The common hamster (Cricetus cricetus) is a facultative hibernator producing up to three litters per year. Juveniles born late in the season have less time to grow and prepare for the winter than early-born ones. We investigated a free-ranging population in an urban environment in Vienna, Austria. We compared body mass, proportion of body fat, as well as head, tibia and hind foot length between juveniles of first and second litters at natal emergence, four weeks post-emergence and shortly before onset of hibernation. In addition we tested for differences in growth rates during the first four weeks after emergence and for potential effects of sex and litter size. Capture-mark-recapture techniques were applied. Body fat content was calculated using a multiple regression model integrating morphometric parameters. At natal emergence, second litter offspring were larger and heavier than those of first litters. Litter size did not account for these differences. During the first week after natal emergence, first litter pups gained body mass faster, and during the first two weeks also showed faster head and tibia growth rates than second litter pups. Four weeks after natal emergence, however, second litter juveniles were still larger and heavier than first litter ones. Body fat content four weeks post-emergence did not differ between first and second litters but decreased with litter size. Shortly before onset of hibernation, however, first litter juveniles, which had more time to grow and accumulate body fat, exceeded second-litter ones in all measured parameters. In all litters investigated, we found no sex difference at natal emergence but males were heavier and larger than females four weeks thereafter demonstrating that the commonly known sexual dimorphism in this species developed during this period. Considering the time constraints late born juveniles face, the con ditional advance at natal emergence is assumed to be adaptive by increasing the chances for these individuals to survive overwinter despite the limited time to prepare for the hibernation period
AKAIKE H. 1973: Information theory and an extension of the maximum likelihood principle. 2nd International Symposium on Information Theory, Tsahkadsor, Armenian SSR: 267-281.
DAY D.E. and BARTNESS T.J. 2003: Fasting-induced increases in food hoarding are dependent on the foraging-effort level. Physiology & Behavior. 78: 655-668.
EIBL-EIBESFELDT I. 1953: Zur Ethologie des Hamsters (Cricetus cricetus L.). Zeitschrift für Tierpsychologie. 10: 204-254.
ENDRES J. 2004: Feldhamster (Cricetus cricetus). Ökoporträt 37, NVN/BSG/BSH.
FRANCESCHINI-ZINK C. and MILLESI E. 2008: Reproductive performance in female Common hamsters. Zoology 111: 76-83.
FRANCESCHINI C. and MILLESI E. 2005: Reproductive timing and success in Common hamsters. Proceedings of the 12th Meeting of the International Hamsterworkgroup, Strasbourg, France: 63-66.
FRANCESCHINI C., SIUTZ, C., PALME R. and MILLESI E. 2007: Seasonal changes in cortisol and progesterone secretion in Common hamsters. General and Comparative Endocrinology. 152: 14-21.
GUERRA R.F. and Nunes C.R. d.O. 2001: Effects of litter size on maternal care, body weight and infant development in golden hamsters (Mesocricetus auratus). Behavioural Processes. 55: 127-142.
HUBER S., HOFFMANN I.E., MILLESI E., DITTAMI J. and ARNOLD W. 2001: Explaining the seasonal decline in litter size in European ground squirrels. Ecography. 24: 205-211.
HUFNAGL S., FRANCESCHINI-ZINK C. and MILLESI E. 2011a: Seasonal constraints and reproductive performance in female Common hamsters (Cricetus cricetus).Mammalian Biology. 76: 124-128.
HUFNAGL S., SIUTZ C. and MILLESI E. 2011b: Diet composition of Common hamsters (Cricetus cricetus) living in an urban habitat. Säugetierkdl. Inf. 8: 69-78.
HUMPHRIES M.M., THOMAS D.W. and KRAMER D.L. 2003: The role of energy availability in mammalian hibernation: a cost-benefit approach. Physiological and Biochemical Zoology. 76: 165-179.
HURVICH C.M. and TSAI C.-L. 1991: Bias of the corrected AIC criterion for underfitted regression and time series models. Biometrika. 78: 499-509.
KAUFMAN D.W. and KAUFMAN G.A. 1987: Reproduction by Peromyscus polionotus: number, size, and survival of offspring. Journal of Mammalogy 68: 275-280.
