Quantitative estimation of population numbers of shrews (mammalia,insectivora) after wintering

Autumn-winter mortality in shrews (Sorex araneus, S. caecutiens, S. minutus) was estimated on the basis of long-term (12 years) live-trapping on the permanent transect lines in Tver oblast. Relative as well as absolute population numbers were estimated. Lesser shrew (S. minutus) has permanently low population numbers. Fall in this species made 40.1%, and it was scattered through this term. Common shrew (Sorex araneus) lose 89.3% of population and in masked shrew (S. caecutiens) those lost was 73.6%. The most lost was found in autumn and winter fall was as least as 38,2% and 30.4% in the latter two species. The mortality is positively dependent on population density in preceding summer and with severity of winter.     

Behavioural mechanisms of conflict avoidance among shrews

Stable co-existence of similar species should be facilitated by mechanisms impairing, besides exploitative, interference competition. We investigated avoidance of intra- and interspecific conflicts in a four-species community of shrews [Sorex minutus Linnaeus, 1766,S. araneus Linnaeus, 1758,Neomys anomalus Cabrera, 1907, andN. fodiens (Pennant, 1771)], using the method of dyadic encounters in a neutral arena. We tested whether the use of passive (habituation, reduction of mobility, increase of inter-individual distance, and stillness) and active (‘to-and-fro’ and ‘keeping distance’ behaviours) forms of conflict avoidance depends on species, size or domination rank. The duration of conflicts was positively correlated with mobility and negatively with inter-individual distance, whereas it was unrelated to time of stillness and the active forms. The repertoire of conflict avoidance mechanisms was not species-specific and the display of these mechanisms depended rather on the size and domination rank of animals participating in a given interaction. In contrast to rodents, shrews did not avoid conflicts by the most passive forms: freeze and stillness reactions. All other forms were used with a higher or lower efficiency by all species. However, consistent with our predictions, large shrews (asN. fodiens) used mainly the passive mechanisms of conflicts avoidance (‘wait-and-see’ strategy), whereas small shrews (asS. minutus) invest proportionally more time in active forms (‘escape’ strategy).     

Overlap of temporal niches among four sympatric species of shrews

Hypotheses about the dependence of circadian activity from metabolic rate and the segregation of temporal niches among competing species were verified by the study of activity patterns in a shrew community of two semiaquatic species,Neomys anomalus Cabrera, 1907 andN. fodiens (Pennant, 1771), and two terrestrial species,Sorex araneus Linnaeus, 1758 andS. minutus Linnaeus, 1766, co-existing in wet habitats of Białowieża Forest (E Poland). In ten trapping sessions, performed in early summer between 1991 and 2000, traps were open 24 hours continuously and patrolled at 1:00, 5:00, 10:00, 15:00, and 20:00. All the shrew species were most active between 20:00 and 1:00, and least active around mid-day (10:00–15:00). However, activity of the twoSorex species was lower than that of the twoNeomys species in the period 20:00–1:00, but higher in the period 15:00–20:00. BothNeomys species displayed clearly nocturnal, unimodal patterns of activity. In contrast, activity of bothSorex species was relatively evenly distributed over 24 hours and they increased their activity earlier (ie after 15:00) than bothNeomys species (after 20:00). These results confirm the idea that small shrew species with higher metabolic rate have more frequent and more equally distributed activity bouts than large species. Overlap of temporal niches was the highest within genera (99.29% between bothNeomys species and 98.36% between bothSorex species), the lowest betweenN. fodiens andS. araneus (88.26%) andS. minutus (89.34%), and intermediate betweenN. anomalus and bothSorex species (91.78 and 93.34%, respectively). Such high interspecific overlaps in activity suggest a joint-action of other mechanisms that separate ecological niches of these species also in other dimensions (eg food, microhabitat).     

Evaluation of the physiological activity of venom from the Eurasian water shrew <Emphasis Type="Italic">Neomys fodiens</Emphasis>

Background

Animal toxins can have medical and therapeutic applications. Principally, toxins produced by insects, arachnids, snakes and frogs have been characterized. Venomous mammals are rare, and their venoms have not been comprehensively investigated. Among shrews, only the venom of Blarina brevicauda has been analysed so far, and blarina toxin has been proven to be its main toxic component. It is assumed that Neomys fodiens employs its venom to hunt larger prey. However, the toxic profile, properties and mode of action of its venom are largely unknown. Therefore, we analysed the cardio-, myo- and neurotropic properties of N. fodiens venom and saliva of non-venomous Sorex araneus (control tests) in vitro in physiological bioassays carried out on two model organisms: beetles and frogs. For the first time, we fractionated N. fodiens venom and S. araneus saliva by performing chromatographic separation. Next, the properties of selected compounds were analysed in cardiotropic bioassays in the Tenebrio molitor heart.

