The occurrence of the Pigmy shrew Sorex minutus on moorland, and the implications for its presence in Ireland

Throughout most of its range in western Europe, the Pigmy shrew Sorex minutus is sympatricwith the Common shrew Sorex araneus but greatly outnumbered by it. This makes it difficult to explain the presence of the Pigmy shrew, in the absence of its congener, in Ireland. A limited pitfall trapping exercise in England has shown that in moorland on deep peat, the Pigmy shrew may in fact outnumber the Common shrew. Reference to the literature on the ecology of the two shrews shows that this result is readily explained by existing knowledge of their diet; earthworms are a major prey for Common shrews and are absent from waterlogged, acidic, peats. Further, evidence on the nature of the possible land bridge from Scotland to Ireland suggests that it was at best low-lying, and probably partly flooded. By analogy with moorland, such a land bridge might have been suitable for Pigmy shrews but not for Common shrews.     

Studies on the distribution, food, breeding biology and relative abundance of the Pygmy and Common shrews (Sorex minutus andS. araneus) in upland areas of northern Engl and.

The distribution and relative abundance of the Pygmy and Common shrews were investigated over two years at 42 sites across northern England and at a further seven sites in one year. Most of the sites were in upland areas above 250m in altitude. At almost all sites, the Pygmy shrew was more abundant than the Common shrew, often by a considerable
A correlation exists between the numbers of shrews captured at a site and the abundance of invertebrates revealed by pitfall trapping. I t is recorded that Common shrews fed on earthworms (which are almost completely absent on peatlands) whilst Pygmy shrews did     

Trophic relationships of common frog (Rana temporaria) and pigmy shrew (Sorex minutus) in upland Co. Antrim, Northern Ireland

The common frog and the pigmy shrew are common vertebrate predators in the uplands of Co. Antrim, Northern Ireland. This report concerns their habitat preference and trophic biology which are poorly documented at higher altitudes. Frogs preferred damp, grassy, reclaimed habitats while pigmy shrews appeared to favour moorland dominated by Calluna vulgaris. Both frogs and shrews were absent from pitfall trap collections from December to February and numbers of both were low until late spring. This corresponded to the period of lowest invertebrate abundance. Examination of stomach contents suggests that frogs are less selective feeders and utilize a greater diversity of prey items than pigmy shrews. Although sample size is low early in the year, diversity of the diet of pigmy shrews apparently increased from the first to the second quarter and again in the third quarter of the year. This led to an increase in food niche overlap with frogs in late summer but at a time of year when food supply was greatest. It is unlikely, therefore, that dietary overlap constitutes a basis for interspecific competition between frogs and shrews. This is likely to be ameliorated by habitat and behavioural differences between the two predators.     

Interspecific competition in the shrews Sorex araneus and Sorex minutus (Soricidae, Insectivora): a population study of the Irish pygmy shrew

Sorex araneus and S. minutus , which are likely to show a temporary vertical habitat segregation, are largely sympatric, except in Ireland, where S. minutus occurs alone. Two mechanisms for this segregation may be suggested: a direct interspecific interaction or an evolutionary fixed relationship.
Population densities and surface activity were measured, both in areas where the two species occur together (The Netherlands) and in areas in Ireland, in (order to investigate the possibility of a habitat shift and its influence on population density. No such effect was found in the present study.     

Evidence for echolocation in the common shrew, Sorex araneus

In this laboratory experiment it is shown that, like four North American soricid shrew species, the European common shrew Sorex araneus L. is able to use echolocation to identify open and closed tubes at a distance of 200 mm.
Three common shrews captured in Sweden were used for the experiments, which were carried out in darkness and within a sound-proof box. The experimental set-up eliminated orientation using sight, sound or scent from outside the experimental cage. Echolocation calls consisted of broadband ultrasonic clicks at low sound pressure. These were recorded using an ultrasound detector.
The ecological significance of echolocation in shrews is discussed. It is proposed that common shrews use echolocation to locate protective cover, thus minimizing the risk to be taken by, e.g. owls.
Echolocation may also be used for detecting obstacles in subterranean tunnels. Hence, echolocation could be of certain importance when abandoned burrows in the periphery of the tunnel system are restored during periods of increasing population densities. Since density peaks in most populations occur regularly each summer, and may reach extreme magnitudes in cyclic populations, the ecological significance of echolocation in shrews may be considerabl.     

