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Prolonged growth during the food-restricted dry season in a small African mammal
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Edité par CCSD ; American Society of Mammalogists -
International audience. Studying how different environmental parameters, such as resource availability and ambient temperature, affectgrowth rates aids to understand the evolution of different growth strategies. Low levels of food availabilityrestrict growth, and high ambient temperature can constrain growth via trade-offs between body temperaturemaintenance and heat produced during digestion. We studied growth of African striped mice (Rhabdomyspumilio), a small mammal living in a seasonally arid habitat. Striped mice are born during spring with high foodavailability and low ambient temperature, and typically enter the food-restricted dry season before reachingadulthood. 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 measuredbody length of 369 free-living individuals, examined how ambient temperature and food availability influencedgrowth rate, and seasonal changes in growth rate. In addition, we investigated whether mice (N = 27) born insummer (atypical breeding season) have slower growth rates than those born in spring. Growth rate increasedwith increasing food availability and decreased with increasing ambient temperature. Individuals born in summergrew 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 livefor less than 1 year, this period encompasses the entire life for most individuals, but stops at old age, which couldindicate senescence. Our results demonstrate a positive influence of food availability on growth, a relationshipmediated by ambient temperature. We conclude that striped mice enter the food-restricted dry season beforepostnatal growth is terminated, and early exposure to harsh environmental conditions during the long dry seasonlikely explains the prolonged growth period in striped mice.
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