The effects of seed availability on habitat use by a specialist seed predator

Pierro, Erica A. Di; Ghisla, Anne; Wauters, Luc A.; Molinari, A.; Martinoli, Adriano; Gurnell, John; Tosi, Guido

doi:10.1007/s10344-010-0469-7

Cited by 15 publications

(30 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Each year between 26 July -9 August, the new (current year) maturing cones were counted in the canopy of sample trees of all conifer species to estimate food availability. Methods are described in detail elsewhere (Salmaso et al 2009;Di Pierro et al 2011). Based on species-specific energy values per cone (kJ/cone) and data on tree species composition and density (Salmaso et al 2009), these counts allowed us to estimate the average yearly tree seed-energy production in each study area ( Table 1).…”

Section: Study Areas and Food Availabilitymentioning

confidence: 99%

Habitat-dependent effects of personality on survival and reproduction in red squirrels

Santicchia

Gagnaison

Bisi

et al. 2018

Behav Ecol Sociobiol

Self Cite

View full text Add to dashboard Cite

Variation in intrinsic (body mass, reproductive condition) and extrinsic factors (habitat quality, spatiotemporal variation in food availability) can affect the costs and benefits of personality traits. Relationships between personality and fitness components can vary with changes in population density and/or habitat quality. Here, using capture-mark-recapture data of individually marked Eurasian red squirrels (Sciurus vulgaris), we explored whether indices of boldness and exploration are correlated with local survival in either of the sexes and with a measure of reproductive success in females, under different conditions of food availability. PCA scores derived from the number of captures (trappability) and number of different traps where an individual was captured (trap diversity), in the first one or two years of presence, were used as indices of personality (boldness and pure exploration). The relationships between boldness and local survival differed between habitats in both sexes. Bold squirrels survived better than shy ones in Norway spruce forest, while in the other two study areas (Scots pine, or mixed spruce-fir forest) survival was lower for bolder squirrels. Pure exploration behavior was negatively correlated with local survival in all habitats and in both sexes. Female reproductive success increased with body mass and decreased with the tendency to explore, a relationship consistent across habitat types. Bolder females did not have a reproductive advantage in years of poor food availability. We suggest that costs and benefits of boldness vary with spatio-temporal differences in availability of high-quality food resources which may help to maintain variation in personality in red squirrels in heterogeneous landscapes.

show abstract

Section: Study Areas and Food Availabilitymentioning

confidence: 99%

Habitat-dependent effects of personality on survival and reproduction in red squirrels

Santicchia

Gagnaison

Bisi

et al. 2018

Behav Ecol Sociobiol

Self Cite

View full text Add to dashboard Cite

show abstract

“…Thus, if foraging would be determined mainly by (i) rate of energy-intake, (ii) cone morphology, in particular the reduced amount of protective tissue (Molinari et al 2006), or (iii) temporal availability of the food source, red squirrels should strongly select fir seeds between mid August and mid October, when they are available in the tree canopy. However, squirrels prefer Norway spruce over fir seeds in all seasons and years and fir seed consumption is limited, occurring to some extent only in years with spruce seed-crop failure (Di Pierro et al 2011). Since previous studies on squirrel food choice have demonstrated that tannins and terpenes contained in seeds and/or cone scales of some tree species induce animals to reduce consumption of these food items, we have considered the hypothesis that avoidance of fir seeds is caused by higher ratio of some PSMs on dry mass or by higher concentrations of specific PSM(s) in silver fir seeds and/or cones.…”

Section: Parametermentioning

confidence: 98%

“…Our previous work, including observations of feeding behaviour Di Pierro et al 2011), showed that also red squirrels prefer spruce and avoid fir seeds.…”

Section: Fir Versus Sprucementioning

confidence: 99%

“…It selects seeds of different conifer species and from individual trees within species, based on characteristics that permit to maximise rate of energy-intake and minimise the animal's feeding effort, such as accessibility, a cone structure allowing an easy recovery of seeds, and the correct degree of seed maturation (Moller 1983;Lurz et al 2000;Molinari et al 2006). The study of the relationship of treeseed abundance and squirrel population dynamics ) and space-and habitat use in mixed Norway spruce (Picea abies) -silver fir (Abies alba) forests (Di Pierro et al 2011), indicate that squirrels feed only rarely on silver fir seeds. Of all alpine conifers, fir has the highest energy-content per cone (Table 1) and the highest ratio of seed/cone mass, hence the lowest amount of protective tissue (Table 1, from Salmaso et al 2009).…”

