home-range size and the number of females overlapped during mating season. Overall, the results appear to support our hypothesis that in the absence of larder hoards, the spacing behavior of Mearns's squirrels should be different from larder-hoarding congeners and more similar to scatter-hoarding rodents. [ABSTRACT FROM AUTHOR]

Life-history theory predicts that in hibernators age of maturation is related positively to body size and negatively to the duration of active season aboveground. Yellow souslik is a large-sized ground squirrel with long hibernation, which suggests late maturation. We used four-year field observations of marked individuals to determine the age of maturation in males through analysis of age-dependent variation in body size, mass, androgen status, timing of spring emergence, ranging patterns and social behavior during the mating season. Yearling males were smaller, lighter, had lower level of fecal testosterone, emerged later and had smaller home ranges than older males. Social activity and the number of females encountered did not differ between age classes. After the second hibernation none of the studied parameters varied with age. Cluster analysis revealed two behavioral tactics: "active" males (adults only) emerged earlier, ranged more widely, initiated more contacts, encountered more females and were heavier than "passive" males (both yearling and adult). Thus, males of S. fulvus reached adult size and matured after two hibernations, which is relatively fast for such a big species with short active period. Indirect evidence for copulations and high variation among yearlings in all parameters suggest that some of them might successfully compete with adults. Active tactic of wandering and searching for females is energetically costly, and probably only adult males in good physical condition can afford it, whereas passive tactic of residing is energy saving and good for adults in poor condition and for yearlings that are continuing to grow. [ABSTRACT FROM AUTHOR]

Behavioral, hormonal, and genetic processes interact reciprocally, and differentially affect behavior depending on ecological and social contexts. When individual differences are favored either between or within environments, developmental plasticity would be expected. Parental effects provide a rich source for phenotypic plasticity, including anatomical, physiological, and behavioral traits, because parents respond to dynamic cues in their environment and can, in turn, influence offspring accordingly. Because these inter-generational changes are plastic, parents can respond rapidly to changing environments and produce offspring whose phenotypes are well suited for current conditions more quickly than occurs with changes based on evolution through natural selection. I review studies on developmental plasticity and resulting phenotypes in Belding’s ground squirrels (Urocitellus beldingi), an ideal species, given the competing demands to avoid predation while gaining sufficient weight to survive an upcoming hibernation, and the need for young to learn their survival behaviors. I will show how local environments and perceived risk of predation influence not only foraging, vigilance, and anti-predator behaviors, but also adrenal functioning, which may be especially important for obligate hibernators that face competing demands on the storage and mobilization of glucose. Mammalian behavioral development is sensitive to the social and physical environments provided by mothers during gestation and lactation. Therefore, maternal effects on offspring’s phenotypes, both positive and negative, can be particularly strong. [ABSTRACT FROM AUTHOR]

Studies of Sciurus niger (Fox Squirrel) in the Southeast have focused on habitat relationships with limited emphasis on other life-history characteristics. We estimated survival rates for 51 radio-collared Sciurus n. niger (Southeastern Fox Squirrel) on Fort Bragg, NC, during March 2011–June 2012 using the Kaplan-Meier staggered-entry design. Also, we calculated composite and seasonal 99% kernel-density home-range estimates for male and female Fox Squirrels. During our study, 22 radio-collared Fox Squirrels died: 8 were depredated, 2 were hunter harvested, and 12 died of unknown causes. Survival rates differed among the seasons when the sexes were combined; survival was greatest in the winter and lowest in the fall. Male annual survival (0.35) was lower than female annual survival (0.66) at the α = 0.10 level. Male home ranges were larger than female home ranges, potentially exposing them to greater predation risk. High mortality of male Fox Squirrels may warrant reevaluation of harvest regulations for declining, hunted Fox Squirrel populations. Additionally, large space requirements for Fox Squirrels may be indicative of low availability of forage on the landscape, a condition that should prompt land managers to adjust management actions to improve habitat conditions for Fox Squirrels. [ABSTRACT FROM AUTHOR]

This work describes the foraging techniques, body positions and behavior of free-ranging Ingram's squirrel Guerlinguetus ingrami Thomas, 1901 in a region of the Araucaria moist forest, in the Atlantic Forest of southern Brazil. The animals were observed using the "all occurrence sampling" method with the aid of binoculars and a digital camcorder. All behaviors were described in diagrams and an ethogram. We recorded five basic body positions, 24 behaviors, two food choices, and three feeding strategies utilized to open fruits of Syagrus romanzoffiana (Cham.), the main food source of Ingram's squirrels. We also observed a variance in the animals' stance, which is possibly influenced by predation risk, and discuss the causes of some behaviors. [ABSTRACT FROM AUTHOR]

