ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00267.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe form of squirrel described as the British race is reputedly amongst the most easily distinguished of all the races ofSciurus vulgaris, having ear tufts and tail which bleach to a milky whiteness during the summer months. Today most squirrels in the British Isles appear to be variable in colour. The aim of this project was to discover ifS. v. leucouruspossessed a distinctive skull shape.Differences in skull shape due to age were insignificant in comparison with those due to sex; therefore all age classes were pooled and analysed according to sex by multivariate methods. Apart from S.v. argenteusand 5.v. mantchuricus, of which there was insufficient material, onlyS. v. lisdemonstrated a clear‐cut discontinuity from the other subspecies in both sexes. Skulls of the Persian squirrel (Sciurus anomalus), the most closely related species, were distinguishable fromvulgarisonly in the females. The subspeciesS. v. lis, on the basis of skull shape, therefore appeared to have better claims to specific rank.S.v. fuscoaterwas the most heterogeneous in skull shape of all the subspecies analysed.S. v. leucouruswas second and overlapped the distribution of ten of the other seventeen subspecies.Of the British Museum's collection ofS. v. leucourus(1879–1935) 38% had skull shapes unique to the subspecies. By contrast none of the skulls collected by the Forestry Commission (1972‐74) differed in shape from other subspecies, though 8/14 were of the light‐tailed variety. Moreover, only one of the twelve squirrels with bleached tails in the B.M. collected before 1913 was distinguishable fromS. v. fuscoateron skull shape, and then only marginally. The seven skulls in the B.M. which differed most markedly from other races had skins which were indistinguishable from the red form of squirrel on the continent. Therefore S.v. leucourusmay describe a sport rather than a sub

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00268.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe changing fortunes of the native Red squirrel and the introduced Grey squirrel, as revealed by surveys conducted since 1930, are described The increasing distribution of the Grey squirrel is accompanied by a decline in distribution of the Red squirrel. The Grey squirrel is now found in most parts of England and Wales south of Cumbria and Northumberland, whilst the Red is located mainly in Cumbria and Northumberland, East Anglia, parts of Wales, with smaller isolated colonies on the Isle of Wight and elsewhere. In Scotland, the Grey squirrel continues to spread slowly but it is less widely distributed than the Red squirrel.

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00269.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractRed squirrels occur most commonly in conifer habitats where their basic year round diet is conifer seed, supplemented by seed, berries and fruits of deciduous species when available. Conifer buds and shoots are important foods in winter and spring, as are flowers in late spring and early summer. Fungi are eaten throughout the year but mostly in autumn. Grey squirrels occur most commonly in hardwood forests where their primary food is nuts and samaras of deciduous trees and shrubs. Buds, shoots and flowers are substituted in spring and early summer, along with a variety of coarse plant and animal foods in summer. Both species prefer seed, so other plant foods predominate in the diet only in places or times when seed crops are small. Seeds of the same species are used by both Red and Grey squirrels when and where available but there have been no quantitative studies of diet of both species in closely similar habitats, so food preferences within the range of foods used by both species are unknown.Squirrels have strong preferences for particular food species, trees within a species and even between individual seeds and buds within each tree. Diet varies between individuals and between sex and age groups within squirrel populations. The determinants of these food preferences remain unknown, despite natural advantages of squirrels for testing foraging models.

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00270.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractDaily and seasonal patterns of free‐ranging Red squirrels (Sciurus vulgaris) were studied by means of radiotracking. On a seasonal basis, two distinct daily activity rhythms were exhibited. In winter, the squirrels had a short, uninterrupted active phase which is probably an adaptation for conserving energy by minimizing the period of heat loss. In summer, the active phase was more than twice as long as in winter, and was usually broken by a rest period. The activity patterns at the equinoxes were intermediate between summer and winter patterns.In summer, the biphasic pattern of daily activity of individuals gave rise to a trend towards bimodality in the activity pattern of the population as a whole, although the rest periods and second active periods of different squirrels were not synchronized. Onset of daily activity was associated with daybreak, but cessation occurred well before nightfall.Superimposed onto the basic seasonal patterns of activity were the effects of feeding requirements, foraging accounting for a mean of 82% of a month's activity. As well as immediate nutritional requirements, the habit of scatter‐hoarding mast had a marked influence on the duration of foraging, causing a peak in activity in September. Although throughout most of the year the foraging time appeared to influence the duration of activity, active time in late winter appeared to be self‐determining, causing squirrels to lose body‐weight rather than to extend the foraging period. Other factors affecting activity patterns are di