Results

The venom of N. fodiens caused a high decrease in the conduction velocity of the frog sciatic nerve, as well as a significant decrease in the force of frog calf muscle contraction. We also recorded a significant decrease in the frog heart contractile activity. Most of the selected compounds from N. fodiens venom displayed a positive chronotropic effect on the beetle heart. However, one fraction caused a strong decrease in the T. molitor heart contractile activity coupled with a reversible cardiac arrest. We did not observe any responses of the insect heart and frog organs to the saliva of S. araneus. Preliminary mass spectrometry analysis revealed that calmodulin-like protein, thymosin β-10, hyaluronidase, lysozyme C and phospholipase A2 are present in the venom of N. fodiens, whereas thymosin β4, lysozyme C and β-defensin are present in S. araneus saliva.

Conclusion

Our results showed that N. fodiens venom has stronger paralytic properties and lower cardioinhibitory activity. Therefore, it is highly probable that N. fodiens might use its venom as a prey immobilizing agent. We also confirmed that S. araneus is not a venomous mammal because its saliva did not exhibit any toxic effects.

     

Shrews (Sorex spp.) somatometry and reproduction in Slovakia

The morphometrics and reproduction of shrews (Sorex araneus, S. minutus, S. alpinus) was studied in Slovakia. Significant differences in weight, body length and tail length were recorded in adult and subadult shrews. Adult individuals and males had higher mean somatometric values (apart from tail length of subadults). The hind foot length was the least variable characteristic, which can be considered as the most stable taxonomic somatic characteristic of shrews. Weight and body length varied considerably. Values of somatic characteristics in S. araneus and S. minutus increased with increasing altitude, apart from hind foot length in S. araneus, which decreased with increasing altitude. The values of somatic characteristics declined with increasing continentality, but tail length gradually increased in the direction west — east at the highland level. Sorex minutus was characterized by the greatest reproductive activity (length of reproductive cycle April–October, average number of embryos 6.97). The lowest reproductive activity was observed in S. alpinus (average number of embryos 5.72). The mating season of S. araneus began at the end of March and ended in August with an average number of embryos of 6.12.     

First results on the feeding ecology of sympatric shrews (Insectivora: Soricidae) in the Tai National Park,Ivory Coast

The feeding ecology of a multi-species community of shrews inhabiting secondary forest and cacao-coffee plantations in the Tai National Park (Ivory Coast) was investigated. A total of 553 shrews were captured and 194 alimentary tracts were examined. Ten species were found, includingSylvisorex megalura and nine species ofCrocidura, forming a series with respect to body size. New ecological data on these little known African species are presented. All species of shrews ate a wide diversity of arthropods, with Coleoptera, Araneae, Formicidae and Diplopoda making the largest dietary contributions. Lumbricidae were eaten by two species.C. obscurior had an exceptionally long intestine for its size but there was no evidence of dietary specialisation in this or other shrew species. All species investigated ate predominantly small prey and there was no correlation between size of prey items consumed and body mass of shrew species. There was little evidence of resource partitioning amongst the shrews, despite differences in body size.     

Comparative feeding ecology of Tropocyclops prasinus mexicanus (Copepoda, Cyclopoida)

The herbivorous and carnivorous feeding biology of Tropocyclopsprasinus mexicanus, an especially small cyclopoid copepod, wasstudied under in situ food conditions in three different lakesand under experimentally augmented food supplies. The mass-specificfood uptake is compared to that of two larger species—Cyclopskolensis and Cyclops vicinus. Under in situ food conditions,T.p.mexicanus depended to a larger extent on algae than invertebrateprey and showed lower mass-specific ingestion rates than thetwo larger species. Daily mass-specific uptake rates for algaeranged between 10 and 24% of its body mass versus 0.7–7%for invertebrate prey. The larger species C.vicinus and C.kolensisingested a total dry mass equivalent to 106% or up to 143% oftheir body mass with algae contributing 66 and 81%. However,under enriched food availability, T.p.mexicanus is able to ingesta biomass equivalent to its body mass, with an algae (54%) andprey (40%) portion similar to that of the larger species. Bodysize appears to be an important factor for the relative importanceof algal versus invertebrate prey for cyclopoid copepods.     