Allozyme variability in common shrew Sorex araneus of Western Siberia

The allozyme variability of the common shrew Sorex araneus of Western Siberia is studied. The small level of genetic variability and lack of reliable differences in indices of polymorphism for taiga, subtaiga, and forest-steppe populations are revealed. A significant level of genetic differentiation in populations belonging to adjacent chromosomal races—Novosibirsk and Serov (F _st = 0.3) — has been shown.     

The occurrence of Centrorhynchus (Acanthocephala) in shrews (Sorex araneus and Sorex minutus) in the United Kingdom

Encysted acanthocephalans belonging to the genus Centrorhynchus were found in the body cavities of Sorex araneus (common shrew) and Sorex minutus (pygmy shrew) from Boxworth, Cambridgeshire, U.K. Fifty percent of the male S. araneus and 67% of the male S. minutus examined were found to be infected, with the mean intensity (+/-SD) being 54.3 +/- 91.3 and 14.7 +/- 18.4, respectively. The species of Centrorhynchus in the shrews may be Centrorhynchus aluconis, which is distributed widely in tawny owls, Strix aluco, in the United Kingdom. Shrews appear to serve as paratenic hosts for C. aluconis.     

Structure of the sinus hair follicle in the big-clawed shrew,Sorex unguiculatus

The structural features of sinus hair follicles in Sorex unguiculatus were studied by macroscopic dissection, serial section light microscopy and electron microscopy. The shrew has about 540 sinus hairs regularly arranged on the snout. The maxillary nerves innervating them are extremely thick, while the optic nerves are very thin. Thus the follicle must be one of the most important sense organs in this animal. In the follicle the ring sinus is well-developed and the trabeculae of the cavernous sinus are reduced in number and thickness. The ring bulge is not a unified structure but a pair of bodies which consist of head, stalk and attachment plaque. It is characterized by the presence of numberous thick collagen fibrils (400 nm) and appears to be mechanically rigid. Lanceolate nerve terminals, free endings, Merkel cells with nerve terminals and unmyelinated fibers are observed, but encapsulated endings are lacking in and around the follicles. Straight lanceolate terminals on the posterior side of the follicle are thick and three-sided in cross section, while those on the anterior side are thin and two-sided. Free endings are located on the anterior side of the follicle. These and other findings are discussed on the basis of the assumption that the Sorex sinus hair follicle is more specialized as a vibrating system than in other mammals.     

Cases of coat colour anomalies in the common shrew, Sorex araneus L

Coat colour anomalies in the common shrew, Sorex araneus L., in the geographical range of this species, including Poland, are extremely rare. This study describes atypically coloured common shrews. Light colouration of the coat is a result of lack ofpigment in the entire hair or hair fragments. It appears that atypically coloured shrews occur more often in isolated populations whose gene transfer with neighboring populations is limited.     

Biotope distribution of cestodes from the common shrew Sorex araneus in southern Karelia

Specific features in the formation of cestode species composition in the common shrew in different biotopes have been analyzed. Four categories of parasites have been recognized depending on a degree of dominance: dominants (Neoskrjabinolepis singularis, Molluscotaenia crassiscolex), subdominants (Ditestolepis diaphana), adominants A (Staphylocystis furcata, Vigisolepis spinulosa, adominants B (Hymenolepis scutigera, Dilepis undula, D. secunda, Taenia mustelae). A significant similarity was discovered between the species diversity and the dominance characteristics of cestodes. It was found that the distribution of mass species of parasites in the host population corresponds to the gamma distribution model. In regard to cestodes examined, a hypothesis considering the spatial structure and size of territory occupied by stable parasitic system is put forward.     

