Body weights in grey and red squirrels: do seasonal weight increases occur in conifer woodland?

Lurz, P. W. W.; Lloyd, Amanda

doi:10.1111/j.1469-7998.2000.tb01237.x

Cited by 11 publications

(9 citation statements)

References 24 publications

(21 reference statements)

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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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“…Additionally, recent mild winters [ 64 ] together with an influence of an urban island heat effect, reaching as far as the outer districts of Warsaw [ 65 ], may be facilitative. As shown in a previous study, forest squirrels occupied relatively small home ranges [ 23 ], which suggested rich natural food supply [ 61 ]. In contrast, park squirrels were more active, assumingly trying to adjust activity to the reduced presence of park visitors in winter [ 34 ], which might help them to retain fat resources.…”

Section: Discussionmentioning

confidence: 86%

“…In general, the body mass of red squirrels may change seasonally, according to food availability, weather and reproductive status [ 54 , 61 ]. In deciduous habitats, body mass is typically highest in autumn [ 55 , 62 ], when squirrels feed mainly on high-energy tree seeds and accumulate fat for the winter period [ 54 , 62 ].…”

Section: Discussionmentioning

confidence: 99%

“…In deciduous habitats, body mass is typically highest in autumn [ 55 , 62 ], when squirrels feed mainly on high-energy tree seeds and accumulate fat for the winter period [ 54 , 62 ]. On the other hand, no autumn or winter increase in body weight was observed in coniferous habitat, which was explained by more predictable food supplies [ 61 ]. In winter, food availability remains high, but due to high thermoregulation costs, fat reserves may become depleted [ 55 ].…”

Section: Discussionmentioning

confidence: 99%

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Body Condition and Breeding of Urban Red Squirrels: Comparison of Two Populations Affected by Different Levels of Urbanization

Beliniak

Gryz

Klich

et al. 2022

Animals

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The red squirrel is among the mammals that have adjusted well to urban habitats. Here, we focused on the two populations inhabiting Warsaw: in a park (with year-round supplemental feeding) and in an urban forest. We hypothesised that park squirrels would have higher body mass (and better body condition), being more stable over the year, and would have a higher breeding rate (i.e., the share of breeding females). Contrary to our hypothesis, forest squirrels were heavier and had better body condition than park squirrels. The body masses of squirrels from both areas were quite stable (with the highest values obtained in spring). Females in better body conditions were more likely to breed. More breeding females and sub-adults were trapped in the park. Regardless of the study site, the highest share of breeding females was in spring, but they also bred in winter and in the remaining seasons. The lower body mass/condition of park squirrels may be possibly explained by high intraspecific competition, or by stable food (and thermal as typical for the city) conditions, in which accumulating fat was not crucial. Mild winter conditions may have also enabled squirrels to breed early. This study showed the high plasticity of red squirrels living in human-transformed habitats.

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“…We have extensively studied red and grey squirrel population dynamics and space use in upland conifer forests (Cartmel, 2000;Lurz and Lloyd, 2000;Wauters et al, 2000) and combined our knowledge of the species to develop population models. This approach, together with the recent introduction of GIS techniques in forest management and design, make upland conifer forests such as Kidland an ideal system to investigate squirrel population viability using SEPMs.…”

Section: Young Oakmentioning

confidence: 99%

Planning a red squirrel conservation area: using a spatially explicit population dynamics model to predict the impact of felling and forest design plans

Lurz¹,

Geddes²,

Lloyd³

et al. 2003

Forestry

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SummaryThis paper describes the use of a spatially explicit population model (SEPM) to investigate the effects of different forest management strategies on a red squirrel conservation area. The study was based in woodland managed by Forest Enterprise, which manages 75 000 ha of woodlands in Northumberland, Co. Durham, Tyne and Wear, and east Cumbria. The forests contain the largest remaining red squirrel populations in northern England and the area of the study, Kidland Forest, is one of five key areas or refuges where red squirrel conservation is a priority. The SEPM integrates expert knowledge on red and grey squirrels, based on 10 years of fieldwork in the area and information from the scientific literature. We investigated the current tree species composition, distribution and proposed felling plans as well as the future restocking for Kidland Forest, an area of 2050 ha of predominantly conifer species. The assessment also included a proposed planting of 15 ha of oak and its likely consequences on grey squirrel population viability. These results were then applied to develop a forest design plan to ensure red squirrel persistence over the next rotation. Results indicated that red squirrels were at risk of extinction due to a drastic reduction in the availability of suitable habitats through clear-felling. Furthermore the proposed planting of 15 ha of oak could lead to a substantial grey squirrel population at Kidland once the trees matured and assuming that grey squirrels colonize the area. The felling profile was therefore revised, allocating a proportion of the tree crop on more wind-firm sites to long-term retentions. The approach adopted at Kidland illustrates how geographical information systems, expert knowledge on the threatened species and spatially explicit models can be integrated to assist forest managers in assessing the suitability of a site for red squirrel conservation.

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Body weights in grey and red squirrels: do seasonal weight increases occur in conifer woodland?

Cited by 11 publications

References 24 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

Body Condition and Breeding of Urban Red Squirrels: Comparison of Two Populations Affected by Different Levels of Urbanization

Planning a red squirrel conservation area: using a spatially explicit population dynamics model to predict the impact of felling and forest design plans

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