Does interspecific competition with introduced grey squirrels affect foraging and food choice of Eurasian red squirrels?

Wauters, Luc A.; Gurnell, John; Martinoli, Adriano; Tosi, Guido

doi:10.1006/anbe.2001.1703

Cited by 46 publications

(56 citation statements)

References 32 publications

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“…There was no evidence of autumn fattening (Wauters and Dhondt 1989b, Lurz and Lloyd 2000, Wauters et al 2001a) in these alpine populations. Significant area by year interactions showed that patterns of changes in body mass were complex.…”

Section: Discussionmentioning

confidence: 69%

Effects of spatio-temporal variation in food supply on red squirrel Sciurus vulgaris body size and body mass and its consequences for some fitness components

Wauters

Vermeulen²,

Dongen³

et al. 2007

Ecography

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Food availability is likely to influence body condition and, in turn, fitness. The intensity of this response may vary between populations of the same species on a small spatial and temporal scale. We used 5 yr of data from 6 Eurasian red squirrel Sciurus vulgaris populations from the southern Alps to explore differences in body size and body mass among neighbouring populations, in relation to habitat type and variation in food supply. We also investigated sexual dimorphism in these traits and whether phenotypic variation affects local survival and female reproductive success. Mean hind foot length, a measure of body size, did not differ between sexes but differed between areas. Seasonal variation in body mass was small with no evidence for fattening in autumn. Females were slightly heavier than males, but this difference was largely explained by mass gain of females during reproduction. The size of conifer seed crops, the major food supply, varied strongly over years and between habitats, but this variation corresponded only weakly with autumn body mass. Differences in size and mass between populations were partially explained by habitat-related differences in body size and variability of seedcrops, suggesting differential selection for smaller squirrels in spruce-larch forests against selection for larger and heavier animals in mixed broadleaves and conifer forests and in Scots pine forests with more stable seed production. The probability of reproduction by females increased with body mass, but varied strongly between habitats and years, with more females reproducing in years with rich seed-crops. In both sexes, body mass positively affected probability of settlement and length of residency. Our results suggest that in temporally variable environments that differ in overall amount of food resources, individual variation in body mass is related to habitat type, and that having a relatively high body mass, within each population, positively affects male and female settlement success and local survival, and female reproductive success.The amount of food animals consume will affect their fitness in various ways. Food assimilation produces energy necessary for body growth and/or maintenance of body condition and for reproductive investment, as well as essential nutrients such as proteins, carbohydrates, minerals, and vitamins (Robbins 1993, Cuthill andHouston 1997). A diet rich in lipids allows a high rate of energy intake and, in a large variety of species, the accumulation of fat reserves that cause a (seasonal) increase in body mass. In many vertebrates, a relatively high body mass in relation to body size is an indication of good condition: such individuals are more likely to survive critical periods of food shortage or extreme weather conditions (Blem 1990, Millar and Hickling 1990, Schulte-Hostedde et al. 2001. Moreover, heavier animals often are more likely to reproduce successfully, particularly in female mammals, and tend to be better competitors (social dominance) than conspecifics of smaller size or les...

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Section: Discussionmentioning

confidence: 69%

Effects of spatio-temporal variation in food supply on red squirrel Sciurus vulgaris body size and body mass and its consequences for some fitness components

Wauters

Vermeulen²,

Dongen³

et al. 2007

Ecography

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“…seeds (two species), even though they could be used by squirrels. For example, squirrels in Japan ate seeds of mono maple (Acer mono) (Lee 2002) and those in Italy ate seeds of field maple (Acer campestre) (Wauters et al 2001). the lack of feeding signs on the above species (and also on other trees, which produce seeds consumed by squirrels, such as beeches (Moller 1983) or magnolias (Lee 2002)) could be explained by the short study interval.…”

Section: Discussionmentioning

confidence: 99%

Density of red squirrels and their use of non-native tree species in the Rogów Arboretum

Krauze‐Gryz

Mazur

Gryz

2016

Forest Research Papers

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Abstract. the aim of the study was to compare the densities of red squirrel (Sciurus vulgaris) in the arboretum and a neighbouring forest and to investigate which tree species the squirrels used. the study was conducted in the area of the rogów arboretum (53.76 ha) and the so-called Zimna Woda and Wilczy Dół forest complexes (altogether 536 ha), all being part of an Experimental Forest station in rogów. the density of squirrels in the arboretum and the neighbouring forest was estimated and compared by means of snow tracks on transect routes. changes in the abundance of squirrels throughout one year as well as their behaviour were determined on the basis of direct observations along transects running through the arboretum. More than half of the area of the arboretum was searched in order to record feeding signs of squirrels. additionally, trees with bark stripping were recorded.the density of snow tracks was higher in the arboretum (0.19 tracks/100 m/24 h) than in the neighbouring forest (0.09 tracks/100 m/24 h). the largest number of observations of red squirrels along transects was made between February and april, in July and August and in October and November. In about half of the cases, squirrels were feeding on one of six non-native tree species (most often on cones of Macedonian pine, Pinus peuce). Feeding signs were found on 39 plots (17%) and 16 different tree species. The most numerous feeding signs were found on plots with Douglas fir (Pseudotsuga menziesii) and also on plots with the western hemlock (Tsuga heterophylla), swiss pine (Pinus cembra), mountain silverbell (Halesia monticola) as well as shagbark (Carya ovata) and shellbark hickories (C. laciniosa). on eight plots, trees with signs of bark stripping were found, most commonly on sawara cypress (Chamaecyparis pisifera). its soft bark was probably used to build dreys. in the area of the arboretum, the natural food sources (seeds of native trees) are supplemented with numerous non-native tree species, which seeds are also consumed by squirrels. the highly abundant and diverse food sources promote a higher density of the red squirrel in the area of the arboretum. additionally, when tree seeds are scarce in the neighbouring forest, squirrels migrate into the arboretum.

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“…In broadleaf woodlands where they temporarily co-occur, the two species show a high niche-overlap, basically selecting the same tree seed species as major food supplies, have similar space use and activity patterns, and grey squirrels seem to pilfer many of the seeds scatter-hoarded by the congener (Wauters and Gurnell 1999;Wauters et al 2001aWauters et al , 2002a. Moreover, in deciduous woods, grey squirrels heavily feed on acorns, while red squirrels feed much less on this often abundant seed supply, resulting in the introduced species having an advantage in terms of food-energy available in its home range (Kenward and Holm 1993;Gurnell 1996a;Kenward et al 1998;Wauters et al 2001a, b, b).…”

Section: Study Speciesmentioning

confidence: 98%

“…Every 2 weeks, they were checked for squirrel hairs, and sticky tape containing hairs was removed. Hairs were identified as pertaining to red or grey squirrels using a reference collection and following methods in Gurnell et al (2001a).…”

Section: Study Area and Data Collectionmentioning

confidence: 99%

Modelling the Expansion of a Grey Squirrel population: Implications for Squirrel Control

et al. 2006

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Does interspecific competition with introduced grey squirrels affect foraging and food choice of Eurasian red squirrels?

Cited by 46 publications

References 32 publications

Effects of spatio-temporal variation in food supply on red squirrel Sciurus vulgaris body size and body mass and its consequences for some fitness components

Effects of spatio-temporal variation in food supply on red squirrel Sciurus vulgaris body size and body mass and its consequences for some fitness components

Density of red squirrels and their use of non-native tree species in the Rogów Arboretum

Modelling the Expansion of a Grey Squirrel population: Implications for Squirrel Control

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