The prenatal hormonal environment plays an important role in organizing sex differences in the morphology, physiology and behavior of humans as well as other vertebrates. Currently, all related research on rodents has been focused on Myomorpha. This study presents data on sex differences in the anogenital distance (AGD) and the ratio of the second to the fourth digit length (2D:4D) from 44 wild David's rock squirrels Sciurotamias davidianus captured from the Qinling Mountains, China. This was the first study of a species from Sciuromorpha. The AGD as well as body mass are sexually dimorphic. There are no sex differences or lateral asymmetry in 2D:4D. Significant correlation was not found between AGD and 2D:4D for any paw. The findings indicate that 2D:4D may not be fixed or influenced by the prenatal steroidal environment in David's rock squirrels. [ABSTRACT FROM AUTHOR]

The production of offspring by vertebrates is often timed to coincide with the annual peak in resource availability. However, capital breeders can extend the energetic benefits of a resource pulse by storing food or fat, thus relaxing the need for synchrony between energy supply and demand. Food-hoarding red squirrels ( Tamiasciurus hudsonicus) breeding in the boreal forest are reliant on cones from a masting conifer for their nutrition, yet lactation is typically completed before the annual crop of cones is available for consumption such that peaks in energy supply and demand are not synchronized. We investigated the phenological response of red squirrels to annual variation in environmental conditions over a 20-year span and examined how intra- and inter-annual variation in the timing of reproduction affected offspring recruitment. Reproductive phenology was strongly affected by past resource availability with offspring born earlier in years following large cone crops, presumably because this affected the amount of capital available for reproduction. Early breeders had higher offspring survival and were more likely to renest following early litter loss when population density was high, perhaps because late-born offspring are less competitive in obtaining a territory when vacancies are limited. Early breeders were also more likely to renest after successfully weaning their first litter, but renesting predominantly occurred during mast years. Because of their increased propensity to renest and the higher survival rates of their offspring, early breeders contribute more recruits to the population but the advantage of early breeding depends on population density and resource availability. [ABSTRACT FROM AUTHOR]

Nests play a crucial role in the life history of tree squirrels, and can be a critical component of their biology that enables them to be a successful invasive species. Red-bellied squirrels (Sciurus aureogaster) were introduced to Elliott Key, Florida, in the late 1930s, and spread to nearby islands. Red-bellied squirrels were believed extirpated by Hurricane Andrew in 1992, but were rediscovered on Elliott Key in 2005. In 2006 and 2007, we surveyed for squirrel nests and measured vegetation to evaluate forest characteristics associated with nest-site selection by squirrels, and compared these data to measurements collected at random locations. Squirrels placed nests in large trees with more canopy linkages in mixed-hardwood forest, and the nest trees were in areas with large trees, high tree density and canopy cover, and lower recent hurricane damage. Red-bellied squirrels selected characteristics of nest trees and forest structure in similar ways to individuals in their native range, and to other species of tree squirrels in general. Results from our research allowed land managers to assess possible management actions and provided important information for them to develop an effective management strategy. Park officials are currently working toward complete eradication of the introduced population of red-bellied squirrels from the Florida Keys. We suggest that behaviors of individuals in native ranges may elucidate patterns for individuals introduced to novel environments; however, we also caution that care must be taken in further extrapolation. Our findings emphasize the importance of understanding ecology of introduced species for effective management. [ABSTRACT FROM AUTHOR]

Historically, melanistic fox squirrels have been found in Council Bluffs, Iowa, and along the Missouri River in Eastern Omaha, Nebraska. However, recent anecdotal observations suggest that the melanistic trait in fox squirrels is expanding westward into Omaha. Squirrels were surveyed in the autumn of 2010 and 2011 along transect lines within five major city sections and different habitat types; comparisons were made to a survey performed in 1973. Proportion of melanistic squirrels in Council Bluffs remained at levels similar to 1973 surveys (~50% melanistic). Since 1973 melanistic fox squirrels have increased in Omaha, with a higher proportion of melanistic squirrels in northwest (7.4%) and northeast (7.6%) compared to southwest or southeast Omaha (4.6%). Melanistic squirrels were found in higher proportions in parks (12.1%) and residential (10.9%) habitats compared to business (6.1%), industrial (7.4%), or golf course (8.0%) habitats. Melanistic squirrels were also observed more frequently at colder temperatures than rufus squirrels. The results yielded significant variation in the percent of melanistic individuals in each section and suggest the proportion of melanistic individuals is increasing westward. [ABSTRACT FROM AUTHOR]

