Never too late?: Consequences of late birthdate for mass and survival of bighorn lambs
Never too late?: Consequences of late birthdate for mass and survival of bighorn lambs
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DOI：
10.1007/s00442-008-1035-9
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发表时间：
2008-07-01
期刊：
影响因子：
2.7
通讯作者：
Jorgenson, Jon
中科院分区：
文献类型：
--
作者：
Feder, Chiarastella;Martin, Julien G. A.;Jorgenson, Jon
在强烈的季节性环境中，出生的时间会对健康产生重要影响。我们研究了影响分娩日期的因素，以及出生日期如何与性别、母亲特征和环境变量相互作用，从而影响阿尔伯塔省一个显著种群的大角羊（Ovis canada）羔羊的生长和存活。在14年的时间里，216只羔羊的估计出生日期在5月21日至7月18日之间。分娩日期是遗传的，与母体先前的体重有遗传相关性。断奶羔羊会使第二年的分娩延迟7天左右。出生日期对夏季生长率没有影响，但晚出生羔羊在9月中旬（大约断奶时间）比早出生羔羊体重轻。出生日期对断奶存活率没有影响，但晚出生会使公羊羔的存活率降低至1年。以粪便粗蛋白质测定的饲料质量对1年以内的存活率没有影响。一旦我们计算了9月中旬羔羊的质量，出生日期就不再影响成活率，这表明晚出生缩短了羔羊的生长季节，从而降低了成活率。由于没有夏季补偿性生长，晚出生的羔羊在冬季开始时比早出生的羔羊小。我们的数据强调了出生日期对生活史特征的重要性，并表明资源稀缺对青少年男性的影响比女性更严重。
In strongly seasonal environments, the timing of birth can have important fitness consequences. We investigated which factors affect parturition date and how birthdate interacts with sex, maternal characteristics and environmental variables to affect the growth and survival of bighorn sheep (Ovis canadensis) lambs in a marked population in Alberta. Over 14 years, the estimated birthdate of 216 lambs ranged from 21 May to 18 July. Parturition date was heritable and genetically correlated with maternal mass the previous fall. Weaning a lamb delayed parturition the following year by about 7 days. Birthdate did not affect summer growth rate, but late-born lambs were lighter in mid September (the approximate time of weaning) than early-born ones. Birthdate did not affect survival to weaning, but late birth decreased survival to 1 year for male lambs. Forage quality, measured by fecal crude protein, did not affect survival to 1 year. Once we accounted for lamb mass in mid September, birthdate no longer affected the probability of survival, suggesting that late birth decreased survival by shortening a lamb's growing season. Because there was no compensatory summer growth, late-born lambs were smaller than early-born ones at the onset of winter. Our data highlight the importance of birthdate on life history traits and suggest that resource scarcity had more severe consequences for juvenile males than for females.