Moose (Alces alces) have evolved to store adequate body fat to emerge from winter in adequate nutritional condition that is key to annual productivity and neonatal survival. Blood consumption by winter ticks (Dermacentor albipictus) affects survival and productivity of moose, often resulting in marked local and regional die-offs of calves. Concurrent with an unprecedented frequency of winter tick epizootics (>50% calf mortality) in the northeastern United States, productivity but not mortality of adult female moose also has declined because of low rates of twinning and calving. Chronic blood loss to winter ticks in late winter-early spring negatively affects pregnant cows in their energy- and protein-costly 3rd trimester of pregnancy that will eventually calve and lactate initially in an environment low in digestible energy and protein. To describe this dynamic, I calculated the endogenous fat balance of different-sized pregnant cows by developing energy-balance equations that accounted temporally for gestation, winter tick infestation, and lactation under two consumption levels. The analysis revealed the critical importance of body mass and body fat as only large cows (25% pre-winter body fat) were immune from depletion of body fat at birth in all scenarios. Mid-sized cows (20% body fat) depleted fat reserves during gestation in most scenarios, and small cows (15% body fat) in all scenarios. The infestation and forage- consumption levels influenced the predicted date of fat depletion up to several weeks, and failed calving or mortal mass loss associated with rapid loss of endogenous protein was possible in mid-sized and small cows. The continual decline in demographic parameters points to reduced body mass and body fat over time, or increased numbers of mid-sized and small cows in the population with lower reproductive potential. This regional population is confronted with a unique and sustained combination of environmental and parasitic conditions associated with a warming climate that markedly affects its survival and reproduction in quality habitat, a unique occurrence in their evolutionary history.

中文翻译：

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冬季蜱虫感染对驼鹿的代谢和种群影响：独特的进化环境？

驼鹿 (Alces alces) 已经进化到可以储存足够的身体脂肪，以便在充足的营养条件下度过冬天，这是年生产力和新生儿存活率的关键。冬季蜱（Dermacentor albipictus）的血液消耗会影响驼鹿的生存和生产力，通常会导致小牛明显的局部和区域性死亡。与美国东北部前所未有的冬季蜱流行（> 50% 小牛死亡率）同时发生的同时，由于双胞胎和产犊率低，成年雌性驼鹿的生产力而非死亡率也有所下降。在冬末早春，冬季蜱虫的慢性失血会对怀孕母牛的能量和蛋白质成本产生负面影响，这些母牛在妊娠的第三个三个月内最终会在可消化能量和蛋白质含量低的环境中产犊和产奶。 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 为了描述这种动态，我通过开发能量平衡方程来计算不同大小怀孕奶牛的内源性脂肪平衡，这些方程在两个消耗水平下暂时考虑了妊娠、冬季蜱虫感染和泌乳。分析揭示了体重和体脂的重要性，因为在所有情况下，只有大型奶牛（25% 的冬季前体脂）在出生时不会出现体脂消耗。在大多数情况下，中型奶牛（20% 的体脂）在妊娠期间消耗了脂肪储备，在所有情况下，小型奶牛（15% 的体脂）都会消耗掉脂肪储备。侵染和草料消耗水平影响脂肪消耗的预测日期长达数周，并且在中型和小型奶牛中，与内源蛋白质快速损失相关的产犊失败或死亡体重损失是可能的。人口统计学参数的持续下降表明，随着时间的推移，体重和身体脂肪会减少，或者繁殖潜力较低的中型和小型奶牛数量增加。该地区人口面临着与气候变暖相关的独特而持续的环境和寄生条件组合，这显着影响了其在优质栖息地的生存和繁殖，这是他们进化史上的独特现象。