Maternal winter body mass and not spring phenology determine annual calf production in an Arctic herbivore

Warming of the Arctic has resulted in earlier snowmelt and green-up of plants in spring, potentially disrupting the synchrony between plant phenology and breeding phenology in herbivores. A negative relationship between offspring survival in West-Greenland caribou and the timing of vegetation emergence was the first finding of such a mismatch in Arctic mammals. However, other studies indicate that the energy for foetal growth and early lactation is predominantly drawn from stored energy reserves typical of ‘capital’ breeders, suggesting that conditions well before spring influence calf production more than the timing of spring onset. Here we use 20 years of observations of marked Svalbard reindeer to evaluate determinants of annual recruitment, as measured by the presence of a calf at foot in mid-summer. Spring temperatures and the Enhanced Vegetation Index were used as proxies for spring onset, while data on body mass and pregnancy rates in late winter allowed us to determine maternal ...北极变暖已引发春季积雪消融提前与植物返青，或潜在干扰植食动物的植物物候与繁殖物候间的同步性。西格陵兰驯鹿（West-Greenland caribou）的后代存活率与植被出苗时间呈负相关关系，这是北极哺乳动物中此类物候错配的首项研究发现。不过，其他研究显示，胎儿生长与早期泌乳所需能量主要源自“资本繁育者”（capital breeders）典型的储存能量储备，这表明春季来临前的环境条件对幼崽产出的影响，甚于春季起始时间。本研究依托20年间对经标记的斯瓦尔巴德驯鹿（Svalbard reindeer）的观测数据，以仲夏时节幼崽随行这一指标衡量年度种群补充率，以此评估其影响因素。研究采用春季气温与增强型植被指数（Enhanced Vegetation Index, EVI）作为春季起始时间的替代指标，同时借助晚冬季的体重与妊娠率数据，得以分析母畜……