1,721,019 research outputs found
Behavioural and population responses of ground-dwelling rodents to forest edges
Full text linkForest edges can affect the behaviour, physiology and demography of small mammals. We tested whether there was a response in abundance, distribution, personality selection or foraging behaviour of ground-dwelling rodents to a forest–meadow edge in two study areas in Northern Italy over a 1-year period. We used capture-mark-recapture to evaluate species distribution, abundance, survival and personality, while Giving-up Density was used to test their foraging behaviour and the cost associated to it. All tests were carried out on the forest edge and at 50 and 100 m from the edge along three parallel transects 90 m long. We detected two species in both areas: Apodemus sylvaticus and Myodes glareolus. We found a neutral effect of the edge on species number, survival and on individual’s personality (activity/exploration tendency). Bank voles occurred more along the edge and both taxa took more seeds from trays along the edge. The hypothesis of edge avoidance was not confirmed in any of the variables examined. Our study supports evidence that edge effects can be species-specific and that populations should be studied with a multiple test approach to investigate different eco-ethological responses to the edge when trying to reveal the functioning of ecotonal systems
Effects of spatial variation in food availability on spacing behaviour and demography of Eurasian red squirrel
No full textIn heterogeneous habitats with limited resources, spacing behaviour will affect individual variation in breeding success and density of populations, and is thus of general interest to ecologists. We investigated how red squirrels Sciurus vulgaris adapt their social organisation to fine-grained heterogeneity in habitat quality, studying spacing behaviour, habitat use and population dynamics in a forest in north Italy, characterised by a mosaic of high-quality (chestnut-pine) and poor-quality patches. We compared the data with those from more homogeneous broadleaf and mixed woodlands with similar overall tree seed abundance ("stable" habitats). Squirrels lived at lower densities (pre-breeding density 0.39-0.58 ha-1) than in "stable" habitats, although breeding rate was not reduced. Female breeding success was related to being primiparous as yearlings, and increased with body mass and proportion high-quality habitat in the home range. Persistency rate of females was as in stable habitats. It was higher than male persistency, but immigration and recruitment rates were male biased, resulting in even sex-ratio. All residents occupied high-quality patches, and no subadults established a permanent home range in poor-quality habitat. Home range and core-area size was typically larger in males than in females and a male's core-area overlapped those of other males and of females. Female core-areas were overlapped by males but not, or very little, by other females (intrasexual territoriality). Home ranges, or core-areas, were not smaller than in "stable" habitats, nor did we find a higher degree of core-area overlap. We conclude that in patchy habitats dominant, resident red squirrels exclude dispersing animals from preferred, high-quality habitat, producing a spacing pattern referred to as ideal despotic distribution, and that poor patches were only used temporarily by transient individuals, resulting in a reduction of density in comparison to populations in "stable" habitats
Interspecific competition mediated by climate change: Which interaction between brown and mountain hare in the Alps?
No full textCO2 levels and consequently temperatures are expected to increase in the next years. Such quick and
drastic changes in climate are likely to affect species distribution. According to future climate scenarios
some species will have the possibility to colonise new areas, mainly due to expansion of suitable habitat
conditions, whereas other species could be negatively affected due to habitat reduction. In this study,
we analysed, in the perspective stated above, the distribution of two hare species: the mountain hare
(Lepus timidus) and the brown hare (Lepus europaeus), across Central Italian Alps. Mountain hare on the
Alps is a relict species, while brown hare is widespread all over Italy and also across the Alps at lower
elevations. We applied future climate scenarios to both hare species to understand how climate change
could affect their distribution in the next 70 years. Mountain hare distribution surface area is predicted
to decrease in the next few years at its southern edge, but the species should expand its range in northern
areas. Interestingly, brown hare distribution seems to be unaffected by climate changes, since no evident
“area of substitution” appeared in our simulations. Hence, contrary to one’s expectations based on the
two species different niches, while we were able to predict a reduction in mountain hare distribution,
our simulations did not show a substitution of the mountain hare by the more generalist brown hare at
the southern margins of its distribution
Does interspecific competition with introduced grey squirrels affect foraging and food choice of Eurasian red squirrels?