Abstract: Skeletal muscle atrophy is a very common clinical challenge in many disuse conditions. Maintenance of muscle mass is crucial to combat debilitating functional consequences evoked from these clinical conditions. In contrast, hibernation represents a physiological state in which there is natural protection against disuse atrophy despite prolonged periods of immobilization and lack of nutrient intake. Even though peroxisome proliferator-activated receptor γ (PPARγ) coactivator 1-α (PGC-1α) is a central mediator in muscle remodeling pathways, its role in the preservation of skeletal muscle mass during hibernation remains unclear. Since PGC-1α regulates muscle fiber type formation and mitochondrial biogenesis, we analyzed muscles of 13-lined ground squirrels. We find that animals in torpor exhibit a shift to slow-twitch Type I muscle fibers. This switch is accompanied by activation of the PGC-1α-mediated endurance exercise pathway. In addition, we observe increased antioxidant capacity without evidence of oxidative stress, a marked decline in apoptotic susceptibility, and enhanced mitochondrial abundance and metabolism. These results show that activation of the endurance exercise pathway can be achieved in vivo despite prolonged periods of immobilization, and therefore might be an important mechanism for skeletal muscle preservation during hibernation. This PGC-1α regulated pathway may be a potential therapeutic target promoting skeletal muscle homeostasis and oxidative balance to prevent muscle loss in a variety of inherited and acquired neuromuscular disease conditions. [Copyright &y& Elsevier]

Mast seeding by oaks ( Quercus) and other seed species has fundamental impacts on the behavior of individual scatter-hoarding animals as well as their population and community dynamics. Scatter-hoarding squirrels are highly sensitive to acorn germination schedule and stop germination by removing the embryo of non-dormant acorns to prevent losses of energy and nutrients by rapid germination. However, we know little about how this behavior is affected by mast seeding. We investigated foraging decisions made by free-ranging Pére David's rock squirrel ( Sciurotamias davidianus) with three species that produce non-dormant seeds and two species that produce dormant seeds ( Fagaceae) during mast and non-mast years in Central China from 2007-2010. Consistent with the food perishability hypothesis that squirrels make decisions to minimize the perishability of their caches, non-dormant seeds were hoarded at a lower rate, but had a higher probability of embryo removal than dormant seeds. Compared with non-mast years, a lower proportion of seeds were harvested during mast years, but a higher proportion of the harvested seeds were hoarded. In addition, the probability of embryo removal in the hoarded seeds was higher during mast years. Squirrels also dispersed seeds at shorter distances during mast years. Moreover, the interactions between mast seeding and seed germination schedule had significant effects on squirrel foraging decisions, including embryo removal. This study is the first to demonstrate that squirrels show greater sensitivity to seed germination potential when seeds are abundant. [ABSTRACT FROM AUTHOR]

North American red squirrels Tamiasciurus hudsonicus often produce a loud territorial rattle call when conspecifics enter or invade a territory. Previous playback experiments suggest that the territorial rattle call may indicate an invader's identity as squirrels responded more intensely to calls played from strangers than to calls played from neighbors. This dear-enemy effect is well known in a variety of bird and mammal species and functions to reduce aggressive interactions between known neighbors. However, although previous experiments on red squirrels suggest some form of individual differentiation and thus recognition, detailed acoustic analysis of potential acoustic cues in rattle calls have not been conducted. If calls function to aid in conspecific identification in order to mitigate aggressive territorial interactions, we would expect that individual recognition cues would be acoustically represented. Our work provides a detailed analysis of acoustic cues to identity within rattle calls. A total of 225 calls across 32 individual squirrels from Sheep River Provincial Park, Kananaskis, AB, Canada, were analyzed with discriminant function analysis for potential acoustic cues to individual identity. Initial analysis of all individuals revealed a reliable acoustic differentiation across individuals. A more detailed analysis of clusters of neighboring squirrels was performed and results again indicated a statistically significant likelihood that calls were assigned correctly to specific squirrels (55%-75% correctly assigned); in other words squirrels have distinct voices that should allow for individual identification and discrimination by conspecifics. [ABSTRACT FROM AUTHOR]

We developed an exercise for a university-level ecology class that teaches hypothesis testing by examining acorn preferences and caching behavior of tree squirrels (Sciurus spp.). This exercise is easily modified to teach concepts of behavioral ecology for earlier grades, particularly high school, and provides students with a theoretical basis for examining commonly observed squirrel behavior. Students gain experience in testing hypotheses and revising predictions. They evaluate how well predictions of competing hypotheses are supported by statistically analyzing and interpreting class data using t-tests and chi-square tests. [ABSTRACT FROM AUTHOR]

