Habitat-dependent effects of personality on survival and reproduction in red squirrels
Variation in intrinsic (body mass, reproductive condition) and extrinsic factors (habitat quality, spatio-temporal 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 1 or 2 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.
Differences in personality among individuals can affect their survival or reproductive success. We investigated the relationship between personality traits and fitness components in Eurasian red squirrels under different food availability. We scored boldness and exploration using indices derived from capture-mark-recapture data. Bold red squirrels survived longer than shy ones in spruce forest where food availability varied strongly between years. Instead, in mixed forests with more stable food supplies, shy individuals survived longer. Heavy females produced more litters in their lifetime than those with lower body mass. Explorative squirrels were more likely to die young and to produce no or few litters, independent of the habitat they lived in. Our results suggest that variation in personality traits within populations of Eurasian red squirrels was maintained by changing fitness benefits in relation to habitat type in pulsed resource systems.
KeywordsBoldness Capture-mark-recapture Exploration Habitat variability Sciurus vulgaris Trappability
We thank the Gran Paradiso National Park, the Orobie Valtellinese Regional Park, the province of Sondrio for allowing fieldwork in the three study areas. We like to thank Ambrogio Molinari, Erica Di Pierro, Marco Adamo and Aleksandar Pizzul for help with the fieldwork and Stefan Van Dongen for statistical advice. Constructive comments by two referees and the Associate Editor greatly helped us to improve the manuscript. Data analysis and writing were carried out in 2015–2016 by the first author as part of her PhD project. This study is part of the ASPER (Alpine Squirrel Population Ecology Research) project (paper # 28).
This work was supported by the Committee for Research and Exploration of the National Geographic Society, Washington DC, USA (grant number 6997-01) to LAW and SB; and by the Italian Ministry of Instruction, University and Research (MIUR, Ministero dell’Istruzione, dell’Università e della Ricerca, COFIN project number 2003053710-006) to Università degli Studi dell’Insubria.
Compliance with ethical standards
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the current law on animal research in Italy and were carried out under permission of the authorities for wildlife research and management of Lombardy region (Decree n.18064 of 14/07/2000; Decree n.10816 of 10/06/2002; Decree n.1861 of 16/02/2004; Decree n.2456 of 07/03/2006) and Gran Paradiso National Park (Authorization prot. n. 1716/9.3.7 of 06/07/200 and prot. n 1071//9.3.7 of 07/05/2003). No specific approval from ethics committee was required.
Conflict of interest
The authors declare that they have no conflict of interests.
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