Northern elephant seal development: The transition from weaning to nutritional independence
Northern elephant seal development: The transition from weaning to nutritional independence
复制标题
北象海豹的发育：从断奶到营养独立的转变
DOI：
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发表时间：
1978
影响因子：
2.3
通讯作者：
B. L. Boeuf
中科院分区：
文献类型：
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作者：
Joanne Reiter;Nell Lee Stinson;B. L. Boeuf
摘要1.在加州的Año努埃沃岛，对北方象海豹幼仔从断奶到离开繁殖地的2个半月进行了研究。在4周大断奶后，幼崽完全禁食，同时学习游泳和潜水，然后出海寻找食物。公仔出生时和断奶时体重比母仔重，哺乳期平均长一天。3.一些刚断奶的幼仔通过从哺乳期的母仔那里偷奶或被养母收养来延长哺乳期。男性更持久，更成功地偷奶比女性，因此，特别大的断奶总是男性。这些性别差异是从成年人最大限度地提高生殖成功率的方式中预测出来的。体型和条件上的优势对雄性的好处比雌性大得多。雄性的蜕皮和犬齿萌出的时间晚于雌性，这种差异可能是雄性的一种适应性变化，有利于偷乳。4.在最早期的社会交往中，性别分化是明显的。男性比女性更频繁地互动，他们的较量持续时间更长。雄、雌相互作用的行为成分类似于各自性别的战斗成虫。5.断奶仔猪开始入水时为6-7 1/2周龄。他们逐渐学会游泳和潜水。随着游泳水平的提高，它们会冒险远离出生地。它们是优秀的游泳者，在3-3个半月大时离开繁殖地时，可以在水下停留15分钟。在繁殖季节后期断奶的幼犬会受到早期断奶幼犬的刺激而进入水中。离开繁殖地与海岸上升流的开始有关，后者与海洋中的食物丰富有关。死亡原因包括成年雄性和雌性动物造成的伤害、风暴和高海浪造成的创伤或溺水、过热、事故和鲨鱼捕食。8.第一次海上生活后至7个月大的存活率至少为50%。此后，存活率逐渐下降，3岁时最低为12%。2岁时的存活率没有性别差异。在繁殖季节早期出生的幼仔在第一年的存活率比在繁殖季节后期出生的幼仔高;在繁殖季节早期出生的雌性在3.9岁时在其队列中表现出最高的产次率。
Summary1.The 2 1/2-month period from weaning to departure from the rookery was studied in northern elephant seal pups at Año Nuevo Island, California. After being weaned at 4 weeks of age, pups fast completely while learning to swim and dive before going to sea in search of food.2.Pups increase their birthweight by a factor of 3–7 times on mother's milk alone. Males weigh more than females at birth and at weaning, and are nursed an average of one day longer.3.Some newly weaned pups prolong the suckling period by stealing milk from nursing females or by being adopted by foster mothers. Males are more persistent and more successful at milk stealing than females and, consequently, exceptionally large weaners are always males. These sex differences are predicted from the manner in which adults maximize their reproductive success. An advantage in size and condition benefits a male much more than a female. Molting and canine eruption occur later in males than in females and these differences may be an adaptation in the former which facilitates milk stealing.4.Sexual differentiation is evident in the earliest social interactions. Males interact more frequently than females and their bouts last longer. Behavioral components in the interactions of males and females resemble those of fighting adults of each respective sex.5.Weaners begin entering the water when 6–7 1/2 weeks old. They learn to swim and dive gradually. As swimming proficiency increases, they venture further away from their birthplace. They are excellent swimmers and can stay underwater for 15 min by the time they leave the rookery at 3–3 1/2 months of age.6.Although pups are born over an 8-week period, the majority of them depart the rookery over a 3-week period. Pups weaned late in the breeding season are stimulated to enter the water by those weaned earlier. Departure from the rookery is correlated with the onset of coastal upwelling and the latter is correlated with food abundance in the ocean.7.Few weaned pups die before leaving the rookery. Mortalities result from injuries inflicted by adult males and females, trauma or drowning due to storms and high surf, overheating, accidents, and shark predation.8.Survival after the first period at sea to 7 months of age is at least 50%. Thereafter, the survival rate declines gradually to a minimum of 12% at 3 years of age. There are no sex differences in survival to age 2. Pups born early in the breeding season exhibit a higher survival rate during the first year than those born later in the season; females born early in the season exhibit the highest parity rate in their cohort at age 3.9.Early sex differences are interpreted as subserving the different adult reproductive strategies of each sex.