Muscle capillary supply in hind limb and diaphragm of the common shrew (Sorex araneus)

Shrew species of the subfamily Soricinae have unusually high metabolic rates when compared to Crocidurinae shrews and other similar-sized mammals. The aim of this study was to clarify whether the high basal metabolic rate of Soricinae shrews is reflected in a high capillary density in their muscles. To this end, the capillary supply of four limb muscles and diaphragm of the common shrew (Sorex araneus) was quantified from cross-sectioned muscles. The capillary densities of the limb muscles were 2575 ± 329, 3111 ± 299, 2812 ± 197 and 2752 ± 173 capillaries mm⁻² fibre area in gastrocnemius lateralis, g. medialis, plantaris and soleus, respectively. Capillary density of the shrew diaphragm (6691 ± 1057) was double that of the limb muscles. This value is among the highest ever measured in mammals. In general, the capillary supply in the hind limb of the common shrew is about 3–4 times higher than commonly found in the leg muscles of the laboratory rat or other bigger mammals, but similar to those in Crocidurinae shrews and some small rodents. Thus the high resting metabolism of the common shrew is not associated with an extraordinarily high capillary density. The apparent disparity between basal metabolic rate and muscle capillary supply in S. araneus is probably due to the small aerobic scope of shrews in the subfamily Soricinae. Accepted: 22 January 1998     

Foraging behaviour and prey discrimination in the bluespotted maskray Dasyatis kuhlii

A study observing the foraging behaviours and prey discrimination of a common demersal stingray, the bluespotted maskray Dasyatis kuhlii was performed under controlled laboratory conditions. A selection of prey species and masses were offered at depths of 10 and 50 mm in sand. Foraging efficiency and prey selection at both burial depths were compared. Dasyatis kuhlii selected the ghost shrimps, Trypaea australiensis and T. australiensis >2·5 g, range ± 0·2 g though foraging errors represented by prey being excavated and not consumed suggested a limited discriminatory ability at the point of detection. Burial depth did not influence prey species, mass selection or discriminatory ability.     

Analysis of animal spatial patterns on the basis of marking on transects: An example of red-toothed shrews

The spatial patterns of individually marked juveniles of red-toothed shrews—the masked shrew (Sorex caecutiens), common shrew (S. araneus), and pygmy shrew (S. minutus)—have been determined by comparing the ratio of traps visited by different numbers of animals (0, 1, 2, 3, etc.) with the Poisson distribution and by using the index of relative variance σ²/m. These tests characterize both the distribution of animal load over different points of the study area and the spatial pattern of individual home ranges. A random type of spatial pattern within relatively uniform biotopes prevails in juveniles of all three red-toothed shrew species, regardless of their properties, abundance, and factors accounting for it. This facilitates the formation of a system of non-overlapping home ranges of adult females after wintering. The stability of spatial patterns contributes to the efficiency of population self-regulation.     

Distribution of cryptic shrew species of the genus Sorex (Mammalia) on the plain between the Don and Kuban rivers as inferred by molecular markers

Microsatellite and mtDNA markers have been used to identify two pairs of cryptic species Sorex araneus L. (Sorex satunini Ogn.) and Sorex minutus L. (S. volnuchini Ogn.). The new data were obtained on the distribution of these species on the plain between the Don and Kuban rivers. The shrew S. volnuchini and Caucasian mole are distributed on the plain areas up to the Eya River. The endemic species of the Caucasus, the shrews S. satunini and S. volnuchini, are widely distributed across the valleys alongside small streams on the steppe plain. Both species are most abundant on thick grasslands, bushy scrub, and deciduous woodlands. They don??t show any clear differences in habitat preferences.     

Aging and cohort dynamics inSorex shrews

In the shrewsSorex araneus Linnaeus, 1758 andS. minutus Linnaeus, 1766 a short period of fast post-natal development in the nest is followed by a longer summer period of developmental stasis and then by autumn regression. The aim of this paper has been to test whether this period of developmental stability also is accompanied by inhibited development of the eye lens — the most continuously growing organ of the mammalian body. If it is not, then can this be used as an age indicator in studies on shrews, and can it serve in distinguishing seasonal cohorts of young born in consecutive summer months? This aspect was examined on material comprising dead shrews collected from live traps and pitfalls set for rodent research in the marshy habitat of a river valley in Bia?owie?a Forest, Poland, in 1997–1999. In fact, the eye lens in shrews was shown to increase in size continuously; therefore it may be used as a reliable age indicator. Body mass of weaned young shrews also continued to increase slowly with age until autumn. On the basis of the distribution of individuals in successive lens-mass classes, three age groups (cohorts) of young could be distinguished each season in theS. araneus population, and two inS. minutus. In the former species, consistent patterns to the relative abundance of the three seasonal cohorts were observed. The consequences of time of birth on individual fitness inSorex shrews are discussed.     