Synaptonemal complexes of the common shrew, Sorex araneus L., in spermatocyte spreads

This paper presents an electron microscopic analysis of the behavior and morphology of the sex chromosomes and autosomes during prophase I in the common shrew, Sorex araneus L. The pairing patterns of the X/Y1Y2 and autosomal Robertsonian trivalents are described.     

Ecomorphometric variation and sexual dimorphism in the common shrew (Sorex araneus)

We investigated the evolution of the biomechanics of the mandible in island and mainland populations of the common shrew on the west coast of Scotland. We predicted that climatic differences between populations should cause differences in prey composition leading to changes in the mechanical potential (MP) of the mandible. In females, MP was correlated with climate, with greater MP in warmer and drier habitats. In males, MP was significantly greater than in females but there was no relationship between male MP and climate. This led to increased sexual dimorphism in colder and wetter climates. The same pattern was found after a phylogenetic least squares analysis was conducted to account for shared phylogenetic history. We discuss possible reasons for this pattern, including male–male combat and the greater necessity of females to feed as efficiently as possible to meet their extremely high energy requirements during lactation.     

Factors responsible for a karyotypic polymorphism in the common shrew, Sorex araneus

A Robertsonian karyotypic polymorphism in the common shrew in the Oxford area, first described in the 1950s, was re-examined. The polymorphism involves chromosome arm combinations kq, no and pr (characteristic of the Oxford karyotypic race), ko (characteristic of the Hermitage karyotypic race) and jl (found in both races). The polymorphism for jl was sporadic along a north-south transect through the Oxford area, with the frequency of the twin-acrocentric morph never exceeding 10%. The frequency of the Oxford race-specific metacentrics decreased and the frequency of the Hermitage race-specific metacentric ko increased from north to south along the transect. At a latitudinal grid reference of about 180 km, there was a high frequency of individuals with chromosome arms k, n, o and q in the ancestral acrocentric state. This was coincident with the area of occurrence of ko-kq and ko-no Oxford-Hermitage hybrids. Such hybrids are double Robertsonian heterozygotes with monobrachial homology and are likely to suffer reduced fertility in consequence. It is proposed that this is a source of selection against the monobrachial hybrids and hence results in an increase in frequency of the acrocentric morphs. This scheme goes some way to explain the clines of polymorphism for arm combinations kq, no and ko, but it is suggested that other selective factors are involved. It cannot explain the cline of polymorphism for pr, which is in general terms similar to that for kq and no, but is more shallow and centred further north.     

Arrangement and structure of sinus hair muscles in the big-clawed shrew,Sorex unguiculatus

The arrangement and structure of sinus hair muscles in the snout of the shrew, Sorex unguiculatus, were studied by electron microscopy and serial section light microscopy. Both striated and smooth muscles are directly associated with sinus hair follicles. The striated muscle fibers originate from the base of a follicle and insert onto the superficial portion of adjoining caudally positioned follicles. Some fibers insert into the corium instead of inserting into a follicle. The fibers show a fine structure typical of red fibers. Smooth muscle cells form a network with elastic fibers beneath the corium. Some cells are directly attached to the capsule of the sinus, thus forming a type of M. arrector pili. Striated muscle fibers that appear to end in the corium are connected with the smooth muscle network through the elastic fibers which appear to function as the tendon of these two types of muscle cell.     

Contribution to the knowledge of home range in common shrew Sorex araneus L.

Summary Population density of shrews in a clearing in the submountain spruce forest was established per 1 hectare 17.5 individuals of common shrew, 4.6 of pygmy shrew and 1.1 of alpin shrew. The mean radius of activity in common shrew amounts to 13 m. The ratio of shrew to rodents was 1:3 or 1:2 in summer and autum respectively. Theoretical home range reached 532 m². The importance of home range studies for synecological studies and theory of natural focality was demonstrated.District Station of Hygiene and Epidemiology, Olomouc, SSR.