No full textSelective predators or choosy fishermen? Relation between fish harvest, prey availability and great cormorant (Phalacrocorax carbo sinensis) diet
No full textThe increase in numbers and range of the continental subspecies of great cormorant Phalacrocorax carbo sinensis in Europe has led to a growing number of conflicts with commercial fisheries and recreational angling. We investigated the dietary preferences (fish species and size classes) of wintering cormorants in two freshwater basins in Northern Italy, using pellet analysis and data on fish community composition. First, we compared cormorant diet (biomass of fish species consumed) with the annual harvest by professional fishing (biomass/year). Second, we compared diet with a measure of prey availability: direct fish sampling with nets of different mesh size. Cormorants preyed mainly on cyprinid fish. A comparison of pellet analysis and commercial fishing data showed that some fish species consumed by cormorants did not occur in the commercial harvest. Using only species that occurred in the diet and in the commercial harvest, there was no relationship between the amount of fish of different species taken. A positive correlation between pellet analysis data (consumed) and data from scientific fish sampling (available) showed that cormorants exploited fish resources on the basis of prey availability. Comparing the size of fish collected from nets and fish consumed by cormorants also showed that birds were selective with respect to prey size, picking mostly small individuals (< 110 g). We conclude that potential effects of cormorants on commercially important fish will mainly depend on habitat type (fish ponds, natural deep lakes, others), and that in the natural lakes in Lombardy cormorants mainly concentrate on species which are of limited value for commercial fishing
Spacing behaviour, kinship, and population dynamics of grey squirrels in a newly colonized broadleaf woodland in Italy
No full text Eastern grey squirrels, Sciurus carolinensis, introduced to Britain and northern Italy are replacing the native Eurasian red squirrel, Sciurus vulgaris. We studied the pattern of colonization of a high-quality broadleaf woodland by grey squirrels by means of livetrapping and radio-tracking. The studies started in July 1996, when six grey squirrels (four males, two females) first colonized the woodland, and lasted until November 1998, when densities exceeded those of the local red squirrel population. Grey squirrel colonization was rapid, with a high proportion of adult and yearling females breeding. Juvenile recruitment was also higher than in stable populations in Britain. Adult survival was better in 1997 (83%) than in 1998 (47%), with predation accounting for 67% of losses in 1998. This indicates the effects of local predator communities on the colonization process. Densities of grey squirrels were moderate in 1998, with a maximum of 1.9 squirrels/ha and we expect density to increase further. Adult home range sizes were three to four times larger than those of subadults, and male ranges were larger than those of females. Body mass was positively correlated with both total home range size and core-area size. Core-area size for adults was inversely correlated with food availability. Juvenile female grey squirrels were philopatric, forming female kin groups, while most juvenile males settled outside the mother's home range. </jats:p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Shifts in immune responses of an invasive alien species: A test of the evolution of increased competitive ability hypothesis using American Eastern gray squirrels in Italy
No full textBased on the Evolution of Increased Competitive Ability (EICA) hypothesis, a reduced investment in immunity, consequent to parasite loss, could partly explain the success of invasive alien species. We investigated variation in parasite load and immune responses of alien Eastern gray squirrels (Sciurus carolinensis) along the invasion wave of an expanding population. We first verified by fecal analyses that 1) parasite abundance decreased moving from the core towards the invasion front. Next, we used multiple measures of immunity to investigate whether, in response to the lower parasite pressure, individuals at the invasion front 2) dampened their costly inflammatory response, and 3) increased their investment in less expensive acquired immunity. We first explored variation in hematological variables related either to the inflammatory or the acquired response. On a subset of individuals, we carried out ex vivo cell cultures to analyse the basal expression of MHC class II genes and the expression of TNF-α genes in response to an immune challenge. Platelet counts and TNF-α expression suggested higher inflammation in individuals living at the invasion core, whereas parameters associated with an acquired response (lymphocyte counts and MHC II expression by spleen cells), conversely, were higher in squirrels at the front. Overall, our results suggest a shift between different immune strategies along the invasion wave, supporting a reduced investment in costly inflammatory responses and an increased investment in acquired immunity in individuals at the expanding edge of the range, which are subjected to high selective pressures for dispersal and reproduction
The advantage of living in the city: effects of urbanization on body size and mass of native and alien squirrels.
Full text linkIn an ever more urbanized world, animals have to cope with different challenging conditions that may shape the individual’s phenotype in the urban environment. Since body mass and body size are found to be related to fitness in many species, investigating the variation in these two morphological traits along the rural-urban gradient, is a first step to understand how animals adapt to urbanization. Here we studied two tree squirrels, the native Eurasian red squirrel (Sciurus vulgaris) and the invasive Eastern grey squirrel (Sciurus carolinensis), using a pseudo-experimental design with replicated study sites (2 rural, 2 suburban and 2 urban sites for each species). We investigated whether squirrels differed in body size and body mass along the urbanization gradient and whether the invasive alien squirrels had more marked differences along the gradient, showing a higher adaptation capacity. We did not find variation in body size in red squirrels along the gradient, but invasive grey squirrels were slightly larger in urban than in other area-types. In both species, animals of either sex were heavier in the urban than in the rural sites, while the difference between urban and suburban areas depends on species and sex. Hence, morphologically both native and invasive species showed similar changes, with higher body mass in urban habitat, which could result in higher fitness, since body mass in squirrels species is positively related to reproductive success
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