Editorial

Interspecific interactions between the shrews Sorex araneus and S. minutus F. J. M. ELLENBROEK Noordbrabants Natuurmuseum, Postbus g24, 5000AX Tilburg, Netherlands Foraging in the European Hedgehog, Erinaceus europaeus ANDREW J. WROOT Department of Zoology, Royal Holloway College (University of London), Egham, Surrey TW20 0EX     

Use of hair tubes to survey for shrews: new methods for identification and quantification of abundance

• 1 Accurate and sensitive survey and monitoring methods are needed for shrews. We present a new design of hair tube and a new, simple method of species identification from multivariate analysis of four parameters measured from shrew guard hairs using a binocular microscope with incident light.
• 2 Multivariate analysis of these parameters measured from hairs of known identity showed that they can be used to identify hair to the species level with 85% accuracy.
• 3 We compared our indices of abundance from hair tubes (the hair tube index) with those from live trapping in 40 field margins. Capture‐mark‐recapture methods showed that capture rate did not vary systematically across sites, so that number of individuals captured was used as an index of abundance.
• 4 The hair tube index showed a significant association with the number of individuals captured for Sorex araneus and Neomys fodiens. The lack of a significant association for Sorex minutus may be because hair tubes are more sensitive in detecting this species than live trapping.
• 5 Hair tubes have additional advantages over live trapping, since they do not require frequent checking, are much lighter and cheaper than live traps, and no licence is required for their use in the UK. We therefore recommend consideration of their use in future surveys and monitoring studies of shrews. We provide an equation so that other researchers can use our multivariate method.

     

Bergmann's rule in shrews: geographical variation of body size in Palearctic Sorex species

According to Bergmann's rule, individuals of a given species tend to be larger in colder (northern) climates. Traditional explanation points to the relatively lower surface‐to‐volume ratio in larger animals and, consequently, relatively lower costs of thermoregulation. We examined intraspecific covariation of body size with geographical location and climate in five species of Sorex shrews, animals that are among the smallest extant mammals. The condylobasal length of skull (CBL), compiled from literature data and measured on museum specimens, was used as an indicator of the overall body size of shrews. Surprisingly, in three out of five shrew species, the CBL was negatively correlated with latitude, and the same trend, although not statistically significant, was found in the fourth species. In general, shrews were smaller in colder areas, as evidenced by the positive correlations between the CBL and temperature. In two species, these positive correlations appeared when the effect of longitude was held constant in the partial correlation analysis. Characteristically, the strongest negative correlation with latitude and positive with temperatures was found in S. minutus, the smallest species under study. Shrews were in general larger in environments with high actual evapotranspiration. Body mass reviewed in S. araneus paralleled the pattern found in the CBL variation in this species, i.e. it decreased northward, both in summer‐ and winter‐caught animals. In addition, contrary to the widely accepted ? but not rigorously tested ? belief, body mass recession from summer to winter (the Dehnel Effect) did not correlate with latitude. We concluded that shrews followed the converse to Bergmann's rule, and hypothesize that part of their body size variation along the west‐east axis may be explained by character displacement. We also hypothesize that scarcity of food, especially in winter, is a major factor selecting for small body size in shrews in northern areas, as smaller individuals should require less food. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 78 , 365–381.     

Estimating the long-term repeatability of food-hoarding behaviours in an avian predator

Food-hoarding behaviour is widespread in the animal kingdom and enables predictable access to food resources in unpredictable environments. Within species, consistent variation among individuals in food-hoarding behaviours may indicate the existence of individual strategies, as it likely captures intrinsic differences in how individuals cope with risks (e.g. starvation, pilferage). Using 17 years of data, we estimated the long-term repeatability of 10 food-hoarding behaviours in a population of Eurasian pygmy owls (Glaucidium passerinum), a small avian predator subject to high temporal fluctuations in its main prey abundance. We found low repeatability in the proportion of shrews and the average prey mass stored for both sexes, while females were moderately repeatable in the mass and the number of prey items stored. These two pairs of behaviours were tightly correlated among individuals and might represent two different sets of individual strategies to buffer against starvation risks.     

