@article{GraccevaHerdeGroothuisetal.2014,
  author    = {Gracceva, Giulia and Herde, Antje and Groothuis, Ton G. G. and Koolhaas, Jaap M. and Palme, Rupert and Eccard, Jana},
  title     = {Turning shy on a winter's day: Effects of season on personality and stress response in Microtus arvalis},
  series = {Ethology},
  volume    = {120},
  journal   = {Ethology},
  number    = {8},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0179-1613},
  doi       = {10.1111/eth.12246},
  pages     = {753 -- 767},
  year      = {2014},
  abstract  = {Animal personalities are by definition stable over time, but to what extent they may change during development and in adulthood to adjust to environmental change is unclear. Animals of temperate environments have evolved physiological and behavioural adaptations to cope with the cyclic seasonal changes. This may also result in changes in personality: suites of behavioural and physiological traits that vary consistently among individuals. Winter, typically the adverse season challenging survival, may require individuals to have shy/cautious personality, whereas during summer, energetically favourable to reproduction, individuals may benefit from a bold/risk-taking personality. To test the effects of seasonal changes in early life and in adulthood on behaviours (activity, exploration and anxiety), body mass and stress response, we manipulated the photoperiod and quality of food in two experiments to simulate the conditions of winter and summer. We used the common voles (Microtus arvalis) as they have been shown to display personality based on behavioural consistency over time and contexts. Summer-born voles allocated to winter conditions at weaning had lower body mass, a higher corticosterone increase after stress and a less active, more cautious behavioural phenotype in adulthood compared to voles born in and allocated to summer conditions. In contrast, adult females only showed plasticity in stress-induced corticosterone levels, which were higher in the animals that were transferred to the winter conditions than to those staying in summer conditions. These results suggest a sensitive period for season-related behavioural plasticity in which juveniles shift over the bold-shy axis.},
  language  = {en}
}
@article{EccardRoedel2011,
  author    = {Eccard, Jana and Roedel, Heiko G.},
  title     = {Optimizing temperament through litter size in short-lived, iteroparous mammals in seasonal environments},
  series = {Developmental psychobiology : the journal of the International Society for Developmental Psychobiology},
  volume    = {53},
  journal   = {Developmental psychobiology : the journal of the International Society for Developmental Psychobiology},
  number    = {6},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {0012-1630},
  doi       = {10.1002/dev.20547},
  pages     = {585 -- 591},
  year      = {2011},
  abstract  = {A number of short-lived, iteroparous animal species have small broods in the early breeding season and larger broods in later breeding season. Brood size affects not only offspring size, but as recent results suggest, may also affect offspring's temperament, hormonal status, and aggression as adults. Most populations of short-lived, iteroparous mammals fluctuate predictably over the season, with low densities in winter, increasing densities in summer and a population peak in late summer followed by a population breakdown. If animals live only through parts of the season, possibly such differences in density and hence also in social environments among seasons require different personality types to increase individual fitness. We present data on behavior of European rabbits from a field enclosure study. These data clearly show that aggressiveness is higher in young from smaller litters than in young from larger litters, and smaller litters are usually born during the early breeding season. Moreover, our data suggest that behavioral types of the young rabbits are stable over time, at least during their subadult life. We suggest, that changes in mean litter size over the course of the breeding season may not only be a product of mothers' age or food availability, but may also have an adaptive function by preparing offspring characteristics for adulthood in a social environment undergoing predictable density changes within the season.},
  language  = {en}
}