Section: Parametermentioning

confidence: 99%

See 1 more Smart Citation

Food choice of Eurasian red squirrels and concentrations of anti-predatory secondary compounds

et al. 2012

Self Cite

View full text Add to dashboard Cite

a b s t r a c tSecondary metabolites (SMs) are organic compounds of low molecular mass that represent a vast chemical diversity. In plants, one of their preeminent roles is their repellent activity against predators. The Eurasian red squirrels (Sciurus vulgaris) is one of the most important predators of conifer tree seeds in boreal and alpine forests in Europe. Its population dynamics and space use are strongly affected by the size of Norway spruce (Picea abies) seed-crops, but not by silver fir (Abies alba) seed-crops. Moreover, squirrel heavily feed on spruce seeds but tend to avoid fir seeds, although the latter has a higher seed-energy content per cone. We tested the hypothesis that a higher concentration of some SMs in fir than in spruce seeds and/or cone scales, the protective tissue of seeds, was related with squirrel feeding preferences. We determined terpene concentrations in the cyclohexane extract of seeds and scales by gas-chromatography-electron ionisation mass-spectrometry (GC/EI-MS), and measured the protein precipitation activity of tannin contained in spruce and fir seeds and scales. Of the nearly 300 separated chemical entities, only limonene, ␣-and ␤-pinene and myrcene occurred in all samples and their levels accounted for 80% or more of all cyclohexane-extractable materials of fir and for less than 50% of that of spruce. In fir, limonene was by far the most abundant compound, and fir scales had a 13 times higher concentration of ␣-pinene than spruce scales. Fir seeds had much higher limonene concentrations than fir scales and than seeds or scales of spruce. Tannin concentrations were higher in cone scales than in seeds, with no differences between the two tree species. This study suggests that high concentrations of limonene might reduce the feeding activity of red squirrels on fir seeds, and that the preferred spruce seeds had much lower monoterpene concentrations. Feeding trials using food items treated with different concentrations of limonene will be carried out to confirm this hypothesis.

show abstract

“…Given the general lack of understanding of how rodent populations are affected by high interannual variation in conifer seed production, and the significance of their population fluctuations for structuring bird and insect population dynamics (McShea 2000;Ostfeld & Keesing 2000), long-term data sets on annual conifer seed production and intensive rodent trapping can provide valuable insights into this important interaction in forest ecosystems. The effect of conifer masting on consumer population dynamics, and its implications for the predator satiation hypothesis and the evolution of masting, have recently been documented for North American (Tamiasciurus hudsonicus) and Eurasian (Sciurus vulgaris) red squirrels, two dominant pre-dispersal seed predators (Boutin et al 2006;Wauters et al 2008;Fletcher et al 2010;Di Pierro et al 2011;Archibald et al 2012). However, the efficacy of this hypothesis for post-dispersal seed predators is unclear.…”

Section: Introductionmentioning

confidence: 99%

Indirect and mitigated effects of pulsed resources on the population dynamics of a northern rodent

Lobo

Millar

2013

Journal of Animal Ecology

View full text Add to dashboard Cite

Summary1. Pulsed resources have significant effects on population and community dynamics in terrestrial ecosystems. Mast seeding is an important resource pulse in deciduous forests; these boom and bust cycles of seed production generate strong lagged population responses by post-dispersal seed predators such as rodents, which then cascade through multiple trophic levels and regulate population dynamics of their predators and prey. However, similar interactions in another major pulsed system, coniferous forests, are inconsistent, and the effects of interannual variation in conifer seed production on many consumer populations are largely unknown. 2. We used large-scale manipulation and intensive monitoring to examine the population dynamics of deer mice (Peromyscus maniculatus) in relation to fall seed production by two northern conifers, white spruce (Picea glauca) and subalpine fir (Abies lasiocarpa). Previous studies have shown that spruce seeds are a preferred food source of mice, while fir seeds are generally avoided if other foods are available. Therefore, we expected that there would be a positive relationship between mouse demography and previous spruce seed production, but no effect of fir mast seeding. 3. Supplementation of a mouse population using spruce seeds indicated that increased fall spruce seed availability can enhance overwinter survival and population densities in the following spring, summer, and fall. However, long-term population monitoring indicated that mouse demography was not positively affected by spruce mast seeding, likely due to strong interspecific competition with the North American red squirrel (Tamiasciurus hudoniscus), a dominant pre-dispersal spruce seed predator. 4. Conversely, we observed an unexpected delayed effect of fir mast seeding, where increased fall fir seed production did not influence overwinter or spring mouse demography, but instead enhanced summer survival, body masses and pregnancy rates of overwintered adults. This led to increased summer population densities and may have been mediated by population responses of invertebrate post-dispersal seed predators to increased fir seed availability. 5. Our results indicate that rodent responses to resource pulses in coniferous forests are more complex than in deciduous environments and reveal previously unobserved direct and indirect consumer-resource dynamics that require further examination. This system is ideal for the large-scale, integrative ecosystem studies that ecologists are encouraged to pursue.

show abstract

The effects of seed availability on habitat use by a specialist seed predator

Cited by 15 publications

References 38 publications

Habitat-dependent effects of personality on survival and reproduction in red squirrels

Habitat-dependent effects of personality on survival and reproduction in red squirrels

Food choice of Eurasian red squirrels and concentrations of anti-predatory secondary compounds

Indirect and mitigated effects of pulsed resources on the population dynamics of a northern rodent

Contact Info

Product

Resources

About