Abstract

Studying how different environmental parameters, such as resource availability and ambient temperature, affect growth rates aids to understand the evolution of different growth strategies. Low levels of food availability restrict growth, and high ambient temperature can constrain growth via trade-offs between body temperature maintenance and heat produced during digestion. We studied growth of African striped mice (Rhabdomys pumilio), a small mammal living in a seasonally arid habitat. Striped mice are born during spring with high food availability and low ambient temperature, and typically enter the food-restricted dry season before reaching adulthood. We predicted low food availability and high ambient temperature would negatively affect growth. We therefore expected an extended period of slow growth during the long dry season. We repeatedly measured body length of 369 free-living individuals, examined how ambient temperature and food availability influenced growth rate, and seasonal changes in growth rate. In addition, we investigated whether mice (N = 27) born in summer (atypical breeding season) have slower growth rates than those born in spring. Growth rate increased with increasing food availability and decreased with increasing ambient temperature. Individuals born in summer grew slower than those born in spring. Sexes reached asymptotic body length at 258 days (females) and 285 days (males), which is an unusually long growth period compared with other small rodents. As most striped mice live for less than 1 year, this period encompasses the entire life for most individuals, but stops at old age, which could indicate senescence. Our results demonstrate a positive influence of food availability on growth, a relationship mediated by ambient temperature. We conclude that striped mice enter the food-restricted dry season before postnatal growth is terminated, and early exposure to harsh environmental conditions during the long dry season likely explains the prolonged growth period in striped mice.

中文翻译：

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小型非洲哺乳动物在禁食干旱季节的长期生长

抽象的

研究不同的环境参数（例如资源可用性和环境温度）如何影响增长率，有助于了解不同增长策略的演变。低水平的食物供应会限制生长，而较高的环境温度会通过维持体温和消化过程中产生的热量之间的折衷来限制生长。我们研究了非洲条纹小鼠（Rhadomdoms pumilio）的生长），生活在季节性干旱的栖息地中的小型哺乳动物。条纹小鼠出生于春季，可食用性高且环境温度低，通常在成年前进入限制食物的干燥季节。我们预测食物供应不足和环境温度升高将对生长造成负面影响。因此，我们预计在漫长的干旱季节中，缓慢增长的时间将会延长。我们反复测量了369名自由生活个体的体长，检查了环境温度和食物供应量如何影响生长率以及生长率的季节性变化。另外，我们调查了小鼠（N= 27）在夏季（非典型繁殖季节）出生的婴儿的生长速度要比春季出生的婴儿慢。生长速度随着食物供应量的增加而增加，而随着环境温度的增加而降低。夏天出生的人比春天出生的人成长慢。性别达到渐近的体长，分别为258天（雌性）和285天（雄性），与其他小型啮齿类动物相比，这是一个异常长的生长期。由于大多数条纹小鼠的寿命不到1年，因此这一时期涵盖了大多数个体的整个生命，但是到了年纪就停止了，这可能意味着衰老。我们的结果证明了食物供应量对生长的积极影响，这是环境温度介导的关系。我们得出的结论是，条纹小鼠在出生后生长终止之前进入了食物受限的干旱季节，