1,721,054 research outputs found
Monitoraggio dello scoiattolo comune (Sciurus vulgaris L.) con l’utilizzo di hair-tubes in foreste di conifere della provincia di Sondrio
No full textUna delle tecniche più efficaci ed economiche di monitoraggio della presenza di sciuridi è rappresentata dall’impiego di trappole per peli (hair-tube), e dalla successiva identificazione dei peli al microscopio. Questo lavoro presenta dati relativi alla distribuzione e alla densità di popolazioni di scoiattolo comune (Sciurus vulgaris L.) nel territorio della Provincia di Sondrio. Il lavoro è stato svolto grazie alla collaborazione con l’amministrazione provinciale e un apposita formazione delle Guardie Ecologiche Volontarie (GEV) per il monitoraggio della specie. E’ stato riscontrato un incremento della densità nel 2008 rispetto all 2007, in parte attribuibile alla tendenza da parte degli scoiattoli a visitare gli hair-tube in modo più assiduo col procedere del monitoraggio, in parte ad un aumento effettivo delle densità. Le densità riscontrate con questo metodo di monitoraggio siano paragonabili a quelle riscontrate in letteratura, indicando come la tecnica si addica agli habitat forestali alpini. Le
analisi dei peli hanno dimostrato l’assenza di esemplari di scoiattolo grigio (Sciurus carolinensis Gmelin) nelle aree campione. Viene discusso la necessità di continuare il monitoraggio dello scoiattolo, su medio-lungo termine, aumentando il numero di transetti nelle diverse tipologie forestali
Analisi a lungo termine delle interazioni tra produttori e consumatori: lo scoiattolo comune (Sciurus vulgaris) come specie modello.
No full textThere is strength in numbers: first results of red squirrel monitoring in sinergy among Province, Volunteers and University.
No full textWithin-sex density dependence and population dynamics of red squirrels Sciurus vulgaris
No full text1.
Social organization and dispersal of red squirrels (
Sciurus vulgaris
L.) differ between
sexes, and intrasexual competition is intense. Therefore, we predicted that demographic
parameters should be gender-specific: that is density-dependent factors will be more
strongly related to density of the same sex than to density of the opposite sex. We studied
the relative importance of within- and between-sex density-dependent factors and of
density-independent factors (habitat type, food abundance, winter temperature) on different
demographic parameters, in two populations in northern Belgium.
2.
Spring density of males was positively correlated with tree-seed abundance in the
previous year, but this was not the case for females. None of the population parameters
we measured differed between habitats, indicating that the same density-dependent and
density-independent mechanisms prevailed in coniferous and deciduous habitat.
3.
Within each sex, we found several demographic parameters that were dependent on
the densities of the same sex; however, none of these parameters was found to be
dependent on the density of the opposite sex.
4.
Reproductive rate increased with food abundance and decreased with female density.
Adult survival of females decreased with female density in autumn–winter, while survival
of adult males in spring–summer increased with the size of the previous year’s seed crop.
5.
Immigration rate of males was higher in spring than in autumn, and spring immigration
increased with food abundance. Male recruitment rate, in both seasons,
increased with food abundance, but was male density dependent. However, spring–
summer loss rates also increased when food supplies were good, suggesting that despite
high food availability, emigration of juvenile and subadult males increased when intrasexual
competition was intense. Recruitment rate of females decreased with increasing
female density. After a good seed crop, more subadult females dispersed, but their settlement
success (recruitment) was lower at high female density.
6.
Seed crop size positively affected red squirrel densities through increased reproduction,
immigration and adult survival of males, but density-dependent reproduction and withinsex
density-dependent recruitment of locally born juveniles and dispersing subadults limit
the fluctuations in numbers and regulate densities in winter–early spring, as well as in summer
Are Eurasian red squirrels (Sciurus vulgaris) maladapted to early seed-dispersal in silver fir (Abies alba)?
No full textAbstrac
Interspecific competition between native Eurasian red squirrels and alien grey squirrels: does resource partitioning occur?
No full textIn heterogeneous environments, differential niche selection by two competing species will result in niche partitioning so that individuals of each species can maximise their fitness under different sets of environmental variables. Thus, niche partitioning is considered essential to allow co-existence of ecologically related species. To assess whether niche partitioning was occurring between native red squirrels and alien grey squirrels living together in a 13-ha high-quality mixed deciduous woodland in north Italy, we investigated temporal and spatial patterns in their activity and foraging behaviour between 1996 and 1998. We used live trapping and radio-tracking to study numbers, distribution and behaviour of squirrels. Daily and seasonal temporal activity patterns, and activity on the ground and in the trees, were similar in the two species. However, grey squirrels were more tree specialists and had a narrower tree-species niche width than red squirrels, in particular making greater use of oak. Other studies of red and grey squirrels in allopatry show that the two species differ in the extent they utilise oak. Overall, tree-species niche overlap was about 70%. Grey squirrels had larger home ranges than red squirrels. Home ranges and core areas of both species were larger in males than females. Also, intraspecific home range and core-area overlap patterns were similar to those found in allopatric populations of these species. Overall, there was no evidence that the use of space of one species was affected by the other. Our results show that there was no niche partitioning of activity or foraging behaviour in time or space during the study. This suggests that, at moderate grey-squirrel densities, red squirrels are unable to avoid competition with grey squirrels, and that competition for food and/or space will occur when these resources become limiting
Evolutionary arms-race between trees and squirrels: a long-term study of red squirrels in mixed conifer forests.
No full text
Consumption of hypogeous and epigeous fungi by the red squirrel (Sciurus vulgaris) in subalpine conifer forests
No full textThe consumption of epigeous and hypogeous fungi by red squirrels Sciurus vulgaris in subalpine conifer forests in the Alps
was studied by determining the presence and taxa (genus level) of fungal spores in fecal samples. Nearly all live-trapped
squirrels in summer and autumn had eaten fruit bodies of hypogeous fungi, but only some animals had consumed epigeous fungi
of the genus Boletus and/or Laccaria. From two (spring) up to nine (summer–autumn) genera of hypogeous fungi were eaten.
The mean number of genera of fungi and the mean number of spores per mg fecal material differed between study areas and
seasons. Fruit bodies of hypogeous, and to a lesser extent epigeous, fungi seem to present an important seasonal food resource for
red squirrels in conifer forests of the Alps. We suggest that squirrels, having large home range size and dispersal distances, are
likely to play a major role as spore dispersal agent for hypogeous fungi.The consumption of epigeous and hypogeous fungi by red squirrels Sciurus vulgaris in subalpine conifer forests in the Alps was studied by determining the presence and taxa (genus level) of fungal spores in fecal samples. Nearly all live-trapped squirrels in summer and autumn had eaten fruit bodies of hypogeous fungi, but only some animals had consumed epigeous fungi of the genus Boletus and/or Laccaria. From two (spring) up to nine (summer-autumn) genera of hypogeous fungi were eaten. The mean number of genera of fungi and the mean number of spores per mg fecal material. differed between study areas and seasons. Fruit bodies of hypogeous, and to a lesser extent epigeous, fungi seem to present an important seasonal food resource for red squirrels in conifer forests of the Alps. We suggest that squirrels, having large home range size and dispersal distances, are likely to play a major role as spore dispersal agent for hypogeous fungi. (C) 2004 Elsevier B.V. All rights reserved
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