Urbanization-driven climate change increases invertebrate lipid demand, relative to protein—a response to dehydration

1. Climatic change alters not only animal energy balance, but also water balance, but this latter topic has received less attention. Water can be obtained through consumption of moist food and metabolism of dry food. The breakdown of carbohydrates, lipids, and proteins can produce metabolic water. Metabolism of lipids produces large amounts of water, whereas excretion of nitrogenous waste related to protein metabolism requires water losses.

2. Here we tested the hypothesis that climatic shifts associated with urbanization influences animal lipid demand relative to protein, due to shifts in water balance.

3. We placed artificial diets high in lipid or protein, and either with or without supplemented water, at 16 pairs of sites along an urbanization gradient in Toledo, OH, USA.

4. Lipid consumption, relative to protein, increased with urbanization and mean temperature, but water supplementation reduced the magnitude of this association. Ants were ~50% of the observed consumers.
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1. 气候变化不仅会改变动物的能量平衡，还会影响其水平衡，但后者这一研究主题迄今受到的关注相对不足。动物可通过摄取湿润食物以及代谢干性食物获取水分：碳水化合物、脂质与蛋白质的分解代谢均可产生代谢水；其中脂质代谢可产生大量水分，而与蛋白质代谢相关的含氮废物排泄过程则会造成水分流失。
2. 本研究验证了下述假说：与城市化过程相伴的气候变化会通过改变动物的水平衡，进而影响其相对于蛋白质的脂质需求。
3. 我们在美国俄亥俄州托莱多市沿城市化梯度设置了16组样点，并在每组样点放置高脂质或高蛋白质的人工饲料，同时设置补水与不补水两组对照处理。
4. 相较于蛋白质，动物的脂质取食量随城市化水平与平均温度升高而增加，但补水会削弱这一关联的强度。观测到的取食者中，蚂蚁占比约50%。