Communal nesting has been observed frequently in arboreal squirrels of the genus Sciurus and Glaucomys, but only occasionally in Tamiasciurus. During 2006 and 2007, we trapped and radiocollared 38 adult Mearns's squirrels (Tamiasciurus mearnsi) in Baja California, Mexico, to examine their nesting behavior. We report for the first time instances of communal nesting in Mearns's squirrels. Same-sex groups were more common than mixed-sex groups. Females engaged more in communal nesting than males. Communal nesting behavior in Mearns's squirrels seems to be similar to other species of arboreal squirrels; decreasing as mean monthly temperature increases and during the breeding season. [ABSTRACT FROM AUTHOR]

Philopatry and dispersal result in selection of habitat locations that may differ in resources and social environment and thus should influence fitness components like survival and reproduction. We examined short-distance movements of young and adult females from natal or previous nesting sites within a colony of Columbian ground squirrels ( Urocitellus columbianus) in the Rocky Mountains of Alberta, Canada, over a 17-year period. Females of all ages were strongly philopatric, yet a few (10-15%) exhibited movements that took them to new home ranges. We tested three hypotheses to explain the pattern of female natal and breeding movements: (1) that movements of philopatric females promote proximity to close kin; (2) that range shifts favour close kin via bequeathal of territory and (3) that dispersers move to lower density areas where competition for resources is lower. Tests of these three hypotheses revealed that: (1) philopatry and movements of young and older philopatric females led to proximity to mothers and local presence of close kin; (2) breeding dispersal did not result in bequeathal of home range to daughters, but movements of philopatric females suggested that they shared space with close kin and (3) adult females moved to new ranges with lower local densities, though dispersing females also left ranges where local density was significantly lower than for philopatric females. Natal and breeding movements among years produced two opportunities for territorial females: close spatial proximity to close kin via short philopatric movements, and habitats with fewer competitors via longer dispersal movements. [ABSTRACT FROM AUTHOR]

The article presents a study of the locomotion and substrate use of wild pygmy squirrel Scuirillus pusillus in French Guyana. It says that S. pusillus extensively used medium vertical supports, exhibited claw-climbing and reversion at a great extent, but insignificantly displayed quadropedalism. It adds that this squirrel largely forage for bark and/or exudates, which can be also seen in African and Asian pygmy squirrels.

Small mammals play key ecological roles in grassland ecosystems, yet little is known regarding small mammal communities in large (>50 km2), high-elevation prairies embedded in ponderosa pine (Pinus ponderosa) forests in north central Arizona. To provide information on community composition and habitat relationships, we live-trapped small mammals on 6 transects in 2 prairies in 2008. We captured 78 individuals in 5501 trap occasions. Capture rates were low and varied widely among transects. Community composition was simple, with only 3 species of small mammals captured. In order of relative abundance, these species were deer mouse (Peromyscus maniculatus, n = 44 individuals), Mogollon vole (Microtus mogollonensis, n = 22), and spotted ground squirrel (Spermophilus spilosoma, n = 12). Deer mice were captured on all transects and voles on all but one transect. In contrast, spotted ground squirrels were captured on only 2 transects and were relatively common on only one transect. There were no previous records of spotted ground squirrels in these prairies. Deer mice were positively associated with rock cover and vegetation height. Voles were positively associated with shrub cover and combined cover of live and dead vegetation and were negatively associated with bare ground. Spotted ground squirrels were positively associated with forb cover. This study provides baseline data on small mammal communities in these prairies and documents the presence of a previously unknown species. Further studies would be desirable to better understand spatial and temporal variation in these communities, habitat relationships, and effects of land-use practices on small mammals and their habitats. [ABSTRACT FROM AUTHOR]

Mammalian hibernation involves virtual cessation of energetically consumptive processes normally vital to homeostasis, including gene transcription and protein synthesis. As animals enter torpor, the bulk of initiation of translation is blocked at a body temperature of 18°C in golden-mantled ground squirrels [Spermophilus (Callospermophilus) lateralis]. Previous data demonstrated regulation of cap-dependent initiation of translation during torpor. We asked what happens to cap-independent, specifically, internal ribosome entry site (IRES)-mediated initiation of translation during hibernation. We analyzed polysome fractions for mRNAs that are known to contain or not to contain IRES elements. Here, we show that mRNAs harboring IRES elements preferentially associate with ribosomes as a torpor bout progresses. Squirrels allowed to naturally complete a torpor cycle have a higher IRES preference index than those animals that are prematurely aroused from torpor. Data indicate that this change in preference is not associated with gene expression, i.e., change is due to change in mRNA association with ribosomes as opposed to mRNA abundance. Thus, although processes like transcription and translation are virtually arrested during torpor, ribosomes are preferentially loaded with IRES-containing transcripts when squirrels arouse from torpor and translation resumes. Differential translation of preexisting mRNAs may allow for the preferential production of key stress proteins critical for survival of physiological insults that are lethal to other mammals. [ABSTRACT FROM AUTHOR]

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