KAYSER A., WEINHOLD U. and STUBBE M. 2003: Mortality factors of the Common hamster (Cricetus cricetus) at two sites in Germany. Acta Theriologica. 48: 47-57.
KIRN N. 2004: Ontogenese des Europäischen Feldhamsters (Cricetus cricetus) unter dem Einfluss verschiedener prä-und postnataler Photoperioden. Dissertation, Tierärztliche Hochschule Hannover.
MAZEROLLE M. 201:. AICcmodavg: model selection and multimodel inference based on (Q) AIC (c). R package version. Vol. 1.27.
MILLESI E., HOFFMANN I., ASCHAUER A. and FRANCESCHINI C. 2004: Reproduction and hibernation in females: a comparison of two sympatric ground-dwelling rodents.In: BARNES, B.M., CAREY, H.V., (eds) Life in the Cold . Evolution, Mechanisms, Adaptation, and Application. Institute of Arctic Biology, University of Alaska Fairbanks. 27: 367-375.
NEDERGAARD J., CANNON B. and JAENICKE R. 1990: Mammalian Hibernation (and Discussion).Philosophical Transactions of the Royal Society of London. B, Biological Sciences. 326: 669-686.
NELSON R.J., BADURA L.L. and GOLDMAN B.D. 1990: Mechanisms of seasonal cycles of behavior. Annual Review of Psychology. 41: 81-108.
NEUHAUS P. 2000: Weight comparisons and litter size manipulation in Columbian ground squirrels (Spermophilus columbianus) show evidence of costs of reproduction.Behavioral Ecology and Sociobiology. 48: 75-83.
NIETHAMMER J. 1982: The Common hamster (Cicetus cricetus) (LINNAEUS, 1758) - Hamster (Feldhamster). Handbuch der Säugetiere Europas, 2/1 Rodentia, Akademische Vertragsgesellschaft, Wiesbaden: 7-28.
SCHMELZER E. and MILLESI E. 2008: Activity patterns in a population of European hamsters (Cricetus cricetus) in an urban environment. Proceedings of 11th Meeting of the International Hamsterworkgroup. Budapest, Hungary: 19-22.
SELUGA K., STUBBE M. and MAMMEN U. 1996: Zur Reproduktion des Feldhamsters (Cricetus cricetus L.) und zum Ansiedlungsverhalten der Jungtiere. Abh. Ber.Mus. Heineanum. 3: 129-142.
SIUTZ C. and MILLESI E. 2012: Effects of birth date and natal dispersal on faecal glucocorticoid concentrations in juvenile Common hamsters. Gen. Comp. Endocrinol. 178: 323-329.
SIUTZ C., PLUCH M., RUF T. and MILLESI E. 2012: Sex Differences in Foraging Behaviour, Body Fat and Hibernation Patterns of Free-Ranging Common Hamsters. In: RUF, T., BIEBER, C., ARNOLD, W., MILLESI, E. (eds) Living in a Seasonal World, Springer, Berlin: 155-165.
TEAM R - Development Core 2008: A language and environment for statistical computing. R Foundation Statistical Computing, 2008.
VOHRALIK V. 1974: Biology of the reproduction of the common hamster, Cricetus cricetus (L.). Vestnik Ceskoslovenske Spolecnosti Zoologicke. 38: 228-240.
VOHRALÍK V. 1975: Postnatal development of the common hamster (Cricetus cricetus L.) in captivity. Academia.
WASSMER T. 2004: Body temperature and above-ground patterns during hibernation in European hamsters (Cricetus cricetus L.). Journal of Zoology. 262: 281-288.
WEINHOLD U. and KAYSER A. 2006: Der Feldhamster. Die Neue Brehm-Bücherei Bd. 265.Westarp Wissenschaften, Hohenwarsleben.
WENDT W. 1989: Zum Aktivitätsverhalten des Feldhamsters, Cricetus cricetus L., im Freigehege. Säugetierkundliche Informationen. 3: 3-12.
WOLFF J. O. 2007: Social biology of rodents. Integrative Zoology. 2: 193-204.