Distribution and coexistence of shrews in patchy landscapes: A field test of multiple hypotheses

Despite the important role of shrews (Soricomorpha: Soricidae) in the functioning of ecosystems, as predators and prey, the effects of habitat loss and fragmentation on this guild of mammals are still unclear. We studied the distribution of 5 species (the greater white toothed shrew Crocidura leucodon; the lesser white toothed shrew Crocidura suaveolens; the pigmy shrew Sorex minutus; the Appennine shrew Sorex samniticus and the Etruscan shrew Suncus etruscus) in a fragmented landscape in central Italy.Shrews were trapped with pitfall traps made from plastic water bottles, the number of traps increased with patch size. A total of 170 individuals, of 5 species of shrews were captured. Shrews were widely distributed in our study area, however patch occupancy was determined mainly by vegetation and geometrical characteristics of the patches. Our data supports the hypotheses that patterns of habitat selection and the dynamics of seasonal abundance (habitat and temporal partitioning between similarly sized species) reduce competitive pressure, thus allowing coexistence of shrews in relatively species-rich assemblages, for such small amounts of habitat. The most important outcome of our results is the crucial role played by vegetation structure in determining distribution patterns. These results strongly suggest that measurements of the vegetation structure of habitat patches should always be included as explanatory variables when studying the distribution of shrews in fragmented landscapes.     

Distribution patterns and microhabitat segregation in gastrointestinal helminths of Sorex shrews

We studied the distribution patterns and microhabitat use in gastrointestinal helminths of the shrews Sorex araneus and S. caecutiens in Finland. The distribution of species prevalences was bimodal, and in S. araneus the abundance (mean intensity) was positively associated with commonness (prevalence), as assumed by the core-satellite species hypothesis (Hanski 1982). However, the positive correlation between prevalence and intensity was observed only when the effects of helminth body size and taxonomic group (cestodes vs nematodes) on intensity were controlled for. The nematodes of the genus Longistriata occurred predictably as core species, whereas the identity of the core cestodes was more variable between host species and regions. Helminth body size and taxonomic group were not related to the degree of aggregation in shrew populations, but helminth body size seemed to explain the differences in the distribution patterns of helminths between shrews and voles. The core species did not show more segregation in microhabitat use than randomly selected species. In fact, the two core nematodes showed largely overlapping intestinal distributions. We conclude that linear intestinal space is not a key resource for shrew nematodes, but it may be for shrew cestodes.     

Structure and Seasonal Dynamics of the Ectoparasite Community of the Pygmy Shrew <Emphasis Type="Italic">Sorex minutus</Emphasis> in the Ilmen-Volkhov Lowland

The species composition and seasonal dynamics of ectoparasites of the pygmy shrew Sorex minutus L., 1756 were studied in coniferous and mixed forests of the Ilmen-Volkhov Lowland (Novgorod Province of Russia) in 1999–2003. Examination of 265 specimens of the pygmy shrew revealed 670 specimens of ectoparasites that belonged to 13 species: 8 species of fleas, 2 species of ixodid ticks, 1 species of gamasid mites, and 2 species of myobiid mites. In total, 55.8% of shrew specimens were infested with ectoparasites. No more than 4 species of ectoparasites were found simultaneously on one host, and most of the examined shrews (64.8%) were infested with only 1 ectoparasite species. The pygmy shrew had lower infestation intensity and species diversity of acarines and fleas as compared with those of the common shrew Sorex araneus L., 1758 and the bank vole Myodes glareolus (Schreber, 1780) (13 vs. 23 and 29 species, respectively). Unlike these two other hosts, the prevalent ectoparasite of the pygmy shrew was the tick Ixodes trianguliceps Birula, 1895.     

Effects of late quaternary climate change on Palearctic shrews

The Late Quaternary was a time of rapid climatic oscillations and drastic environmental changes. In general, species can respond to such changes by behavioral accommodation, distributional shifts, ecophenotypic modifications (nongenetic), evolution (genetic) or ultimately face local extinction. How those responses manifested in the past is essential for properly predicting future ones especially as the current warm phase is further intensified by rising levels of atmospheric carbon dioxide. Here, we use ancient DNA (aDNA) and morphological features in combination with ecological niche modeling (ENM) to investigate genetic and nongenetic responses of Central European Palearctic shrews to past climatic change. We show that a giant form of shrew, previously described as an extinct Pleistocene Sorex species, represents a large ecomorph of the common shrew (Sorex araneus), which was replaced by populations from a different gene‐pool and with different morphology after the Pleistocene Holocene transition. We also report the presence of the cold‐adapted tundra shrew (S. tundrensis) in Central Europe. This species is currently restricted to Siberia and was hitherto unknown as an element of the Pleistocene fauna of Europe. Finally, we show that there is no clear correlation between climatic oscillations within the last 50 000 years and body size in shrews and conclude that a special nonanalogous situation with regard to biodiversity and food supply in the Late Glacial may have caused the observed large body size.