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00271.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractDirect calorimetry, respirometry and gravimetric techniques have been used independently to study the energy requirements of Grey and Fox squirrels (Sciurus carolinensisandS. niger, respectively). Studies using direct calorimetry and respirometry have produced similar values for the resting metabolic rate (RMR). In contrast to studies on other small mammal species, the average daily metabolic rate (ADMR), as measured by respirometry, has been found to be higher than RMR. RMR is closely correlated with temperature, and young squirrels require more energy per gram of body weight than adults; the effect of other variables on the metabolic energy requirements have not been studied. The experimental conditions of several gravimetric studies have differed and there is a consequent variation in the results; these data do not compare with ADMR values. The seasonal cycle in the daily duration of activity, the availability of food and the stress brought about by human disturbance and confinement in small cages, all affect the daily energy requirement of captive wild squirrels. Accurate analyses are hindered by the wide variation in results for individual squirrels and the difficulty in quantifying production and urinary losses. For these reasons, the compiled energy budgets of laboratory‐held squirrels are unlikely to represent the energy budgets of free‐living individuals or populations. Directions for future research are sugges

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00272.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractHome range patterns of squirrels in the generaSciurusandTamiasciurusare reviewed. Emphasis is placed on the need to use analytical techniques which are appropriate to the questions of interest, and certain weaknesses in published studies are outlined. Variation in home range size between different species, populations of the same species and individuals of the same population is discussed in relation to ecological theory and the biology of tree squirrels. Larger species do not necessarily have larger home ranges. There is an inverse relationship between home range size and population density, but its interpretation is not clear in the absence of experimental studies. Differential utilization of space within the home range is considered to be a common pattern, although it is rarely explicitly described in tree squirrel studies. In general, species of the genusTamiasciurusdefend exclusive territories, whilst those of the genusSciurusdo not. Explanations for these patterns are discussed in terms of ‘economic defendability’ and resource heterogeneity. Problems for future study are sugges

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00273.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThis is a literature review of the relationship between the abundance of tree seeds and the productivity, survival and dispersal of Holarctic tree squirrels. Causal links between changes in tree seed supplies and changes in squirrel numbers are often masked by various factors including intraspecifk and interspecific competition for seed, weather, predation and seed hoarding; density‐dependent relationships have not been clearly established.TamiasciurusandSciurusspecies have different seed‐hoarding strategies which are associated with differences in their social and spatial organization. Average squirrel densities in the long‐term are discussed in relation to forest habitat type, and directions for future research indi

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00274.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe Grey squirrel shows two peaks of litter production in spring and summer, but this does not necessarily mean that all female squirrels have two litters per year. Captive female squirrels do not show regular oestrous cycles, and there is evidence that both the presence of a male and adequate space is necesssary for the induction of oestrus. After day sixteen of gestation, the ovaries are not necessary for the maintenance of gestation. Our studies indicate that the male Grey squirrel has a seasonal period of t esticular regression in the autumn, which may be short‐lived so that full breeding condition is attained by December In some years, localized populations of Grey squirrels may have a prolonged period of testicular regression throughout the winter, with a consequent absence of spring breeding, and there is some evidence that this may be related to available foo

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00275.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractForty Red (Sciurus vulgaris) and thirty‐five Grey squirrels (S.carolinensis) have been subjected to full post‐mortem examinations since 1967. The results, together with other reports of disease in Britain affecting free‐living squirrels, are discussed. There appears to be a higher incidence of disease in Reds than in Greys.Parapoxvirus infection, which closely resembles contagious pustular dermatitis or orf of sheep, appears to be common in Reds in Norfolk, but does not appear to occur in Grey squirrels. Coccidiosis (Eimeria sciuroruminfection) is common in Reds. Both species of squirrels frequently harbourEimeriaspp. parasites in the intestinal tract. Other protozoa that occur include haemogregarines (probablyHepatozoonsp.) andToxoplasma.Helminths are relatively uncommon, butEnterobiusspp. were found in the gut of Reds. Both species of squirrels are commonly infested with fleas, mainlyMonopsyllus sciurorumin Reds andOrchopeas howardiin Greys. Lice, especiallyNeohaematopinus sciuri, and ticks (Ixodes ricinus) also occur in both species.In spite of reports to the contrary, there is no proof that either species of squirrels contract mange caused bySarcoptesmites. It is likely that alopecia due to ectoparasitism in both species and parapoxvirus infection in Reds have been mistaken for mange. Fungal and bacterial infections appear to be unusual, althoughPasteurella multocidainfection was diagnosed in a Red andYersinia enterocoliticain a Grey squ

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1983.tb00276.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY