Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna, Savoyenstraße 1, 1160 Vienna, Austria
Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna, Savoyenstraße 1, 1160 Vienna, Austria.
J Exp Biol. 2018 Oct 15;221(Pt 20):jeb183558. doi: 10.1242/jeb.183558.
Entire populations of edible dormice () can skip reproduction in years without mast seeding of deciduous trees (particularly beech or oak seed), because juveniles require high-calorie seeds for growth and fattening prior to hibernation. We hypothesized that, in mast failure years, female dormice may be forced to spend larger amounts of time foraging for low-quality food, which would increase their exposure to predators, mainly owls. This may lead to chronic stress, i.e. long-term increased secretion of glucocorticoids (GC), which can have inhibitory effects on reproductive function in both female and male mammals. We monitored reproduction in free-living female dormice over 3 years with varying levels of food availability, and performed a supplemental feeding experiment. To measure stress hormone levels, we determined fecal GC metabolite (GCM) concentrations collected during the day, which reflect hormone secretion rates in the previous nocturnal activity phase. We found that year-to-year differences in beech mast significantly affected fecal GCM levels and reproduction. However, contrary to our hypothesis, GCM levels were lowest in a non-mast year without reproduction, and significantly elevated in full-mast and intermediate years, as well as under supplemental feeding. Variation in owl density in our study area had no influence on GCM levels. Consequently, we conclude that down-regulation of gonads and reproduction skipping in mast failure years in this species is not caused by chronic stress. Thus, in edible dormice, delayed reproduction apparently is profitable in response to the absence of energy-rich food in non-mast years, but not in response to chronic stress.
整个人口的食虫松鼠 () 可以跳过繁殖在没有mast 播种的几年落叶树 (特别是山毛榉或橡木种子), 因为青少年需要高热量的种子生长和育肥之前冬眠。我们假设, 在 mast 失败的年份, 雌性食虫松鼠可能被迫花费更多的时间觅食低质量的食物, 这将增加他们暴露于捕食者, 主要是猫头鹰。这可能导致慢性应激, 即长期增加糖皮质激素 (GC) 的分泌, 这可能对雌性和雄性哺乳动物的生殖功能有抑制作用。我们监测了自由生活的雌性食虫松鼠在 3 年的不同水平的食物供应, 并进行了补充喂养实验。为了测量应激激素水平, 我们确定了在白天收集的粪便 GC 代谢物 (GCM) 浓度, 这反映了前一个夜间活动阶段的激素分泌率。我们发现, 山毛榉 mast 的年际差异显著影响粪便 GCM 水平和繁殖。然而, 与我们的假设相反, 在没有繁殖的非 mast 年,GCM 水平最低, 在完全 mast 和中间年以及补充喂养时显著升高。在我们的研究区域内猫头鹰密度的变化对 GCM 水平没有影响。因此, 我们得出结论, 在这个物种中, 在 mast 失败的年份下调性腺和繁殖跳过不是由慢性应激引起的。因此, 在食虫松鼠中, 明显的延迟繁殖是有利的, 以应对非 mast 年缺乏富含能量的食物, 而不是对慢性应激的反应。
