Differences in growth rates and pre-hibernation body mass gain between early and late-born juvenile garden dormice

Stéphane Blanc,Claudia Bieber,Thomas Ruf,Sylvain Giroud,Stefan Stumpfel

doi:10.1007/s00360-016-1017-x

Abstract

Juvenile hibernators have to allocate energy to both growth and fattening, to survive winter, and to avoid possible disadvantages during their first reproductive season. Being born late in the active season may have important effects on growth and fattening. This study aimed at determining potential differences in rates and maximal level of growth, and in pre-hibernation body fat mass between early and late-born juvenile garden dormice (Eliomys quercinus), and kept in outdoor enclosures with ad libitum food and water. We first assessed mean pup mass in early and late-born litters (n = 31) from birth to their early weaning phase, at which time body composition was determined. Then, growth and body mass of early and late-born individuals (six males and six females, for each group) were measured weekly until hibernation onset (n = 24). We also assessed fat content in a group of juveniles during pre-hibernation fattening (n = 16) and after their first winter hibernation (n = 18). During the pre-weaning phase, young from early and late litters mainly grew structurally and gained mass at similar rates. After weaning, late-born juveniles grew and gained mass twice as fast as early born individuals. Body mass was positively associated with fat content during pre-hibernation fattening. Late-born females reached similar structural sizes, but had lower pre-hibernation fat reserves than early born females. Conversely, late-born males showed lower maximal size and pre-hibernation body fat content, compared with early born males. Thus, individuals born late in the season cannot fully compensate the lack of available time before the winter onset.

Highlights

To survive the winter season, many small mammals enter hibernation, a state of reduced metabolic rate and body temperature, and rely mainly on their body fat stores throughout winter
Pre-hibernation body mass (BM), which is a good indicator of fat content (Schaefer et al 1976), correlates positively with overwintering survival (Armitage et al 1976; Rieger 1996)
Among the 24 juveniles included in the main experiment (Table 1, ‘main experiment’), sizes of early and late litters were 5.0 ± 0.8 and 5.3 ± 1.3 pups, respectively, and did

Summary

Introduction

To survive the winter season, many small mammals enter hibernation, a state of reduced metabolic rate and body temperature, and rely mainly on their body fat stores throughout winter (for review see Dark 2005). Pre-hibernation body mass (BM), which is a good indicator of fat content (Schaefer et al 1976), correlates positively with overwintering survival (Armitage et al 1976; Rieger 1996). This seems especially true for juveniles due to their lower fat reserves prior to hibernation (Dark 2005). Obtaining sufficient fat stores is difficult for juveniles, especially for those born late in the season of reproduction, due to the limited time available for growth and fat accumulation prior to their first hibernation season (Lenihan and van Vuren 1996). Juveniles born when the summer season is well advanced have less time to grow and to gain sufficient BM for hibernation compared to conspecifics born earlier in the season (Pilastro et al 1994; Dmitriew 2011). Armitage et al (1976) found that juvenile yellow-bellied marmots (Marmota flaviventris) weaned earlier

Objectives

Methods

Results

Discussion

Conclusion